I-NRLF SDI 3m TI-E BOOK OF THE DAIRY LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class THE BOOK OF THE DAIRY ' - < -- THE BOOK OF THE DAIRY A MANUAL OF THE SCIENCE AND PRACTICE OF DAIRY WORK TRANSLATED FROM THE GERMAN OP W. FLEISCHMANN, Pn.D. PROFESSOR OP AGRICULTURE AND DIRECTOR OP THE AGRICULTURAL INSTITUTE, KONIGSBERG UNIVERSITY, PRUSSIA HONORARY MEMBER OF THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND BY C. M. AIRMAN, M.A., SC.D., F.R.S.E., F.I.C. FORMERLY LECTURER ON AGRICULTURAL CHEMISTRY, GLASGOW TECHNICAL COLLEGE, AND EXAMINER IN CHEMISTRY, GLASGOW UNIVERSITY AND R. PATRICK WRIGHT, F.H.A.S, F.RS.E. PROFESSOR OF AGRICULTURE GLASGOW AND WEST OF SCOTLAND TECHNICAL COLLEGE UBRT?> OF THE r I UN/VERS/TY ) LONDON BLACKIE & SON, LIMITED, 50 OLD BAILEY, E.C. GLASGOW AND DUBLIN SENERAL PREFACE. The English editors have prepared this edition of Professor Fleischmann's comprehensive treatise on Dairying in the belief that in doing so they are placing in the hands of British dairy-farmers a work on the science and practice of their difficult art which will be found invaluable alike for study and for reference. They also believe that it forms a text-book specially well fitted to supplement and explain to students at our numerous Dairy Schools and Agricultural Colleges the practices of dairy management there shown in operation. Professor Fleischmann has long enjoyed the reputation of being one of the greatest living authorities on the science and practice of dairying, and his treatise in German is familiar to all specialists as the best work on the subject. The great advances made in agricultural education in this country in recent years have been the means of calling into existence a number of excellent works in the different depart- ments of agricultural science; but the editors believe that Professor Fleischmann's work, in an English form, supplies, in the -conventional phrase, "a felt want". They trust that the addition of a considerable number of illustrations (not included in the German edition) will still further enhance its value. The great importance of milk and other dairy products as articles of diet renders any work dealing with the subject of great interest to many others besides the dairy-farmer and V J 22300 VI PREFACE. the agricultural student. It is anticipated by the translators that the work will be found of value by medical men gener- ally, and more especially by officers of public health. They also hope that it may afford some assistance to agricultural and analytical chemists, as well as to other sanitary authorities charged with the administration of the Adulteration of Foods and Drugs Act. The monetary value of the interest involved in dairy produce is pointed out at greater length in the Introduction. It may suffice here merely to refer to the fact, that an annual income of over 32,000,000 is estimated to be derived in this country from the sale of dairy produce, or one-sixth of the whole income of British agriculture. But enormous as this sum is, it is not all that is paid by the consumer for dairy produce, since we import it from other countries to the extent of over 20,000,000 per annum. Much of the produce represented by the 20,000,000 finds a ready market in Britain chiefly because of its high and uniform quality. There is no reason, however, why dairy produce of an equally uniform and of even a higher quality should not be manu- factured at home, and thus the best position be retained in our own markets. In achieving this object everything which tends to bring about a better and more scientific knowledge of dairying may be said to help, and it is the confident expectation of the translators that the present volume will not be found altogether ineffective in promoting this purpose. CONTENTS. CHAPTER I. THE SECRETION, PROPERTIES, AND COMPOSITION OF MILK. 1-24. Definition of milk. Structure and nature of cow's udder. Teats. Forma- tion of milk. Researches on process of milk secretion. Properties of milk chief constituents of, effect of heat on, physical nature of, nitrogenous matter of. Caseous matter. Albuminoids researches on nature of. Milk- fat or butter-fat specific gravity of, state of division of, its chemical com- position. Milk-sugar action of heat on, properties of. Inorganic or mineral constituents composition of. Other constituents of milk. Percentage com- position of cows' milk. Specific gravity of milk. Relation between specific gravity and fat and total solids of milk. Formulae showing relation. Colostrum or beastings. Its composition. Corps granuleux. Secretion of milk in udder. Intervals of milking. Lactation periods. Age of cows. Effect of bulling. Working of milk cows. Feeding. Result of increasing digestible constituents of food. Relation between feeding and richness in fat of milk. Feeding stan- dards. Utility of foods. Composition of foods. Suitable foods. Effect of food on properties of milk. Milk yields. Conditions influencing yield of milk. Milk-yielding capacity of cows. External appearances indicating high milk- yielding capacity. Milk faults bitter, coloured, ropy, lazy, and sandy milk. Milk difficult to churn goats' milk, sheep's milk, mares' and buffalo milk, pp. 1-57 CHAPTER II. THE EXTRACTION, IMMEDIATE SALE, AND TESTING OF MILK. 25-35. Milking position of hands in, importance of cleanliness in. Treatment of milk after milking cooling of, addition of preservatives to. Pasteurizing of milk. Lawrence refrigerator. Distribution of milk. Railway milk-cans. Cart milk-can. Value of milk for fattening purposes. Value of milk as an article of sale. Profitable methods of disposal. Precautions in sale of. Milk adulteration. Adulterants. Milk testing value of chemical analysis in. Formulas for calculating composition of milk. Soxhlet's aerometric fat method. Lactocrit-Marchand method. Byre test. Variations in composition of milk. Supervision of milk trade in towns tests necessary for. Conditions regulating sale of milk. Cream. Supervision of milk in large collecting and co-operative dairies. Selling milk according to its percentage of fat. Milk-ferment and rennet test. Supervision of the production and manufacture of milk. List of dairy instructions. Analysis of milk. Determination of water, total solids, fat, nitrogenous matter, milk-sugar, and ash. Detection of adulteration, . pp. 58-89 vii Vlll CONTENTS. CHAPTER III. MILK IN ITS RELATION TO MICRO-ORGANISMS, DAIRYING, AND BACTERIOLOGY. 5-46. Bearing of bacteriological research on dairying. Importance of cleanliness in dairying. Lower fungi. Different forms of bacteria. Action of bacteria. Distribution of lower fungi. Forms and life conditions of bacteria. Effect of temperature on bacteria. Sterilization of milk. Intermittent sterilization. Contaminated milk. Methods of sterilization. Spontaneous coagulation of milk and souring of cream. Lactic fermentation. Different kinds of milk diseases. Premature coagulation of milk. Slimy or ropy milk. Development of colours in milk. Bacteria causing colours. Micro-organisms in cheese. Fission fungi. Organisms necessary for ripening of different cheeses. Organisms deleterious to cheese. Characteristics of milk owing their origin to micro- organisms. Kephir. Destruction of micro-organisms. Practical application of bacteriology, pp. 89-105 CHAPTER IV. THE MANUFACTURE OF BUTTER. 47-106. Different methods in which butter is made. Methods of obtaining cream. Old method of cream-separation. Cream -raising. Rising of fat globules to surface of milk. Conditions necessary for creaming. Different methods of cream-raising. Temperature for cream-raising. Older methods of cream-raising. Swartz method. Cold water method. Collection and storage of ice. Unit of heat. Methods of cream-raising. Cream-yielding coefficient. Centrifugal force. Value of centrifugal force for cream-raising of milk. Alexandra cream separator. Milk in the separator drum. Inflow of milk into separator. Outflow of cream and skim-milk from separator. Regulation of proportional weights of cream and skim-milk in separation of milk. Size and reliability of separator drums. Milk-separators at present in use. Lefeldt separator. Separators made by Separator Co., Stockholm. Laval separators. Laval hand separators. Alpha separators. Burmeister & Wain's separators. Peterson patent separator. Vic- toria separators. Balance separators. Separators at present in use in Germany. Best separators. Cream-raising coefficient in connection with use of separators. Conditions influencing cream-raising coefficient in separators. Supervision of revolving rate of drum of separators. Supervision of quantity of milk creamed per hour. Regulation of temperature in separation of milk. Regulation of relative quantity of cream and skim-milk in use of separators. Condition of cream and skim-milk from separators. Lawrence refrigerator. Laval cream - cooler. Proper working of centrifugal machines in dairies. Forces brought into action in operation of separators. Hand separators. Separator residue. Cream. Composition of cream. Skim-milk. Composition of skim-milk. General remarks on butter-making. Butter churns. Churns. Swinging, cradle, and rocking churns. Churns with horizontal barrels. Churns with vertical barrels. Churns of uncommon and special construction. Practical value of different churns. Preparation of milk for churning. Churning. Temperature for churning. Churning of sour cream. Churning of milk. Experiments made to obtain butter by uncommon methods. Centrifugal butter separator. Colour- ing of butter for use. Salting of butter. Working and kneading of butter. Butter worker. Curd knife. Holstein butter worker. Butter trough. Yield CONTENTS. ix of butter. Different kinds of butter. Fresh butter. Preserved butter. Whey butter. Melted butter. Butter-milk. Composition of butter-milk. Properties of good butter. Common faults of butter. Chemical composition of butter. Analysis of butter. Determination of water, fat, ash, proteids, non-nitrogenous bodies, preservatives, and colouring matters in butter, pp. 106-199 CHAPTER V. CHEESE AND CHEESE-MAKING. 107-128. Coagulation of milk and properties of coagulum. Curd. Coagulum or raw cheese. Coagulation of milk by acids. Chemical composition of casein, paracasein, and whey-protein. Rennet and its properties. Strength of action of rennet. Directions for using rennet. Rennet powder. Rennet substitutes. Preparation of rennet. Application of rennet in practice. Time for coagulation. Testing of rennet solution. Colouring of cheese. Utensils necessary in prepara- tion of cheese. Cheese vat for steam. Cheese vat for hot water. Steam cheese kettle. Oneida cheese vat. Cheese tub. Treatment of curd before moulding. Cheese breaker and ladle. Curd stirrer and knife. Shaping of rennet cheeses. Cheese rooms. Pressing of rennet cheeses. Wooden cheese vat. "Two in one" double cheese press. "Gleed" press. Swiss lever press. Lever press. Salting of cheeses. Ripening room for cheeses. Art of cheese-making. Function of bacteria in ripening. Ripening of cheese chemical changes effected by, function of fungoids in. Defects of cheese. Preparing of cheeses for market. Different kinds of cheese and their classification. Cheeses of a soft and oily character made from cows' milk. Soft cheeses. Preparation of Neufchatel cheese. Rennet cheese of a firm character, made from cows' milk. Hard cheeses. Preparation of cheddar cheese in America. Preparation of cheddar cheese in England. Preparation of Edam cheese in Holland. Preparation of Emmenthal cheese in Switzerland. Bacillus diatrypeticus casei. Cheese from sheep's milk. Pre- paration of Roquefort cheese in France. Cheese from goats', buffalo, reindeer, and mixed milk. Sour milk cheeses. Curd mill. Cheshire curd mill. Cheese- like products from refuse of cheese manufactories. Mysost. Schottensicht. Ziger cheese. Liquid residue of cheese. Its composition. Yield of cheese. Chemical composition of cheese. Analysis of cheese. Determination of water, fat, ash, nitrogenous matter, and milk-sugar. Composition of different cheeses, pp. 200-275 CHAPTER VI. PREPARATION OF KEEPING MILK, FERMENTED MILK, AND THE BYE-PRODUCTS OF MILK. 129-138. Keeping milk. Pasteurized milk. Laval milk-scalder. Different forms of Pasteurizing apparatus. Temperature necessary for Pasteurization. Steri- lized unthickened milk. Sterilizing apparatus. Properties of sterilized milk. Condensed milk. Vacuum pan for condensing milk. Composition of condensed sweetened milk. American unsweetened condensed milk. Fermented milk. Ropy milk. Kephir its properties, its preparation, its composition. Koumiss its preparation, its composition. Ropy milk. Milk-sugar its preparation, its composition. Bye-products of milk of minor importance. Keschk. Lactarine. Lactite, '.'.,/.... pp. 276-295 : CONTENTS. CHAPTEE VII. THE ECONOMIC ASPECTS OF DAIRYING. 139-146. Sale of milk for direct consumpt. Utilization of milk by making it into butter. Utilization of milk by making it into fat cheese. Countries adapted for making milk into cheese. Difficulty of marketing cheese. Utilization of milk in different countries. Calculations for different methods of milk utiliza- tion. Amounts realized by different milk products. Profit from sale of milk for direct consumption. Profit from manufacture of fatty soft cheese. Profit from hard cheese. Profit in ice treatment and manufacture of butter and half-fat cheese. Keeping of books. Machine for weighing milk. Milk registers. Yields of various milk products. Payment of milk according to weight and composi- tion. Payment of milk in dairy companies in which fatty hard cheeses are made. Payment of milk in dairies having a limited trade. Structure and arrangement of a large dairy pp. 296-315 CHAPTER VIII. MARGARINE AND MARGARINE CHEESE. 147_8. Margarine history of its discovery, extent of trade in, fats used in manu- facture of. Butterine fraudulent manufacture of. Development of trade in different countries. Composition of Margarine. Margarine cheese limited demand for, preparation of, pp. 316-326 CHAPTER IX. 149. EXPLANATION OF TABLES IN APPENDIX, pp. 327-330 LIST OF ILLUSTRATIONS. PLATES. PAGE AYRSHIRE Cow "POLLY II. OF KNOCKDON", - - Frontispiece. THE Cow's UDDER Double Coloured Plate (figs. 1 and 2), - xx JERSEY Cow "CHESTNUT II.", 48 DEXTER Cow "ROSEMARY", 58 SHORTHORN Cow "MOLLY MILLICENT", 88 ENGRAVINGS IN THE TEXT. pia. 3. Bundle of Elastic Fibres and Connective Tissue Fibres of Cow's Udder, - 1 4. Gland-lobules, 2 5. Alveoli, 2 6. Cylindrical Epithelial Cells, - 2 7. Capillaries of Mammary Glands, .... 2 8. Milk-cistern and Outlet Tube of Milk-gland laid open. (Two-thirds of natu- ral size), 3 9. Plaster of Paris Cast of the Posterior Milk-cistern, with the Canal of the Teat, of an Ayrshire Cow, 4 10. Plaster of Paris Cast of the Posterior Milk-cistern, with the Canal of the left side of the Udder of a Dutch Cow, 4 11. Plaster of Paris Cast of the Milk-cistern and Milk-ducts of the Milk-gland of a Dutch Cow. (Natural size), 5 12. Plaster of Paris Cast of the Canal traversing the Teat and Nipple, - - 6 13. Section of Membrane of Lower and Narrow Portion of the Canal of the Teat, 6 14. Section of Sebaceous Gland, 7 15. Tallow Follicle of the Nipple, 7 16. Tallow Follicle of Nipple, 7 17. Milk-globules, - 19 18. Colostrum Corpuscles, 36 19. Pyrenean Milking Goat, .... .54 20. Friesian Milking Sheep, - - 55 21. Position of Hands in Milking, 59 22. Lawrence Refrigerator, 61 23. Railway Milk-can, 62 24. Top of Milk-can, with Seal and Pincers, showing Mode of Fastening, - - 63 25. Cart Milk-can, - 63 26. The Lactocrit, - 70 27. Different Forms of Bacteria, 91 28. Sectional Illustration of the Alexandra Cream-separator, .... 121 29. Lefeldt's Separator. (Section), 127 zi Xll LIST OF ILLUSTRATIONS. FIO. PAGE 30. Arnoldt's Hand Separator. (Perpendicular Section through the Drum), - 128 31. Steam-turbine Separator, 129 32. Perpendicular Section of Steam-turbine Separator, - - - - - 130 33. Two Laval Separators with Milk Warmer, 131 34. Perpendicular Section through the Drum of the Laval Hand Separator, - 131 35. Alpha Separator, No. 1, - - - - - i - - - - 132 36. Alpha Hand Separator (K), - 134 37. Alpha Baby Hand Separator, 134 38. Alpha Hand Separator (B), 134 39. Danish Centrifugal Cream-separator (Burmeister and Wain). (Perpendicu- lar Section), ---'-.-..' - 135 40. Hand Separator (Burmeister and Wain), 136 41. Burmeister and Wain's Hand-power Separator. (Perpendicular Section), - 137 42. Victoria Hand-power Cream-separator, 138 43. Sectional View of 'Victoria Hand-power Cream -separator, - 139 44. Section of the Balance Separator, 140 45. Lawrence's Refrigerator, -,.------- 148 46. Laval Cream-cooler, -, 149 47. Cotswing Churn, - 162 48. Box Churn, 162 49. Diaphragm Churn, . -. 163 50. Victoria Churn, 164 51. Centrifugal Butter-separator, 175 52. Butter-worker, 180 53. Butter-knife, 180 54. Butter-worker, ... 181 55. Holstein Butter-worker, 181 56. Butter- trough, - - 182 57. Cheese Vat for Steam, - 214 58. Cheese Vat for Hot Water, - 214 59. Fixed Cheese Kettle with Movable Firing. (Perpendicular Section), - - 215 60. Fixed Cheese Kettle with Movable Firing, 215 61. Steam Cheese Kettle. (Perpendicular Section), - - 216 62. Oneida Cheese Vat. (Perpendicular Section), 217 63. Cheese Tub, - - 218 64. Cheese Ladles, - 219 65. Curd Stirrer, - - . - - - 219 66. Curd Breaker, , - - ' 219 67. Curd Knife, - - , - - - - - - ; - - 219 68. Curd Knife with Horizontal Plates, - - - * - ' -' * - 219 69. Curd Stirrer, - - - - 219 70. Wooden Cheese Vat to open with Key, - - - i - - - - 224 71. "Two in One" Double Cheese Press, - - - - - - - 224 72. Gleed Press for Soft Cheeses, ---..-. - 225 73. Swiss Lever Cheese Press. - - ' - - - - 225 74. Lever Press, - - - - ' - .-.-.- - - 226 75. Bacillus Diatrypeticus casei, - - . . . . . - - 260 76. Curd Mill, ..... . - . . . . . - 266 77. Cheshire Curd Mill, - . . , . . . .- . -267 78. Laval Milk Scalder, - - ..-.-.. . .. ' " - 277 LIST OF ILLUSTRATIONS. xiii FIG. PAGE 79. Pasteurizing Apparatus (Burmeister and Wain), - - - ... 278 80. Pasteurizing Apparatus (Lefeldt), 279 81. Sterilizing Apparatus, 281 82. Vacuum Pan for Condensing Milk, 283 83. Machine for Weighing Milk, .... .... 306 84. Machine for Weighing Milk, 307 85. Model of Large Dairy, 315 INTRODUCTION BY THE ENGLISH EDITORS. It is generally allowed by those who have given attention to the progress of agriculture during the past thirty years, that perhaps the most prominent feature in its history has been the great change that has taken place in that time, in the methods and processes of dairying, and in the relative importance assigned among English- speaking peoples to dairying as a branch of agricultural science and practice. This is very clearly evidenced in all works on agricultural science and practice written prior to the present decade, in which it will generally be found that, while some pages are devoted to a description of dairy breeds of cattle, very little space is accorded to the consideration of questions relating to the management and treatment of milk, and the manufacture of butter and cheese. The comparative neglect of dairying science, up to the present time, is probably attributable to two causes. In the first place, other branches of agriculture contributed in a much larger degree then than now to the revenue of agriculture; and in the second, dairying as an art was imperfect and empirical, and as a science had little or no existence. Up to the time when the import of foreign wheat to Britain began to assume large dimensions, the income and profits of our farmers depended in very great measure on the returns from wheat and other cereal grains. In the year 1869, for example, the total area under wheat in the United Kingdom was 3,862,202 acres, which was estimated 1 to yield 113,331,777 bushels of an average value of 6s. OJd per bushel. The total value of wheat (grain only) to the agriculture of the United Kingdom in 1869 was, therefore, more than 34,000,000 sterling. As the value of wheat, however, from that year underwent a steady decline owing to a con- stant increase in the foreign supply, the cultivation of this cereal was gradually abandoned by farmers as the returns became unpro- 1 K. F. Crawford, in Journal of the Royal Agricultural Society, 1895. xv XVI INTRODUCTION. fitable, and by the year 1893, the value of wheat in British agricul- ture had suffered a remarkable diminution. In that year the area under wheat in the United Kingdom had fallen to 2,215,355 acres. The yield was estimated at 67,717,160 bushels, and the price was 3s. 3 ^d. per bushel. The total value of the home-grown crop (grain only) in 1893 was, therefore, a little over 11,000,000 ster- ling, or less than a third of its value fifteen years previously. A similar, though less extreme, change had in the meantime taken place in the prices of barley, oats, and other less extensively grown grains; and other of the more important sources of farm income had undergone a similar depreciation in value. Beef, which along with grain constituted a chief source of income on the greater part of arable area in Britain, also suffered a serious fall in value in the same period. This heavy depreciation in values told not less seriously on the agriculture of Canada and of America than on that of Britain. Over a very large area, in both of these countries, the income of the farmer depended primarily on the price of wheat; and as the price has suffered year by year a steady decline, the position of the farmer has been constantly changing for the worse. Mean- time, while all departments of agriculture have suffered more or less severely from the heavy fall in the value of beef, mutton, and grain, farmers whose income depended more largely on returns from dairy produce, remained, up till 1894, in a relatively prosperous condition. Not only have cheese and butter continued at high prices, but, with the steady increase of the population of the United King- dom, as well as of America and of the Colonies, a much-increased demand has developed for articles of dairy produce, such as milk and cream, in which there has been no foreign competition of such a character as to affect prices seriously. Moreover, apart from increase of population, the practice of using milk as a regular article of diet has undergone a remarkable development during these years. This has probably originated in a more extensive knowledge of the value of milk as a food, and its intrinsic cheapness as compared with other foods; but it has also been encouraged in great measure by improvements in the supply, brought about by the development of railway enterprise, and by the guarantees of good quality which have been secured in all our large towns by the strict and careful enforcement of the measures and stringent regulations prescribed by local authorities for the construction of byres, the arrange- ment of dairies, and for the control of the milk supply and the (M175) INTRODUCTION. xvil prevention of adulteration. Not a little of the increase in the consumption of milk has been due to the enterprise of dairymen and milk-sellers, and to the larger dairy companies in our cities, who, by attention to cleanliness, by prompt and convenient supply, and by the employment of the best-known means for the detection of adulteration, have succeeded in inspiring the public with confi- dence in the soundness and quality of the dairy produce supplied by them. Consequently, while other articles of farm produce have been steadily falling in value, milk has remained in good demand at a comparatively high level of prices, at prices that were, indeed, rising during a number of the years when the depression in arable agriculture, outside of the dairying districts, had reached its most acute and disastrous stage. The effect of these various influences, the fall in the. value of other articles of agricultural produce, together with the increased consumption of dairy produce and the maintenance of high relative values alike for milk and its manufactured products, has been to raise dairying gradually into a much more important position as a branch of agriculture in Britain than it has ever before occupied. If consideration be given merely to the value of dairy produce sold off the farms, the following estimates recently made by Mr. R. Henry Rew 1 may be quoted to show the present importance of dairying relatively to other branches of agriculture. According to these estimates, the value of the whole amount of agricultural produce of the United Kingdom sold off the farms is 197,749,477, while the value of the whole dairy produce of the United Kingdom sold off the farms is 32,493,000. The particular forms of dairy produce from which the income is derived are estimated by Mr. Rew to be as follows: Description of Produce. Quantity Sold off Farms in U.K. Average Price. Total Value. Milk, 576,000,000 galls. 6Jd. per gall. 15,600,000 Butter, 2,000,000 cwts. 112s. per cwt. 11,760,000 Cheese, 2,000,000 51s. d. 5,133,000 Total, 32,493,000 From these estimates it appears that one-sixth of the whole income of British agriculture is derived from the sale of dairy produce. There remains, in addition, a large proportion that is consumed on the farm in the form of the milk supplied to calves, iSee Journal of Royal Agricultural Society, 1895. (M175) 6 " XV1U INTRODUCTION. and the milk, butter, and cheese consumed by the farmer, his house- hold, and the labourers on the farm. The data of total produce, however, that have been quoted com- prise the returns from extensive areas of mountain land the income from which is realized, to by far the greatest extent, in the forms of mutton and wool. Hence statistics that include the returns of a large acreage of uncultivated land place dairying in a relatively less important position than would be assigned to it if the income derived from arable land only were taken into consideration. Its exact position may perhaps, therefore, be more exactly appreciated from the statistics bearing on the number and kinds of cattle in Britain. The total number of cows and heifers, in milk or in calf, in the United Kingdom in 1894, was 3,925,486, or considerably more than one-third of the total number of cattle, at that time, in the kingdom. The amount of milk yielded by this number may be estimated at 1,766,468,700 gallons. If it be assumed that one- eighth part of this yield of milk is used in rearing calves, there would remain 1,545,660,112 gallons of milk for home consumption; either in a raw condition as fresh milk, or in the manufactured forms of butter and cheese. The science of dairying in the United Kingdom, therefore, has for its subject-matter the management, rearing, and feeding of about four millions of cows, and the pro- duction, treatment, and sale of nearly eighteen hundred million gallons of milk, and the whole processes of the manufacture of the greater part of this enormous quantity into butter and cheese. But great as the dairy industry is in Britain, its extent is, how- ever, already rivalled by that of some of her colonies, and is far exceeded by that of the United States of America. The total dairy produce of the United Kingdom falls far short of the requirements of her population; while that of the United States not only supplies all that is required by her own greater population, but enables her to export large quantities both of butter and of cheese. It was about the end of the first quarter of the present century that the manu- facture of dairy produce in the United States first attained to such dimensions as to exceed the needs of the home population, and to render new markets necessary. In 1826 the export of cheese to England, then recently begun, amounted only to 735,399 Ibs. In 1847 it had increased to 15,000,000 Ibs.; and from that date till about 1860, the total amount of cheese made in the United States was estimated to be annually about 100,000,000 Ibs. By that time, INTRODUCTION. xix however, the system of making cheese in special factories, started in 1851, had begun to be widely adopted. In 1860 there were 23 such factories. In 1866 these had increased to 500. In 1862-63 the system that had been hitherto applied only to cheese-making was also applied to butter-making, and the first butter factory was opened. In 1866 there were 500 cheese factories, in addition to butter factories. In 1884 the number of cheese and butter factories had increased to over 4000. This rapid extension of the factory system was accompanied by a corresponding extension of dairy farming. In the twenty-two years from 1862 to 1884 the butter production of the United States is estimated to have increased from 500,000,000 Ibs. to 1,500,000,000 Ibs. About 1861 a new branch of dairy manufacture began to attract attention in the United States, viz., the manufacture of condensed milk. This branch of the dairy industry proved so prosperous that twenty years afterwards the quantity of milk treated in this fashion amounted to about 60,000,000 Ibs., and the industry is still extending. A comparison of the available statistics for the period of thirty years from 1850 to 1880 shows, perhaps, more clearly how much more rapid was the growth of dairy farming in the United States than of even the rapidly increasing population. In 1850 the num- ber of cows in the States was 6,392,044. In 1880 the number was 12,443,120. The butter made in 1850 amounted to 313,345,306 Ibs., as compared with 806,672,071 Ibs. in 1880. In 1850 the amount of cheese made was 105,535,893 Ibs. In 1880 it had increased to 243,157,850 Ibs. The total value of the dairy produce of the country, including milk, was estimated in 1880 to be about from 2 to 2J times as great as it was in 1850. In 1847 the export of cheese to Britain amounted to 15,000,000 Ibs. In 1894 it amounted to 75,302,864 Ibs., or five times as much, in addition to about 3| million Ibs. of butter. In Canada the progress of the dairy industry, though more recent, has been even more rapid. In 1864 the dairy produce of Canada was insufficient for the consumption of her population, and imports were made from the United States. The population in the thirty succeeding years has increased with great rapidity; yet, not only is the consumption of dairy produce fully met by home manu- facture, but the exports to England in 1894 amounted to over 1000 tons of butter; while the exports of cheese amounted to over 67,000 tons, and constitute Canada by far the largest single source of XX INTRODUCTION. supply of the latter product to Britain. New cheese factories are now being built, and there is every prospect, therefore, that the future export will be still greater than it is at present. In still more recent years a steady development of dairying has occurred in Australia and New Zealand, owing to the fact that the shipping of butter and cheese in good condition to this country has been proved to be practicable. The exports from Australia have proved so profitable to the producers that every year witnesses a great increase in the quantity sent over; while the home demand of these colonies for dairy produce is naturally becoming greater in proportion to the rapid increase of population. Thus, in the first six months of 1894, Australia exported to Britain 198,004 cwts. of butter, while in the first six months of 1895 the export had increased to 241,665 cwts., or a growth in one year of over 20 per cent. The total import of butter into England in 1894 was 32,000 tons more than in 1889, and nearly half of that additional quantity came from Australia. There is every probability in the near future that the Australian export of dairy produce will assume much greater dimensions; for the dairy industry in Australasia, now that an export trade to Britain has become fairly established, is advancing by leaps and bounds. A further illustration of this is found in the fact that the export of butter, which was about 3f millions of Ibs. in 1891, had risen in 1892 to 6J millions of Ibs. In 1891-92 the number of cheese and butter factories existing was 74, while in the following year there were 109. In the Province of Victoria alone, there were in 1892-93 upwards of 400,000 milk cows, which yielded over 120 millions of gallons of milk. Of this it has been estimated that about one-third was consumed in its natural state, that about 75 millions of gallons were made into butter, and the remaining five millions of gallons into cheese. In New Zealand the energetic efforts of the Department of Agriculture have been very successfully directed to the encouragement of dairying. Only a few years ago there were no co-operative factories in existence, and, practically, there was no export trade. Cheese and butter were made only on a small scale, and almost entirely for local consumption. But in 1893 about 180 factories and creameries had become established, and in 1894 these were increased by about thirty more. The pro- duction was estimated in 1892-93 at 8,167,500 Ibs. of cheese, and 6,722,303 Ibs. of butter; while the exports alone in 1893 amounted to 58,147 cwts. of butter, and 46,198 cwts. of cheese. There is every - : * 11*113 illl II ; 3> ""si *! ai -i r'S-e f *ri 5 "Sf iiil *-\ w^ > ctf r! M *? P-bi ; liif Si Sc>dCS>>.=> fljtlmj SiS:i ^1l^p,g 2S^^I P5 m INTRODUCTION. XXI reason to expect that this development of dairying in New Zealand will continue to make rapid progress. l ^O5O50SOOOOSOS co~co c^f r-i~ r-T cT oT krT rH-^OCOvOOSCOOS Tjl 00 t 00 CO rH O .r-Tio 1 ir? of t^ O OS - 00 1-1 OS cr5f irT ^ rti rH 1O OOSXOVOCOOOCOOS OCOD(N(MCO(M sf & OO CO -* (M 00 rH oC 3 lti OS ^ OS OS CO O rH OO CO OO t^ OO or-dTwrTnT (M CO rH O rH t>- !>. Oi CO OS t-- O tN ^ CO t> sss's" *- O O . O rH icTof cTt>T (M OS )O C^ BO" _g "S f (N O O O - 00 IG> t~- OO oToo"i^rio'i>r (M O O rH \O OS CO OS IM O OS CO O CO O * CO_ co 1 vrT od" od" co 1 O OO XXI] INTRODUCTION. The total amount of the imports of dairy produce into with the sources from which they come, is fully shown in th^ table on p. 21. It will be seen from the foregoing table that while the imports of dairy produce into Britain from the United States are still lar^e, and while those from Canada and Australia are rapidly increasing, there are also large, and, in some cases, still increasing, supplies sent in from the several European countries which, for many years before the development of the trans-oceanic trade, formed our chief source of foreign supply. So far as cheese and cured butter are concerned, the home manu- facturer of these products has little advantage in the markets over the foreign producer, except what is afforded by any injury that may be done to the quality and flavour in the course of transit, and the costs involved in the transport of the foreign product. This, however, owing to the low rates of shipping freights that have ruled for a number of years, confers only a limited protection, and it in now generally admitted that the only hope the British dairyman has to compete successfully with the large foreign competition is by the manufacture of produce of distinctly superior quality. This can only be effected by giving the butter and cheese makers of this country such a training as will enable them to attain to the highest perfection in the practice of their delicate and difficult art. Unfor- tunately, up till quite recent years technical instruction in dairying received almost no attention in Britain. An empirical art, differing in various details of practice not only in every parish and county but even on adjacent farms, was handed down from father to son, or communicated from neighbour to neighbour in an unsystematic and incomplete form that wholly prevented any general improve- ment in the art of dairy manufacture. Consequently the manufac- tured products were very variable, and often of an inferior character and value. While the art of dairying was thus imperfectly communicated, the science of dairying, as it is now known, had till very recently no existence. Thirty years ago there was practically no EnglisK dairy literature. Appliances for the manufacture of butter and cheese were few, and were imperfect. The principles that regulated their manufacture were not understood, and the practice was accord^ ingly irregular and unsatisfactory. There were no dairy schools, and no recognized means of obtaining intelligent instruction in INTRODUCTION. Xxiii dairying. Neither can it be said, though great improvements have taken place in recent years, that the old condition of things has yet come to an end. A number of dairy schools have now indeed been established, and have done excellent work. Systematic training in the art of butter and cheese making can be obtained without much difficulty in most parts of the country, and something is also beginning to be generally understood of the principles on which these arts should be based. A dairy literature, largely drawn from American, and indirectly from German, sources, but still to a great extent empirical, has begun to be founded; and in the practice of dairying, apart from increased knowledge or skill on the part of the operator, much advantage has been derived from the possession of modern and more suitable utensils. But with all the progress that has been made in the past twenty years, it is undeniable that our knowledge alike of dairy practice and of dairy science is still far behind that of many of our continental competitors. This is due in great part to the position of greater importance the dairy industry holds in agricultural coup- tries, such as Denmark and Holland, than in a country like Britain, whose wealth is derived in large measure from minerals and manu- factures. In all the countries, without exception, that contribute materially to swell the imports of dairy produce into Britain, great efforts have been put forth by the respective Governments to develop and to carry to perfection manufactures on which the wealth of these countries is so largely dependent. In Britain, up till a few years ago, it was left wholly to private enterprise to provide technical instruction in dairying, and even now the amount contributed by Government to the assistance of dairy schools and colleges imparting dairying instruction amounts to not more than a few hundreds of pounds for the whole kingdom. In consequence of this, little attention has been paid in Britain to a study of the many important questions on which dairying demands the assistance of the botanist, the chemist, and above all the bacteriologist. In Denmark and Germany there are numerous and important dairy schools and agricultural colleges, largely endowed and supported by Government, in which the whole time of many able men is devoted to dairy teaching, and to the investigation of the many difficult problems that confront alike the practitioner of the dairy art and the student of dairy science. Hence it is that till recent years English agricultural literature XXIV INTRODUCTION. has been deficient in an adequate exposition of the science and practice of dairying as now understood. Undoubtedly the most valuable information available to the English reader on this subject is to be found in the admirable Bulletins issued, from time to time, by the United States Department of Agriculture, in which the results of the more important researches in the domain of dairying science are epitomized. We are also indebted to America for some of the most recent improvements in methods and appliances, which have greatly facilitated and improved the operations of the practical art of dairying. It is to German and Scandinavian authorities, however, that we have to turn for a complete exposition of the science of dairying; and among continental authorities a first place has for many years been assigned to Professor Fleischmann. The English editors and translators cherish the hope that in rendering Professor Fleischmann's comprehensive text-book on The Science and Practice of Dairying available to the English reader they may contribute something to the development of the most enlightened dairy practice. A large number of new illustrations- have been introduced into the English edition; while here and there short passages have been omitted which possessed interest Jr o r for German readers only. 1 1 The English editors desire to acknowledge their indebtedness to Dr. Paul Vieth, Director of the Hameln Milchverschaftliche Institut, and to Mr. John R. Campbell, B.Sc., lecturer on Dairying in the West of Scotland Technical College, Glasgow, for assistance in reading a- portion of the work while in proof. C. M. AIKMAN. January, 1896. R. PATRICK WRIGHT. THE BOOK OF THE DAIRY. CHAPTER I. THE SECRETION, PROPERTIES, AND COMPOSITION OF MILK. 1. Definition. By milk, 1 in the widest sense of the term, is understood the secretion of the special glands of the female mammal. It is a white, opaque liquid, of the character of an emulsion, with a faint odour and a slight flavour; and it is produced during a longer or shorter period after parturition. It consists chiefly of water, fat, case- in, albumin, milk- sugar, and mineral salts, and is spe- cially adapted for the sustenance of the young. 2. The Cow's Udder. The par- ticular glands in which the milk ori- ginates the milk glands form the most important portion of the milk-secreting udder (see plates of cow's udder, figs. 1 and 2). The cow's udder is divided into two by a strong fibrous 1 By the term milk is always to be understood whole milk, and not skimmed milk. ( M 175 ) 1 A 3. Structure of Cow's Udder. Bundle of Elastic Fibres (a), and Connective Tissue Fibres (&). (x200.) (Fiirstenberg.) SCIENCE AND PRACTICE OF DAIRYING. partition, running longitudinally. Each of the halves contains a large milk-gland of a reddish-gray colour, or more correctly speak- ing, an accumulation of glandu- lar structures, called the gland- basket. In the case of adult milk-cows, each milk-gland is from 24 to 52 centimetres (9J to 20 inches) in length, 16 to 31 centimetres (6J to 12 J inches) in depth, and 10 to 21 centimetres Fig. 4. Gland-lobules, e, Outlet tube, (x 60.) (Fiirstenberg.) Fig. 5. Alveoli, d, Common duct, (x 200.) (Kurstenberg.) (4 to 8 inches) in breadth. They contain, embedded in a white con- nective tissue (fig. 3), the delicate gland-lobules (fig. 4), in which occur Fig. 6. Cylindrical Epithelial Cells, a, Cells grouped together; b, process of basement membrane ;/, free cylindrical cells, (x 600.) (Ftirstenberg.) numerous round cavities, the microscopic gland-lobules or alveoli (fig. 5), which are terminal or lateral dilations of numerous and extremely fine canals. When the cow is in milk the alveoli have a THE UDDER. length of about 12 to '20 millimetre ('0047 to '0078 inch) and a breadth of -09 toll millimetre ('0035 to '0043 inch). According to Heidenhain, the delicate tissue which sur- rounds the alveoli consists of a structureless membrane, the so- called tunica propria, to the inside of which is attached cel- lular tissue. The internal surface of this net-work of cells is further lined with a continuous single layer - of epithelial cells (fig. 6). The diameter of these cells, on an average, is about '04 millimetre, and their form shows extraordinary variations, according as the cow is in milk or not. In the latter case Fig. 7. Capillaries of Mammary Glands, (x 180.) (Fiirstenberg.) -o Fig. 8. Milk -cis- tern and Outlet Tube of Milk -gland, laid open. Two thirds of natural size. a, Basis of teat; b, upper end of milk- cistern ; d, loAver end of same and upper end of teat ; e', dilatation of canal of the teat; /, rosette on end of lower portion of canal of teat; h, small, and o, large gland-ducts. (Fiirstenberg.) the epithelial cells are low and flat, while in the former they are swollen and protrude comparatively far into the alveolian cavity. On the outside, the membrane of the gland-lobules is surrounded by a highly SCIENCE AND PRACTICE OF DAIRYING. developed net-work of capillary vessels (fig. 7), in which the material for the formation of milk circulates through numerous lymph tracts, and also by means of very fine nerve fibres, which promote special physiological functions of the glands. The duct- lets, of which the alveoli are the dilations, unite together among themselves in gradu- ally ever-widening ducts the milk-ducts, and end eventually in large hollow cavi- ties, the so-called milk-cisterns or milk- reservoirs (figs. 8-11). Four of these, which lie above the teats, are present in each udder, two on each side. The connective tissue, which encloses the lobules of the gland, and which unites them to the large closed milk -glands, is enveloped in adipose tissue, and this in turn is covered by the skin, which is interspersed with many blood-vessels. On the udder there are, as a rule, four teats (fig. 12), corresponding to the four milk-cisterns, from which milk can be drawn; while behind them frequently occur some undeveloped teats, very rarely provided with outlet tubes. The duct of the teat (figs. 13-16) is about 4 millimetres in length, and is shut at its end by means of a smooth sphincter muscle. The capacity of both milk- glands, together with that of the four milk- reservoirs, in the udder of an average cow, after the left 8ide of the Udder ' , . of a Dutch Cow, yielding milking, may be stated at about 6 to 7 cubic 3000 quarts of miik yearly decimetres. 1 The internal space of the udder Haw natural size. (Fursten- available for retaining milk, however, does not admit of accurate estimation, owing to the great elasticity of the surrounding tissue. The udder of a cow of ordinary milking capa- city, carefully examined by us after slaughter, was found to have a About 10J to 11| pints. Fig. 9. Plaster of Paris Cast of the Posterior Milk-cistern, with the Canal of the Teat of the left side, from the Udder of an Ayr- shire Cow, yielding 1200 to 1300 quarts of milk yearly. Half natural size. (Fiirstenberg.) THE UDDER. 5 total storage capacity of about 3 cubic decimetres; and for one milk- cistern, on an average, '25 cubic decimetre. It is unnecessary, for the purposes of this book, to enter into a detailed description of the distribution of the muscles, ligaments, adipose tissue, nerves, blood and lymph vessels, and of the skin and hair of the udder. Fig. 11. Plaster of Paris Cast of the Milk-cistern and Milk-ducts of the posterior half of the Milk-gland of a Dutch Cow. Natural size. (Fiirstenberg.) Four milk-glands are often spoken of, as if there were two on each side of the udder, an assumption warranted neither by the course of the milk- ducts leading to the two milk-cisterns, situated on the same side, nor by any other anatomical structure. The physiological action which gives rise to the secretion of milk in the udder has, as its chief centre, the above described gland-lobules, which are covered inside with an epithelial cell-layer, and outside with a net-work SCIENCE AND PRACTICE OF DAIRYING. of capillary vessels. The practical importance of this is that the amount and quality of the milk secretion principally depends on the number of gland-lobules present in the udder, and the number and course of the vesicles distributing the blood- stream through the milk-organ. The difference in the milking qualities of different cows is primarily due, therefore, to the inherited individual characteristics. -e 3. Formation of Milk. We conclude that, since none of the organic constituents, present Fig. 12. Plaster of Paris Cast of the Canal traversing the Teat and Nipple. Na- tural size. a, Basis of teat; d, lower end of milk-cistern, and upper end of nipple; e, small gland-ducts ; ', di- latations of the canal of the teat; /, rosette on the lower end of canal of the teat; g, lower end of outlet tube of milk-gland. (Fiirstenberg.) in milk, is present in the blood, they are all formed in the gland-lobules from the circulating fluids, the blood and the lymph, found in the udder. But the changes which take place in this operation are little understood. Before entering into a description of them, so far as they are at present known, it should be pointed out that the milk-glands are not equally active during Fig. 13. Section of Membrane of Lower and Narrow portion of the Canal of the Teat (x 85.) (FUrstenberg.) I, Epidermis; e, superficial layers of epidermis; d, sebaceous gland; /,/, section of bundle of muscle-fibres. FORMATION OF MILK. the whole lifetime of the animal. Their action is broken by alter- nate periods of rest. Even during the same lactation period the work of the glands does not continue at the same rate, but varies, Fig. 14. Section of Sebaceous Gland. a,Sebaceous gland ; b, superficial layer of epidermis ; c, epidermis ; d, horny layer, (x 100.) (Fiirstenberg.) on the one hand, with the period of lactation, and, on the other hand, according to the surrounding physical conditions. According to the theory regarding the origin of milk which obtained prior to the year 1840, it was believed that the milk-glands acted as a sort of filter with a wide surface, for certain constituents of the blood, and that in milk we were dealing with a filtrant from the blood, the amount Fig. 15. Tallow Follicle of the Nipple, (x 100.) a, Outlet ducts. (Furstenberg.) Fig. 16, -Tallow Follicle of Nipple, (x 180.) (Furstenberg.) and quality of which was determined solely by the amount and quality of the food. When, however, it had been proved, by chemical investigation, that not one of the organic constituents of milk occurred ready formed in the blood, but that they were all formed in the milk-gland, this theory had to be abandoned. The labours, during the last forty years, of different physiologists, such 8 SCIENCE AND PRACTICE OF DAIRYING. as Nasse, Henle, Van Bueren, Rheinhardt, H. Meyer, &c., who have carried out researches on the origin of the fat globules in milk, Have demonstrated the fact, that, of all the milk constituents, fat alone, in the form of the fatty cell, is recognizable by the aid of the microscope. One of the first who submitted the gland substance to careful microscopic investigation with a view of elaborating a theory of milk production was Will of Erlangen. By means of his investigations, the theory first dis- tinctly expressed by Virchow, regarding the origin of milk, was formulated. According to this theory, the milk-gland must be regarded, morphologically, as a kind of sebaceous gland. The separation of milk in it takes place just in the same way as that of tallow in the many-layered epithelium of the alveoli; it represents, in reality, the pathological occurrence of a fatty degeneration of the epithelium of the glands. Voit, in his work on the formation of fat in the animal body, supported this theory, which rapidly became popular. He regarded milk as a liquid cell substance as the liquefied cell substance of the milk -glands. By the microscopical investigations of Heidenhain, Voit's conclusions were seriously called in question. According to these researches, the epithelial cells of the alveoli of the glands are only present in one layer; the colostrum bodies possess no significance for the morphology of the formation of milk; and the epithelial cells of the secreting gland are not subject to fatty degenera- tion. What takes place is rather that their free ends suffer degeneration, and that a renewal of the cell material takes place at the opposite end. C. Partsch also comes to the conclusion, from microscopical observations, that the formation of fat in the epithelium of the gland does not exhibit the slighteWresemblance to the formation of fat in the sebaceous cell. As Partsch nowhere met with cells exhibiting fatty degeneration in the epithelial layer of the active milk-glands, and always found the fat on the points of the epithelial cells in single large drops, and the increase in the percentage of albumin in the cells accompanied by an increase in the separation of fat, he regarded it as not proven that the fat of milk is an example of retrogressive metamorphosis of the epithelial cell, but rather that it is separated through the special activity of the cell in the true sense of the word. Subsequently Heidenhain, as well as Nissen, advanced the opinion that during the period of lactation the nuclei of the gland -cells constantly increase and successively degenerate. They are then extruded from the cells in which they have been formed, and are finally broken up in the cavities of the glandular vesicles. This explains at the same time the method in which the nucleo- albumin, discovered by Lubavin and Hammarsten to be a constituent of milk, enters it. FORMATION OF MILK. 9 Bizzozero and Vassate, by their elaborate investigations on the increase of the constituents of the growing glands of the mammals, and on their capacity for undergoing regeneration when fully developed, came to the conclusion that in milk we have not to deal with a secretion of the gland- cells. At the same time they established the fact that no evidence exists of a direct or indirect division of the epithelium of the glands during lactation, and hence that the process of milk formation is independent of the destruction of cells or of cell nuclei, as Heidenhain and Nissen had affirmed. Rauber regards milk-fat as a decomposition product of the lymph bodies of the blood, which, as he believes, can be proved to float in the gland alveoli, and expresses the opinion that the source of the caseous matter is also to be sought for in the lymph bodies. According to him, a single principle runs through the whole scheme of nourishment of the young mammal, in so far as the lymph bodies already play an imp'ortant part in the nourishment of the egg and of the embryo. With the birth of the young mammal, exit for the lymph bodies on the uterus is closed and a new exit is opened in the milk-glands, so that one and the same material is used for the nourishment of the egg and the embryo as for the nourishment of the young mammal. Through the above-mentioned researches of Heidenhain, Parstch, Bizzozero, and Vassate, the basis of Rauber's conclusions has been for the most part destroyed. According to another series of investigations on milk formation, the origin of the different organic constituents of milk in the milk-gland is to be traced to certain maternal substances, and is carried out by certain ferments. Hoppe-Seyler, at the end of 1850, made the observation that if milk be allowed to stand exposed to the air, small quantities of fat, probably from protein matter, were formed. This formation of fat is accompanied by the absorption of oxygen and the evolution of carbonic acid gas. This observation has been confirmed by Kemmerich and Soubotin. It is a matter of dispute, however, whether this process, if it does take place, is to be regarded as a physiological one, or whether it is to be accounted for by the action of bacteria. To decide this point, Kemmerich in 1867 first introduced a method of research which consists in observing the behaviour of the secretion from the milk-gland at the temperature of the body. Supported by the results of a number of experiments, Kemme- rich believed he had established the fact that during the secretion of the milk at animal heat a physiological process goes on, in which caseous matter is formed at the expense of a fermentative decomposition of albumin. This theory of Kemmerich, which in the main was also adopted by Zahn, was totally disproved in the year 1882. Schmidt- Muhlheim, by means of careful researches, proved that during the decom- 10 SCIENCE AND PRACTICE OF DAIRYING. position of milk at animal heat the percentage of its albumin remains- unaltered, and that its percentage of caseous matter, instead of becoming increased, is rather diminished, while the percentage of peptones present in it increases. Following the researches of Kemmerich, Danhardt endeavoured in 1870 to separate a ferment from the milk-gland of a guinea-pig. In this he succeeded, and with it he was able, by digesting in it a dilute and slightly alkaline solution of egg albumin, to obtain a body having the properties of casein. In 1833, H. Thierf elder published a work which likewise aimed at tracing the formation of the constituents of milk to maternal substances and ferments in the milk-gland and in the milk. Thierfelder believed that his researches pointed to the fact that during the digestion of the milk-gland at animal heat, a body (perhaps milk-sugar) was formed by fermentation processes, which not only pos- sessed the reducing power, but also the properties of casein (perhaps casein itself). The researches of Hoppe-Seyler, Kemmerich, Soubotin, Zahn, Danhardt, and Thierfelder, however, which have been mentioned above, have collectively raised the important objection, that these experiments were not carried out with sufficient care, to exclude the possibility or probability of contamination with micro-organisms, through want of cleanliness in the materials experimented with. What takes place in the formation of milk in the udder is, therefore, not as yet well understood. We do not know to what extent the constituents of the blood, the fat, the albuminoids, the carbohydrates, as well as the lymph bodies and the substance form- ing the epithelial cells of the alveoli of the glands, are utilized in the formation of the organic constituents of milk; and still less do we know the changes that take place in the materials which are converted into the constituents of the milk. It may be regarded as- probable that milk-fat is a secretion of the epithelial cells of the gland vesicles of the udder, and that it is derived from different sources, viz., partly from the fat present in the blood, and partly from the products of the changes that take place in the animal tissue. With regard to the albuminoids, the milk-sugar, and the other constituents of milk, despite many researches, little is known. All the most recent scientific investigations, combined with num- berless practical observations of cow-feeders, so far agree that the secretion of milk depends primarily on the direct influence of the greater or less activity, as well as the efficiency, of the milk-gland r and on the particular conditions under which the animal lives; and secondly, on the kind of food and condition of the blood. This PROPERTIES OF MILK. 11 conclusion, although of a very general nature, is nevertheless of great practical importance. 4. Properties of Milk. Milk, obtained under the usual condi- tions, is a pure white fluid, which appears completely opaque when in large quantities. In thin layers, however, it is slightly transparent. It possesses a slight smell, similar to the exhalation from the skin of the cow, and is of a mild, rich, slightly sweetish taste. It exhibits a slight amphoteric (alkaline and acid) reaction, and can be boiled without coagulating. If left standing undisturbed at the usual temperature, a collection of microscopically minute globules of fat rises to its surface, and forms a layer of cream. When kept standing some time longer, the milk spontaneously coagulates. Previous to coagulation the milk is in such a condition that, although at ordinary temperatures it undergoes no change, yet on boiling, or even on slightly heating it, the milk immediately changes. Even at the ordinary temperature it is coagulated on the addition of a minute quantity of a strong acid, or on the addi- tion of carbonic acid. On milk standing at a temperature of over 50 C., a skin is formed, consisting of coagulated albuminous matter, enclosing small quantities of the other milk constituents. As often as this skin is removed it renews itself. It is the formation of this skin on the surface of the milk that causes it when it is boiled to froth over so easily. Boiling imparts to the milk a peculiar taste and smell (cooked taste). The chief constituents which milk contains are water, albuminous bodies (proteids), butter-fat, milk-sugar, and mineral salts. Milk has always a greater specific gravity than water. In the case of the milk of single cows, or the milk from single milkings, its specific gravity at 15 C. rarely exceeds the limits of 1*028 and 1*034, and a mixture of the milk of five or more cows, or of two or three milkings, rarely exceeds a specific gravity of 1'029 and 1*033. On an average its specific gravity may be stated at 1*0312. The specific gravity of the total solids of milk varies between 1*30 and 1*40, and that of the non-fatty solids is almost always constant, and may be stated with approximate accuracy at 1*6 at 15 C. The opacity and colour of milk is due to the numberless fatty globules suspended in it, as well as to a portion of its albuminoids and mineral matter, which are also in a state of suspension. According to Soxhlet, 12 SCIENCE AND PRACTICE OF DAIRYING. the amphoteric reaction of milk is caused by the presence in it of neutral and acid phosphates and carbonates of the alkalies. By warming the milk the alkaline reaction becomes more pronounced. Warming, however, has no influence on the acid reaction. To phenol-phthalein milk only shows an alkaline reaction after it has been neutralized with a certain amount of alkali. As a rule 100 c.c. of fresh milk require about 7 c.c. of a J normal soda solution for the alkaline reaction. In order to determine the acidity in fresh milk caused by the acid phosphate, Soxhlet and Henkel treat 50 c.c. of milk with 2 c.c. of an alcoholic 2 per cent phenol-phthalein solution, and titrate with a J normal soda solution. The number of c.c. required serve as an indication of the acidity. By the addition of diluted acids milk can be immediately coagulated, and, in a somewhat longer time, by means of a strong rennet solution. Dilute lactic acid and rennet change the milk into a coagulated adhesive mass. Acetic and diluted mineral acids, under similar conditions, produce flocculent coagulation. By warming milk at 50 C., or at higher temperatures, it undergoes changes which specially affect its proteids, as well as its taste and colour. Under such conditions the addition of diluted acids does not produce a lumpy coagulation, but a finely flocculent and pulpy one. The milk is also rendered much more sensitive to the action of rennet, which, under certain conditions, exerts its full coagulating influence. Milk coagulated at a temperature of 130 to 140 C. assumes the peculiar flavour of cooked milk, and becomes slightly yellowish or yellowish brown in colour. The higher milk is heated between the limits of 50 C. and 140 C., the more quickly do the above described changes take place, and the shorter is the time within which increased temperature produces the various changes. It is obvious that heating milk to 100 C. can only be accomplished in a closed vessel. The properties of the proteids of milk are dependent, in the first place, on the nature of the chemical combinations of the mineral constituents of milk, and especially of the lime salts. If, as is actually the case, the constitution of the mineral salts of milk is changed under the influence of high temperatures, and if a portion of the soluble lime salts is converted and precipitated into an insoluble condition, it naturally follows that the condition of the proteids also undergoes change. The peculiar smell and flavour of milk strongly heated is very pro- bably connected with the small quantities of sulphuretted hydrogen which have been proved to be present in boiled milk. (Fresh milk, treated with tincture of guaiacum, assumes a blue colour, while boiled milk does not show this reaction.) The change of colour which takes place on heating milk for some time at temperatures over 80 C., and which increases the higher the tempera- ture and the longer the duration of the exposure to such temperatures, PROPERTIES OF MILK. 13 is explained by the fact that milk-sugar undergoes incipient decomposi- tion, producing small quantities of yellow and brown substances (lacto- caramel 1). Continuous heating affects the fineness of the state of division of the fat of the milk. The microscopically small fatty globules become partly dissolved and run together, forming large drops of fat easily visible to the naked eye. The boiling point of milk is a fraction of a degree higher, and the freezing point a fraction of a degree lower, than the boiling and freezing points of water. The maximum density point of milk is not 4*08 C., as is the case with water, but - -3 C. Possibly these conditions vary with the percentage of solids in the milk, especially of fat, but no 'experiments have been made on this point. The behaviour of milk under the influence of the electric current also requires investigation. The question of how far electricity might be beneficially applied in dairy- ing still awaits investigation. The coefficient of expansion of milk increases with the temperature, as well as with the percentage of total solids, and, between the tempera- tures of 5 and 15 C., is undoubtedly greater than that of water. It follows from this that milk loses more and more of its limpidity as the temperature is reduced, and at temperatures below 10 C. it assumes a slightly viscous condition, and maintains this viscosity on its surface. According to experiments by the author, the variation in the volume of ordinary cows' milk (of a specific gravity 1-0315 at 15 C.) at different temperatures is as f ollows : 1,000,000 volumes at C. 1,000,030 1 C. 1,000,391 4 C. 1,001,273 10 C. 1,002,134 15 C. 1,003,800 20 C. 1,006,414 30 C. 1,014,277 50 C. 1,019,243 60 C. The absorptive capacity of milk for heat (latent heat) is not a constant quantity, but depends, according to experiments carried out by the author in 1874, on the quantity of total solids. For milk of ordinary chemical composition it may be stated at *847, water being taken as 1 '000. When exposed to the action of frost the larger portion of the milk is frozen, a small portion only remaining liquid. The portion remaining liquid is richer in solid matter than the portion frozen. When milk is subjected to dialysis only a portion of the mineral mattei and the milk-sugar diffuse through, and possibly also a trace of nitrogenous matter. 14 SCIENCE AND PRACTICE OF DAIRYING. If a candle light be looked at through a thin layer of milk, the flame usually appears yellow, but occasionally it appears of a reddish colour. The thickness of the milk layer with which this takes place is dependent upon the percentage of fat the milk contains, but is not directly propor- tional to its amount, as it is also dependent upon the size of the fatty globules present. The same quantity of fat retards more light when it is in the form of very small globules, than when it is in the form of larger globules. It is for this reason that the determination of fat by the so-called optical method is so very unreliable. According to Jorgensen, the refractive index of milk serum lies between 1-3470 and 1-3515, and that of curd, coagulated by rennet, between 1-3433 and 1-3465. It may be taken for granted, that the suspended matters of milk the fat, the nitrogenous substances, and the phosphate of lime have the same effect upon the chemical balance and on the hydrometer as if they were in solution, although this does not necessarily follow as a self-evident fact. Mach has shown that very finely divided bodies suspended in liquids only exert their weight on the balance and areometer when they are either at rest, or are moving with a regular speed. That these conditions are fulfilled by the substances in suspension in milk is proved by the fact that tests of the specific gravity of milk conducted in a most careful way, both with the balance and with the hydrometer, give constant and perfectly concurrent results. It is noteworthy that milk, rich in fat, despite this richness in a constituent of low specific gravity, does not generally exhibit a low specific gravity, nor milk poor in fat, a high specific gravity. This is owing to the fact that milk rich in fat is also rich in the other solid constituents, and milk poor in fat is also poor in the other constituents. The specific gravity of milk is always exactly proportional to the percentage of the non-fatty solids. W. Thorner has investigated the resistance which milk offers to the electric current, and has found that the resistance of pure milk is not an absolutely constant quantity. It is more or less increased by the addition of water, diminishes with increasing acidity of the milk, and is independent of the amount of fat it contains. 5. The Nitrogenous Matter in Milk. This forms from 2'5 per cent to 4*2 per cent on an average 3'5 per cent of the contents of milk, and consists of substances of the nature of protein the so-called albuminoids. Duclaux's theory, that there is only one albuminoid in milk, is not consistent with the properties exhibited by it. It is highly probable that milk contains three albuminoids casein, lactalbumin, and globulin the casein being very much in THE NITROGENOUS MATTER IN MILK. 15 excess of the others, and forming about 80 per cent of the total nitro- genous compounds. Casein contains nuclein, a substance which is not found in albumin, and which is characteristic of the cell nucleus. It is rich in phosphorus, and strongly resists the action of pepsin solutions. While it has the properties of an acid it is also able to form saline compounds with bases, and is insoluble in water. On the other hand, its compound with lime (calcium oxide) in which form it is present in milk is soluble in water, or, more correctly speaking, forms with water a bulky colloidal substance, which, when milk is filtered through porous clay cells, does not pass into the nitrate, and is not absorbed when milk is passed through porous clay plates (Lehmann plates). The other albuminoids present in milk are in true solution, i.e. when milk is filtered through porous clay cells they pass into the filtrate. In order to distinguish the casein present in milk, which is in combination with lime, from pure casein, it is called the caseous matter of milk. A very small portion of this caseous matter, at most from *5 to 1 per cent, is removed from the milk in the separators by centrifugal force, and forms the chief constituent of the separator residue. When milk spontaneously becomes sour, or is coagulated by the addition of acids, the lime which it contains is separated from the caseous matter, and the insoluble casein coagulates in the form of a clot. Under the action of rennet, casein is converted into paracasein and curd protein. The former, provided there is a sufficiency of lime salts present to effect precipitation, is precipitated, and the latter remains in solution. In both cases the clots thus formed enclose mechanically the particles of fat present in the milk. When milk is coagulated by rennet, or by the addition of substances which act as dehydrating agents, as, for example, neutral salts or alcohol, the precipitate thrown down contains not merely the fat, but also the calcium phosphate in sus- pension in the milk. If, on the other hand, milk is coagulated by acids, or is allowed to become spontaneously sour, the greater portion of the suspended mineral salts is left in solution, and the coagulated casein contains only minute quantities of calcium phosphate. The extent to which the caseous matter is precipitated varies in the case of milk derived from different sources. Even in the same sample of milk the caseous matter is not coagulated to the same extent, even although the conditions under which coagulation takes place are similar. As a rule, the coagulation obtained is greatest immediately after milking, and diminishes with the lapse of time. 16 SCIENCE AND PRACTICE OF DAIRYING. It is found that in milk standing for a time after milking, a coagu- lation of the caseous matter takes place. The result of this is, that the specific gravity of perfectly fresh milk, determined by means of the hydrometer at 15 C. } will always be found to be higher, to the extent of from *5 to one thousandth than in the same milk when rapidly cooled or allowed to stand for some hours. For this reason special precautions ought to be taken in testing the specific gravity of milk with the hydrometer. The extent to which the precipitation of the caseous matter takes place depends on the tem- perature with a rising temperature it is increased, while with a falling temperature it is diminished. For this reason, in the raising of cream, equable low temperatures in the milk are not favourable, because with low temperatures the fatty globules meet with increased resistance in rising to the top. Among the more important early researches on the nature of the albuminoids and caseous matter of milk may be mentioned those of Scherer, Nasse, Schiitzenberger, Knop, and others. The theory first advanced by Scherer in 1841, which was held for thirty years, that the caseous matter is in the form of potassium albuminate, has now been com- pletely controverted. The view which has been held on the subject of the nitrogenous matter in milk, since 1875, is based on the reactions exhibited by milk with certain reagents. If milk be precipitated, at the ordinary temperature, by dilute vinegar, the larger portion of the nitrogenous matter is thrown down as a precipi- tate. If the filtrate from this precipitate be heated, a second precipitate is formed. The filtrate from this precipitate again gives a third precipitate with alcohol; and by treating the filtrate from this last precipitate with Millon's reagent, a fourth precipitate is obtained. It was consequently believed that each one of these precipitates represented a separate albuminoid, and these were distinguished as casein, albumin, albuminose (Bouchardat and Quevenne), and lactoprotein (Millon and Commaille). But it may be pointed out, that the behaviour of the milk, as above described, admits equally of the view which regards the nitrogenous substance of the milk as consisting of one substance only. It merely practically proves that the nitrogenous substance of the milk, at ordinary temperatures, is only partially precipitated by vinegar, more completely by vinegar at boiling temperature, and still more perfectly by alcohol, and that it is completely precipitated by certain salts of the heavy metals. No necessity exists, for inferring, on these grounds, the existence of four separate albuminoid bodies, any more than for supposing, for example, without further evidence, that there are four different kinds of lime, THE NITROGENOUS MATTER IN MILK. 17 because lime is more or less perfectly precipitated from its solutions, by different reagents, under different circumstances. An important advance in our knowledge of the nature of the nitro- genous matter of milk was made by the comprehensive and thorough researches of 0. Hammarsten of Upsala. These researches render it highly probable, that the large amount of albuminous matter which is precipi- tated, at ordinary temperatures, by acetic acid, and which has long been known as casein, is a characteristic albuminoid, with distinctive properties, and that in addition to this body there are two other albuminoids present in milk, viz., lactalbumin, and, in very small quantities, globulin. Hammarsten considers casein a nucleo-albumin a body in which nuclein is in complex chemical combination with albumin. According to him, the chemical composition of pure casein is as follows : Carbon, 52-95 Hydrogen, 7 "05 Nitrogen, 15-65 Oxygen, 22'78 Sulphur, 072 Phosphorus, 0*85 100-00 His lactalbumin contains neither nuclein nor phosphorus, and has 1*7 per cent of sulphur that is, about as much as pure egg-albumin, which contains 1*6 per cent. The lactoprotein of Millon and Commaille, Hammarsten considers to be made up of a mixture of imperfectly preci- pitated casein, and small quantities of albumin, partially converted into syntonin and peptones. He further holds that the acid character of casein is due to the fact that the condition of the casein in milk depends on the calcium phosphate, and that the coagulation of milk cannot take place without calcium phosphate. What the nature of the relationship existing between the casein and the calcium phosphate is, he does not state. Eugling's assertion, that the casein is always present in milk in chemical combination with normal calcium phosphate, rests on observations which, on examination, do not appear to be reliable. According to Danilewski and Kadenhausen, milk contains no fewer than seven different nitrogenous bodies, which belong to the albuminoid group, or are nearly related to it. Their highly artificial theory that casein is a mixture of caseo-albumin and caseo-protoalbumin bodies lacks sufficient proof. More recently Duclaux has again revived the original theory, that the albumin and the remaining nitrogenous substances are not really <. M 175 ) B 18 SCIENCE AND PRACTICE OF DAIRYING. different, and that in milk there is only one albuminoid, viz., casein. According to him, the changes which the milk undergoes, as above described, are to be accounted for by the fact that casein in solution, and when precipitated, acts differently. Lactoprotein and albumin arc, as Duclaux assumes, nothing else than casein in conditions more or less soluble in water. Among the most recent investigations on the nature of the nitrogenous substance of milk, undoubtedly the most valuable work is that by Soldner, entitled, The Salts of Milk and their Relations to the Conditions of Casein. Soldner opposes to Hammarsten's vaguely expressed theory that casein and calcium phosphate are present in the milk in solution, the exact and well authenticated theory that the caseous substance of the milk must be regarded as consisting of a neutral calcium compound of casein, and that the action of the rennet does not depend on the presence of calcium phos- phate, but chiefly on the presence of a soluble lime salt. Further on, in the Chapter on the Preparation of Casein, we will have an opportunity of again referring to Soldner's work. Within the limits of to 100 C., the amount of acid or neutral salts which is necessary to effect the precipitation of casein, decreases with an increase of temperature ; while within the limits of and 42 C., the length of time which elapses before the spontaneous coagulation of the milk takes place also decreases with the increase of temperature. Normal sodium carbonate, caustic alkalies, normal sodium phosphate, and other salts, which effect the precipitation of solutions of calcium phosphate, although they are themselves solvents of casein, yet in the process of coagulation cause its precipitation. This is effected by the fat and casein becoming mechanically entangled with the precipitated tricalcium phosphate, and carried down with it. The addition to milk of a small quantity of a caustic alkali, or of a carbonate of the alkalies, diminishes its opacity. Solutions of caseous matter, on standing at temperatures of over 50 C., become covered with a skin, and when heated in close air-tight vessels to 130 to 140 C. become coagulated, and exhibit greater laevo-rotatory pro- perties than solutions of albumin; and are precipitated by dilute acids, by most of the salts of the heavy metals, by alcohol, and by rennet, provided the dissolved calcium salts necessary for this purpose are present. The heat equivalent of casein, according to Stohmann's investigations, amounts to 5715 calories per gram of substance. Schiibler gives the specific gravity of fresh casein as I'lOO, and of boiled casein as 1-259. According to the investigations of the author, the pure nitrogenous matter of milk at 15 C. has a specific gravity of 1'486. Of equal interest, both from a theoretical and practical point of view, is the relationship which exists between the nitrogenous constituents of MILK-FAT. 19 milk on the one hand, and the mineral salts on the other. All influences that are able to change the constitution of the salts of milk, such as the prolonged action of high temperature, the evolution of carbonic acid from milk fresh from the cow, the formation of lactic acid through fermentation, the diseases of cows, their feeding, the time since calving, the age of the cow, the boiling of milk, &c., also exercise an influence on the nature and properties of the nitrogenous substances, especially on the caseous matter. They alter to a slight extent the specific gravity of the milk, cause the rising of the cream to take place either more rapidly or more slowly, and make the milk more susceptible, less susceptible, or entirely unsusceptible, to the action of rennet. They favour or retard its coagulation by acids, and influence the nature of the curd produced by the action of rennet or acids. 6. Milk-fat (Butter-fat). Milk-fat is present in milk in a very fine state of division, viz., in the form of innumerable little drops or globules of varying size, which are all oo of them invisible to the naked eye. In the milk of cows the diameter of the smallest and the largest of these globules is respectively '0016 mm. and 01 mm., so that the former is almost 6-25 times as small as the latter (fig. 17). The globules vary in size between these limits, and are present in vary- ing proportions. It appears probable ^^ axtMon; &> large nes f und that the number of the different-sized globules is in inverse ratio to their size, or, what is the same thing, the weight of the sum of all the globules of the same size is equal for the entire number of different sizes. At anyrate, the microscopical examination of milk shows that the smaller the globules the more numerous they are. Under the ordinary conditions which prevail in Germany, the percentage of fat in cows' milk, with very few exceptions, varies between 2'5 and 4'5, and may be stated, on an average, at 3*4. For the north and north-east of Germany, the average may be stated at 3-25. 1 1 The average of all complete American analyses of milk made up, 1891, is 4% of fat, the limits being from 2 to 8%; while the average of over one hundred and twenty thousand samples of English milk, as analysed by Dr. Vieth, is 4*1% of fat. (See Aikman's Milk: its Nature and Composition (A. & C. Black), p. 11.) English Editors. 20 SCIENCE AND PRACTICE OF DAIRYING. The fat globules are not surrounded with a membranous en- velope. Owing to the action of molecular force, the little globules are surrounded by a thin watery covering of serum, and act very much as if they were actually surrounded by a membrane. The influence of the molecular force, manifested in all emulsions, explains why the fat globules in a layer of cream, at ordinary temperatures, do not cohere, and explains why the application of a not inconsiderable force in churning is required to bring them together, and why they offer some resistance to the solvent action of ether. As the specific gravity of fat is less than that of milk serum, all the fat globules are under the influence of a force which compels them to ascend to the surface. It has been calculated that this influence acts very rapidly. Thus by keeping a layer of milk 10 to 20 cc. in depth for a day and a night, at rest and at ordinary tem- perature, about four-fifths of its total fat comes to the surface. The smallest globules containing the rest of the fat do not experience a motion of their own, because their tendency to rise is no longer sufficient to overcome the opposition offered by the friction of the coagulated casein in which they are enveloped. The use of separators has done much to increase the yield of fat. By their aid all the fat may be extracted to within 5 per cent from the milk or cream treated. It is in the highest degree probable that the fat globules, both in milk and cream, are present in a liquid form at ordinary temperatures, and that they are only converted into a solid form by the action of churning. The superior digestibility of milk-fat, when partaken of in the form of milk, cream or butter, may be traced to the extreme minuteness of its state of division. The composition of the fat of milk does not resemble that of fat obtained from other sources. It is of a much less simple chemical nature than that of other fats. Butter is distinguished from them by its more agreeable taste. The soft condition of butter fat at ordinary temperatures renders it in a special degree suitable for spreading on bread. As is the case with other organic substances of complex composition, it is readily liable to change, is less easily preserved than the other edible fats, and quickly loses its fine flavour under unfavourable circumstances. These special properties of milk-fat render butter the most valued and the most highly prized of all fats. MILK-FAT. 21 The fat globules were first discovered and described in 1697 by A. Von Lesuwenhoeck. The number of these fat globules in a drop of milk varies ; but it is almost impossible to count them. A conception of the fineness of the state of division of the fat in milk is best obtained, so far as it is pos- sible to measure it, by means of a simple calculation, from which we obtain the following results, in the case of a sample of milk containing 4 per cent of fat (taking the specific gravity of pure milk-fat as '924 at 17*5 C.): Diameter, in -01 mm. Diameter in -0016 mm. The weight of a globule, - '000,000,483,8 rag. '000,000,002,0 mg. The number of globules in 1 kilo, (approximately), - 80,000 millions, 20 billions. The surface area of the glo- bules in 1 kilo, of milk is approximately, 25 square metres, 157 square metres. If the diameter of the largest globule be 6 '25 times that of the smallest, then its weight will be 244 times that of the smallest. The impetus 7 and which a globule receives through its weight and centrifugal force may be stated as follows: and = a' (f - l)- ( 2 6 ' *) 2 - r, u\ in which a, and a', indicate the respective coefficients of resistance, 8, and <$', the viscosity of the milk serum and milk fat, g the acceleration due to specific gravity, and TT the Ludolph number, r the radius vector, and u the number indicating the circumference of the globule. The movement of the fat globules in milk towards the cream layer in the ordinary rising of cream, as also in the separation of cream by centrifugal force, is obviously not an accelerated one, but is uniform throughout. The other animal fats, which, in addition to milk-fat, act as foods, are chiefly made up of stearin, palmitin, and olein; while milk-fat only contains, on an average, about 91 to 92 per cent of these neutral fats. The remaining 8 to 9 per cent prob- ably consists of seven other neutral fats, among which butyrin and caproniu predominate Other five, viz. caprylin, caprinin, laurin, myristin, and butin, are present in very minute quantities, some of them in the most minute traces. If pure butter-fat be saponified, and the butter so obtained be carefully decomposed with sulphuric acid, as in the Hehner and Angell process, the separation of the characteristic group of non-volatile and insoluble fatty acids (stearic, palmitic, oleic, myristic, and butic acids), from the remaining volatile and soluble fatty acids, can be easily effected, and their exact per- centage determined. It is, however, impossible to estimate, even approxi- mately, the percentage of the individual fats of either the non-volatile or 22 SCIENCE AND PRACTICE OF DAIRYING. volatile groups, The individual members of both groups exhibit such slight differences in their chemical behaviour and distinctive properties, that as yet it has been found impossible to separate them from one another, or to determine their composition. On this account the proportion of stearin, palmitin, and olein in milk-fat, generally stated in the literature of the subject, is practically unreliable. At the most, by determining the so-called iodine coefficient of milk-fat, which is proportional to the amount of olein it contains, it can be ascertained which of two given samples of milk-fat contains most olein. For the approximate determination of the amount of the individual volatile fatty acids in milk-fat, Duclaux has devised an ingenious method of determination. By this method the fatty acids are reckoned as triglyce rides, and the probable average composition of milk-fat is calculated approximately as follows : Palmitin, stearin, olein, and traces of myristin and butin, 91 '50 Butyrin, 4'20 Capronin, 2*50 Caprylin, caprinin, and traces of lauriii, 1'80 1001)0 The percentage of insoluble and soluble fatty acids varies according to the length of time after lactation, the amount of the soluble fatty acids gradually diminishing, and that of the insoluble acids increasing, with the increase of the duration of this period. To a certain extent the amount is influenced by the individuality of the animal, and by the breed, probably also by the age of the cow; but the influence of feeding has not yet been proved with certainty. According to Adolf Mayer the percentage of the volatile fatty acids in milk-fat is distinctly increased by feeding with fresh meadow hay, and is diminished by feeding with straw and poppy-cake. The percentage of olein in milk-fat appears to increase with the lapse of time after lactation. Butter-fat, containing a small percentage of volatile fatty acids, contains, as a rule, a correspondingly larger percentage of non- volatile fatty acids. Lecithin, a substance containing nitrogen and phosphorus, may be mentioned as a characteristic constituent of milk-fat. It is further to be noticed with regard to the chemical composition of milk-fat, that it contains less carbon than other kinds of fat. Milk-fat, freshly separated from cows' milk, is, at ordinary temperatures, a soft yellowish mass, which soon assumes a granular structure, and possesses a mild taste and very slight odour. If melted butter-fat be allowed to cool gradually, it occasionally occurs that a separation of the mass into two parts takes place, viz. a solid portion, and a portion called butter-oil, which remains liquid at ordinary temperatures. Milk-fat melts usually between 31 C. and 36 C. ; occasion- MILK-FAT. 23 ally at not less than 41 C. to 42 C. In the case of most other fats the melting-point is higher. The majority of the insoluble fatty acids which make up milk-fat (palmitic, stearic, and oleic acids) melt at temperatures between 38 C. and 39 C., or, according to Adolf Mayer's researches, between 41 C. and 44 C., and become solid between 35 C. and 38 C. The solidifying point of milk-fat lies, as a rule, between 19 C. and 24 C. It may, however, vary between 27 C. and 12 C. At the moment of solidification only a slight rise in temperature takes place, which proves that the latent heat of milk-fat is very slight. The consistence and colour of milk-fat depend on the influence of feeding, and vary according to the lapse of time after the lactation period. They appear also to be dependent on the age and individuality of the animal. The melting point of milk-fat is said to be lowered by feeding with easily digestible carbohydrates, and raised by feeding with fodders poor in sugar, such as straw and oil- cakes. The specific gravity of milk-fat in air at 15 C. (distilled water taken at the same tempera ture = 1) is, on an average, '930717; and in vacuum (water taken at 4 C. as 1) it is, on an average, -93002. At the boiling point of water, and at a barometric pressure of 760 mm., reduced to C., it varies between '8650 and '8685. Most of the other fats, at the boiling point of water, possess a specific gravity of less than -8610. According to M. Schrodt, the refraction exponent of milk-fat is only subject to small variations, and is neither affected by the feeding of the cow, nor by the lactation period, and is, at 22 C., on an average, 1'4590. With the diminution of the percentage of the fatty acids it appears to increase. If pure milk-fat be preserved from the action of air for some time, it becomes rancid, that is, decomposition sets in, and small quantities of volatile fatty acids, and particularly butyric acid, are set free. Free exposure to air and sunshine hastens the decomposition. Under such conditions volatile fatty acids, directly derived from the glycerides of butter-fat, are also set free, and other fatty acids, of which formic acid is probably one, are formed, oxygen being absorbed from the air. Milk-fat, in this process of decom- position, possesses not merely a rancid and strongly tallowish smell and taste, but also assumes a white colour. Certain moulds, when the milk becomes infected with them, produce decomposition, which is accompanied by a gradual diminution of the volatile fatty acids of the milk-fat. In this process butyrin shows itself to be less easily decomposed than capronin, and the latter less easily decomposed than the neutral fats of the essential fatty acids. Although the hypothesis that the larger and the smaller of the fatty globules of milk contain different kinds of fat, has not, so far, been con- clusively proved, it has become more and more probable. The fat of the 24 SCIENCE AND PRACTICE OF DAIRYING. larger globules appears to be finer in flavour, and to possess a more oily appearance. Bouchardat and Quevenne drew attention, as early as 1857, to the fact that the average size of the fatty globules in human milk was different from that found in the milk of cows or of sheep. It is probable that the average size of the fatty globules of cows' milk, in the same cow, is not at all times, and under all conditions, the same; and that in the case of different cows, perhaps also in the case of different breeds of cows, even under similar circumstances, the size varies. On this subject we know as yet very little. The methods, according to which the numbers and the determination of the average size of the fatty globules have been made, are the same as have been applied for the purpose of counting the number of yeast cells, blood corpuscles, &c., and consist of utilizing very fine capil- lary tubes of glass. Milk -fat is soluble in ethyl -ether, chloroform, carbon bisulphide, benzine, &c. The common solvent is ethyl-ether. 7. Milk-sugar. Milk-sugar occurs in solution in the milk of all mammals, but does not elsewhere occur in nature. It is a carbo- hydrate, and is one of the sugars capable of being converted directly into alcohol by means of fermentation. In German milk the per- centage of milk-sugar ranges between 3 and 6 per cent, and is on an average 4 '6 per cent. 1 In a state of solution, as it is in milk, the milk-sugar quickly and easily undergoes decomposition, and is converted into lactic acid. This is effected by a large number of different kinds of bacteria, the so-called lactic bacteria. The transformation of milk- sugar into lactic acid may, or may not, be accompanied by the formation of small quantities of carbonic acid, with or without alcohol. As the bacteria which give rise to the formation of lactic acid are to be invariably found more or less abundantly on the cow's udder or in the byre, in the dairies or in the vessels contain- ing the milk, and have therefore easy access to the milk, it follows that milk, on keeping, becomes sooner or later subject to lactic fermentation. As soon as a sufficient quantity of lactic acid is produced, milk sours and becomes unsuitable for its chief uses, both in the house and the dairy. In milk which has become spontane- ously sour, several kinds of lactic bacteria may be identified. With regard to one kind of bacteria, viz. the bacillus acidi lactici, I. 1 The same holds good for English milk. American milk ranges from 4 to 5'5, with an average of 4'95. (See Aikman's Milk: its Nature and Composition, p. 11.) English Editors, MILK-SUGAR. 25 Hueppe, Hueppe has shown that its development ceases below temperatures of 10 C., is very feeble at 12 C., increases very much above 15 C., and goes on briskly at temperatures between 35 C. and 42 C. When the temperature is raised above 42 C. its development diminishes, until, at between 45'3 C. to 45'5 C., it entirely ceases. Practical experience has shown that with regard to other bacteria effecting lactic fermentation, rapid development only begins at a temperature above 15 C. 15 C., therefore, may be regarded as the temperature below which warm milk should be cooled as quickly as possible if it is to be kept, and above which cold milk should not be warmed if its keeping quality is not to be impaired. The reason, therefore, why milk at 16 C. to 20 C. will keep, even under the most favourable conditions, for only some 50 hours, and why it becomes necessary to have recourse to costly and inconvenient preservative measures, is due almost entirely to the milk-sugar present in the milk. In practice the only admissible physical means for the prevention of premature souring in milk is the cooling of the milk below 10 C., or heating it above 50 C. The treatment of milk with chemicals (sodium carbonate, boracic acid, salicylic acid, hydrogen peroxide, &c.) for effecting this purpose is to be absolutely condemned. Milk-sugar (Iodine, lactose, C 12 H 22 O n . H 2 0) was first discovered as a constituent of milk in 1619 by Bartoletti. It crystallizes in deep rhombic prisms, of a white transparent colour, and contains 5 per cent of water of crystallization. It is comparatively hard, and is insoluble in absolute alcohol and ether. It is soluble in 2J parts of boiling water, and 6 parts of cold water. In concentrated solutions it presents a viscous appearance, and exhibits a tendency to form supersaturated solutions. It is only slightly sweet to the taste. Its specific gravity, compared with water at 4 C., is 1'545, and its elementary composition is as follows: Carbon, 40'00 Hydrogen, 6-11 Oxygen, 48*89 Water of crystallization. ... ... ... 5*00 100-00 Crystallized milk-sugar does not part with its water of crystallization when heated to 100 C. On being heated for some time to a temperature of from 100 to 130 C., it becomes slightly brown in parts, and begins to decompose : a slight quantity of oxygen is absorbed, and a corresponding 26 SCIENCE AND PRACTICE OF DAIRYING. amount of carbonic acid is given off. At 130 C. further decomposition takes place, its water of crystallization is given off and galactose is formed. This brown coloration becomes more pronounced as the temperature rises. Lactocaramel, which is dark brown in colour, begins to be formed at 175 C., and is accompanied by the development of a characteristic smell. Grape-sugar is perhaps also formed. In milk this decomposition begins when the temperature rises above 70 C., and is rendered apparent by the slightly brown coloration (more or less pronounced according to the length of time the milk is heated) which the milk assumes. Three different forms of anhydrous milk-sugar are known. The optical behaviour of solutions of milk-sugar under the polariscope is complicated, since they exhibit bi-rotation and half rotation. It is not as yet certain whether milk-sugar is rendered anhydrous, or retains part or the whole of its water of crystallization, when it is heated in the process for the determination of its total solids; or whether, indeed, under the varying circumstances under which such desiccation may take place, it behaves always in the same manner. It would seem probable that this is not the case, since, as is well known, the total solids in milk do not admit of such accurate determination as is the case with the milk-fat. Solutions of milk-sugar, at ordinary temperatures, reduce alkaline copper solutions. Treated with yeast or dilute sulphuric acid, galactose and grape-sugar are formed. Galactose, an isomere of grape-sugar, and a direct product of the fermentation of the sugars, can be obtained in small white plate-shaped crystals. If milk-sugar be warmed with nitric acid, mucic and oxalic acids are formed, and also saccharic and tartaric acids. With bases milk-sugar forms saccharates. Galactose yields, when boiled with nitric acid, double the amount of mucous acid yielded by milk- sugar when treated in the same way. When heated with hydrochloric acid it yields laevulin acid. When heated with chalk, milk-sugar yields isosaccharine and metasaccharine. Although a molecule of milk- sugar and a molecule of water contain the elements of four molecules of lactic acid (C 3 H 6 3 ), in the case of ordinary lactic fermentation, decom- position never takes place so completely and exactly that the milk-sugar is entirely converted into lactic acid. Small quantities of a number of other products in addition to lactic acid are formed, possibly from the milk-sugar and possibly also from the nitrogenous matter of the milk. The most extensive and thorough of recent researches on lactic fermenta- tion have been carried out by Hueppe. His pupil Scholl has isolated and given an exact description of ten different kinds of bacteria. The facul- tative lactic bacteria are not of immediate importance since they are rarely found in milk. The same applies to the few moulds (yeast) which THE INORGANIC CONSTITUENTS OF MILK. 27 have the power of converting milk-sugar into lactic acid and alcohol. By the gradual formation of free lactic acid in the process of lactic fermenta- tion, the lime and alkaline salts, present in milk possessing a faint alkaline reaction, are gradually changed, and the amphoteric reaction of milk disappears, and the acid reaction alone remains, and gradually increases in strength. With the lapse of time this takes place to such an extent that, although the milk remains liquid at ordinary temperatures, a slight increase in temperature, or the introduction of carbonic acid, causes coagulation of the milk. Finally, the casein, even at ordinary tempera- tures, is decomposed from its combination with chalk, and is precipitated in the form of a white, cohesive gelatinous mass, which encloses all the remaining constituents of the milk. 8. The Inorganic Constituents of Milk (Mineral, Incombustible, or Ash Constituents). The mineral salts of milk, as has already been indicated, form a very important part of the milk, inasmuch as they influence its properties considerably. When one carefully ignites a portion of milk, a mineral residue is obtained possessing a weak alkaline reaction, which, on treatment with strong acids effervesces, and which, therefore, contains carbonic acid, but at the very most not more than 2 per cent. This residue varies in most cases between *4 and '86 per cent, and constitutes on an average '75 per cent of the milk. Closer examination will reveal, in addition to small quantities of carbon, compounds of the metals potassium, sodium, calcium, magnesium, and iron, in combination with chlorine, phosphoric acid, sulphuric acid, and carbonic acid. If it be desired to make a quantitative determination of the ash, and to ascertain in what combinations the above metals are present in the milk, the followino; considerations must be taken into account: o (1) The carbonic acid present in the ash of the milk is formed, if not entirely, yet largely, during the incineration of the organic nitrogenous constituents. Carbonic acid is probably not present in chemical combination in fresh milk, or if it be, it is certainly only in such very small quantities that its effect on the solubility of the salts of milk is only of trifling importance. On this account it requires no further consideration. (2) For the same reasons the sulphuric acid may be excluded, as it occurs, at most, only in traces, and is probably not found in milk at all, and is a product of the combustion of the sulphurous nitro- genous matter. As casein contains "85 per cent of phosphorus, every 1 per cent of casein will yield, when burned, '0194 per cent 28 SCIENCE AND PRACTICE OF DAIRYING. of phosphoric acid (P 2 O 5 ). Milk containing the average percentage of ash, viz. '75 per cent, and the average percentage of casein, viz. 3*2 per cent, contains, therefore, in its ash, "062 per cent of phos- phoric acid. Of this '062 per cent, about 8 per cent is derived from the phosphorus in the casein. In order, therefore, to find the quantity of phosphoric acid which is present as such in milk, 8 per cent has to be deducted from that found in the ash, which is, on an average, 2 7 '5 per cent of the total ash. If this be done, and carbonic acid be deducted as well as the sulphuric acid, and the small quantity of carbon present, the follow- ing results, when the remaining portion is calculated to percentage and the metals reckoned as oxides, are obtained, from which the average percentage of the different mineral constituents of milk may be seen: Potassium oxide, 25-64 Sodium oxide, ... ... ... ... 12-45 Calcium oxide, ... ... ... ... 24-58 Magnesium oxide, 3-09 Ferric oxide, ... ... ... . . ... 34 Phosphoric acid, ... ... ... ... 21 '24 Chlorine, 16-34 103-68 Deduct oxygen for chlorine, 3-68 100-00 If we examine these figures more particularly, it will be found that the chlorine (which without doubt is entirely combined with the alkali metals) and the phosphoric acid, do not suffice to convert the bases present into soluble salts possessing neutral or amphoteric reaction, and that a large quantity of free calcium oxide remains over. Even when we reckon that the casein, which plays the part of an acid, forms a soluble compound with the lime, and that accord- ing to Soldner this compound consists of 100 parts of casein and 1*55 parts of calcium oxide, there is yet an excess of the latter. Since the carbonic acid which may be present in fresh milk in a state of chemical combination is far short of being sufficient for effecting neutralization, and since lactic acid is not present in fresh milk, it necessarily follows that other acids organic acids are present in the milk and conduce to bring about this amphoteric reaction. THE OTHER CONSTITUENTS OF MILK. 29 Indeed, Henkel has proved that citric acid is a normal con- stituent of milk. Whether, in addition to it, other organic acids not yet discovered, may be present in milk, it is impossible to say. If citric acid only is present, milk must contain on an average some- where about '25 per cent of it. Till now, perhaps in consequence of the difficulty attending the exact quantitative determination, only '1 to "15 per cent has been found. The following, according to Soldner, are the probable combinations in which the mineral con- stituents of milk are present (neglecting the small traces of iron): Sodium chloride, 10'62 Potassium chloride, ... ... ... ... 9*16 Monopotassium phosphate, 12 -77 Dipotassium phosphate, ... ... ... 9'22 Potassium citrate, ... ... ... ... 5 '47 Dimagnesium phosphate, ... ... ... 3 '7 1 Magnesium citrate, ... ... ... ... 4*05 Dicalcium phosphate, 7 -42 Tricalcium phosphate, ... ... ... -8 '90 Calcium citrate, ... ... ... ... 23*55 Calcium oxide in combination with casein, 5'13 100-00 In the above combinations of the mineral salts, if they could be obtained unchanged, they would form '90 per cent of milk. Accord- ing to Soldner's experiments, 36 to 56 per cent of the phosphoric acid present in milk, and 53 to 72 per cent of the calcium oxide, are not in solution, but are in a state of suspension in the form of dicalcium and tricalciuin phosphates. To the above-mentioned constituents the following substances must be added, as present in the ash of milk: silica, iodine (in districts near the sea), calcium fluoride, and calcium carbonate. The chemical combina- tions of the mineral salts of milk are not constant, but vary within certain limits according to the state of health, the feeding, the period of lactation, and perhaps also the age of the animal. 9. The Other Constituents of Milk. In addition to the chief con- stituents of milk enumerated and described above, several other substances must be briefly referred to which, although occurring as normal constituents, are always present only in very small quan- tities, and partly in the gaseous form. These substances, therefore, 30 SCIENCE AND PRACTICE OF DAIRYING. as a rule, are not taken into account in the quantitative analysis of milk. Among these are nuclein and lecithin substances which have been already mentioned as constituents of the caseous matter and of the fat of milk urea, hypoxanthin, ammonia, citric acid, cholesterin, sulphates, sulphocyanates, carbonic acid, oxygen and nitrogen gas. Small quantities of substances derived from the food of the cow, but which possess no nutritive properties, such as colouring substances and odorous substances, are also found as occasional constituents. Peptone does not belong to the normal constituents of milk, and it is doubtful whether milk, in addition to milk-sugar, contains any other carbohydrate of the dextrine class in small quantity as has been asserted. F. J. Harz has recently found in milk and in milk products such a body, and has named it amyloid. A peculiar interest attaches to the discovery of citric acid in cows' milk, made by Henkel and confirmed by Anton Scheibe. It is found also in goats' and in human milk. The percentage of citric acid in cows' milk varies considerably. This variation, however, does not depend on the feeding of the cow. On an average, it amounts to *1 to -15 per cent of the milk. From the researches of Scheibe it appears that citric acid is a specific constituent of milk, since, like the organic constituents of milk, it is not originally present in the milk-glands in this form. In condensed milk, viz. that condensed without the addition of sugar, and in sterilized or preserved milk, concretions or bulky precipitates com- monly occur, as Henkel has pointed out, which consist almost entirely of pure calcium citrate. Cows' milk contains only about *007 per cent of urea. Milk fresh from the udder always contains a certain quantity of gases, oxygen, nitrogen, and carbonic acid the carbonic acid predominating. They may amount to 6 per cent or more of the volume of the milk. S. M. Babcock claims to have shown that milk contains j^^^ of a per cent of fibrin; but this requires further confirmation. 10. The Percentage Composition of Cows' Milk. Very consider- able variations are to be found both in the specific gravity and in the composition of milk drawn even from the same cow at different times (morning, mid-day, and evening). In the whole day's milk, yielded by a single cow on the same day, the variations are within narrow limits. This is still more the case where the samples are representa- tive of a quantity of milk, drawn at the same time; and still more to a quantity of day's-milk from a number of cows (more than five). THE PERCENTAGE COMPOSITION OF COW'S MILK. 31 The following figures are based on extensive experiments which the author has carried out during a long period of years in different places in Germany, as well as on other available German observa- tions, and represent the average chemical composition of the day's milk of large herds of cows (75 to 150), and the limits within which the percentages of the separate constituents of such milk vary. Average. Limits of Variation. Water, 87'75 87-5 to 89-5 Fat, 3-40 2-7 4-3 Nitrogenous matter, ... 3*50 3'0 4'0 Milk-sugar, 4-60 3'6 5-5 Mineral matter ., '75 '6 ,, '9 100-00 The specific gravity of milk of this composition is 1 '031 65 at 15 C. The ratio of fat to nitrogenous substance is 100 : 103; and the nutritive ratio 1 : 3"74. The composition of the total solids is as follows: Fat, 27-75 Nitrogenous matter, 28*57 Milk-sugar, 37"56 Mineral matter, 6*12 100-00 Under ordinary conditions, the milk-sugar is the largest con- stituent of the milk solids. The nitrogenous matter is slightly in excess of the fat. The average composition, according to the author's observations, of the whole day's milk of comparatively large herds of cows in North Germany, and of the countries bordering on the German Ocean, which contain large-sized lowland cattle, is as follows : Specific gravity, 1-0314 Water, 88-00 Fat, 3-25 Nitrogenous matter, ... ... ... 3 -40 Milk-sugar, 4'60 Mineral matter, 0*75 100-00 By the term " total solids " is understood all the constituents of 32 SCIENCE AND PRACTICE OF DAIRYING. milk, except water. These amount, on an average, for Germany, in the case of the day's milk of large herds, to 12*25 per cent. 1 The per- centage of fat may be stated at 27'75 of the total solids, and 3*4 per cent of the whole milk, and the specific gravity at 15 C., at 1-334. By deducting the percentage of fat from the total solids, the non-fatty solids are obtained. These amount to 8'85 per cent of the whole milk, and have a specific gravity, which remains very constant, of T6. The annual returns show that the specific gravity, for comparatively large herds, if expressed in the form of degrees, 2 rarely rises or falls more than 10 per cent, for milk of the different milking-times, taken for a whole year. Similarly, the rise or fall of the percentage of fat rarely exceeds 30 per cent, of total solids 14 per cent, and of "solids not fat" 10 per cent. The percentage of the several constituents in milk, obtained at different milking-times, from comparatively large herds, in the course of a year, seldom falls below 2*4 per cent of fat, 10*5 per cent of total solids, 7 '8 of "solids not fat", and 1*028 specific gravity. The specific gravity of the total solids rarely exceeds 1*37. In the case of the milk of single milkings of single cows the limits above stated are, of course, largely exceeded. It is almost unnecessary to cite examples for the purpose of showing to what extent this may take place in certain cases. The milk of single cows, for example, as has been observed by the author, may contain, when the cow is in heat, less than 1 per cent of fat, and shortly before becoming dry as much as 8 per cent. The greatest variation among all the constituents is found in the milk-fat, and the least in the " solids not fat ", and the specific gravity. For this reason, in testing milk, for the purpose of forming an opinion of its quality, the determination of the specific gravity and of the "solids not fat " are of especial value. Few observations have been made with regard to the variation in the percentage of the nitrogenous matter and the milk-sugar. 11. The Relation between the Specific Gravity of Milk and its Percentage of Fat and Total Solids. That there is a relation between the specific gravity of milk and its percentage of fat and solids is clear; and it is obvious that these three factors are dependent on one another. It is open to question whether the ratio between these *The average percentage of total solids in English milk, according to Vieth, may be taken at 12'90 per cent, and that of the fat at 4'1 per cent; while the total solids in American milk may be taken at 13 per cent, and that of the fat at 4 per cent (Aikman's Milk: Its Nature and Composition, Chapter II. A. & C. Black). * The thousandth part of the specific weight is called a degree. The specific weight 1-0332 expressed in degrees would therefore be 33 '2. SPECIFIC GRAVITY AND PERCENTAGE OF SOLIDS. 33 three factors is the same for all kinds of milk, and whether it holds universally true and is practically useful, and can be stated in a definite form. If these three factors be respectively denoted by the letters s, /, and t, the ascertained specific gravity of the milk-fat by the letter 8'57 14 T67 2-34 07 2-40 22 1-82 18 02 5-26 48 2-55 13 26 90 25 23 01 08 1-80 86 48 02 14 2-51 !See Johnston's Elements of Agricultural Chemistry, 17th edition, revised by Dr. Aikman r pp. 382-85 and p. 465 (Blackwood & Sons). 46 SCIENCE AND PRACTICE OF DAIRYING. It should be noticed, however, that the digestibility of the nutrients is by no means inconsiderably lessened by the addition of bulky fodder, containing much non-nitrogenous substance, to a ration. It must not be forgotten that such a lowering of digestibility would be exercised in the case of the above ration by the 20 Ibs. of turnips which it contains. It is hardly necessary to say that putrefying food of any kind should on no account be given to milk cows. Milk cows must also not be fed with beans, peas, lupines, pea-straw, or with large quantities of barley-straw. 1 The most suitable foods, and those which have the most favourable action, besides good grass and hay, are the grain of cereals, especially oats, and the different kinds of bran, especially coarse wheat bran. All kinds of roots, including mangel and chopped turnips, may be mixed with the eighth part of their weight of good cut straw, and potatoes with about half their weight of straw. Approximately about eight kilograms potatoes per day per 500 kilograms of live weight (17J Ibs. to 1100 Ibs.) may be recommended. If large quantities of potatoes are used in feeding it is best to steam them. Where the conditions of the farming are such that very watery foods, such as distillery refuse and sliced roots, have to be given, which are better adapted for fattening cattle than for milk cows, care should be taken that the cows receive, if possible, at least 5 kilos, of coarse fodder daily per 500 kilos, of live weight (11 Ibs. per 1100 Ibs.), and also ample quantities of digestible protein in their total ration. Where roots are used, care should be taken to measure exactly the quantities which are daily given. It is impossible, however, to fix a precise limit to the quantity which it is advisable under all circum- stances to allow. As soon as the rations are no longer eaten by the cows with appetite, and the roots are no longer perfectly digested, both the flavour of the milk and the milk-fat are in danger of being affected by the root feeding. In the case of feeding with distillery refuse, the mangers, which are apt to become contaminated with acid and fungoid ferments, should be carefully kept clean, and, along with all places which come in contact with the food, should be washed with freshly-prepared milk of lime at least once a week. The following conclusions drawn from practice are well worthy of attention, even if they are not to be invariably relied on: Milk-fat becomes hard in its texture, in the case of feeding with peas, 1 In reply to an inquiry by the translators, Prof. Fleischmann writes that all the foods mentioned can be successfully and properly used in feeding milk cows, provided they form a moderate proportion only of a ration, otherwise suitable ; but that if used in excess they produce an unfavourable influence on the milk products. Thus barley-straw has been found to influence quite perceptibly and unfavour- ably the flavour of butter, and linseed-cake tends to produce a hard butter that has not the desired texture. Experience in Germany has also gone to show that such foods as beans, peas, and lupines can be more freely and advantageously given to feeding cattle than to milk cows ; and that when given to the latter, it should only be in moderate and suitable quantity. Editors of English Edition. FEEDING. 47 vetches, rye, linseed -cake, cotton -seed cake, palm-cake, and palm -nut meal. The milk-fat becomes soft when rape-cake, oats, and wheat bran are used. Wheat, barley, and rye, earth-nut and cocoa cake, and malt combs have no distinct influence on the texture of milk-fat. When oil-cakes are used, it should be a rule that not more than 2J Ibs. at the very most of each kind of cake should be given per head of cattle. The value of oil-cakes for milk-production may be placed in the following decreasing order. The most useful is undoubtedly rape-cake, then follow in the second place palm-cake and palm-nut cake, while cocoa, earth-nut, and cotton-seed cakes, sunflower and hemp cakes, follow in the third place. It is quite an erroneous belief to suppose that the cakes mentioned in the third division exercise a generally detrimental effect on the production of milk. This is by no means the case. These cakes have a distinctly marked efficacy, as is also more especially the case with rape-cake and palm-cake. If the milk-fat be hard and brittle, it can with certainty be made soft and oily by using rape-cake, and by using palm- cake, milk-fat which is soft and oily can be made to assume a firm con- sistency. In winter rations, which consist largely of straw and potatoes, a pound of rape-cake should never be omitted. According to the experi- ments of Adolf Mayer, the melting point and also the firmness of butter are dependent on the food, in so far that easily digestible carbohydrates lower the melting point, while feeding with fodders poor in sugar raises it. It is not advisable to feed milk cows with linseed-cake. Malt combs must also be used with great caution, as under certain circumstances they exercise a peculiar irritating effect on the sexual organs. In the production of excellent and good keeping butter, the lest results may be most certainly obtained by using, for the winter feeding of cows, good hay and oat straw, with moderate quantities of beets or carrots, and with oats, wheat bran, and rape-cake. Care should always be taken that the food supplied to cows is not only nutritious and concentrated, but also palatable. In the rations pro- vided, suitable quantities of salt should not be omitted, as well as pure water of a proper temperature. The addition to the food of small quantities of aromatic herbs may sometimes prove very useful. Alterations in the mixture of the food rations are scarcely felt, if the composition of the food, in digestible nutrients, is maintained at the same point, and if the alterations be slowly and carefully effected. On the other hand, sudden changes always produce distinct disturbances on the yield of milk, a point which may be specially shown by analysis of the milk. Changes in food do not, however, produce a distinct effect in changing the milk from day to day. The effects are only clearly shown after the lapse of several days. 48 SCIENCE AND PRACTICE OF DAIRYING. It is well known that milk may be watered through the animal body T either intentionally or unintentionally. The more the custom of buying milk according to composition prevails, the more rarely will this kind of adulteration take place. 19. Milk Yields. The amount of the average yield which the different breeds of cows give in their own districts is of minor interest. It is more instructive to inquire what is the average yearly yield of a cow at present for the whole of Germany; and whether this may be regarded as satisfactory. There are in Germany (and in this matter we need not deceive ourselves) still large districts, in which herds of cows, 20 and 30 in number, do not yield on an average more than 2000 kilos. (4400 Ibs.) of milk per annum. On the other hand, there are isolated agricultural districts, in which herds of 80 and 100 yield, on an average, 4000 kilos. (8800 Ibs.) of milk per annum. There is no doubt that in Germany, on the whole, except- ing in narrowly limited and advantageously situated districts, the feeding of milk cows, both in quantity and composition of the food, is not yet in proportion to their natural milk-yielding capa- city. We are yet far from having reached the limit of the possible economic development of the milk-yielding capacity of the cow. Whether, under the present conditions of German dairying, we have reached a yearly milk yield of 2500 kilos, per 500 kilos. (5500 Ibs. per 1100 Ibs.) of live weight, that is, five times the amount of live weight, the author does not venture to decide; it is certain, so far as his experience goes, that this yield has not been exceeded. With regard to the endeavours which have been made to increase the milk yield of our cows by intelligent breeding, much success, on the whole, has not been attained. The solution of the much- discussed question as to how to improve the quality of the milk, up to the present time has hardly even been considered. In the case of single cows, unusually large yields of milk have been observed, amounting to 8000 kilos. (17,600 Ibs.) per annum, or 36 kilos. (79 Ibs.), and even more, per day. Cows giving the largest quantity of milk, however, do not always give the most profitable yield. The relative moistness of the air, and the percentage of water in the food, especially in the case of grass and the ordinary roots, which vary in the different districts according to their geographical position, appear to exercise, through their continued operation, a powerful influence on the MILK-YIELDING CAPACITY OF COWS. 49 development of the milking capacity of cows, and mainly to fix the average yearly yield of milk of the different groups of cattle in their native districts. Those kinds of cattle which are recognized as the richest milkers, the black and the gray coloured Dutch breeds of the North German lowland cattle, as well as those breeds, the milk of which is characterized by its extraordinary richness in fat, such as the Channel Islands breeds, the Jersey, the Guernsey, and Alderney, have their homes in districts with a maritime climate of the above-described nature. Despite the commonly and emphatically expressed statement that animals yielding a large supply of milk, always yield a milk with little fat and solids, the question may be asked whether the animals and herds in which this fact has been noticed are always fed with a sufficiently rich and nourishing diet sufficient to enable them to attain to the limit of their milking capacity. If this and the author believes that those who have large experience of practical dairying have not a doubt on the subject is not generally the case, we must freely admit that we know very little with regard to the capacity of cows, yielding large quantities of milk, when they are fed in such a way as to enable them to yield up to their full capacity. There is no necessity, from a physiological point of view, for inferring that a large milk capacity is necessarily always united with a low percentage of fat and solids. 20. Milk-yielding Capacity of Cows. A high milk-yielding capa- city, i.e. the capacity to yield, within a certain time, a large quantity of milk in proportion to live weight, and the secretion of a quantity of milk greatly in excess of what is required for the sustenance of the young, are independent of the form of the skeleton and the form of the body of the mammal. Among the different kinds of ruminant domestic animals, this capacity is most strongly developed in the case of the goat, and least so in the case of the sheep. The power of yielding large quantities of milk is not a natural characteristic of the animals, but has been gradually developed in them, in the course of time, through the influence of treatment by man. This property is connected with hereditary qualities, but it is also, in a very variable degree, an individual quality. Therefore, when special groups or breeds of cattle are spoken of as being rich milkers, this denotes nothing more than that it has been found by experience that rich milking cows are more common in these breeds than in others. The capacity, which has been artificially developed in a herd or breed, for yielding a large quantity of milk, may be very quickly and very largely lost again, if care be not continually taken to maintain the (M175) D 50 SCIENCE AND PRACTICE OF DAIRYING. inherited property to its full extent. For this purpose a proper selection of breeding animals must first be intelligently made, and a careful superintendence of subsequent breeding, rearing, and suitable feeding must be exercised, while attention, careful treatment, and every other precaution must be exercised in regard to such circum- stances as may exercise an influence on the milk yield. A thoroughly reliable judgment on the value of a cow can only be obtained from an exact record of her actual performances. Since, in the case of calves and stirks, there can be no such record, and in the case of cows which are for sale, till now, unfortunately, such records have only been available in very few cases, in order to obtain a standard for judging this question, it is very common to have recourse to certain external properties, such as the shape of body, &c., which stand in direct relation to the usefulness of the cow, and give very probable indications with regard to her value. Among external appearances which testify to high milk-yielding capacity the following should be noted: (1) A very powerfully developed udder, which ought in no case to be fleshy. A good milk udder is broad, and stretches back to the neighbour- hood of the sexual organs, and in front to the neighbourhood of the navel ; while on its lower surface it is well rounded arid not pointed. The teats should be set wide apart, and in the full udder should point outwards. The so-called secondary teats should not be wanting. (2) A rich net-work of fine knotty veins, strongly developed milk veins, and broad milk cavities, covering the entire udder, and showing distinctly through its soft skin. The development of the whole system of milk veins gives no reliable information as to the amount of blood circulating in the udder, since a portion of the blood flows through the pubic vein of the sexual organ, and there may also be found in fleshy udders highly developed veins. (3) In the perineum the occurrence of numerous narrow folds lying in regular order beside each other, which are especially well seen in an empty udder, are soft to the touch, and are very loosely connected with what lies under them. (4) A dusty secretion of fine, hairy scales, on rubbing the greasy skin of the udder and of the perineum. (5) Fine glossy hairs, fine thin horns, fine hoofs, a widely - spread escutcheon, and a fine elastic skin. As these properties are dependent on a strongly developed cutaneous gland system, one has a certain right to infer from their presence a large development of the milk-glands, which are likewise included among the cutaneous glands. The milk -yielding capacity of an animal is widely believed to be indicated by the condition MILK-FAULTS. 51 of the hairs around the nose, the eyes, the ears, and the stomach, the inside soft portions of the bone, the anus, the tail, and the hoofs. (6) A general feminine appearance of the whole body. This is im- portant, inasmuch as the activity of the milk-glands is intimately connected with the discharge of the functions of the sexual organs of the female animal. (7) A fine head and tail, and fine limbs; in short, a fine bone system, carrying a weighty body which has been built up by previous rich feeding. (8) A barrel-shaped belly, deep, and the hind part of which should not be tucked up, indicates the existence of good organs of digestion and the capacity of making good use of food. (9) A wide distance between the tuft of hair on the line of the back and the edge of the frontal bone, wide interspaces between the spinous process of the chest and the lumbar vertebrae, and a large space between the ribs, as indications of a long chest and a lengthy body. (10) A deep breast, as wide as possible, and a deep, broad pelvis. The presence of the above characteristics may be taken as an indication that the animal belongs to a carefully developed, good breed. Although none of the above indications can be regarded as infallible, all are worthy of careful attention. Bulls for breeding should be regarded as specially valuable when they have had for their ancestors cows with feminine qualities and good milk yields. Special care should be taken, in the case of a bull, to have an animal with an equable temper and a body free from defects. External signs of the latter are fine skin, glossy hair, fine horns, widely-placed ribs, a broad posterior, and a well-formed escut- cheon. Great stress is also laid on having the four rudimentary teats of the scrotum well formed, and placed relatively in proper position. 21. Milk-faults. Under the designation of milk-faults were for- merly described the extraordinary behaviour shown by milk, which sometimes suddenly occurred from causes quite unknown, and which seriously interfered with the dairy industry. When we read that, in the period between 1815 and 1830, in an agricultural district of Mecklenburg, the disease of blueness in milk lasted for eight years, and that in earlier times, in the best agricultural districts of Schleswig-Holstein, butter was unsaleable owing to the fact that the cream became cheesy in summer for months at a time, we realize that the subject of milk-faults possesses the greatest practical interest. It is of less practical importance at the present time, as such defects seldom now occur. As the practice has extended of creaming milk by centrifugal force, a practice which permits any quantity of milk to be dealt with in a few hours, and as the use of ice in the treatment 52 SCIENCE AND PRACTICE OF DAIRYING. of milk has become common, and the necessity of taking suitable precautions has become recognized, the more rarely have such milk defects shown themselves. They still exist in various places in small dairies, but in large dairies in which intelligent and clean methods of working are followed, they no longer, and, indeed, should no longer exist. Although the changes which milk in certain cases undergoes have not been fully elucidated, we know, nevertheless, that the causes are for the most part not to be found, as was formerly surmised, in the chemical condition of the food, the condition of the soil or pasture-land, the illness of animals, &c., but are to be sought for in the activity of lowly organized forms of life. Only a few diseases are traceable to other sources. It was not uncommon in the past, for milk which had been standing for about two days for the purpose of creaming, to become subject to putrid fermentation, to curdle prematurely, to assume a bitter taste, to become red or yellow in colour, stringy, slimy, or soapy in texture; or for the cream, after 24 hours' standing in the cream-vat, to become curdy, stringy, and bitter in taste; or such difficulties might only show themselves in the butter. Such undesirable phenomena rarely occur now in the larger- dairies, and if so, only in the case of the cream. Should they threaten to manifest themselves, it is now easy to combat them if the desire and requisite knowledge are possessed by the dairyman. With regard to changes commonly occurring in milk or cream, which are not caused by ferments, the following may be mentioned : Milk in which Cream Rises Slowly (Lazy or Dead Milk). This fault is only found to any extent when milk is treated with ice. It manifests itself in a striking diminution of the yield of butter under ordinary treatment, even when there is an equal, perhaps even an increased, percentage of fat in the milk. In order to prevent its development the milk should be creamed by centrifugal force, or by the Holstein process, or should be churned as whole milk. The milk of cows which have been long milked is often subject to this unwelcome fault. It not merely occurs in autumn, as has been asserted, when the cows are for the most part becoming dry, but also in the spring, shortly before they receive green food, or are turned out to pasture. Undoubtedly it arises from the fact that the original condition of the nitrogenous matter of the milk becomes changed in an abnormal manner, so that a large portion of the fatty globules experiences an opposition which prevents them from rising freely. It has been noticed that milk which exhibits a difficulty in creaming con- tains less calcium phosphate than ordinary milk. GOATS' MILK. 53 Milk Difficult to Churn. The cause of this fault, which greatly impedes the churning of milk or cream, and which, indeed, can even make it impossible, may be traced for the most part to gross violation of the rules of dairy management. Occasionally, perhaps, bacteria may also be implicated. AYhen it shows itself in milk from old milking cows, churn- ing is often rendered possible by raising the temperature, under certain circumstances, up to 25 C. Again, cream sometimes becomes excessively soured, and hence is difficult to work. It may be made suitable for butter-making by treating it with a soda solution (200 grams to 1 litre of water), so as to make it very slightly alkaline, and then again very cautiously making it slightly acid with hydrochloric acid (12 c.c. of the commercial acid to 1 litre of water). Sandy Milk. This fault, it would seem, is essentially caused by the peculiar condition of the food, or by disease of the cow. It arises from the fact that, inside the vessels and canals and milk-cisterns of the udder, phosphate of lime is separated out in fine crystals, and causes the stop- page of the milk-tracts of the teats. Inflammation of the udder arises, accompanied by the formation of milk stones and concretionary nodules in the udder. Further remarks on the subject of milk-faults will be found in Chapter III., where the micro-organisms and their influence on dairying and dairy products are treated. As an appendix to Chapter I., some remarks on the properties of goats', sheep's, and mares' milk may properly find space here. 22. Goats' Milk. In Germany, the milk of goats, with the exception of a very small proportion, which is used in the manufac- ture of cheese, is directly consumed, and is used in the small dairying districts as a substitute for cows' milk. As it is admirably suited for this purpose, it appears desirable that as large an increase as possible in the use of goats' milk should take place, and this all the more because tuberculosis, a disease which is very widely spread among so many breeds of cows, and which is communicable to man- kind, is unknown in goats. Goats' milk has '1 white colour, very often a slight yellowish tinge, a weak characteristic smell and flavour, and a slightly slimy consistency. On an average, it is richer in solids, especially in soluble nitrogenous substance (albu- min), than cows' milk, and is less easily creamed. It would appear that the fatty globules are, on an average, somewhat smaller than those in cows' milk. The smell of the he-goat, which is common in goats' milk, is not a characteristic of the milk itself, but is 54 SCIENCE AND PRACTICE OF DAIRYING. peculiar to the skin of the goat (fig. 19), and is imparted to the milk externally. In the year 1883, 2,600,000 goats were kept in Germany, that is to say, they numbered 5 -8 for every 100 inhabitants. Between the years 1873 and 1883 the number of goats kept increased by 13'8 per cent. It is a well-known fact that goats are characterized by a high milk yield. If we take the live weight of a goat at 30 kilos. (66 Ibs.), and the annual yield of milk at only 300 kilos. (660 Ibs.), it will appear that goats yield in Fig. 19. Pyrenean Milking Goat. milk ten times their live weight. Animals with large milk-yielding capa- cities can, if well fed, yield annually 800 kilos. (1760 Ibs.), or even more. Goats carry their young, on an average, about 154 days, and the lactation period is four to five months. The time of their milk-yielding period in the year is generally about six months, less frequently four months, and on occasion it may extend to ten months. So far as investigations have shown, goats' milk on an average has the following composition : Water, 85*5 Fat, ... 4-8 Caseous matter, ... ... ... ... 3'8 Albumin, 1'2 Milk-sugar, ... 4'0 Mineral matter, '7 Total solids, SHEEP'S MILK. 55 The specific gravity varies between 1*0267 and 1*0380, and may be taken on an average as 1*033, at 15 C. In 9 it has already been noted that goats' milk, like cows' milk, always contains citric acid. 23. Sheep's Milk. On many of the larger estates of North Ger- many, every year in July, after the lambs have been weaned, the ewes (fig. 20) are milked for a short time, but, as a rule, for not more than fourteen days. The milk obtained is made into cream. It Fig. 20. Friesian Milking Sheep. possesses a white yellowish colour, and a characteristic weak, and not very pleasant, smell and taste. It is richer in solids than cows' milk, sours more slowly, and requires for coagulation more rennet than either cows' or goats' milk. It creams with difficulty, and yields a soft oily butter, not suitable for keeping, and possessing an unpleasant flavour. The fatty globules are, as a rule, larger than those either of cows' or goats' milk. In the year 1883 there were over 19,000,000 sheep in Germany, which gave, on an average, 42 to every 100 inhabitants. From 1873 to 1883 the number decreased, owing to causes which are well known, and need not be referred to here, by 23*3 per cent. Although it has been affirmed that milk sheep can give a large supply of milk, up to 700 kilos. (1540 Ibs.) 56 SCIENCE AND PRACTICE OF DAIRYING. yearly, the amount that is obtained, on an average, is only about 50 to 70 kilos. (110 to 154 Ibs.). If the average weight of a sheep be taken at 40 kilos. (88 Ibs.), and the yield of milk annually at 60 kilos. (132 Ibs.), the sheep may be said to give a half more milk than its live weight. Sheep carry their young, on an average, 154 days. The lactation period may last about four months, and the time during which the sheep yields milk from four to six months in the year. Examination has shown that sheep's milk is, on an average, of the following composition : Water, 83*0 Fat, 5-3 Caseous matter, 4'6 Albumin, 17 Milk-sugar, 4*6 Mineral matter, -8 100-00 Total solids, 17*00% The specific gravity of sheep's milk probably lies between 1*035 and T041 at 15 C. The tables, which are suitable for reducing the specific gravity of cows' milk at any temperature to 15 C., are not available in the case of sheep's milk. The results of seven years' consecutive examination of sheep's milk of old milking (of the Boldebucker) breed, at Raden, by the author, gave an average specific gravity of 1*0369 at a temperature between 12 and 18 C. The average composition was as follows: Water, 75*400 Fat, 11-773 Caseous matter, 6*475 Albumin, 1*639 Milk-sugar, 3*651 Mineral matter, 1*062 100-000 Total solids, "24*600% It is well known that the most celebrated of French cheeses the Roque- fort is made from sheep's milk. 24. Mares' Milk and Buffalo Milk. Mares' milk has been made the subject of searching investigations, because some nomadic horse-rearing tribes inhabiting the steppes of the south of Russia and the interior of Asia prepare Koumiss from it a beverage which has been thought to have a good effect in certain diseases. In Germany, mares' milk is never obtained or used, because Koumiss, MARES' MILK AND BUFFALO MILK. 57 whenever wanted, can be made out of the skimmed milk of cows. Mares' milk is characterized by a comparatively small percentage of total solids, and an exceptional richness in milk-sugar. It possesses a watery appearance, a white or bluish colour, and a sweet taste. Mares yield milk, on an average, for 340 days. The mares of Tartary are said to remain occasionally in milk for two years, and to yield 200 to 225 kilos. (440 to 495 Ibs.) of milk annually, exclusive of the milk con- sumed by the foal. According to researches, the composition of mares' milk is as follows : Average. Variations. Water, 90'7 92'53 to 89'05 Fat, 1-2 -12 2-45 Nitrogenous matter, ... 2'0 1'33 3'00 Milk-sugar, 5'7 4'20 7 '26 Mineral matter, -4 "28 1*20 100-00 Total solids, 9'3% The specific gravity is practically the same as cows' milk. Buffalo milk is not known in German dairying. In the districts in which tame buffaloes are kept, their milk is highly prized, on account of its richness in fat and its pleasant flavour. It has, however, been very slightly investigated. In colour it is slightly yellowish. The milk-yielding period of the buffalo lasts probably for ten months, in some cases even to eleven or twelve. During a year, buffalo cows may yield, on an average, somewhere about 800 kilos. indeed, if carefully treated and well fed, the yield of milk may amount to 1500 kilos. (1760 to 3300 Ibs.) and even more. Two samples of buffalo milk investigated by the author, one of which came from Transylvania and another from Eoumania, had, on an average, the following composition: Water, 82'93 Fat, 7'46 Nitrogenous matter, ... ... ... 4'59 Milk-sugar, ... 4'21 Mineral matter, -81 100-00 Total solids, 17'07% The Roumanian sample had a specific gravity of 1*0339 at 15 C. CHAPTER II. THE EXTRACTION, IMMEDIATE SALE, AND THE TESTING OF MILK. 25. Milking 1 . It is of the greatest importance, for the purposes of improving the milking capacity of a cow, and obtaining the largest possible quantity of fat, that the operation of milking should always be carried out in a proper manner. The milk last yielded, as has already been mentioned in 13, is always the richest in fat. In milking, the udder should be perfectly emptied at each milking; and the cows should, above all things, be treated with the indulgence, quietness, and gentle handling required by their nature. Furthermore, the same person should not attempt to milk more cows than he is able to accomplish properly; and the individual cow, during the period of lactation, should, if possible, be milked always by the same person. It is only when milking is carried out by intelligent, careful people, and the cow is hand-milked, that the usefulness of milk cows can with certainty be developed and maintained, and it is only those who are entirely ignorant of the nature of the milking operation who can abandon themselves to the idea of using milking machines of any description for example, milk tubes. 1 The use of milk tubes is only permissible in the case of disease of the udder of the cow. Milking should be done either with the whole hand, or, as is customary in the hilly districts of South Germany, only with the first and middle finger, with the assistance of the bent thumb. On no account must it be omitted to press the udder gently and repeatedly between the hands, not merely at the beginning of milking, but also during the process of milking. The custom prevalent in these hilly districts exercises a greater strain, but is far cleaner than milking with the whole hand, since by the latter method it is almost impossible to avoid bringing the milk into contact with the palm of the hand, which is often very dirty. It is hardly necessary to say that the hands of a milker should be washed before milking, and whenever necessary, the udder and the teats should be carefully cleansed. 1 When this sentence was written by Prof. Fleischmann, the Thistle Milking Machine had not been invented. Editors of English Edition. 68 ^^:y. v MILKING. 59 Nevertheless, cleanliness in the byre is still believed to be neglected in most of the larger agricultural districts of Germany, more espe- cially in North Germany. Very much can be done, by means of the greatest possible cleanliness in milking, to improve the keeping quality of milk, and to give uniformity to the manufacture of the dairy products. Milk which has been handled without the due observance of cleanli- ness, especially milk which has been con- taminated with cow- dung, or with the dusty particles of hay, is very difficult to ster- ilize. On the other hand, the sterilization of milk which has been handled in a cleanly manner is compara- tively easy to effect. The milk which first comes from the teats should be put aside, and not mixed in the milk -pails with the rest of the milk; and in milking (fig. 21) old cows which have been giving milk for some time, a sample of the milk from each teat should be tasted, in order if necessary to put aside the whole milk of the cow. In every well-regulated dairy, samples should be taken regularly in order to ascertain the record of each cow. It is advisable in this operation to weigh the milk rather than to measure it, and to test the milk in all circumstances at least once a week. Fig. 21. Position of Hands in Milking. (From Grotenfelt's Principles of Modern Dairy Practice.) In the hilly districts of South Germany milking is done by men, but in North Germany it is generally done by women. When the cows are rest- less or hold hack their milk, the cause always lies in a disordered condition of the udder, whether due to accumulation of blood in the veins, as is believed by Fiirstenberg, or to its accumulation in the arteries of the 60 SCIENCE AND PRACTICE OF DAIRYING. udder, as is believed by Von Rueff. Force in such a case will never help matters. Many cows have warts on the teats, which increase the difficulty of milking. It is asserted that when the warts are injured, the blood flowing from them may cause formation of new warts where the blood falls and dries. 26. Treatment of Milk after Milking. After milking, everything depends on treating the fresh milk in such a way that it may undergo the least possible change before it is used or manufactured. For this purpose care ought to be taken to provide the conditions most favourable for its keeping. The milk should be removed as quickly as possible from the byre, and from any buildings in im- mediate communication with it, and should be placed in a room with pure fresh air. If it is not to be immediately used, it should be at once strained and cooled quickly to at least 12 C. The lower the temperature to which it is cooled and kept at, the better will it keep. If there be no ice to effect this, the keeping power of the milk may be improved by Pasteurizing, a process well suited for milk designed for consumption, which has to be kept for some time before it is used. It cannot be doubted, however, that the spontan- eous coagulation of milk is delayed by Pasteurizing, and at ordinary temperatures, only takes place, on an average, twenty-four hours later than in the same milk which has not been Pasteurized, but which has been otherwise subjected to the same treatment. More- over, the practical carrying out of this process may be regarded as very unreliable. Especially is this the case if the hot milk, when removed from the Pasteurizing apparatus, to be cooled down to the necessary temperature of at least 12 C., comes into contact with air heavily laden with spores of ferments. The addition of chemicals, so-called "preservatives" to milk, such as bi-carbonate of soda, boracic acid, salicylic acid, peroxide of hydrogen, &c., is, under all circumstances, to be emphatically con- demned on principle. The two first-named preservatives act only temporarily, by neutralizing the free acid present in the milk, and by dissolving some of the coagulated caseous matter, but instead of arresting the lactic fermentation, tbey actually help it. The other preservatives exert an antiseptic property. In various places the creaming of milk by means of the centrifugal separator, and also the cooling of warm milk fresh from the cow, is allowed to take place in the byre itself, or in some room in immediate connection THE DISTRIBUTION OF MILK. 61 with the byre. It is unnecessary to say that such a practice is totally against all rules of proper dairying. By the Pasteurizing of milk is understood a process of heating the milk, for a short time, under the boiling point of water (between 56 and 80 .C.). Milk is usually Pasteurized by placing it in the inside of a Pasteurizing apparatus, and then heating up to 70 or 80 C., and subsequently cooling to 12 C. It has been proved by experiment that the bacilli effecting lactic fermentation are, for the most part, destroyed by a momentary exposure of the milk to a temperature of about 80 C., and the vita- lity of the remaining bacilli, along with the rest of the lower micro-organisms present in the milk, is so impaired that their action is temporarily stopped, and their develop- ment checked for a time. If this process be carefully car- ried out, Pasteurized milk does not exhibit, or exhibits only to a very slight extent, that peculiar unpleasant taste possessed by boiled milk, which is so disagreeable to many people. We shall have something to say in a subse- quent chapter on the Pasteur- izing of milk. For the purpose of effecting the rapid cooling of milk for general use, the milk-cooler or refrigerator (fig. 22) constructed on the plan designed by Lawrence is thoroughly to be recommended. It is able to treat per- fectly from 200 to 1200 litres (44 to 263 gallons), of milk in an hour. It is believed in America that milk should be aired by means of special apparatus, in order to free it from the so-called animal smell. In Europe this custom is not general, and in Germany it is regarded as useless and unnecessary. l 27. The Distribution of Milk. In the moving about of milk, it is necessary to protect it from rapid fermentation, violent shaking, contamination, or adulteration. Milk in its warm condition may only be moved short distances, such as, for example, from the byre iThis apparatus has been employed in some cases in Britain with advantage. Editors of English Edition. Fig. 22. Lawrence Refrigerator. 62 SCIENCE AND PRACTICE OF DAIRYING. to the dairy, and then it should only be in open or loosely-covered vessels, in order that it may become cooled by the cooler air, and that evaporation may take place from it without hindrance. When carried further, milk must first be cooled to 12 C., and tightly closed vessels must be used. Care must also be taken that the cooled milk does not attain on the way a temperature at which rapid fermen- tation may take place. If wooden vessels be used, this is not difficult to effect, since wood is a bad conductor of heat. It is more difficult to accomplish when metal vessels are used, which is neces- sary when milk is sent longer distances by rail. In order to avoid, as far as possible, the formation of lumps of butter in the milk, through violent shaking, a light waggon is used for the conveyance of the milk, and the barrels are filled full, or if not full, carefully cleaned wooden floats are used. For the purpose of distributing the milk from one place to another in the country, large wooden vats are best, with wide openings and suitable floats. Such vats are not so quickly or so easily cleaned as metal vessels, but in other respects are pre- ferable, inasmuch as they preserve the milk excellently from the action of external warmth, and they also last longer and are cheaper. For all other purposes, especially for the distribu- tion of milk by rail, metal cans are most suitable, and they are easier to handle (figs. 23-25). Very useful and suitable are the conical cans, holding 36 to 77 litres (8 to 17 gallons), made of steel plates, which are used in England, although, unfortunately, they are still unknown in Germany. In Germany only cans made of white metal are used, which contain, for the most part, only 20 to 25 litres (4J to 5 gallons). 28. Value of Milk for Fattening Purposes. The use of milk for the fattening of swine is not economical, and ought only to be adopted in rare cases. On the other hand, the fattening of calves with milk is much practiced, and under favourable circumstances is attended by very good results. The treatment of fattening calves in feeding requires great attention and care, as well as skill of a special kind, which everyone does not possess. For obvious reasons, this practice Fig. 23. -Railway Milk Can. THE VALUE OF MILK AS AN ARTICLE OF SALE. 63 more generally prevails, and gives better results, on the smaller than on the larger farms. If, as is commonly the case, the fattening process last from eight to twelve weeks, it may be assumed that on an average 10 kilos. (22 Ibs.) of milk make 1 kilo. (2'2 Ibs.) of live weight. The value of the kilo, of milk must be considered with reference to the price of veal. It is well known that the flesh of calves which have been exclusively fed on fresh milk is of excellent quality, and possesses the desired yellow colour of good meat. The fattening of swine with milk was formerly very common in some districts of the Archduchy of Oldenburg, but is now almost entirely Fig. 25. Cart Milk Can. Fig. 24. -Top of Milk Can, with Seal and Pincers, showing Mode of Fastening. abandoned. In the case of fattening calves it is impossible to give any definite figures of the daily amount of milk to be used. As much should be given daily as the calves care to drink, but great care should be exer- cised against over-feeding, and against allowing them to drink too quickly. A drink three times a day at least, with milk of a suitable temperature, is necessary. It is also necessary to keep the calves in separate boxes, in narrow byres, shaded from light, in order that they may remain as quiet as possible. The byres should always be kept clean. 29. The Value of Milk as an Article of Sale. It is often the case that milk is not treated on the spot where it is produced, but is sold. 64 SCIENCE AND PRACTICE OF DAIRYING. Before determining to sell milk, the question should be considered whether this method of utilizing it is really the most remunerative. A very simple calculation in each case will enable this question to be easily answered. A few remarks will be made on this subject in Chapter VII. The most profitable way of disposing of milk is to the private consumer, since the price of milk in all the larger towns is almost always at a figure which can very rarely be obtained, and that only under the most favourable circumstances, when milk is churned or otherwise disposed of. The practice least to be recommended, as a rule, is that of selling the milk to small milkmen, because this method is often very inconvenient and troublesome. In order to avoid this difficulty, farmers in recent times have founded many associations for the purpose of calling into existence town dairies, which may effect the sale of milk, and in which whatever milk remains over unsold is daily worked up or churned. Such arrange- ments have worked very well. Through the development which has followed the extension of railways, agriculturists who live less than twenty miles distant from a town, and not too far from a railway-station, may become members of a town company, or partners in a town dairy business. In all cases in which the sale of milk is either exclusively or chiefly made for direct consumpt, the seller may be regarded as silently assuming the moral obligation to make every effort to supply all his milk unadulterated and as rich as possible. The proper arrangements for the supplying of towns with milk, carried out in the shops of milk merchants in large milk businesses in towns, and in shops for the sale of specially prepared milk for children and invalids, can scarcely be regarded as coming within the scope of purely agricultural industries, and therefore need not be described here. The author contents himself with a few remarks regarding them. If milk in the milk-market, which comes from small milk merchants in the towns, or from milk producers direct to the consumers, suffers in the matter of cleanliness or percentage of fat and total solids, the blame is undoubtedly with the small dealers or with the milk producer. No doubt they should not alone bear the blame of the matter, for the blame must also be shared by the great public, which patiently allows itself to be imposed on. It is in the interests of the public good to limit as much as possible MILK ADULTERATION. 65 retail business, and in a suitable way to effect a concentration of the business of milk selling. Every large town milk business should be conducted in the same way as every large town milk association. On the one hand, the milk suppliers should be bound to pay attention to the cleanly treatment of milk, to cool the milk immediately after milking in a prescribed manner, to feed the cows in a proper way, and to give notice at once in the event of disease breaking out on the farm either in the case of persons or animals; and, on the other hand, to appoint inspectors charged with the carrying out of the regulations and the superintending of the distribution of milk from the central place. In institutions in towns where the milk treatment for invalids is practised, or in institutions for the supply of children's milk, too great care cannot be paid to cleanliness in the byre, to the animals, to the food, to milking, to the whole subsequent treatment of the milk, and especially to the health of the cows. Up till now it has not been possible to devise precautions for prevent- ing milk sold in the streets, from barrels in milk- carts and tapped by means of a cock, from having the 'cream separated by rising to the surface, and the customers from receiving milk of different values. If the milk be not removed from the barrel by means of a cock, but be removed by means of a measure, it is easy to provide every customer with milk of equal quality. Milk-cans for milk-carts have recently been patented in Germany, in which, by a special arrangement inside of the barrel, the rising of the cream of the milk during distribution is prevented. Experience has not yet demonstrated whether these cans fulfil the object aimed at, and whether they are practically useful. 30. Milk Adulteration. Cows' milk may be regarded as adulter- ated whenever the average chemical composition differs in any way, by the addition of foreign ingredients, from the average composition of milk obtained by the continuous and perfect milking of the udder of the cow. The milk adulteration that has to be dealt with in practice consists in the watering of the milk, or in its partial creaming, or in both creaming and watering. Occasionally, but much more rarely than was at one time the case, milk is mixed with skim-milk, which produces a similar effect to a partial removal of the cream. Adulterations of any other sort are very seldom met with in practice. On the other hand, the milk trade suffers from many trickeries and intentional deceits, which are constantly being practised. For example, old milk, or milk collected from milk remnants, is palmed off as fresh milk, or skim-milk is sold for whole milk, or the seller gives false measure, and similar deceits. (M175) E 66 SCIENCE AND PRACTICE OF DAIRYING. According to the nature of the conditions under which, as has just been described, milk is to be regarded as adulterated, every kind of preservative used for milk must also be regarded as an adulterant. Indeed, it may be concluded that there is something of a deceitful intention in the secret use of such agents, since the buyer is under the impression that the sweet condition of the milk is the result of its fresh state, or of the careful and cleanly treatment to which it has been subjected before sale, and is thus grossly deceived. In former times, before much experience had been obtained in the supervision of the milk trade, it was customary to draw up a formal list of adulterants said to be found in milk, as well as methods for detecting all possible and impossible adulterants, which were systematically arranged in a tabular manner. Thus, in addition to the adulterants above referred to, adulteration with albumin, white of egg, caramel, artificial emulsions, meal, gum, dextrin, glue, bird-lime, soapy water, calcium and magnesium carbonates, the pulverized brains of calves, sheep, and horses, and many other things were spoken of. The large experience which has been gained in the course of the last twenty years has shown that in Germany, at least, hardly one of the above-mentioned and highly improbable adulterants have been used. Further reference need not be made to them, since they have no general interest, and if they ever were practised would, by means of the present methods of chemical analysis, be very easily detected. 31. Milk Testing. In consequence of the adulterations of milk described in 30, it has to be determined, in testing milk, whether the average chemical composition of the milk has been altered, by external influences, after it has left the udder, so as to differ from that of milk furnished by continuous and perfect milking, and, in the case of any change having occurred, to discover the nature of the influence that has produced the change. In the first place, it is necessary to obtain as accurate a determination as possible of the properties of the suspected milk ; in the second place, an exact knowledge of the usual average chemical composition and the usual nature of the milk obtained in that district; and thirdly, it is necessary to have an ample knowledge, gained by experience, of the limits of variation in the composition and specific gravity of milk. Chemical analysis of all the constituents, and the determination of the specific gravity, afford the most reliable evidence of the quality of the milk. As, however, in earlier times it was only in very exceptional cases possible to conduct such an investigation, it was MILK TESTING. 67 necessary to form an opinion from single constituent properties of the milk. For this object a number of so-called milk -testing methods of a most varied kind were employed. In this matter practice, more shrewd than theory, adopted the determination of the specific gravity as affording the most valuable test. For a period of ten years the importance of this test was quite undervalued on account of the careless, unscientific method in which some early in- vestigators carried it out, and it has only been re-established by later investigations. Chemists on their side recommended the determin- ation of one or other of the milk constituents, generally the milk- fat, and, in addition to this, quite a number of other tests of milk. Many of these tests were proved to be worthless on account of a want of knowledge of their true significance, as well as because they were often based on false assumptions, due to ignorance of the true composition of milk. Owing to the advance in our knowledge of the nature of milk, made since 1876, the improvement in methods of chemical analysis, and the discovery of Soxhlet's areometric method of determining fat which gives results as reliable as those obtained by gravimetric methods, and dispenses with the use of the chemical balance, while it is simpler and more con- venient to apply, the older methods in use have been replaced, and have now become antiquated; indeed they possess now only historic interest. For the purpose of judging milk, it is quite immaterial whether the quantities of nitrogenous matter, milk-sugar, and mineral matter are determined separately, or all together, as " solids not fat ". In the first place, we know too little with regard to the variation which these constituents with perhaps the single exception of the mineral matter are subject to, to form a decisive opinion based on the amount of any one of them. In the second place, the respective ratio of the three constituents is not at all, or very slightly, altered by such adulteration as is commonly met with in practice, so that it may be said to give little assistance to our judgment; and thirdly, in the case of watered milk, the diminution in the quantity of one or other of these constituents furnishes us with no truer indication than the diminution in the total quantity. At present, therefore, a full analysis is seldom made unless we have to do with some particular kind of adulteration. Instead of a full analysis, we generally determine the specific gravity at 15 C. (s), the percentage of fat (/), the percentage of total solids (t), the sum of the three 68 SCIENCE AND PRACTICE OF DAIRYING. above-mentioned constituents, i.e. the percentage of "solids not fat " (r), and lastly the specific gravity of the total solids (m). When it is desired to make an analysis of milk, it is of the greatest importance to obtain a true average sample, this being effected by thoroughly mixing the milk before taking the sample. In this connection, it must not be forgotten how quickly milk changes, owing to the tendency the fatty globules have to rise to the surface. Thorough mixing of the milk, therefore, before taking the sample, must never be neglected. When necessary, the milk should be warmed to 40 C. before sampling. Especial care should be taken in the determination of the specific gravity (s), and to do so, if possible, up to the ten-thousandth figure. For this purpose a glass hydrometer, of the Soxhlet pattern, should be used, in which the divisions indicating thousandths should occupy 7 '5 mms. The temperature of the milk should also be observed, and the results should be corrected, by means of correc- tion tables, to the temperature of 15 C. if the specific gravity has not been taken at that temperature. Special attention ought to be paid to the fact, that freshly-drawn milk yields figures from J to TTr Vffth less than the figures yielded by the same milk, even after the lapse of so short a period as three hours. On this account one can only accept the specific gravity of milk as final when the milk has stood for three hours from the time it was milked. The fat (/) is determined, either by gravimetric methods or by Soxhlet's areometric method, or with the lactocrit. If (s) and (/) have been obtained, the total solids (t) may be calculated by means of formula (3) given in 11. f If, from the value found for (t), the value for (/) be deducted, the value (r) (viz. the "solids not fat") is obtained: From formula (7), given in 11, the value of (m) (viz. the specific gravity of the total solids) can be calculated: This value (m) is altered by creaming the milk, but not by water- ing it. The knowledge of the five values, (/), (t), (s), (r), (m), is MILK TESTING. 69 sufficient for most cases of adulteration occurring in practice, and not only for an answer to the question as to whether milk is adulterated or not, so far as this can be answered, but also for the determination of the nature of any of the above-mentioned adul- terations. Adulteration by watering is most easily seen in the values (s) and (r), since both these values in unadulterated milk of the most different origin vary between far narrower limits than the values (/) and (t), as has been already mentioned in 10. For this reason the determination of the specific gravity of milk furnishes the most important evidence for forming an opinion on it, not only as a preliminary test, but also as a thoroughly reliable ground of final judgment. If, for example, (s) equals 1-0319, and (/) equals 3-50 per cent, with the aid of the table, the calculation is worked out as follows: For (t) the value in the tables is 1*2 x / for 3-5 to 4 '2, and the value of 2-665 101 - for 1-0319 to 8-238 8-24 therefore is 8-240 4-200 =12*440 percent, and r = 12-44 - 3-50 = 8-94': while for (m), by the tables, we find the value of - for 1-0319 to 3-091 ; therefore 12-440 3-091 "9^349)12.440 (1-33 ~ 3-0910 2863 If milk with properties of this kind has been watered so that (s) equals 1-0248, (/) will be found to equal 272 per cent, (t) to equal 9*71 per cent, (r) to equal 6*99 per cent, and (m) to equal 1-33. If, in the case of creamed and watered milk, (s) equals 1 -0270 and (/) equals 1-695 per cent, (t) would be found to equal 9'041, (r) to equal 7-346, and (m) to equal 1'41. By simply watering milk, the original values of (s), (/), (t\ and (r) are diminished throughout; while, on the other hand, the original value of (m) remains unchanged, because the actual ratio of the individual con- stituents of the dry substance does not suffer alteration. By creaming, the original values of (s) and (m) are increased, and to a lesser extent that of (r); but the original value of (/) is very considerably lowered, and that also of (/), but to a somewhat lesser extent. 70 SCIENCE AND PRACTICE OF DAIRYING. If milk is both creamed and watered, and the watering has been checked by the use of the hydrometer, or if the milk is only slightly watered, the original values of (s) and (r) remain unchanged; indeed they are even slightly increased. Generally, however, the values of (.9) and (r) are diminished. The original value of (m) is increased, while that of (/) is very considerably diminished, and that of (t) to a less extent. The areometric estimation of fat by Soxhlet's method has been so universally adopted that it is not difficult for anyone to make himself familiar with it. Its principle is a very happy one. The fat in a measured quan- tity of milk is dis- solved in ether, and the specific gravity of the ether solution at a certain tempera- ture is determined in an ingeniously constructed appa- ratus. From this the amount of fat in the milk is calculated the higher the spe- cific gravity of the solution, of course the more fat does it contain. As the difference between the specific gravity of fat and ether is considerable, far more than, for example, the difference in the specific gravity of milk and water, the specific gravity of the ether is correspond- ingly changed by the addition of even a small quantity of fat. This renders it possible to estimate the percentage of fat in milk with very great delicacy. A greater advantage which it possesses is that it esti- mates, with almost an equal degree of accuracy, the percentage of fat in skim-milk as well as in whole milk. In the case of the lactocrit (fig. 26), the coagulated portion of the nitrogenous matter in a measured quantity of the milk, precipitated by continuous boiling of the milk with a mixture of glacial acetic acid and sulphuric acid, is first completely dissolved, and the fatty milk-globules, Fig. 26. The Lactocrit. MILK TESTING. 71 which have been melted at the necessary temperature, thoroughly incor- porated with each other, are enclosed in test-tubes, and subjected to centri- fugal force in the lactocrit. The percentage of fat is estimated by the observed volume of melted fat. Originally this method was only utilized in the investigation of whole milk. Subsequently, in 1890, the mixture of acids was replaced by a quantity of ethylidene-lactic acid and solution of hydrochloric acid, which perfectly dissolved the nitrogenous matter in the milk, without attacking the fat to any extent. The result was a great improvement, both in accuracy and convenience, in determining the fat, and a more extensive application of the method ensued. It enables a determination of fat to be made in skim-milk and butter-milk, as well as whole milk, if not directly, yet with great accuracy. In the method devised by Marchand de Fecamp, which was investi- gated and improved in 1878 by Schmidt and Tollens, the milk is treated in a lacto-butyrometer with alcohol, ether, and a little potash. The fat is dissolved and almost entirely separated in the surface layer of the ether. From the volume of this layer the percentage of fat is calculated by means of a table. A fact which militates against the Marchand method is the retention, in the lacto-butyrometer, in a dissolved condition, of a certain proportion of fat. This amount, although generally the same, may vary under certain conditions. In this method, therefore, conditions have to be reckoned with which are not perfectly under control. All the improve- ments made up to the present time in this process affect only the details, such as greater convenience in working it, more exact methods of reading the degree, &c., and do not affect the accuracy of the process. With milk containing from 3 to 3J per cent of fat this method gives good results, the variations from gravimetric methods being generally less than 2 per cent. It is well suited for practical use in agriculture generally, and is useful, for many purposes, in large dairies. For scientific work, however, or for legal purposes, and for the determination of the commercial value of milk, it is not sufficiently accurate to be relied upon. It cannot be used for solutions containing more than 1'339 per cent of fat. The methods for fat determination already described, and more especially the Soxhlet and lactocrit, are thoroughly accurate, delicate, and reliable scientific processes. Where it is impossible to estimate the percentage of fat, and the above methods of milk -testing are consequently inapplicable, a milk-test devised by Muller may be found to serve the purpose. The specific gravity at 15 C. is determined, and the milk is allowed to stand for 24 hours in a Chevalier cremometer at a temperature 72 SCIENCE AND PRACTICE OF DAIRYING. as near 15 C. as can be obtained. The depth of the cream layer is noted for the purpose of calculating its percentage volume, after which it is removed. The specific gravity of the skim-milk at 15 C. is then determined, so that it may be seen whether it remains within the usual limits. This method has been found extremely useful for testing milk suspected of having been creamed and watered, especially in hilly districts, where the conditions of milk production do not exhibit such wide variations as are often found in some districts of flat lands. The "byre -test" furnishes a complement to this formerly largely-used method of milk-testing. The byre-test is carried out in the following manner. If, on investiga- tion, a sample of milk of known origin is found to yield unusual results, the byre is visited as soon as possible and the milk investigated. The results thus obtained are compared with the previous ones, so that it may be ascertained whether the earlier results are confirmed. Where the results of the byre-test are to be given as evidence in a court of justice, the test must be carried out in the presence of witnesses, and care should be taken that the cows are thoroughly milked. It is advisable, therefore, that a skilled milker should be employed, or that the operation should be carried out under his directions and to his satisfaction. The quicker the byre-test follows upon the seizure of the sample of milk, the more valuable are its results for purposes of proof. The same milking-time as that at which the suspected sample was obtained should be chosen, as well as the same cows which have been milked, and the test, if possible, should be applied within 24 hours, and in no case should more than three days be allowed to elapse. It is necessary generally to submit the milk coming from the whole of the cows in question to investigation. In this way the milk of each single cow can be tested. If no important change in the feeding and treatment of the cows have taken place in the interval between the time of the milking of the suspected sample and the milking of the sample taken for the by re -test, then the duplicate results, in the absence of adulteration, should show a variation of not more than a two-thousandth in specific gravity, equivalent to a difference in fat of not more than 3 per cent, and a difference in the total solids of not more than 1 per cent. Where larger variations than the above are found, then the sus- picion of adulteration is confirmed, and in some cases may be absolutely proved. Caution must always be exercised, however, since it has been noticed occasionally in very few cases, it is true that the specific gravity of the milk of single cows has shown a difference, from day to day, of several thousandths, indeed, as many as six, and a difference in the MILK TESTING. 73 percentage of fat of from 2 '5 to 3 per cent. As a result of the author's own experience, he has found that the byre-test is only valuable where two milkings per day are generally practised, and where the conditions of milking in all the byres from which the milk is collected are essentially similar, as is the case, for example, in many districts of Switzerland, Austria, and the hilly districts of South Germany. As far as North Ger- many and the middle districts of Germany are concerned, where the con- ditions vary greatly in the different byres, it is absolutely worthless. For the detection of the less common adulterants of milk, such as the presence of poisons, or the identification of bacteria, it is obviously impossible in this work to give a more detailed descrip- tion of the mode of investigation which must be adopted. In the case of the milk of single cows, the question as to whether it is adulterated or not is a most difficult one to decide. With market milk, however, which almost invariably represents the milk of a number of cows, it is not so difficult; while in cases where the milk of the larger herds is concerned, the detection of adulteration is rendered much easier. The fixing of standards by which the purity of milk should be determined is almost impossible. We shall, at any rate, not attempt to lay down any limits of composition to which the unadulterated milk of single cows is subject. Such figures would not be of any assistance in forming a judgment. The following figures which the author quotes, and which apply to market milk, in which the variations found in the milk of single cows are neutralized, are therefore to be used with very great caution. In the majority of cases of German milk, produced under ordinary conditions, the following figures may be taken as showing the variations in its composition: Specific gravity at 15 C. a variation from 1*029 to 1*033. Fat, 2-50 per cent to 4 -50 per cent. Total solids, 10-50 ,,14-20 Solids not fat, ... ... 8 ,, 10 The specific gravity of the total solids should not exceed 1 '400. It must be strongly emphasized that the above figures, which apply to market milk, must not, in any case, be held as applying universally; but they may be found to hold fairly well in the majority of cases. In different districts of Germany, however, they must, in one or other of the particulars, be departed from. Also, it 74 SCIENCE AND PRACTICE OF DAIRYING. must not be assumed that milk which differs in composition from the above-stated figures is consequently adulterated, but merely that milk, in which this is the case, possesses unusual properties, which warrant suspicion, and justify further testing for its purity. It can also hardly be contended that the occasional variation of milk from any one of the above figures points to adulteration. Adulteration on a small scale is, as a rule, impossible to detect in milk. The opinion of anyone with regard to the genuineness of a sample of milk, who has not taken the precaution, during a year at least, of making himself familiar with the conditions of treatment and the properties of milk, in the districts where the milk-tests are carried out, and who has not performed a very large number of milk analyses, is not worthy of regard. The same may be said also of anyone who neglects to take into consideration a proper study of the action of all the influences which affect the secretion of milk. We have already considered the nature and properties of cows' milk, and of the influence which interrupted milking of the cows, or incomplete milking (not milking dry), or of milking at irregular intervals, exercises on the composition of milk. The variations which the composition of milk from day to day and from milking-time to milking-time exhibits, in short, all the influences which affect the secretion of milk, and which have to be taken into careful consideration in the testing of milk, have already been treated in Chapter I. 32. The Supervision of the Milk-trade in Towns. This has to do, in the first place, with the discovery of the sellers of suspected samples of milk, and, in the second place, with the discovery of how and in what manner the milk has been adulterated. The police supervision of the milk-trade in towns is consequently of a double character, viz. the preliminary testing at the place of sale, and the formation of a final judgment by an experienced and skilled analyst. Careful observations should be constantly if possible daily insti- tuted at the places of sale, and the appearance, smell, flavour, and reaction of the milk should be tested. The specific gravity should be taken with a correct hydrometer, and an observation of the tem- perature of the milk also made. A determination of the percentage of fat, by means of a lactoscope, should perhaps also be made. It should also be noted whether the capacities of the milk-vessels are THE SUPERVISION OF THE MILK-TRADE IN TOWNS. 75 of the proper standards, and if the measures of the seller are correct and properly stamped. In the supervision of places for the sale of milk, only practised and experienced men should be employed. When it has been thoroughly mixed, an average sample of the milk is taken and transferred to the specially-prepared bottle, which is corked and sealed. This should be accompanied, if possible, by exact details furnished by the seller as to the source of the milk. The examination described in paragraph 31 should then be carried out. The rough practice of many under-officials, charged with the arbitrary power of directing that all milk which does not come up to the standards of purity should be poured into the sewers, is unworthy of the present time. It is, in short, destroying a food which has only been partly robbed of its nutritive properties. Supervision of the milk-trade in towns, which limits itself to the prevention of fraud and gross adulteration, can only be said to be fulfilling half its functions. There are other duties which it ought to perform in the protection of the community, and in the furtherance of general health duties which may be described as even higher and more important. It should see: (1) That the milk exposed for sale is not only unadulterated, but that it is of such a quality as is obtained by the perfect milking and thorough admixture of the entire milking of a single cow, or of the milk of several cows. If, in the case of large quantities of milk, thorough mixing does not take place before it is separated into the sale cans, it is quite impossible that the percentage of fat in the contents of the single milk-cans should be the same. Milk sold under such conditions favours one customer at the expense of another. (2) It is desirable that, for the purposes of cooking and churning, the milk should possess the ordinary (normal) properties of good milk, and should be devoid of abnormal properties. Milk with any uncommon properties, such as, for example, colostrum milk, milk showing any of the milk-faults, milk containing coagulated masses or lumps of butter, milk which exhibits unusual behaviour when treated with rennet or when boiled, and milk which shows an unusual bluish-white colour, or a strange smell or taste, should never be allowed to come to the market. 76 SCIENCE AND PRACTICE OF DAIRYING. (3) Only sweet milk, which remains unchanged at ordinary temperatures, for some time after sale, without becoming coagulated, and which stands boiling, should be provided. (4) The milk should be worth its price, that is to say, it should have the average percentage of total solids and fat, found in the milk which is obtained in the respective districts, from properly-fed and well-tended cows. (5) Only milk which comes from healthy cows, free from foreign ingredients, and uncontaminated with pathogenic germs, should be sold. The milk of cows which have had fever, or have been treated internally or externally with medicines, is unsuitable for sale. Care ought also to be taken that the milk is kept clear of contact with people suffering from infectious diseases, or people having charge of such persons. The stringent demands which we are justified in making at present on the milk-trade, and which in some places are beginning to be timorously enforced, will become more easily and more perfectly granted the more the milk-trade is concentrated. The supervision of the sale of milk is uncommonly difficult in towns in which the sale of half -milk, that is, a mixture of creamed evening milk with whole morning milk, is practised. In addition to milk, cream, skim -milk, butter-milk, and whey are sold in commerce. Cream, as it is usually sold, contains from 11 to 25 per cent of fat; but the want of definite regulations concerning its sale has never been felt. The same may be said with regard to butter-milk and whey, which only come into the market in small quantities. With regard to the super- vision of the trade in skim-milk, where it is desired, the tests should be limited to its appearance, smell, and flavour, and to ascertain whether ii stands boiling, and is free from unusual properties. The determination of the specific gravity (which in the case of skim-milk obtained from centrifugal machines generally containing not more than '5 per cent of fat, varies between T0335 and 1-0360) will reveal the addition of any large quantity of water. Since the high value which skim-milk possesses as a nutritive food depends entirely on its percentage of albuminous matter, it is quite immaterial whether it contains a tenth of a per cent of fat more or less ; and for this reason it is quite wrong to prevent its sale unless it has been proved to contain a certain percentage of fat. The analysis and testing of skim-milk is carried out very much THE SUPERVISION OF MILK IN LARGE DAIRIES. 77 in the same way as that of sweet-milk. Further details will be given in Chapter III. 33. The Supervision of Milk in large Collecting and Co-operative Dairies. In the interests of the milk trade, it is necessary that the milk coining from each separate dairy should have its appearance, taste, and smell tested. Its temperature should also be taken, in order to see if it has sufficiently cooled down after milking. It is further necessary to ascertain whether it has been contaminated with dirt, to determine its specific gravity, and to see that the vessels used for carrying it are suited for the purpose. The milk should be tested by boiling it, and a preliminary estimation of its fat should be made. If the milk from any dairy appears suspicious, an average sample should be taken, with all due precautions, before witnesses, and sent for accurate analysis to the nearest public chemical laboratory. At the same time, in order to hinder as much as possible any fermentation during transit, the milk should be cooled in ice before being sent away, and every endeavour should be made to hasten the transit. Since the conditions of clear profit are greater the richer the milk is in fat, the managers of dairies should make a point of discovering those suppliers who send in unusually poor milk, and they should either cease dealing with them, or should induce them to increase gradually the percentage of fat in their milk. The best way of avoiding the imposition which is daily practised, when milk of varying value is simply sold according to weight, consists in buying it from producers at so much per kilogram according to the percentage of fat it contains, in short, in selling it according to the percentage of fat it contains as well as according to its weight. In order to carry out this method of purchase, it is necessary that the milk obtained from each supplier be regularly tested by some method or other for its percentage of fat. If such tests are not made often enough, it can hardly be expected that reliable data will be available for ascertaining what the true average percentage of fat of single milk consignments really is, for it is not impossible that, in the case of an incorrect average being taken, the payment for milk may be as far, or even further, from being a just one than is the case in buying milk of varying value simply by weight; and thus all the trouble and expense involved be really of no use. To obtain reliable data the milk of each customer should be examined at least once a week. If in any district and in Germany there are many such districts 78 SCIENCE AND PRACTICE OF DAIRYING. the external conditions under which milk is obtained are similar, and the single consignments of milk differ comparatively little in their relative percentages of fat, it is not worth the trouble of introducing this costly and inconvenient method of milk valuation. If all parties are agreeable, the lacto-butyrometer may be used for investigating the milk. The Soxhlet method, however, is by far the better one. Where it is impossible to overtake the number of milk inves- tigations that are required to be made by this method, the lactocrit may be used. This process, even where a large number of investigations have to be made, is not likely to give unreliable results. According to the author's experience, where the number of fat determinations amounts to 30 per week, or to 15 determinations twice a week, it is almost as cheap despite the high price of the apparatus as the Soxhlet method; and where the number of determinations exceeds this, the cheaper, propor- tionately, does it become. One worker, provided he is supplied with assistance in the cleaning of the apparatus, &c., can easily undertake the determination of fat in more than 100 samples of milk daily, and in over 600 samples in a week. The indirect determination of the percentage of fat in milk by means of the thickness of the cream layer, as, for example, by the Fjord milk-control apparatus, is now quite antiquated, especially for the purpose here referred to. With regard to the method of fixing the price per kilogram of milk, according to the percentage of fat it contains, reference will be made in 145 In dairies in which cream cheeses are made out of the milk obtained from different dairies, where any difficulty may occur, the so-called milk-ferment test and the rennet test are useful. For the carrying out of the milk-ferment test special apparatus is required. The improved milk-ferment apparatus of Walter, or that of Denkelman, known as the lacto-fermentator, for example, may be used. In the application of this test, the milk of each milk-supplier is set in small quantities, in suitable vessels, for some time (12 hours) at a temperature of 40 C. At this temperature the action of injurious low ferments which may be present is developed more quickly than at the ordinary tempera- ture. Pure milk, under the above conditions, coagulates into a cohesive homogeneous mass, resembling the albumin of a boiled egg, and possessing a pure acid smell. If the milk in any of the vessels has not become coagulated, or presents a ragged, flocculent coagulation, floating in a muddy serum, or occurs in non-homogeneous slimy clots, full of gas-bubbles, and possesses, instead of the purely acid smell, a strange, unpleasant odour, it is to be inferred that the milk which this sample represents is SUPERVISION OF PRODUCTION AND MANUFACTURE OF MILK. 79 likely to impair the quality of the cheese. If, on repetition of the experiment within the next few days, similar results are obtained, and if the quality of the cheese is unimpaired so long as this questionable milk is excluded, it is quite justifiable to hold the supplier of the contaminated milk responsible for any damage that may have arisen. Just in the same way as the milk-ferment test renders it possible to trace milk contaminated with deleterious fungoid growths, the rennet test renders it possible to detect milk which possesses unusual properties, and which would exert a deleterious action in cheese-making. The rennet test is applied in the same way as is done in testing the strength of rennet, and consists in treating with rennet the milk which is being investigated, and observing whether it coagulates quickly or slowly, or whether it coagulates at all, and whether the coagulated mass obtained possesses the ordinary properties. 34. The Supervision of the Production and Manufacture of Milk. In the supervision of milk production in country districts, all that can be done is to take care that the cows are fed as suitably and richly as circumstances permit, and that regular tests of the milk are made as above described. This object will be attained if similar quantities of butter are made from equal quantities of milk obtained from a mixed herd of cows. As this is not always the case, and as the average percentage of fat in the milk of cows differs very much according to their surroundings, attention must be paid not only to the yearly quantity yielded by each cow, but also to the quality of the milk, in order to utilize the most valuable cows for breeding purposes. Those that yield a less satisfactory return ought to be removed, and in this way it will be possible gradually to increase the yield of the entire herd. If sufficient attention has not hitherto been paid to the quality of the milk, the neglect has been chiefly due to the fact that a correct method for the determin- ation of the percentage of fat, which could be carried out at once rapidly and easily, and which was at the same time accurate and reliable, was awanting. The Foser Lactoscope, formerly recom- mended for this purpose, no longer satisfies present demands. Since the lactocrit has been devised, however, and has been proved to be as handy as it is reliable, a regular testing of the milk of single cows for its percentage of fat, especially in large herds, is no longer so very difficult to carry out. It is to be hoped that a reliable method of determining fat will soon be discovered, so convenient and at the same time so cheap that it may be capable of being 80 SCIENCE AND PRACTICE OF DAIRYING. employed on small farms. A wide field of activity still remains in Germany, which has hardly yet been entered upon, for efforts for the purpose of increasing the milk yields and the capacities of cows, in which amply repaying success and a rich return for the money, time, and trouble spent, can be safely promised. Perhaps it may be also necessary to pay attention to the adapta- tion of the calving-time of cows, in the most advantageous manner, to the different agricultural conditions, to the intermittent yield of the cows, and to the recurrent variations in price that commonly occur throughout the year. In general, these conditions have hitherto received too little attention. In the supervision of the utilization of milk, the first duty is to strictly maintain the most absolute cleanliness in the byre, in the milking of cows, and in the treatment of milk. Care should also be taken that milk-cows are well treated, and are thoroughly milked at each milking, and that the milk of diseased cows, or milk exhibiting any unusual properties, should not be utilized, and that the milk should not come into contact with sick persons. In dairying, only careful, capable adult dairymen should be employed, and the arrangements should be such that every operation should go on smoothly, and that every precaution adopted should be effec- tively carried out. A simple tabular list of instructions of daily and technical details, which should include hints on branches of the business of dairying, should, without fail> be put on the walls of byres and dairies. Finally, it is to be recommended that samples of milk, skim-milk, and butter-milk should from time to time, if no other method offers, be sent to a research station to be tested for the percentage of fat, in order that the dairyman should be in a position to judge whether the yield of butter corresponds to the percentage of fat, and if not, to what extent it is deficient. 35. The Analysis of Milk. It is not difficult to make one's self familiar with Soxhlet's widely used apparatus for the determina- tion of the percentage of fat in milk, or with the working of the lacto-butyrometer and the lactocrit. Opportunities for this purpose are easily obtained. Opportunities for becoming acquainted with the method of carrying out the full analysis of milk occur less frequently. The detailed description of the nature and properties of milk given in earlier paragraphs must have excited a desire to obtain at least a description of the methods which render it possible to determine the single constituents of milk, and to estimate their THE ANALYSIS OF MILK. 81 percentage. Chiefly for the purpose of satisfying this desire, a short description is given in what follows of how an analysis of milk is made. Before proceeding to the analysis, the milk is tested in respect of its appearance, smell, taste, and reaction. Its specific gravity is taken at 15 C., and it is tested by boiling. The action of rennet on it is also tested and its percentage of cream estimated by allowing it to stand for 24 hours at from 12 to 18 C. in a Chevalier cremometer. Further, it is desirable, where possible, to obtain information as to whether the milk is from one cow or from several, whether milking is carried on in the byre from which it has come, twice a day or oftener, and from which milking the milk comes. Particulars with regard to breed, treatment, feeding, age, length of time after calving, general health of the cow, and the method in which the sample has been taken, so as to decide whether the analysis represents correctly the composition of a milk such as should have been obtained under these conditions, should also be obtained. When a sample of milk is drawn for analysis, the milk should not only be thoroughly mixed, but should also be brought always to the same temperature, for example, 15 C. Determination of the Percentage of Water, or of Total Solids. Into a thin porcelain basin is placed 15 grams of washed, ignited sea-sand which has been treated with hydrochloric acid. The basin with the sand is dried at 100 C. till the weight is constant. It is then removed to a desiccator, and, after being cooled, is weighed. About 30 c.c. of milk are then poured into a clean small beaker of about 40 c.c. capacity, and a small glass stirrer which does not reach above the lip of the beaker is added. The beaker is covered with a watch-glass and v/eighed. After removing the watch-glass and stirring the milk with the stirrer about 10 c.c. of the milk are poured over the weighed sand in the porcelain vessel, the watch-glass is again replaced and the beaker weighed. The difference between the two weigh- ings gives the weight of the milk used. This is added to the weight of the vessel containing the sand. Drying is first carried on in the water- bath; the porcelain basin with its contents is then introduced into the drying-bath and dried for 45 minutes at 100 C., and then for 15 minutes at 105 C., cooled in the desiccator and weighed. It is then introduced into the drying-oven for 30 minutes at 100 C., again cooled in the desic- cator, and again weighed. This is repeated until two successive weighings show no greater difference than 1 '5 mg. The loss in weight, subtracted from the original weight, represents the weight of the water driven off, and by subtracting this from the weight of the milk used, the weight of the total solids is obtained. ( M 175 ) F 82 SCIENCE AND PRACTICE OF DAIRYING. If in the same sample of milk two determinations of the total solids be carried out, it is quite possible that, despite the greatest care, a difference of plus or minus -15 per cent may be obtained. This difference may be chiefly ascribed to the peculiar behaviour of the dissolved milk-sugar when being dried, as has been already described in paragraph 7. The experi- mental errors in the determinations of the total solids may therefore amount to plus or minus *15 per cent. If the exact percentage of fat and the specific gravity of milk be obtained, the percentage of total solids can be calculated from the formula given in 11. The correctness of this determination is as great or greater than the indirect determination, and can be used in corroboration. Determination of the Percentage of Fat. For this purpose the residue obtained in the determination of the total solids can be utilized. It is better, however, to weigh out 10 to 12 grams of milk in the way pre- viously described, using a roomy porcelain dish, about 10 centimetres in diameter, with as much sand as will perfectly absorb the milk, and then to place this on the water-bath. In order to prevent the milk from sticking firmly to the porcelain basin, it should be stirred with a small sharp -edged glass stirrer. As soon as the mass shows a tendency to become cohesive, the whole should be stirred and all the little lumps broken up before they become hard, so that eventually one obtains a uniform coarse powder. If this does not become baked to the slightest extent after remaining 15 minutes undisturbed in the water-bath, it is rubbed with a small porcelain pestle, which is allowed to stand in the middle of the basin. It is retained 15 minutes longer in the water-bath; the powder is then carefully removed, every single particle being cleared from the vessel on to a Swedish filter -paper which contains no fat, shaped in the form of a cylinder, and resting on glazed paper. It is then introduced into the tube of a Soxhlet fat - extraction apparatus. The paper cylinder is made by wrapping a piece of filter-paper cut at right angles twice round a wooden cylinder, the diameter of which is about 4 mm. less than the diameter of the extraction tube, and then placing on the level surface of the wooden cylinder a piece of paper of similar diameter to the roll, bending this, and smoothing down the surface as one would close a packet. It is unnecessary to use a plug of cotton wool under the coil in the extraction apparatus. It is better to place some cotton wool, free from fat, above the coil, to prevent any washing out of the powder by the falling drops of the ether. In order to prevent the opening of the syphon at the base of the extraction cylinder from being closed by the coil, a ring made out of a strip of pure tin 3 to 4 mm. broad is used. The upper surface of the cylinder should be at least 3 mm. under the highest point of the syphon bend of the extraction THE ANALYSIS OF MILK. 83 apparatus. Care must be taken that the coil should not be filled with cotton wool to its highest surface, and that the ether which comes from the condenser attached to the apparatus when the extraction is going on should always drop in the middle of the coil. After the coil is placed in the extraction apparatus, a wide-necked weighed flask containing 25 c.c. of pure ether is attached to the lower end of the extraction apparatus. The porcelain dish which has been used, along with the glass stirrer and pestle which have been used, are repeatedly rinsed out with ether, which is then poured on to the coil in the extraction apparatus. Sufficient ether is then added to the extraction apparatus till the syphon is almost full, a condenser is then fixed on above, the wide-necked flask placed in a sand-bath, the temperature of which is maintained at about 60 C., and the extraction is started. As a rule, it is ended in about three hours. Whether this is long enough, or whether the extraction requires to be continued for a longer period, can be proved by the watch-glass test. After the extraction has been finished the flask is taken off, and after the ether has been slowly distilled it is placed in the drying-bath, dried for 45 minutes at 100 C., and then for 15 minutes at a temperature of from 105 to 110 C., cooled in the desiccator, and weighed. The flask is again introduced into the drying-bath, dried for 30 minutes at 100 C., allowed to cool, and weighed again; and this is repeated until the two last weighings are found to show no greater difference than 1 milligram. Nearly always from 60 to 90 minutes is sufficient to effect thorough drying. If the fat has to be determined in skim-milk, sea sand is not used, but gypsum. A larger quantity of this is used than is necessary to absorb the liquid, and the extraction lasts for at least four hours before the watch-glass test is applied for the first time. The limits of experi- mental error for milk may be stated at, for whole milk, plus or minus, -05 per cent, for skim-milk, plus or minus, '03 per cent. The determi- nation of the fat by the Soxhlet method gives equally exact results. The extraction apparatus must be firmly connected with the fat flask, and the condenser to the apparatus. The three pieces of apparatus should not be attached to each other with cork. A much simpler method, and perhaps even a more accurate one in its results, for the estimation of fat, is Adams' process, in which the milk is dried on blotting-paper. A coil of filter-paper, 56 cm. long, and 6*5 cm. broad, which has been previously treated with ether to remove any trace of fat it may contain, is allowed to absorb from 8 to 10 grams of milk, weighed out from a beaker by difference as above described. After a few minutes, and when the milk has thoroughly soaked in, the coil is hung on to a peg in the drying-bath and allowed to dry for an hour at 97 to 98 C. The coil is 84 SCIENCE AND PRACTICE OF DAIRYING. then placed in the extraction apparatus and extracted for three hours, and the weight of the fat extracted is estimated. If the roll after extraction is once more dried for half an hour and is weighed, and the original weight of the strip of paper is subtracted from the weight thus found, the weight of the non-fatty solids is obtained. The sum of the non-fatty solids and the fat gives further the total solids. Determination of Percentage of Nitrogenous Matter. This is carried out according to the method recommended by Ritthausen, which is as follows: 25 c.c. of milk are measured off, weighed, and diluted with 400 c.c. of water. 10 c.c. of a copper sulphate solution (69 -28 grams of pure salt per litre) are added, and then 6*5 to 7 '5 c.c. of a potash solution of such a strength that 1 volume of copper is precipitated for each volume of the copper solution. The solution, after addition of the alkali, must be neutralized with acid till it possesses a weak acid reaction, and may contain a little copper in solution. The precipitate falls down rapidly, so that the supernatant liquid can be quickly filtered through a dried weighed filter, and the precipitate quickly washed by decantation and brought on to the filter. The filtrate, along with the washing water, can be used for the determination of milk-sugar; and the copper precipitate, which, in addition to the entire mass of nitrogenous or proteid matter com- bined with the copper, contains also all the fat which is in the milk, may be used for the quantitative determination of the fat. In any case the fat has to be extracted from the precipitate. For this purpose it is washed with a small quantity of absolute alcohol, any particles of the precipitate adhering to the filter being carefully removed with a platinum spatula, and broken up as much as possible and extracted with ether, either on a glass funnel or in the Soxhlet fat-extraction apparatus. If a quantitative determination of the fat is desired, the alcohol and ether washings may be evaporated and the residue weighed. The precipitate from which the fat has been extracted is still further treated with absolute alcohol, and is dried immediately afterwards until it becomes of a bright blue earthy colour, and easily friable. It is then placed in the drying-bath at 125 C. until its weight is constant. As soon as the weight is constant it is carefully ignited, at first at a low heat, so that the easily combustible proteid sub- stances in combination are entirely burnt off. From the loss in weight the amount of albuminoids contained in the milk is estimated. This estima- tion is liable to a small error (about -08 per cent), and is by that amount too low, since in the ignition residue the sulphuric acid formed by the oxidation of the sulphur of the albuminoids is estimated with it. It is necessary to examine the ignition residue for its percentage of carbon, and if any is found, to weigh it in a weighed filter-paper, and to calculate it to the loss on incineration, which represents the proteid substances. THE ANALYSIS OF MILK. 85 If it be desired to estimate the casein by itself, 25 grams of milk are diluted with eleven times their volume of water, carefully precipitated with acetic acid, and the precipitate collected on a dried and weighed filter. The precipitate is washed, extracted from fat, and dried at 110 C., till the weight is constant. It is then burned, and the weight of the ash deducted from the first obtained weight. According to the method of J. Lehmann, the casein may be determined by the application of porous clay plates. The albumin is estimated by heating filtrate and wash-water got in the determination of the casein to boiling temperature. The clot thus obtained is collected on a dried and weighed filter, washed, extracted from fat, and dried to a constant weight at 110 C., and the weight of the ash obtained after burning is deducted from the weight thus obtained. The percentage of so-called lacto-protein may be estimated in the filtrate and wash-water from the determination of the albumin by means of the method of Ritthausen, by using copper sulphate and potassium hydrate. Determination of Milk-sugar. The determination of the milk-sugar, if not effected by means of the polariscope, is best carried out according to Soxhlet's method. 25 c.c. of milk are weighed out, and diluted with 400 c.c. of water, then first treated with 10 c.c. of sulphate of copper solu- tion (69*28 grams of copper sulphate per litre of water), then with 6'5 to 7 - 5 c.c. of potash solution of such a strength that one volume of copper is precipitated for every volume of the copper solution. After the addition of the alkali, the solution must be neutralized and rendered slightly acid, and may contain a little copper in solution. It is then made up to 500 c.c. and filtered through a dry folded filter. 100 c.c. of the filtrate is treated with 50 c.c. of Fehling solution in a beaker, which is then covered and brought to the boil over a double wire gauze. After it has been boiled for six minutes it is filtered through asbestos, and the reduction of the copper takes place spontaneously in the asbestos tube. A small straight calcium chloride tube (about 12 centim. long and 1*3 centim. wide), whose bulb is half protected by oblique and not too soft asbestos filaments, is washed, then dried over the naked flame while air is drawn through, weighed, and attached to a filter pump. Filtration is then carried on by pouring through an attached glass funnel in the presence of a weak diluted atmosphere, then washing with water, and, after the filter pump has been detached, twice with absolute alcohol and twice with ether. Thereafter the filter tube is removed, stretched, and, after the ether has been for the most part expelled by air, bent on a holder downwards, its upper wide opening connected with a Kipp hydrogen apparatus, then the copper suboxide very carefully heated over a small flame, the top of which is about 5 centimetres under the bulb. The reduction is complete in about two or three minutes. After the asbestos tube has been cooled in a stream of 86 SCIENCE AND PRACTICE OF DAIRYING. hydrogen, air is drawn through and it is weighed. If, after weighing, the metallic copper is dissolved in dilute nitric acid, the tube, after being washed out and dried, but reduced 10 to 15 nig. in weight, may be used again. The estimation of the milk-sugar from the weight of the copper, after Soxhlet : 392-7 mg. copper represent 300 mg. milk-sugar. 363-6 275 333-0 250 300-8 225 269-6 200 237-5 175 204-0 150 171-4 125 138-3 100 For example, if the copper found weighs -291 grams, according to the table this shows 225 x. 291 _ 300-8 grams of milk-sugar in 5 c.c., that is, 4'354 grams in 100 c.c. of milk, or, if 100 c.c. of milk weigh 103'1 grams, 4*223 per cent of milk-sugar. The filtrate which is obtained in the Ritthausen process as above described in the determination of the proteid substances may be used for the determination of the milk-sugar. Determination of the Ash. 25 grams of milk, after the addition of a few drops of acetic acid, are heated to hard dryness on the water-bath in a platinum capsule, and then slowly incinerated over an open flame. The residue, after being boiled several times with water, is burned to a white ash. The platinum capsule is then placed in a water -bath, the watery extract slowly added, evaporated, and then slowly ignited, allowed to cool, and weighed. If milk samples which have been already weighed out for investigation are not immediately analysed, care must be taken that they are kept at a temperature under 12 C., and for only about 48 hours. If the samples are kept longer or are placed in a higher temperature, considerable loss in the total solids may be expected. In addition to what has been above described, we may add one or two details with regard to points which may crop up in the testing of milk. In the year 1883, Uffelmann suggested that since ordinary spring and river water almost always contained ammonia, nitric acid, or nitrates, bodies which are never found in uncontaminated milk, these might be taken as an indication of the addition of small quantities of river water to milk. Unfortunately, however, the proof of the addition of water to milk through the diphenylamine reaction of nitrates and nitric acid is not of THE ANALYSIS OF MILK. 87 such a nature as to permit of its practical application in milk-testing. Nor would this test be very valuable in view of the many adulterations which it would fail to detect. The proof of the addition of carbonates or alkali bicarbonates is most easily obtained by incinerating 300 to 500 grams of milk, and determining the percentage of carbonic acid in the ash. The ash of unadulterated milk does not contain more than 2 per cent of carbonic acid; while anhydrous carbonate of soda contains 41*5 per cent. If the percentage of carbonic acid in milk exceeds 2 per cent, this may be regarded as a certain indi- cation that an alkaline carbonate has been added to the milk. Even an addition of 1'5 grams of anhydrous soda to a litre of milk imparts to it a distinct soapy taste. In Hilger's process 50 c.c. of the milk are diluted with five times the quantity of water, coagulated with a small quantity of alcohol, and filtered. If the filtrate be evaporated to half its bulk, an alkaline reaction indicates the presence of an alkaline carbonate. The presence of salicylic acid in milk is best detected by Pellet's method. 100 c.c. of the milk to be investigated, 100 c.c. of water at 60 C., five drops of acetic acid, and five drops of a solution of mercury oxide in nitric acid are mixed together, shaken, and after the albumin has been coagulated the mass is filtered. The clear filtrate is then shaken with 50 c.c. of ether. After the ether has separated out it is removed, placed in a clean vessel, diluted, the residue dissolved in a few drops of water, and tested to see if it will give, on the addition of two drops of a 1 -per- cent solution of iron perchloride, a violet coloration. If it shows a coloration, its amount can be determined by comparing the depth of colour produced with a standard solution of salicylic acid and iron per- chloride. The amount of salicylic acid can in this way be approximately determined. In order to test the quantity of boracic acid in milk, Meissl recommends the following process: 100 c.c. of milk are rendered alkaline with milk of lime, evaporated, and incinerated. The ash is dissolved in the least possible amount of concentrated hydrochloric acid, the carbon is filtered off, and the filtrate is evaporated to dryness, the hydrochloric acid being in this way completely driven off. A small quantity of a very dilute solution of hydrochloric acid is then used to damp the ash. The crystal- line mass is then treated with kirkuma (a tincture of turmeric, prepared according to Fresenius, Qualitative Analysis, 14th Edition, p. 90) and dried in the water-bath. In the presence of even very small quantities of boracic acid the dry substance exhibits a colour from cinnabar to a cherry-red. The reaction is so delicate that even -001 to '002 per cent of boracic acid can be easily detected in milk. An exact quantitative determination of boracic acid in milk is not possible. The amount present can, however, be SCIENCE AND PRACTICE OF DAIRYING. approximately estimated if the addition is so considerable that the per- centage of ash in the milk is increased above its ordinary amount. Small quantities of benzoic acid are most easily and most certainly detected by the following test (Meissl): 250 to 500 c.c. of milk are rendered alkaline by the addition of a few drops of lime or baryta water, evaporated down to about a fourth of its volume, stirred into a paste with gypsum powder, pumice-stone powder, or sand, and then dried on the water-bath. If condensed milk is to be investigated, 100 to 150 grams of the milk may be treated directly with gypsum and a few drops of baryta- water. The dry mass is then powdered, moistened with dilute sulphuric acid, treated four times in the cold with about twice its volume of a 50-per-cent alcohol solution, which easily dissolves benzoic acid, and which has little or no action on fat. The alcohol washings, which show an acid reaction, and which contain in addition to benzoic acid, milk-sugar and inorganic salts, are then mixed, neutralized with baryta - water, and evaporated down to a small volume. This residue is rendered acid with dilute sulphuric acid, and finally is shaken up with small quantities of ether. On diluting the ether, benzoic acid is left behind in an almost pure condition. If not pure, it only contains traces of fat or ash con- stituents. For quantitative determination it is dried at 60 C. in the desiccator, weighed, the benzoic acid is sublimed, and the residue is again weighed. Sublimation is best effected on the water-bath, and is best carried on in such a way that the small basin containing the substance is covered with another basin of similar size, or with a watch-glass. The sublimate on the little basin lying on the top may be used for qualitative test, while the lower basin is heated uncovered for some time until all the volatile substances are expelled. The qualitative reaction for benzoic acid, which is the most striking, is its reaction with neutral iron chloride; the substance dissolved in water must, however, be treated with a few drops of sodium acetate. Boiled milk may be detected from unboiled milk, in addition to the flavour test, by the ozone reaction, which unboiled milk gives but boiled milk does not. Unboiled milk colours guaiacum tincture blue, boiled milk does not. Potassium iodide starch-paper with oil of turpentine is quickly coloured blue by unboiled milk. Boiled milk does not exhibit this reaction, or at any rate no more quickly than the mixture itself becomes blue. The detection of starch in milk offers no difficulty. If starch has been added to cold milk, it settles on the milk being left standing, and can be easily collected in the bottom of the vessel. In order to detect the presence of boiled starch in milk, a large quantity of an iodine solution is necessary, since a considerable quantity of iodine is required to saturate the albumin- oids before the iodine reaction is exhibited. /, ': A; m {V & \ '11 L y* 1 ..*il 1 /jj| f i I : ; 1 i 111 I : CHAPTER III. MILK IN ITS RELATION TO MICRO-ORGANISMS. DAIRYING AND BACTERIOLOGY. 36. The Bearing of Bacteriological Research on Dairying. Long before it was known that all fermentation and decomposition were caused by micro-organisms, the practice of dairying prescribed the greatest cleanliness in the treatment of milk and the great im- portance of always providing good pure air in all dairies; it showed the danger of exceeding a certain temperature, and recommended in cheese-making a careful regulation of the percentage of moisture in the cheese. The real reasons of these precautions were not known at that time, but experience taught that their observance was the best security against certain injuries to which dairy products were liable. We now know that uncleanliness leads to a rapid development of all micro-organisms, that musty stagnant air is heavily laden with spores of fungi and bacteria, that the activity of growth of these small organisms is influenced by the temperature, and that in general the damper and softer the fermenting mass is, the more rapidly does the development of fermentation take place. It is a fact that many bacteria which act as carriers of deadly infectious diseases, or as the creators of poisonously acting substances, can live in milk and render it poisonous. It has further been proved that certain bacteria cause the so-called spontaneous coagulation of milk, that others can exercise a disturbing influence on the creaming of milk and on the preparation of butter, and that other micro- organisms can cause the ripening of cheese in quite undesired ways. Just as, in dairy practice, it is desirable on the one hand to war against dangerous or unfavourable processes caused by bacteria, so on the other hand it is desirable to promote the action of certain kinds of fission fungi. For example, some are not only absolutely necessary for the process of cream souring, required in the pro- duction of fine butter, but also for the inception and development of the ripening processes to which the different kinds of cheeses owe their characteristic properties. The undisturbed and regular development of dairy manufactures depends upon the successful 90 SCIENCE AND PRACTICE OF DAIRYING. regulation of a large number of fermentation processes. Since the technique of dairying is, as a matter of fact, dependent to a very large extent on ferments, which affect alike the distribution of milk for direct consumption or its utilization for dairy products, the neces- sity exists for everyone who takes an interest, either theoretically or practically, in the domain of dairying, to make himself familiar to a certain extent with bacteriology. It is especially necessary for the directors of agricultural experimental stations and laboratories to make themselves familiar with the science of bacteriology generally, and with the methods and details of the processes of investigation. The gradual abolition of the uncertainty surrounding dairy manu- factures is the present important duty which lies before us, and its solution can only be effected by bacteriology. For this reason bacteriological research is of the highest importance to dairying, and it is this consideration which justifies our devoting a short section to its discussion. 37. The Lower Fungi. Although microscopical organisms, espe- cially bacteria, were discovered in the year 1675 by the Dutchman Leeuwenhoek, our knowledge of them was no further advanced. No idea could then be formed of their enormous distribution in the air, water, or soil, nor was it dreamt that they performed such an important role with regard to human life. Indeed, they were long regarded as harmless, and as performing no functions in terres- trial economy. Nevertheless it was observed that they occurred in large numbers in all fermenting and decomposing bodies. This phenomenon could be explained in two ways. The bacteria and the other low forms of fungoid life could be the exciting cause of fermentation and putrefaction, or, on the other hand, their presence might have nothing directly to do with these processes, and they might only be found in large numbers on such bodies because the fermenting and putrefying bodies provided suitable conditions for their development. In opposition to the vitalists, the supporters of the first-mentioned view, it was sought to trace fermentation and putrefaction to purely chemical and mechanical causes, espe- cially to the oxygen in the atmosphere. At the end of the sixth decade of the present century a very interesting discussion took place between Justus von Liebig, who supported the chemico- mechanical theory of fermentation, and the vitalist, Pasteur. What had already been asserted by Spallanzani, Cagnard-Latour, Schwann, and others, with regard to the process of putrefaction, was soon THE LOWER FUNGI. 91 proved by Pasteur by direct and unbiassed observations to be true for the phenomena of fermentation, viz., that these processes were effected by minute organisms of the class of bacteria, fungi, and protozoa. When it was soon further proved that certain bacteria must be regarded as the undoubted causes of different infectious Fig. 27. Different Forms of Bacteria. a, Coccus; b, diplococcus ; c, streptococcus; d, staphylococcus ; e, bacterium; /, bacillus; g, spirillus; h, kladothrix; i, bacilli with cilife; j, bacilli with spores; k, yeast-cells; I, penicillium glaucum; m, aspergillus (mycelium with conidium); n, mucor stolonifer (I, mycelium bearing sporangia, sp ; II, section through sporangium showing spores) ; o, oidium lactis. All greatly enlarged. After Freundenreich (from the report for 1893 of the Agricultural Experiment Station, University of Minnesota). diseases, the full importance of the lower fungi in relation to health and life became recognized, and the study of their nature became of the highest interest. The micro-organisms, which are of the greatest importance in dairying, as is the case with the majority of all 92 SCIENCE AND PRACTICE OF DAIRYING. those smallest of living growths known under this name, belong to the lower fungoid kind, which in their turn belong to the crypto- gams. The lower fungi can be divided into fungi proper (moulds), budding fungi (yeasts), and fission fungi (bacteria). Their function in nature is to set up in the lifeless higher organic bodies a con- tinuous process of disintegration and decomposition, and finally to mineralize them that is, to convert them into water, carbonic acid, ammonia, nitric acid; in short, to change them into simple inorganic compounds, from which the entire higher plant world builds up its organic material. According to the special phenomena which occur in such de- composition processes, according to the nature of the transition products formed, and according to the nature of the organisms which effect them, the process is called decomposition, putrefaction, or fermentation. No decomposition can take place without the presence of moulds or budding fungi. The characteristic putre- factive processes are essentially caused by fission fungi, and in the production of fermentation, budding fungi (beer and wine fermen- tation), as also acetic, lactic, butyric, and urea ferments, also take part. In the development of their special action the different kinds of the lower fungi exhibit different striking phenomena. Some yield colours, others cause phosphorescence, while others again produce liquids in which grow thick and slimy chemical ferments (enzymes), causing the production of odours and smells or the production of substances, which exercise on human and animal life an extremely poisonous action (ptomaines and toxalbumins). But the action of the lower fungi is not limited to lifeless organic bo lies. There are numberless kinds which are able to take possession of living organisms, some of which not merely exist in living plants and animals or inside the human body, and as parasites feed upon their hosts in exceptional cases, but there are others which threaten them with degeneration and death. The lower organisms possess interest for us in this connection in a threefold manner. For example, they are quite indispensable for the continuance of all living nature, inasmuch as they cause putrefaction and decomposition of dead organic matter, and render possible the development and the existence of the entire higher plant and animal world. Of the greatest utility are those by whose action the growth of certain kinds of our cultivated plants is assisted, and those which act in the preparation of certain foods as bread and DISTRIBUTION OF THE LOWER FUNGI. 93 cheese, as well as the universally appreciated beverages wine and beer. Finally, they are not only deleterious, but also highly dangerous when they act as destroyers of the means of life, and as the exciting causes of many fatal diseases. 38. Distribution of the Lower Fungi. The number and distribu- tion of the spores of the lower fungi of all kinds are'quite enormous in water, in the soil, and in the air. It is quite impossible, even with the exercise of the greatest care and cleanliness, to prevent cows'-rnilk, in the process of milking, a process which takes place in the presence of the air, from coming into contact with the hands of the milker and the milk vessels, and from thus absorbing a very large number of the spores of the lower fungi. Now, as milk, from the fact of its peculiar chemical composition, forms a specially nutritive medium, and offers most favourable conditions for the development of large numbers of budding and fission fungi, the result is that the spores are not destroyed, but, on the contrary, increased with very great rapidity. Frcm a few spores in warm milk an incredible number of bacteria (from thousands to several millions per cubic centimetre) may be developed in the course of a few hours. It is obvious that milk which is strongly contaminated with luxuriant and growing fission fungi must have its ordinary dairying properties affected, and that its direct use may seriously threaten the health of the consumer. Among all the lower organisms which are of first importance in dairying are the bacteria, and for this reason they deserve our special attention. 39. The Forms and Life Conditions of Bacteria. By bacteria, in the widest sense of the term, is understood all fission fungi. All bacteria or fission fungi consist of simple cells which are divided from one another, or are joined to one another in chains, bundles, heaps, or occasionally in firm glutinous masses. According to their form they are distinguished as follows: The round, globular-shaped ones are known as cocci, micrococci, macrococci, and diplococci. The straight staff-shaped are called bacilli, and the spiral-shaped ones are known as spirilli and spirochaeti. The conditions of development in which the cells exhibit active growth is known as the vegetative, and the growing cells are the vegetative cells. Growth always takes place in this way, that the cells divide into two halves (by fission), from each of which anew cell arises; hence the name, fission fungi. In addition, moreover, many bacteria among the staff or spiral formed kind possess the 94 SCIENCE AND PRACTICE OF DAIRYING. power of growth in another way, viz., by shedding seed-like bodies, the so-called spores, which, however, do not multiply as such. During this process, as a rule, there can be seen in the inside of the vessels themselves, brightly glittering bodies, chiefly pear-shaped, which sub- sequently develop into spores. While the vegetative cells are easily killed, the spores exhibit a high degree of resistance to unfavourable external conditions. The spores or the lasting cells, or lasting spores, as they are named, are cells which possess a thin but very compact membrane. Under favourable conditions they germinate and grow into a new and much larger vegetative form of fission fungi. The life of bacteria is to a great extent dependent on temperature. With reference to this, every bacterium has a maximum and minimum, even an optimum degree of temperature at which it flourishes, and further, a point below or above which it dies. With reference to the low death point, it may be remarked that the influence of cold, especially repeated freezing and repeated thawing, according to late researches, is able to destroy many kinds of bacteria. The temperature above which death ensues lies, for the vegetative cells of the majority of bacteria, between 50 and 60 C., while their spores are able to withstand a much higher temperature. Most spores remain capable of germination even after being heated for a short time in liquids at 100 C., and many resist for a comparatively short time even a dry heat of 130 to 150 C. These facts, which have been discovered by careful experiments under reliable conditions, possess the greatest practical importance. They teach that vegetative cells of almost all kinds of bacteria present in liquids are certain to be destroyed by heating for a comparatively long time (about two hours) at a temperature of 60 to 70 C., and that a liquid may be rendered perfectly sterile, i.e. free from resistant spores, if heated at 120 to 130 C., for a similar period. In addition to temperature, the life of the lower organisms is still further influenced by the reaction and by the concentration, that is, the percentage of water of the nourishing liquid or the nutrient soil. Further, it is affected by the presence of bodies which exert a deleterious action on the cells, by the free access or otherwise of the oxygen of the atmosphere to the cells, and finally by electricity and by light. The ferments proper prefer a slightly acid reaction in their nutrient liquid or nutrient soil. The fission fungi, on the STERILIZATION OF MILK. 95 other hand, prefer a slightly alkaline reaction. That dry organic matter is less liable to decay than damp is well known, and also that not only the products of the action of bacteria, but also many other stuffs, such as alkalies, in a state of strong concentration, carbolic acid, corrosive sublimate, chlorine, bromine, sulphurous acid, &c., exert a poisonous action on the bacteria. Many bacteria, espe- cially those of the aerobic sort, are only able to live in the presence of a plentiful supply of free oxygen. Others, the anaerobic kind, on the contrary, as Pasteur first pointed out, require, for their develop- ment, the absence of free oxygen; while lastly there are others, the facultative anaerobics, which can exist under both conditions. 40. Sterilization of Milk. It has been known since the year 1884 that sterilized milk, to which no sugar had been added, enclosed in hermetically-sealed tin vessels, has been known which could be kept perfectly well, and without losing its value, for use on board ship and for export to foreign countries. On the other hand, the great advantages of sterilized milk as an article of food, especially for the feeding of children, have not till recently been recognized. Its preparation has been first rendered possible by the work of Hueppe, and through the indefatigable, inventive, technical genius of Soxhlet. After what has been stated in 39, the question presents itself as the theoretically very simple one of destroying the low organisms in milk. Were the question only the destruction of vegetative cells, the continuous heating for 15 minutes at a tem- perature of 75 C. would be sufficient. This treatment is known as Pasteurizing. This is of exceptional importance for milk con- taminated with pathogenic germs. The more important kinds of this type of germ, viz., those causing tuberculosis, typhus, and cholera, form, so far as present researches show, no lasting spores, and succumb therefore to very low temperatures. In the case of many spores of different kinds of saprophytic bacteria, however, which often occur in milk, and which impair to a very large extent its keeping properties, the only way to destroy these effectually when they are present is by means of a comparatively high temperature, either by simple or intermittent sterilization. Milk is sterilized in the full sense of the term only when it has been rendered entirely free from germ-life by sufficient heating, that is to say, when all the lower forms of life which it contains, vegeta- tive forms as well as lasting forms, are entirely killed, and any 96 SCIENCE AND PRACTICE OF DAIRYING. enzymes formed by bacteria are destroyed. Perfect sterilization can only be effected by submitting the milk to the action of continuous heating for two hours at a temperature of 120 C., or for 30 minutes at a temperature of 130 C., or when it is submitted to intermittent heating at different high temperatures. The latter method of treatment, the so-called intermittent sterilization, avoids the heating of milk at temperatures over 100 C., and consists in heating the milk for two hours at a time at a temperature of from 70 to 75 C., then keeping it for several days at a temperature suitable for germ development, about 40 C., in order to permit the spores which are left behind to germinate and to form vegetative cells, then in order to destroy these to submit the milk for two hours at a time to a temperature of 70 to 75 C., then again to allow the milk to stand for several days at the same favourable temperature, viz., 40 C. These consecutive changes of temperature are repeated five times, one after the other, and at last the milk is brought to a temperature of 100 C. In the above-mentioned treatment of milk, however, its proper- ties undergo considerable changes. Among these changes is the conversion of its soluble lime salts into an insoluble condition. The result is that the milk no longer forms, when treated with rennet, a cohesive coagulation; while it coagulates under the action of acids in a fine, flocculent form. As a further result of this treatment, the fine condition of division of the milk-fat is somewhat altered. A large number of the fatty globules of the milk come together, and after a time there collects on the surface of the milk a cream which resembles butter, and which can no longer be uniformly broken up. Finally the milk assumes a dirty brown yellowish colour and a strong taste of boiled milk. All these undesirable changes, which affect the keeping properties of milk, take place in different cases more or less markedly, according to the method of sterilization, most markedly in the case where milk is heated for a longer period at 120 C., and least markedly in the case where it has been subjected to intermittent sterilization. For this reason the latter method of sterilization is to be preferred to all other methods of sterilization Unfortunately, however, it is such an inconvenient method, and requires so much time, that it is not well suited for general application. No other course, therefore, is at present open than to dispense with perfect sterilization, and to be content with milk which has been temporarily sterilized. STERILIZATION OF MILK. 97 Pathogenic that is, disease-producing germs as well as other dairy microbes of most common occurrence in fermenting milk can be destroyed by a steam heat of 68 to 75 C. for one hour's time, or for three-fourths of that time when the temperature is 100 C. This is so where the amount treated does not exceed one litre. For this reason it is comparatively easy to effect the complete steril- ization without any alteration of its chemical composition, its colour, or the state of its fatty globules, provided the milk does not contain spores of a resistant nature. Unfortunately such pure milk rarely occurs in ordinary practice. Sterilization becomes very difficult in the common case of milk which has been contaminated, through dirty and careless handling, with very resistant spores, such as some bacteria belonging to the species of butyric acid, and hay and potato bacilli (for example, bacillus mesentericus, liodermus, butyricus, and subtilis). From what has been already said, it will be seen that milk is sometimes easy and sometimes difficult to sterilize. Milk containing lasting forms of the above-described nature may keep at ordinary temperatures for about six months unchanged if previously heated for 45 minutes to the temperature of boiling water; yet at a temperature favourable to the development of bacteria it may coagulate, often with considerable development of gases, after only three or four days. Where coagulation ensues, this is never effected by the formation of acid, but always by enzymes formed by bacteria, which are of the nature of rennet. It is in the highest degree improbable, that lasting spores which have not been entirely killed in milk treated according to Soxhlet's method and then consumed should be able to germinate during the short, digestive period and exercise a deleterious action, yet it is not absolutely impossible. For this reason every effort should be made to effect the perfect sterilization of milk. Temporary sterilization, which is at present almost universally practised, would gradually become improved and brought nearer to perfect sterilization if it were only possible to obtain milk in ever-increasing quantities capable of being easily sterilized. For this purpose nothing further is wanted than cleanly handling of milk ; and thus avoiding its contamination with such resistant spores of bacteria as above mentioned. How simple this demand seems to be when stated, and yet how extraor- dinarily difficult it is in practice to have proper attention paid to it! Hueppe recommends that all milk destined for the use of ( M 175 ) G 98 SCIENCE AND PRACTICE OF DAIRYING. children should, before sterilization, be submitted to the action of the centrifugal separator, and the cream and the skim-milk separated in this way should be collected in the same vessel. He asserts that the most of the low organisms, and among them the most dangerous of the lasting kinds, remain behind in the mud residue, and that such treatment of milk renders it much more easy to sterilize. Whether treatment in the centrifugal machine does have this effect on milk is very doubtful. Soxhlet suggests that cows should only be fed with scalded or steamed hay, in order in this way to prevent the contamination of the milk with the spores of the hay bacillus. Although it may be admitted that perfect sterilization is not effected by the widely-known Soxhlet method of the treatment of milk, nevertheless it can be asserted that it, and the milk steriliza- tion apparatus also designed for household purposes by Soxhlet, have proved themselves extremely useful. In the wide-spread application which the apparatus has met with it has proved itself eminently successful, inasmuch as it has undoubtedly contributed very materially to a diminution of the rate of mortality in children. Hueppe recognizes this, but regards the sterilization of milk in single households as only a makeshift, and he would regard it as a distinct improvement if the sterilization of milk could be accom- plished in small bottles, either at the place where it is produced, that is, in the larger farms in the neighbourhood of towns, or in large municipal institutions. Only under such conditions would it become easy, he thinks, to gradually effect the sterilization of milk in large quantities. In the first place it is in the interests of the management of the farm to pay the most careful attention to the cleanly treatment of milk, and in the second place, before sterilizing, the milk should be cleansed or purified in the centrifugal machine. Milk, according to Hueppe, is best sterilized on the spot where it is produced, by pouring it immediately after milking into half-litre bottles and exposing it in these for 45 minutes to a steam heat of 100 C. In the Dresden dairy of Pfund the milk to be sterilized is first heated to 60 C., thereafter it is poured into the patent bottles, and these, after they have been closed, are heated in the steam apparatus for some time at 100 C. Milk intended for the nourishment of children is first treated in a centrifugal apparatus. Milk which is temporarily sterilized, or, in the most favourable COAGULATION OF MILK AND SOURING OF CREAM. 99 cases, perfectly sterilized, lias been recently called permanent milk. In its preparation different kinds of steaming apparatus are in use, among them that of Neuhaus, Gronwald, and (Ehlmann is very popular. This apparatus renders it possible during heating to expel the air from the milk and the bottle, and after the heating has been finished to close the patent bottles by means of a lever in the apparatus itself before its cover is removed. 41. The Spontaneous Coagulation of Milk and the Souring of Cream. The so-called spontaneous coagulation of milk takes place, as has been already explained in 7, as soon as a certain quantity of lactic acid is formed by lactic fermentation. The amount of lactic acid produced depends on the original condition of the milk, and the quantity of ferments present. It is dependent also on the temperature. It has been already noticed that there are a comparatively large number of forms of genuine lactic bacteria very similar to one another both in their form and properties, which together are able to effect the formation of lactic acid and the spon- taneous coagulation of milk. Some, and this especially applies to the bacillus acidi lactis of Hueppe, split up the molecule of milk- sugar with comparative ease into four molecules of lactic acid, and produce at the same time an extremely slight evolution of carbonic acid. Others produce small quantities of secondary bye-products, especially alcohol, and others, again, develop in addition very minute quantities of odorous bodies, regarding which very little else is known. Various indications, as has been pointed out, show that in the spontaneous coagulation of milk the caseous matter does not seem to remain unchanged, as is the case in the artificial precipita- tion by addition of acids, but undergoes slight changes. The most important practical application of lactic fermentation is seen in the souring of cream for the manufacture of butter, an operation which takes place every day in dairies. Bacteriology has already annexed this operation as a suitable field for investigation. Ever since it has been shown to be probable that all kinds of lactic bacilli are not equally well adapted to act as ferments in effecting this change, the attempt has been made to isolate and to cultivate in pure cultures the particular varieties which are believed to produce the best butter with the finest aroma. In order that this may be accomplished, it is necessary to describe exactly how a fresh and pure daily supply of the souring liquid, or, as it is called, the acid generator, is obtained. It has been recommended to infect with a 100 SCIENCE AND PRACTICE OF DAIRYING. pure culture of the bacilli in question a sufficient quantity of fresh skim-milk which has been once, or oftener, heated to 70 C., and then cooled to the temperature required for souring, viz., about 16 C., then to allow it to become sour, and when this has been accomplished to use it as a souring agent. The cream to be soured may be previously Pasteurized, and, it is hardly necessary to men- tion, should be carefully protected from contamination. The daily employment of pure cultures of lactic ferment for cream souring can scarcely be expected to come soon into regular practice, and no wide-spread demand appears to exist for them as yet. On the other hand, in course of time such pure cultures will probably come to be used more and more, and the more so as it becomes better understood that undesirable properties in butter have pro- bably their origin in the improper souring of the cream. 42. Different Kinds of so-called Milk Diseases (Milch -fehler). Occasionally it happens that milk or cream coagulates without any previous lactic fermentation. For example, we need only cite the coagulation of boiled milk, in which the reaction is neutral, and the cheesy appearance assumed by cream, in which the precipitation of caseous matter is certainly not effected by lactic acid. The co- agulation of milk of neutral reaction, spoken of by some as sweet- milk coagulation, is effected by means of different kinds of bacteria, which Duclaux has grouped under the name tyrothrix. These fission fungi, which for the most part belong to the group of the so-called potato bacilli, give rise to enzymes of the nature of rennet, which precipitate the caseous matter in milk possessing a neutral or even a slightly alkaline reaction, and which in time dissolve more or less perfectly the coagulated mass. If milk which has been repeatedly boiled does gradually coagulate, and this while showing an almost entirely neutral reaction, such a condition points to the presence of bacteria of this class, whose lasting spores have been enabled to withstand the boiling temperature which has destroyed the lactic bacilli. Many disturbances of milk, which occur in creaming and in the preparation of butter, and the causes of which were formerly sought for in disease of the cows, in the influence of weather, and espe- cially in the physiological action of certain foods, that is, in quite erroneous causes, have now, through bacteriological investigation, been certainly traced to fission fungi. Where premature or unusually rapid coagulation occurs, there DIFFERENT KINDS OF SO-CALLED MILK DISEASES. 101 can be no doubt that the milk contains an extraordinary quantity of luxuriantly-growing lactic bacilli. If milk during creaming be- comes fermented, or during the manufacture of cheese yields puffy cheese, all these indications point assuredly to the presence of a large quantity of a certain kind of fission fungi, and possibly also of budding fungi. The mystery which formerly surrounded certain changes in milk, by which it was rendered slimy or ropy, has to a certain extent been cleared up. It has now been proved that the viscous consistency of such milk has been caused either through a slimy body produced by the decomposition of the milk-sugar, or is due to the fact that the milk contains masses of bacteria, chiefly cocci, in the form of zoogloa bacteria, the cell membrane of which has experienced a peculiar change, associated with a large amount of swelling. In the first case, certain micrococci produce from the milk-sugar a slimy sub- stance, about which very little is known, and also small amounts of carbonic acid, and occasionally also mannite. In the second case it would appear that no decomposition of the organic constituents of the milk seems to take place by the action of the luxuriantly- growing slimy masses of bacteria. Different kinds of bacteria impart to milk an unpleasant, bitter, slightly rancid, and disagree- able flavour, by either causing the production of butyric acid, and perhaps also formic acid, or by separating peculiar bitter extractive substances. Formerly it often occurred that on the surface of milk set for cream, coloured patches, red, yellow, or especially blue, were after a time developed; or that the entire mass of the milk assumed a similar unusual colour. These phenomena are also caused by the action of fission fungi, viz. colour-producing bacteria. At present only one kind of bacteria is known which can colour milk blue and one which can colour it yellow, viz. the bacillus cyanogenus and the bacillus synxanthus, which are known in several varieties, and which live in symbiosis, that is, live together with other kinds of fission fungi. On the other hand, there are many kinds of bacteria, chiefly belonging to the group of micrococci, which impart a red colour to the surface of milk or cream. The most of these bacteria do not exert a decomposing action on the organic constituents of milk. The widely distributed micrococcus prodigiosus, which under certain conditions produces blood-red patches on the surface of milk, on the contrary effects, in the first instance, a decomposition 102 SCIENCE AND PRACTICE OF DAIRYING. of the caseous matter, and subsequently redissolves a portion of the coagulated mass, leaving in addition in the milk the unpleasant flavour of herring-pickle (trimethylamine). Bacteria lactis ery- throgenes coagulates the milk and imparts to it, if light be excluded, a uniform blood-red colour; and a kind of sarcina produces a brown-red colour in the milk. In feeding with milk which is infected with colour-producing bacteria, no deleterious action has yet been observed to be produced. Such bacteria seem, therefore, not to exert a deleterious action on the animal body. It is obvious that all the influences due to fission fungi, which exert a disturbing effect on dairy practice, can be imparted by means of the organisms and the spores from one mass of milk to another, that is to say, they are infectious. For this reason, the only way of curing them where they exist is by the destruction of the respective fission fungi. It is often very difficult to remove effectively the disease germs present in milk, since the conditions of breeding favourable to the organisms in the milk are not known, and also because almost nothing is known of the development of the individual fission fungi. 43. Micro-organisms in Cheese. That the ripening of cheese is connected with and influenced by micro-organisms, and is successful or the reverse, according to the nature of the organisms that are pre- sent in predominating amount, is beyond doubt. Since it has been proved that the organisms which are present in the cheese from the first are largely developed during the ripening period, and since the ripening will not take place when certain substances which are fatal to germ-life are introduced, although these may not have any in- fluence on the albuminoids of milk, or when fresh cheese is protected from the action of air, it follows that it is the low micro-organisms which effect the ripening in all cheese. Since all the different kinds of micro-organisms produce definite effects, it further follows that each individual cheese requires for its ripening a special kind of micro-organism. As our knowledge of the use of different kinds of micro-organisms for producing the many different kinds of cheeses, and without which the specially desired effects of the ripening are not obtainable increases, the great uncertainty which at present prevails in the manufacture of cheese will gradually vanish. But the application of a knowledge of the specific action of the various micro-organisms to the manufacture of cheeses is not easy, and we can scarcely hope to see it soon successfully effected. The subject is MICRO-ORGANISMS IN CHEESE. 103 a very complicated one, from the fact that the proper ripening of cheese is the result of the co-operation of different kinds of micro- organisms; a symbiosis or metabiosis in which certain kinds of bacteria partly favour and partly retard the simultaneous develop- ment in the same medium of other kinds of bacteria, or in which one kind first prepares the way for and renders possible, to a certain extent, the action of another kind. As has been already pointed out, there are fission fungi which produce peculiar ferments, which exercise a solvent effect on the coagulated caseous matter. Probably no kind of cheese can do with- out the action of these fungi for its ripening, by means of which the original white and friable or fragile cheese is converted into a yellow- coloured, soft, pasty mass. For all cheeses which are soft, arid which have a tendency to become liquid, the fission fungi are without doubt of first importance. In the ripening of some cheeses, for example Roquefort, Gorgonzola, Brie, Stilton, &c., certain fungoid organisms cannot be dispensed with, since they, as has been explained, check the action of the lactic bacteria, and gradually diminish the acid reaction of the mass to such an extent that the bacteria which pro- duce the decomposition of the albumin are permitted to develop. Long before bacteriological investigation had thrown light on the subject, practice had instinctively sought the help of fungoid organisms for producing certain peculiar characteristics of certain cheeses. In the preparation of Roquefort cheese, for example, the cheese-makers were in the habit of mixing the fresh cheese with fungoid organisms, and in the preparation of other kinds of cheese they had endeavoured so to arrange the treatment of the cheese that the colonizing and development of fungoid growths should take place as quickly as possible on its surface and in its inside. On the other hand, in the ripening of other kinds of cheese, the action of the albuminoid destroying bacteria has been held in check by the lactic bacteria, since the cheese would otherwise be liable to premature decay. In Holland, in the preparation of the Edam cheese, practice has likewise preceded theory. In that country, when milk which has to be used for churning is treated with sour milk, there is added to it, if not a pure cultivation, yet one in which the growth of colonies of such bacteria (cocci) predominates, as experience has shown these cannot be dispensed with in the ripening period. In all ripened cheeses the presence of butyric acid can be 104 SCIENCE AND PRACTICE OF DAIRYING. detected, sometimes in larger and sometimes in smaller quantities. It is without doubt formed directly from milk-sugar by butyric acid fermentation. It is indirectly formed for the most part from other substances, which vary according to the kind of cheese and the kind of organism active in the ripening process. Such substances are hydrated milk-sugar, salts of lactic acid, albuminous bodies of milk, milk-fat, or glycerine, formed in the saponification of milk-fat. The organisms which interfere with the processes of ripening, and which influence the products of ripening, have also been inves- tigated. A very objectionable, and, at the same time, very commonly occurring disturbance is the inflation of cheese. Many kinds of lower organisms are already known which, under certain conditions, are able to excite a kind of fermentation in ripening cheeses which is associated with a strong evolution of gaseous bodies. Such are the various kinds of micrococci, the saccharomyces lactis, the yeast discovered by Duclaux, and other kinds of yeast, tyrothrix uro- cephalum, the masticis cocci, bacterium lactis aerogenes, bacterium coli commune, and others. In cheeses, on the surface or inside of which red patches are developed, the presence of moulds, which in the con- dition of sporulating produce a brick-red colour, have been detected, as well as several kinds of micrococci, and also very probably a kind of torula. A peculiar kind of disease cheese is subject to, in which it becomes blue, has been probably traced to a kind of bacteria which only flourishes in the absence of air (de Vries); while the production on parts of the surface of cheese of black patches which easily become sticky have been traced also to several different kinds of fungoid growth. 44. Characteristics of Milk which Owe their Origin to Micro- organisms. That milk which has been standing for some time owes its peculiar properties to bacteria, is known, although little is known as yet regarding their nature. In a similar way the organic ferments which yield the purest and best koumiss still await investigation. Kephir, a slightly effervescing spirituous beverage, prepared from milk, contains the common chief constituents of milk in a slightly altered condition, in addition to minute quantities of car- bonic acid, lactic acid, alcohol, and peptones. It also contains caseous matter in a firm but very finely divided condition, well known as kephir grains. In this beverage, several different kinds of yeasts and bacteria have been identified. The yeasts differ from DESTRUCTION OF MICRO-ORGANISMS. 105 the common beer yeasts, and are not able alone to cause the fermen- tation of milk-sugar. This can only take place after the milk-sugar has been dehydrated by the bacteria present in the kephir grains. These bacteria act in different ways, some being able to induce lactic fermentation, others to dehydrate the milk-sugar in presence of certain yeasts, and others to partly peptonize the caseous matter. 45. Destruction of Micro-organisms. In conclusion we may say a word or two on the methods of destroying the microscopic enemies of dairying, and the methods of effecting complete cleansing of milk- vessels and the disinfecting of dairy rooms. For cleansing of vessels of all kinds, different materials may be used according to their nature, such as steaming under pressure, treating with hot strong alkali solutions, preferably boiling soda solutions, or solutions in which burnt lime has been dissolved. The disinfection of rooms or spaces can be effected by covering the walls and ceilings with freshly prepared milk of lime, or with a solution consisting of calcium sulphate, and sprinkling the floor with an alkaline solution. Bad flooring should be thoroughly repaired or entirely renewed. In order to clean the hands one should wash them over with black soap or a solution of creasote. Poisonous disinfectants, such as mercuric chloride (corrosive sublimate) ought not to be used in dairying. 46. The Practical Application of Bacteriology. From the above statements it may be safely asserted that dairying has already much for which to thank bacteriological investigation. Bacteriology has drawn our attention to the existence of a large number of well ascertained and valuable facts that have new and highly important and practical bearings on dairy practice. It has shown that dairying must reckon in practice with small, and, so far as the naked eye is concerned, invisible friends and foes. It has further taught the desirability of sterilizing and Pasteurizing milk and its liquid by- products, and in this way has conferred great benefits benefits which are not half sufficiently recognized by showing the import- ance of such treatment, not merely from the physiological and sanitary point of view, but also in the technical interests of dairy manufactures. It has further discovered the true causes of many troublesome disturbances or diseases of milk, and has already pointed the way, in at least a large degree, to their cure. Finally, it has opened a prospect of the possibility of successfully combating tuber- culosis in cattle. CHAPTER IV. THE MANUFACTURE OF BUTTER. 47. The Different Methods in which Butter is Made. Butter is the most important product of milk. As usually manufactured, fresh butter contains about 83 to 84 per cent of milk-fat, 14 to 15 per cent of water, and 1*2 to 2 '2 per cent of the other constituents of milk. The percentage of the single chief constituents of the iion- fatty total solids of butter, if not exactly, is approximately the same as in milk. Hitherto it has not been possible to obtain, in the form of butter, all the fat which any quantity of milk contains. In the preparation of butter the object aimed at is to solidify the largest possible number of fatty globules in the milk, and then to incorporate them. This has been hitherto, and still is effected, by churning, which consists in shaking violently the fatty glo- bules, and by this violent motion bringing them into intimate con- tact with one another. Although butter can be obtained by direct churning of the milk, an easier and preferable way is to collect the larger portion of the fatty globules by allowing the milk to be divided into two layers, the top layer, which contains as much fat as possible, constituting the cream, and the lower layer, the skim milk, which may be five to six times deeper than the top layer, and contains the least possible amount of fat. The skim milk is separated and the cream is churned. This separation was effected up to the year 1877 by setting the milk in suitable vessels so as to permit it to collect. It was left for from 12 to 48 hours, and even longer, until the greater part of the fatty globules, owing to their light specific gravity, collected on the top, and formed a layer easily recognizable by the eye. In this way the milk was divided by a sharp line into two layers, the skim milk and the cream. Since the year 1877 centrifugal force has been employed for the separation of cream from milk, and the use of this method has extended every year since. There are thus two methods of obtaining cream, the old and the new. It is perhaps not superfluous to notice that cream and butter are not 100 THE OLD METHOD OF CREAM-SEPARATION. 107 the same as milk -fat or butter -fat. It is not correct to speak of the percentage of cream or butter in milk, since cream and butter are not milk constituents, but milk products. 48. The Old Method of Cream - separation Cream - raising. - According to the formula given in 6, it is easy to calculate the acceleration which drives the fatty globules of the milk to the surface (not taking into account any opposing forces) to be about 120 centimetres, or the eighth part of the acceleration of free-falling bodies. The fatty globules in milk would, therefore, in the first second of their movement, were it not for the friction due to their movement, traverse 60 centimetres. Consequently, in layers of milk not deeper than 60 centimetres the fat globules should be collected on the surface in about a second's time. That this does not actually take place, in point of fact, in cream -raising, is due to the friction, which is exceedingly great in the case of the extremely minute fatty globules. The ease with which single fatty globules overcome resistance of different kinds is dependent solely on their size. The large globules, of which some weigh 244 times more than the smallest, overcome this resistance very easily, for they come to the top in a deep milk layer very quickly, some of them certainly in less than a minute. This is the case in warm fresh milk. The smallest, on the other hand, are unable to overcome this resistance and no longer exhibit independent motion, but follow the milk-serum wherever it carries them. The rate at which the globules tend to come to the surface depends directly on their size. Were all the remaining constituents of milk in a state of solution, the rising of the cream would take place with compara- tive ease, since the fatty globules would only have to overcome the internal friction and resistance which their motion entailed, and the resistance offered by the currents caused by their movements in the serum. But further opposition is experienced by them through the fact that the caseous matter, and possibly also some of the mineral salts of the milk, are not in a state of solution, but are in a precipitated condition. We call the state of precipitation perfect when it offers comparatively little resistance to the motion of the fatty globules, and imperfect when it offers, on the other hand, a large amount. Generally speaking, it may be said that the state of precipitation of the caseous matter is most perfect in fresh milk, and becomes gradually less so in the course of about three 108 SCIENCE AND PRACTICE OF DAIRYING. hours, even although the surrounding conditions are exactly the same. It is further known that, with an increasing percentage of lactic acid in milk up to the point of spontaneous coagulation, the precipi- tation of the caseous matter becomes more and more imperfect. It is also known that it is not the same in samples of milk of different origin, and that it is sometimes more perfect and some- times less perfect, according to the exact composition of the mineral salts of the milk. The fatty globules, in their motion, have to push aside or push through the coagulated masses of serum. It follows from the nature of the molecular forces coming into play in this connection, that the resistance offered by the different causes mentioned diminishes with the rise of temperature and increases with the lowering of temperature, and also that the condition of the precipitation of the caseous matter is more perfect the higher the temperature. The resistance above referred to is only to be reckoned with in the case when the milk-serum is at perfect rest during creaming, or when, at any rate, no vertical current move- ments exist in the milk. It is difficult, however, to prevent currents arising in creaming operations, due to cooling. The colder portion of the milk, being of greater specific gravity, sinks to the bottom, and the warmer portion, being lighter, rises to the top. In this way the collection of fatty globules on the surface is disturbed and impeded. The descending currents carry away more fat with them from the cream layer than the ascending currents bring back to, the surface. It is only after the entire mass of the milk assumes the same temperature as the surrounding air, and when no further changes owing to temperature are induced, that the fatty globules can follow without disturbance their tendency to collect on the surface. For creaming the following conditions are necessary: (1) Milk should be set immediately after milking, since the con- ditions of coagulation of the caseous matter are then most perfect. (2) Cream-raising ought to be carried on at the highest possible temperature, in order to avoid, as much as possible, the resistance the fatty globules meet with in coming to the top. (3) The milk of large and well-fed cows should preferably be used, since it is very probable that such milk will possess the usual properties of milk, and especially will undergo a proper coagulation of the caseous matter. (4) The progress of lactic fermentation, which unfavourably influences the coagulation of the caseous matter, should be retarded THE OLD METHOD OF CREAM-SEPARATION. 109 by all available means, such as cooling the milk to a low tempera- ture, the observance of the greatest cleanliness in handling the milk, as well as in the rooms where cream-raising is carried out, and by taking care that only pure dry air should be provided in these rooms, and that they should be properly ventilated. (5) The currents induced in milk by cooling, especially those moving in a perpendicular direction, should be prevented, or should be reduced to the shortest possible duration. The extent to which these requirements are carried out will depend on the amount of fat obtained in a given time from the layer of cream, and the success of the cream -raising. The requirements which demand that the milk, on the one hand, should be kept as warm as possible in order to minimize the amount of resistance, and those, on the other hand, which demand that the milk should be kept as cool as possible in order to lessen lactic fermentation, are contradictory to one another. Since, however, the second requirement is undoubtedly of greater importance than the first, there is no option but to fix the temperature of cream-raising so low that the milk will keep sweet i.e. that on boiling it will not coagulate at least thirty-six hours. Practice has long demonstrated that this is the case with a temperature of 12, or at the most 15 C., provided all precautions as to cleanliness have been observed. This is, therefore, the temperature to be recommended. Formerly there was a comparatively large number of different methods of cream-raising in use, each one of which possessed special advantages of its own. The most widely used and the most per- fectly developed was that known as the Holstein method, which originated in Schleswig-Holstein. Now, with hardly an exception, all these methods have become antiquated, and are no longer used in the larger new dairies. All the older methods of cream-raising are at one in requiring that the greatest cleanliness should be observed, and that the milk should be set immediately after milking. They all, including the Swartz and Devonshire methods, prescribe also a certain temperature to which the milk, as it comes from the cow, has to be cooled, and require that milk should be maintained in the further stages of the process at the cream-raising temperature. In other respects they show considerable differences in respect of the temperature to which the milk is raised, the greater or less speed with which the warm milk is cooled to the cream-raising tempera- ture, and the method in which the cooled milk is maintained at the 110 SCIENCE AND PRACTICE OF DAIRYING. equable creaming temperature. The time occupied in cream-raising, the form and the material of the vessels used in the cream-raising, the depth of the milk-layer in the vessel, the rules laid down with regard to the condition of the room in which the cream-raising is carried on, and the method in which the cream is removed, also vary according to the method adopted. In all methods of cream-raising the milk possesses an equable temperature during only a portion of the entire cream-raising period. During the first hours, that is, until it has been gradually cooled down to the prescribed tempera- ture, milk creams at a comparatively higher temperature, since the resistance offered to the fatty globules is comparatively less. The creaming temperature is, therefore, the lowest temperature to which milk is cooled down, and at which milk is sought to be kept. It varies in the different methods of cream-raising here considered between 9 and 24 C. The more particular conditions under which the coagulation of the caseous matter is unfavourable for creaming have been already dealt with in 21, when discussing milk which creams with difficulty. It is always a disadvantage if the highly favourable conditions which exist during the first hours after milking are not utilized for creaming. Experience has taught that milk which has been kept for some time after milking and has been cooled, or again disturbed, or left temporarily quiet, and again disturbed, always yields a less satisfactory quantity of cream than milk derived from the same source which is at once set after milking. That the slightest disturbance of milk during cream-raising exercises an appreciable influence on the collection of fat in the cream can be easily understood when we remember the compara- tively small quantity of fat globules distributed throughout the milk. For this reason, it is only natural that under like conditions, the less milk is disturbed, the greater the quantity of fat obtained in the cream. The collection of fat on the surface of milk at first takes place very rapidly, and diminishes the longer it proceeds. Even when the cream-layer which has been formed is no longer increased, its percentage of fat nevertheless continues to increase steadily as long as the creaming continues. For this reason, in every method of cream-raising, there is a certain period of time, the so-called cream-raising time, at the conclusion of which the cream is removed, since the increase in the percentage of fat in the cream after this THE OLD METHOD OF CREAM-SEPARATION. Ill takes place so slowly that it is no longer worth while to let the milk stand. The sooner the vertical currents, due to the cooling of the milk, cease, and the fatty globules are enabled to exercise their tendency to rise to the surface without hindrance, the more successfully will the process of cream-raising be carried on. If metal vessels are used in cream-raising, and care is taken that the milk is cooled by the application of cold to the sides and bottom of the vessel, vertical currents may be altogether avoided, and creaming may be permitted to take place under the most favourable possible circumstances. There are no substances which, when added to milk, hasten the process of creaming, and if chemicals are added to milk for the purpose of retarding premature coagulation, such treatment is liable to be regarded in the light of adulteration. In the case of comparatively high equable temperatures from 10 C. upwards the collection of cream takes place by the formation of a comparatively small layer of cream at first, which is gradually increased. The fatty globules collect in the cream-layer according to their size, the largest globules coming to the surface first, and the smaller ones less quickly. In the case of lower equable tempera- tures 10 C. and downwards the milk-serum is comparatively viscous, and in consequence the fatty globules experience in their movement greater internal friction. As long as the fatty globules in cream-raising are not brought into close contact with one another, they find their way to the surface undisturbed, more or less quickly, without reference to their size. In a short time, however, it is impossible for the larger globules to overtake unhindered the smaller ones. Blocks occur in the ever-increasing swarm of upward-striving globules, and there is seen, as a rule, after a longer time, a com- paratively thick layer of cream, which, owing to the fact that the fatty globules are slowly pressing up on one another, gradually becomes more concentrated. The lower the temperature at the end of the creaming period, the greater is the expansion, weight, and amount of water in the cream-layer, and the smaller is the percentage of its fat, after the lapse of a certain time and in the case of a fixed degree of tempera- ture. On the other hand, if milk of similar composition and under similar conditions be set for creaming, the higher the creaming temperature the less will be the cream, and that cream will contain less water and correspondingly more fat, besides being more viscous. 112 SCIENCE AND PRACTICE OF DAIRYING. The higher and narrower the vessels used for cream -raising are, the deeper and less compact will be the layer of cream, and the less will be the percentage, that is, the absolute percentage of the fat of the cream under otherwise like conditions. As will be seen, the thickness of the layer of cream depends on certain particular conditions under which creaming takes place to a greater extent than on the percentage of fat in the milk. It may happen, as a general rule, that milk richer in fat yields under exactly similar treatment a deeper layer of cream than milk poorer in fat; but this is not always the case, and if milk richer in fat throws up more cream, the depth of the cream-layer of milk from different sources is seldom exactly proportional to the percentage of fat it contains. Conclusions as to the percentage of fat in milk, derived from the depth of the cream-layer, or the amount of fat which creaming yields, are for this reason highly unreliable. 49. The Older Methods of Cream-raising. Under the older methods of cream-raising, the best known are the Holstein, Gus- sander, Swartz, and Reimer methods. Other methods of cream- raising, which have scarcely been attempted in Germany at all, but which have been adopted in other countries, and to which references are often met with in the literature of the subject, are the Dutch, Devonshire, Orange County, Cooley, and the American clotted-cream method. Among these different methods, the only one which is in use at the present day in Germany in the larger dairies is the Swartz method, and a slight variation of this method, viz. the cold water method where the conditions necessary for its utilization are present. The remaining methods of cream-raising which have not altogether died out, viz. the Holstein and the Satten (similar to the Holstein) methods, are no longer suited for present requirements and may well be described as antiquated. The Swartz method will be described in the succeeding paragraph. The methods of creaming which are now obsolete may be enumerated as follows: Holstein (and the Destinon, which is a modification of the Holstein method), the Gussander, the Reimer, the Dutch, the Orange County, the American method of mass-creaming, the Cooley, the Devon- shire, the Pommritz, the Natron, the Tremser, the Becker, the Hacks, the Kellog, the Electrical, the Speedwell, and the Raima. The separation of the cream from the skim-milk is effected either by skimming the milk, or by allowing the skim-milk to flow carefully THE OLDER METHODS OF CREAM-RAISING. 113 away from under the cream. For many reasons the former method is to be preferred. 50. The Swartz Method of Cream-raising. This method, devised in 18G3 by Gustav Swartz, of Hofgaarden, near Wadstena, in Sweden, requires an area of creaming space per cow of as much as half a square metre, so that there is an excessive demand for creaming space. It is directed in this method that the milk be poured into special vessels, known as the Swartz milk-pans. These are long four-cornered tin vessels, with rounded edges 50 centimetres high, and of a capacity of 36 to 50 litres. The milk is poured in to a depth of 40 centimetres. The milk-pans when thus filled are placed in a long square receptacle, which is made of sufficient size to hold at least six or at most ten cans. They are then packed with ice and left standing from 12 to at longest 24 hours. During this time the milk is cooled down to within a few degrees of freezing point. Swartz recommended that the sweet cream should be immediately churned, and he thus gave an impetus in Sweden and Denmark to the first attempt to introduce sweet-cream churning on a large scale, and to place upon the world's market sweet-cream butter (fresh butter) as a keeping butter. 4s soon as the warm milk is placed in ice all vertical currents cease, since cooling takes place chiefly on the bottom and sides of the milk-cans, and not from above. Only currents flowing in almost a horizontal direction, from the outside to the inside and vice versa, take place, which, so long as the milk-can is not broader than say 16 to 20 centimetres, do not to any extent hinder the fatty globules in their ascent to the surface. According to the author's observations, warm milk when placed in ice in Swartz milk-pails requires from three to four hours to cool down to about 10 C. It stands, therefore, for several hours at temperatures at which the opposition offered to the movement of the fatty globules is comparatively slight. This, and the complete absence of vertical currents, are the causes why more fatty globules rise into the cream-layer in the Swartz method, during the first hours of cream-raising, than in any other older methods of cream-raising. Even after 12 hours the yield of cream in the Swartz method is almost always greater than in the Holstein method under similar conditions. As soon as the temperature of the milk falls below 10 C., the opposition in the milk-serum rapidly increases, and impedes the motion of the fatty globules to the surface more and more with the lapse of time. After 24 hours the ( M 175 ) H 114 SCIENCE AND PRACTICE OF DAIRYING. yield of cream in the Swartz method is almost always less favour- able than in the Holstein method, and still more so after 36 hours. In general, it may be said that it is not possible with the Swartz method to get in the course of the year so much fat as is possible with other methods, as for example, with the Holstein or the Gus- sander methods. The Swartz method is only suitable for dairying in which the production of perfectly sweet cream and skim -milk is the object aimed at, and in which the highest possible yield of butter is not aimed at, but where it is desired rather to produce skim- milk of not too poor a quality. Such conditions occur in all dairies where the proprietors are in a position to utilize the perfectly sweet and moderately skimmed skim-milk for cheese-making, or for the rearing of calves, so that a greater return may be obtained for the gallon of milk under these circumstances than if the largest possible yield of butter were obtained at the expense of the condition of the skim-milk. The Swartz method is therefore of great value in many dairies, and will continue to possess that value wherever skim-milk is made to any extent into cheese. It has been introduced with peculiar disadvantage into dairies in which the only object is a high yield of butter, and in which no cheese is made. In the Swartz or ice method, for the cooling of every kilo. (2J Ibs.) of milk, on an average '85 kilo, (about 2 Ibs.) of ice is used. For North Germany, Sweden, and Denmark the price of a kilo, of ice, taking into account the outlay, the depreciation, and the interest on the ice-house, is about '32 pfennig. The cooling costs about 27 pfennig. This is equal to 6 marks per cow (yielding 2000 kilos. of milk in the year). The expense of an ice-house, built according to the Danish method, and suitable for treating the milk of 200 cows, amounts to about 6000 marks, and to about 4500 marks for an ordinary ice-cellar, capable of treating the milk of about 100 cows. 51. The Cold Water Method. A variation of the ice method is the cold water method, 1 which in its correct form only differs from the former by the fact that an abundant supply of cold running water is used instead of ice in cooling the milk, and that the milk is left to cream for 36 hours or longer. In this method, the yield of fat from milk is, on an average, greater than is the case in the ice method. It is admirably suited for hilly districts in which the supply of cold 1 An application of this method, under the name of the Jersey Creamer, has attained con- siderable popularity in England. Editors English Edition. THE COLLECTION AND STORAGE OF ICE. 115 flowing water is abundant, but the method is not suited for districts in which this is not the case. An attempt was formerly made in North Germany to introduce a method of cold water cooling, which consisted of cooling with water that had been pumped through ice, or with spring water that had been allowed to flow through a suitable ice-house or ice-metre. This attempt, however, has met with little success. 52. The Collection and Storage of Ice. As the opinion is becom- ing more prevalent every day that ice is indispensable for all the best- equipped dairies, it may be not out of place to add to the description of the ice method given in 50 a few words on the most suitable method for storing ice. Very few dairies are in the position of being able to purchase at economical prices the supply of ice they require from day to day. Most of them are forced to lay in for themselves larger quantities of ice, and to keep these for a long time in blocks or in ice-houses. For this purpose, the great difficulty is to minimize, as far as possible, the loss which is apt to take place through melting during warm summer weather. The loss is partly due to the contact of the vessels containing the ice with air, or some solid body which has a temperature above the melting point of ice, but to a far greater extent to the fact that during the warm weather a stream of warm air is constantly passing night and day over the surface of the ice- layers. All spaces in the ice-layer filled with air yield up their heat to the ice, and melt a certain quantity of it. The confined air finally assumes the temperature of melting ice, and becomes of heavier specific gravity than the warm air outside, and tends to sink, owing to its weight, through all the fine pores and crevices surround- ing the lower portions of the ice-heap, outwards, and is replaced by warm layers of air coming in from above and from the sides. If ice be preserved in layers, as is commonly done, or in wooden ice-cellars or in wooden ice-houses, it should be surrounded with sub- stances which are bad conductors of heat, and which keep the air from occupying the interstices and pores, besides offering a barrier to the movement of the stream of air. In this way the loss through melting may be largely diminished. If it were possible to prevent absolutely the movement of air over the blocks of ice, the loss would be reduced to a very slight extent, provided the surface remained dry. For this reason it is necessary to take precautions to provide a good covering material for the roof. Sawdust, turf, and ashes are 116 SCIENCE AND PRACTICE OF DAIRYING. well suited for this purpose. It is further important to keep the covering material always dry, since it loses its properties as a bad conductor of heat when it becomes wet. It may, indeed, generate a certain quantity of heat through becoming fermented. It is further necessary to provide every space which contains a heap of ice with a chimney, so that evaporation of the water from any ice that has melted may be allowed to take place, and the covering material thus remain dry. Every ice-store should also be built in such a way that the melted water may quickly run away. Ice should preferably be kept in houses with solid walls which effectually keep out the air, and which are sunk considerably under- ground. They should only possess one entrance towards the top of the building, and it should have double doors and a drain for allowing the melted water to run off. A covering is not only unnecessary, but in the case of its being of an organic nature, it is positively a disadvantage. In such houses the passage of air currents over the layers is very much impeded. The less the intervening spaces between the layers of ice are, the less will be the quantity of air coming into contact with the layers. For this reason it is desirable that ice should be kept in regular rectangular four-cornered pieces, which may rest close together, and which should be cut, not by breaking, but by sawing. It is advis- able to fill up the spaces between the separate pieces with sawdust. Small pounded ice is not suitable for this purpose, nor is it effected by pouring water in cold weather over the layers of ice. The fewer the pores in the ice the better it keeps. On this account firm good ice only should be used, not such as has been subjected for some time to the action of a thaw. In order to obtain ice which is hard and smooth on all sides, special blocks should have the snow cleaned off them after every snowfall. Ice for use should never be taken from the lower portion of the layer. If this be done, every time the ice-stack is opened the cold heavy air which it contains is expelled, and is replaced by warm air, which exerts a deleterious action on the keeping of ice. If, on the other hand, the ice-stack is opened from above, the cold heavy air remains in the stack, and the warmer lighter air from outside cannot penetrate down into it. Ice should be laid in during frost, and snow during a thaw. A snow- stack collected during a thaw, and well compressed, lasts under similar conditions even better than an ice-stack, because it contains fewer air-spaces than the ice-stack. METHODS OF CREAM-RAISING. 117 By a unit of heat is meant the amount of heat which is necessary to raise 1 Ib. of water one degree from the melting point of ice, that is, from to 1 C. The quantity of heat which will raise 1 Ib. of water at any temperature one degree, or, vic& versd, the quantity which must be removed from 1 kilogram of water in order to reduce its temperature one degree, is so similar in amount to that amount of heat which we have just described as constituting a unit of heat, that it may be regarded as the same. According to De la Provostaye and Desains, and Regnault and Petit, the latent heat of water may be taken at 79*25, or, roughly speaking, 79 units of heat on the Centigrade thermometer. In order, therefore, to convert 1 Ib. of ice at C. into water at C., as much heat is required as will convert 1 Ib. of water at C. to 79 C., or to raise 79 Ibs. of water at any temperature 1 C. 1 Ib. of water at 79 C. will be reduced to C. by 1 Ib. of ice after the ice has been melted, or will cool by one degree 79 Ibs. of water of any temperature. Vice versd, I Ib. of ice at C. in melting cools down 1 Ib. of water at 79 C. to C., or will reduce 79 Ibs. of water at any temperature by one degree. In these statements no account is taken of the loss or gain of heat due to surroundings. The specific heat of milk of average chemical composition water being taken as 1 is, as was stated in 4, about '85. In order to cool milk, therefore, there is required only 85 per cent of the quantity of ice that would be required to cool an equal quantity of water. The question whether it is economical and desirable to use ice-manu- facturing machines in dairies has not been properly investigated. According to M. Schrodt's experiments, it would seem profitable to use such machines in very large dairies in towns where ice is unusually expensive to procure, but certainly not in small dairies, or in dairies which can obtain their ice cheaply. 53. Methods of Cream-raising. Before the days of milk-centri- fugal machines, and while the old methods of cream -raising were being perfected, the merits of different methods were often attempted to be tried by comparative tests. In Denmark this was attempted to be done by working on milk of the same origin, churning the cream separated, determining the yield of butter, and regarding as most suitable the method which yielded the largest quantity of butter. This method, although somewhat cumbersome and involving many inaccuracies, had the advantage of not requiring chemical investiga- tion. It is not suited, however, for reliable comparison. The author preferred for this reason, in his comparative experiments, which were likewise carried out on milk of similar quality, to determine the percentage of fat in the milk and the skim -milk, as 118 SCIENCE AND PRACTICE OF DAIRYING. well as the weight of the cream obtained, and to calculate what percentage of the entire fat in the milk was obtained in the cream. This percentage number he called the cream-yielding coefficient. This method has been followed by others. As the cream-yielding coefficient depends not only on the per- centage of fat in the skim-milk, but also on that of the whole milk, and on the relative weight of the cream and the skim-milk, it affords an exact indication of the yield of cream in different cases, provided the milk used in the experiments has a similar percentage of fat, and that the relative weights of the cream and the skim -milk remain constant. The calculation of the cream-raising coefficient is very simple, as the following example will indicate : 100 Ibs. of milk containing 3*4 per cent of fat yielded 20 Ibs. of cream and 80 Ibs. of skim-milk, containing -5 per cent of fat. The total quantity of milk contained, therefore, 3 '4 Ibs. of fat. In the skim-milk there remained = -4 Ib. of fat. 100 In the cream, therefore, there was 3 Ibs. of fat. These 3 Ibs. make l: 9 = 88'24 per cent of the total quantity of the 3-4 Ibs. of fat. The cream-raising coefficient is therefore 88'24 per cent; that is, 88-24 per cent of all the fat contained by the milk was yielded in the cream. In the case of a sample of milk containing the average quantity of 3 f 4 per cent of fat, and yielding on an average 15 per cent of cream, in the Holstein method, and allowing 36 hours for cream-raising, the cream- raising coefficient throughout the year would average 84 per cent. The skim-milk, therefore, would contain in this case '64 per cent of fat, and if 97 per cent of the fat in the cream were converted into butter containing 84 per cent of fat, then from 100 Ibs. of milk 3 '3 Ibs. of butter would be obtained, or for every Ib. of butter obtained, 30 '3 Ibs. of milk by weight are used. Under similar circumstances, it will be found in practice in the ice method of creaming, when the cream-raising period lasts for 12 hours, that the cream-raising coefficient on the average of a year will amount to 74 per cent. In such a case the skim -milk would contain T04 per cent of fat, and for every 100 Ibs. of milk 2 -91 Ibs. of butter would be obtained. That is, 3 4 -3 7 Ibs. of milk are used for every pound of butter produced. In all the older methods, creaming was effected through the influence of gravity, which is practically always the same. It is CENTRIFUGAL FORCE. 119 quite different, however, in creaming milk in centrifugal separators, for in this case the force can be regulated at will within compara- tively wide limits. In such a method, the aim is to separate the largest possible amount of the fat, by centrifugal action, which is much more powerful than the force of gravity, and which in the older methods, depending on the force of gravity, was not obtainable. An accurate indication of how far this is effected is furnished by the percentage of fat present in the skim-milk. The creaming coefficient is not an indication of this. 54. Centrifugal Force. One of the common properties of matter is its inertia. This is manifested in a body by the opposition it offers to any change in its motion. Any such change must be effected by force. Inertia acts in such a way, that a body set in motion tends to maintain the direction of its motion unchanged, i.e. in a straight line. If a body is forced to move in a circle, in every point of its movement it manifests a tendency to move at a tangent to each point of the circle. The direction, therefore, to which it tends to go has to be changed from point to point. The force which effects this is known in physics as centripetal force. It is produced when a body is swung round in a circle at the end of a string by the tenacity of the thread, and in the case of a liquid being put in circular motion in a vessel by the sides of the contain- ing vessel. Since every force requires a counter force, a force which acts in exactly similar but opposite direction, every body moving in a circle is subjected to a force which moves from the centre in the direction of the circumference along the radius, a force exactly similar in its manifestation to the centripetal force. This force is called the centrifugal force. The centrifugal force is the force which overcomes the inertia of the material, and represents the resistance offered by a body in motion, to change in its direction of movement, and acts upon every body, moving in a curve, that is, in a line, the direction of which changes from point to point. In 6 the acceleration 0, which the fatty globules experience when they are subjected to the action of centrifugal force, was shown to be capable of being calculated as follows: In which a L indicates the factor, representing the inertia, 8 and 8 1 the viscosity of the milk-serurn, and the butter- fat; n the Ludolph 120 SCIENCE AND PRACTICE OF DAIRYING. number, u the number of revolutions of a fatty globule in a minute, and r the radius vector of a globule. From this formula, it is seen that the centrifugal force acting on the fatty globule is in simple proportion to the distance of the globule from the centre point around which the revolutions are made, and increases in quadratic proportion to the revolutionary speed. 55. The Value of Centrifugal Force for the Creaming of Milk. The natural force of gravity, which is universally and at all times freely available, and which was formerly exclusively used in cream- raising, acts with uniformity. Not merely does it require a certain time in which to obtain the best possible results, but even under the most favourable conditions it fails to obtain complete separation of the cream from the milk. Much more perfect separation, and a shortening of the time necessary for cream-raising, can only be effected by the application of a force, which will impart to the fatty globules an impetus far exceeding that given by gravity. This force is centrifugal force. It is not to be had gratis, since its application costs money; but it is at all times easily utilized for the purpose of cream-raising, and can be applied in such a manner that its force exceeds that of gravity to the extent of more than a thousand-fold. It is only necessary to subject the milk, in suitable vessels, to a very rapid rotatory motion. The idea of utilizing this force in dairying, and thereby of curtailing the period for the separation of the cream, does not date further back, it would seem, than the middle of the century, when C. J. Fuchs carried out experiments in Carlsruhe on cream separation by centrifugal force. About 1860 similar experiments were carried out by Albert Fesca, in Berlin, and, in 1864, by Antonin Prandtl, in Munich. It was first demon- strated to be practical in 1877 by the German civil engineer William Lefeldt, in Schoningen, in Brunswick, who, after more than fifteen years of arduous experimentation, succeeded in producing a milk- separator, which, if imperfect, was nevertheless practical. Since 1877 the structure of milk-separators has been improved from year to year, and at present there are quite a number of serviceable separators of different structure known by different names. At present all separators are so arranged that when at work they are fed with a continuous stream of milk, and give out in return separated cream and skim-milk. The utilization of these highly serviceable machines has extended more and more, especially since efficient separators, capable of being driven by the hand, have been devised, and they MILK IN THE SEPARATOR-DRUM. 121 Fig. 28. Sectional Illustration of the Alexandra Cream-separator. 2, Float for regulating inflow of milk from large receiving tin ; 3, strainer for new milk ; 107, cast- iron cover ; 108, inlet funnel holding strainer for new milk ; 109, inlet tube in which No. 108 fits to lead new milk into steel cylinder No. 9 ; 6, large tin cover over which the separated milk flows ; 7, small tin cover over which the cream flows ; 9, steel cylinder in which milk is separated ; 10, screw for regulating thickness of cream ; 11, outlet tube for cream ; 12, outlet tube for milk; 13, cast-steel spindle with ball-shaped head, on which the steel cylinder rests and balances itself perfectly in running ; 14, steel pin for bottom of No. 13, which when worn can be taken out by being heated slightly, and another put in ; 15, steel balls for footstep bearing, on which No. 14 runs ; 83, steel set-pin with lock nut for all bottom bearings : by slackening the lock nut and screwing this set-screw to the right or left the spindle No. 13 can be raised or lowered as desired; 84, bevel pinion with 23 teeth, and spur-wheel with 120 teeth; 85, steel pinion with 16 teeth on spindle with leather wheel; 86, leather spur-wheel with 98 teeth and brass flanges each side ; 87, steel pinion with 17 teeth on No. 13 ; 88, steel spindle for carrying leather wheel ; 89, steel spindle for bevel pinion and spur-wheel ; 79, brass bush- ing for No. 88; 80, bottom bearing for No. 79; 81, bottom bearing for No. 13; 82, bottom bearing for spindle with bevel pinion ; 65, bevel wheel with 108 teeth ; 49, handle ; 48, handle spindle ; 28, main bushing for spindle ; 110, india-rubber ring for No. 28, to give elasticity to spindle and prevent vibration with bowl; 111, thin india-rubber ring for cast-iron top, to make same water-tight; 76, cast-iron casing with fastenings and thumb nuts holding cylinder; 77, cast-iron casing holding gearing 78, cast-iron base which can be taken out by unscrewing set-screws and putting the two screw handles sent with each machine in their places. 122 SCIENCE AND PRACTICE OF DAIRYING. are every day displacing to a larger extent the older methods of cream-raising. Up till 1886, the only kind of separators used were the larger separators driven for the most part by steam-engines, or horse-power, and in a few cases by other motors, and the application of which only paid in large dairies. For the sake of simplicity the larger machines driven by steam, &c., may be designated power- separators, as distinguished from separators driven by manual power, which may be called hand-separators. [The illustration in the preceding page of a section of the Alex- andra cream-separator, with the explanation of parts, has been inserted by the Translators to assist students in understanding and describing the construction of the separator.] 56. Milk in the Separator -drum. That portion of the separator which is destined to hold the milk, and which is known as the drum, forms the essential part of every separator, and revolves round a horizontal or vertical axis. Whatever its shape, whether cylindrical or bulbiform, round or pear-shaped, &c., it must always be a rotat- ing body. When in motion, and filled with milk, the force of gravity acting upon the separator-drum may be neglected, when compared with the centrifugal force, which is several thousand times stronger; indeed the force of gravity may be said to be replaced by centrifugal force, and one may assume that the same action and conditions take place in the milk, when shut up in the revolving separator-drum, as take place when milk stands quietly at rest. Just as milk, which is poured in a slow, steady stream into a milk-pan standing at rest, finds at once the lowest part of the can, namely the bottom, and spreads itself over the bottom in a horizon- tal layer, and gradually fills the vessel from the bottom to the top, so does milk allowed to flow into a separator-drum, when revolving, find its way with lightning-like rapidity to the most distant part of the drum, and there spread itself out in a ring bounded by a free and almost cylindrical surface, and the drum is thus gradually filled from the outside to the inside, that is, in a direction exactly opposite to that of the direction of the centrifugal force. All separator- drums, without exception, when in motion, and when the milk is allowed to flow in, are thus filled from the remotest part of the wall to the axis round which the drum revolves. It is quite immaterial what part of the drum the milk flows into. Any other method of filling is inconceivable. THE INFLOW OF MILK INTO THE SEPARATOR-DRUM. 123 Just as milk, standing in a milk-pan at rest, exercises a pressure on the bottom and sides of the pan, due to the force of gravity, so precisely milk, in a separator-drum in motion, exercises a pressure on the sides of the drum, which is caused by centrifugal force, and which is proportional to the strength of that force. In the same way, just as in milk, standing in a milk-pan at rest, the fatty globules move upwards, in a direction opposite to that in which gravity acts, so the fatty globules in a separator-drum, filled with milk and in motion, travel in a direction opposite to that of centrifugal force, that is, from outside to inside. In this case, as in the former case, the layer of cream rises to the surface, which in the separator-drum is that portion nearest to the axis of revolution. 57. The Inflow of Milk into the Separator-drum. The drums of many of the older separators suffered from this disadvantage, viz. that the milk, flowing into them when revolving, was led in on the top of the cream layer, through which it naturally at once sank on account of its high specific gravity. This influenced the amount of fat obtained. Nearly all the drums of the newer separators are so arranged that the milk flowing into them is led in by a suitable arrangement to the inside of the circle of milk, and in this way the very considerable force with which it has to press through the layer of cream is avoided, and the full yield of fat is thereby obtained. 58. The Outflow of Cream and Skim -milk from the Separator- drum. The outflow of the liquid from a filled separator-drum in motion takes place with considerable energy, and is due to the driving power employed, being in no way connected with the centri- fugal force. This force is greater the further the spot is from the revolving axis. Its amount is proportional to the square of the rapidity of the revolving motion at this place, and increases, in a simple regular proportion, with the radius vector of the spot of outflow. In order, therefore, to reduce as far as possible the force with which the liquid flows out, and thus to effect a saving in motive power, the exit for the outflow of cream and skim-milk is chosen as near the revolving axis as can be. The exit for the cream can be placed directly on the surface of the ring of milk, that is to say, as near as it can possibly be to the axis; whereas the exit for the outflow of skim-milk, on account of the higher specific gravity of this liquid, must be placed slightly further back. The skim-milk is con- ducted either by means of tubes, which run back to the wall of the drum to the surface of the milk-ring, or by means of a special space 124 SCIENCE AND PRACTICE OF DAIRYING. made in the drum, and which is only accessible from the wall of the drum, and into which only skim-milk can come. The surface of the skim-milk is thus brought as near as possible to the revolving axis. In the case of such separators as those of Burmeister and Wain, the cream and skim-milk are conducted from the surface, by means of skimming-tubes, to the outside. 59. The Regulation of the Proportional Weights of Cream and Skim-milk in the Separation of Milk by Separators. In the drum of every separator in use, the amount of cream and skim-milk which flows out must be together equal to the amount of milk which flows in. The proportion of the weight of cream to skim-milk is deter- mined by the rapidity with which the milk enters the separator, and in all separators, therefore, without exception, can be regulated at will by this means when the separator is in motion. By this method of regulation the amount of the cream obtained will be altered, a thing which does not happen with an arranged equable motion. For this reason, in almost all separators there are arrange- ments whereby it is possible at will to regulate the quantity of cream with a uniform inflow of milk. In the case of the separators of Burmeister and Wain this is effected by sinking the skimming- tube for skim-milk, either deeper or shallower, in the surface of the liquid, a thing which can be very easily effected when the drum is in motion. In the case of most other separators, the necessary precautionary measures should be taken before creaming begins, and while the drum is at rest. Where the place of outflow for the skim-milk is equidistant, and where the conditions under which the milk flows out are otherwise the same, and the outflow of the cream is riot in any way hampered, the more milk that enters the drum in a definite time, the more cream will be given out, the slower will the drum revolve, and the cooler will be the milk which is to be creamed. The first case needs no further explanation. With regard to the second, less skim -milk flows out in a definite time under reduced pressure, and in consequence of this the surface of the milk- ring is slightly moved towards the revolving axis, while in the third case the friction towards the outflow exit is strongly increased, in virtue of which the amount of skim-milk flowing out in a definite time is somewhat diminished. 60. The Size and Reliability of Separator-drums. The following regulations are deduced from the equations given for calculating the acceleration of separators in 54: THE SIZE AND RELIABILITY OF SEPARATOR-DRUMS. 125 (1) In the case of two exactly similar separator-drums making an equal number of revolutions per minute, but one twice as broad as the other, the acceleration in the former at the spot furthest from the centre is double that of the latter. (2) In the case of two perfectly similar separator-drums of exactly the same size, but one of which revolves at double the rate of the other, that is, has twice the speed of the other, the centrifugal acceleration on the spot furthest removed from the centre is four times as great in the former as in the latter. From this it will be seen that the action of centrifugal force on the milk may be increased in a double manner, namely, either by increasing the size of the separator or by increasing its speed. Since, however, in the case of doubling the diameter of the drum the action is only increased twofold, but, in doubling the speed, fourfold, the second method will be seen to be the more efficacious. The second method is also to be recommended on other grounds. Large drums are less handy, and are more difficult to work than small ones. Since large masses of metal of a perfectly uniform firm quality are more difficult to be obtained than small masses, there is required for large drums a greater degree of security; in other words, the revolving speed of large drums must be measured with very special care, and this can only be done at the expense of efficiency. Finally, it must be borne in mind that large drums which effect the creaming of large quantities of milk in a compara- tively short time require a comparatively large driving power, and that it is more convenient, and generally also cheaper, to utilize a comparatively low driving power for a longer time than a large driving power for a short time. For this reason the use of large drums, such as were formerly largely made, has decreased in the course of time more and more, since they have not been found to be suitable in practice. Separators under 50 kilograms (212 Ibs.) in weight are now generally used with drums, and they can only hold when in work a few kilograms (10 to 20 Ibs.) of milk, generally between 4 and 8. The smaller of these drums is worked at a speed of 6000 to 9000 revolutions per minute. In the case of most of the separators at present in use, milk which has to be separated only remains a short time in the drum, often not one minute, and rarely more than three. When the separator is in use, the sides of the drum have to stand very considerable internal strain, owing to the pressure of the milk 126 SCIENCE AND PRACTICE OF DAIRYING. and their own weight, and must on that account be very strong. The first and most important quality of every separator-drum is its strength. 61. Milk-separators at Present in Use. Since 1877, the construc- tion of separators has been improved from year to year. While the usefulness of separators has far exceeded the most confident expectations at first entertained, it cannot be asserted that we have yet reached their limits of capability; indeed, it would appear as if we had now reached a point from which a fresh start towards further improvement could be made. Not taking into account some of the separators of antiquated construction, and the separators which, although no longer made, are still in use in various places, we find that there are only five different kinds of separators for power-use, and six for hand-use, employed in German dairies, regarding which the following details may be given. 62. The Lefeldt Separator. In the manufactory of Lefeldt and Lentsch at Schoningen, in the Grand Duchy of Brunswick, seven separators of different sizes and construction are made at present, of which three are worked by steam, one by a winch, and three by hand. Separators for hand-use were first constructed in 1877. The separators worked by power have undergone many changes in their construction from the introduction of the first in 1877 to the one at present in use. From the end of 1879 they have been constructed for continuous use. They are sold under a guarantee, and can be unreservedly recommended. The separators worked by power (fig. 29) require good, pure lubricating oil. Of exactly similar construction as at present made, only of different sizes, are the three separators, Nos. 0, 1, and 2, for steam- use. At present a new separator is being made in this manufactory, which is to be called the " multiplex ". The three separators, Nos. 0, 1, and 2, have cylindrical upright drums closed above and open below, constructed with Siemens-Martin steel, with four continuous flanges, and with a thickness in the case of (0) and (1) of I'l centi- metres, and in the case of (2) of 1*4 centimetres. The largest internal diameter measures in the case of (0) and (1) 30, and in the case of (2) 40 centimetres. The first-mentioned two have an under opening of 20 centimetres, and the last of 30 centimetres broad. The milk coming in, runs first into a bowl-shaped aperture in the upper portion of the drum, and is conducted hence by means of THE LEFELDT SEPARATOR. 127 canals, which lie behind the layer of cream formed during the motion, into the internal portion. The cream flows over the surface of the lower circular opening into the lower space of the covering of the drum, and the skim-milk is conducted by means of four tubes, leading almost to the edge Fig. 29. Lefeldt's Separator. (Section.) of the drum and the drum-lid, and passes through the drum-lid into the neighbourhood of the surface of the ring of milk, where it is conducted into the upper covering. By setting the drum in motion one can make the exit for the skim-milk at the upper end of the tube narrower or wider, so that during the operation more or less cream may be obtained. A hand- 128 SCIENCE AND PRACTICE OF DAIRYING. indicator is connected with the well of the drum. After creaming has been effected, the drum, gradually settling to rest, empties itself. The three separators for hand-use, Nos. '0, 0, and 1, and the separator for the winch, possess an improved arrangement which Fig. 30. Arnoldt's Hand Separator. (Perpendicular Section through the Drum.) has been devised lately by the senior engineer of the factory, Herr Oswald Arnoldt (fig. 30). The milk enters through one of the taps, and the cream and skim-milk are conducted away through separated divisions of a tap, which is surrounded by double rings of white metal. Their thick- ness in the case of No. (0) is exactly '1, and in the case of the others *3 centimetre, and the greatest internal diameter in the case of (0), (0), and (1), and (2) (for winch power) is respectively 5, 9, 9, and 11 '5. Further details are contained in the following table: SEPARATORS MADE BY THE SEPARATOR CO., STOCKHOLM. 129 Number of Lefeldt Separator. Weight of Drum with Spindle. Milk Contents of Drum in Motion. Number of Revolu- tions per Minute. Milk Separated Horn-. The Cost Observations. of Separator. of Gearing. Ky. Kg. Kg. M. M. O 27-5 6-0 7,000 600 500 100 Steam-power. I 32-5 9-0 6,500 900 750 100 II 66-0 16-0 6,000 1200 1000 150 oo O 3-00 5-50 0-3 1-3 10,000 8,750 60 100 175 250 TI ,1 ^l 45 ~ 50 Hand ^handle-turns I 7-25 2-3 8,750 250 500 P wer l per minute. II 9-25 4-0 8,750 400 600 100 Winch. 63. Separators made by the Separator Co., Stockholm. This com- pany is represented in Germany by the Bergedoff Iron Co., in Bergedoff, near Hamburg, and makes in all, at present, four- teen different separators for machine and hand use. They may be divided into separators of the De Laval and the Alpha types. (a) De Laval Separators. Of these there are at present two kinds. The De Laval separators have in course of time been very much improved. The first was introduced into Germany in 1879, and was used at the co-operative dairy at Hamm, in Hamburg. It was the first employed to do con- stant work in Germany. Its drum had three independent parts, which were screwed to- gether, and were made tight with rubber rings. In the year 1881 the arrangement of the drum received its first improvement, which consisted in replacing the three independent parts by one piece, consisting of a cup-like box provided with flanges. In 1883 the drum received the simple form which it still retains. In the year 1886 Dr. De Laval invented his steam-turbine, which he ( M 175 ) I Fig. 31. Steam-turbine Separator. 130 SCIENCE AND PRACTICE OF DAIRYING. applied directly to the separator, and by means of it he imparted to the creaming of milk by centrifugal machines a simplicity that had been previously undreamt of. The first steam-turbine sepa- rator, worked in Germany, was used in the co-operative dairy at Elmshorn, in Holstein, where it was placed in the beginning of the year 1887. By means of the turbine the use of steam-engines and the customary con- nections for securing speed could be dis- pensed with. Thus was effected a large saving of plant, of capital, of space, and of lubricating oil, while the efficiency of the work was increased. In order to set it in motion, all that is necessary is to press the cock gradually up- wards, which connects the steam with the turbine. The De Laval separators (figs. 31 and 32) require, there- fore, according to the claim of the manu- facturer, steam of only 45-lbs. pressure, and the Alpha, steam of only 30-lbs. pressure. Nevertheless it is advis- able to use steam of 60 and 45 Ibs. pressure respectively. The De Laval separators are especially characterized by the simplicity of their structure and their serviceableness, and by the fact that they are not easily susceptible to disturbing influences. They are excellently suited for private dairies in which creaming is necessarily left to unskilled workers. They have stood the test of Fig. 32. Perpendicular Section of Steam-turbine Separator. SEPARATORS MADE BY THE SEPARATOR CO., STOCKHOLM. 131 time, and can be unreservedly recommended. So also can the Alpha Fig. 33. Two Laval Separators with Milk Wanner. separators, which have been well tried, and which have given great satisfaction wherever they have been used. Fig. 34. Perpendicular Section through the Drum of the Laval Hand Separator. The upright drums, open at the top, and -9 cm. broad in their broadest place, are made out of malleable cast steel, have a bulbous form, a cylindri- cal-shaped neck, 11-2 centimetres in width, and a large internal diameter of 132 SCIENCE AND PRACTICE OF DAIRYING. 28 -8 centimetres, and a continuous flange inside. In the case of No. 2 the drum is somewhat higher. The milk which comes in falls through the top opening of the drum into a cup 5*2 centimetres wide, resting upon the foot of the drum, and flows from this to a tube under the layer of cream, formed dur- ing the operation. The cream runs outwards through a narrow, shallow slit in the side of the neck of the drum, and the skim- milk through a tube leading up from the widest part of the drum, then through a small opening about half- way up the neck of the cylinder, which can be set, when the drum is at rest, either narrower or wider, and of course each liquid by itself runs into a special circular-shaped re- ceiver at the top of the cover. A simple indicator, which is placed in the well, renders it possible to determine the rapidity of the re- volutions of the drum per minute. Fig. 35. Alpha Separator No. 1. (Perpendicular Section.) (6) De Laval Hand-separators. Dr. De Laval devised the first useful hand-separator in 1886. At present two such machines are made, the separator (K), which has a horizontal cylindrical drum, and the Baby separator, which has a vertical cylindrical drum. The drums of both these separators have short cylindrical necks, THE SEPARATORS OF BURMEISTER AND WAIN. 133 two continuous ilanges in the inside, and a thickness of '25 centi- metre. The hand-separator (K) has a horizontal drum, which, in the widest place in the inside, is 10 -7 and in the neck 6 -7 centimetres wide. The milk enters at one side of the drum, and on the other it passes through an opening in the neck of the drum, the skim-milk being separated by means of two white-metal tubes, which surround the neck of the drum. One of these tubes, when the drum is at rest, can be adjusted either narrower or wider. The Baby separator is, in essential points, of similar construction to the separators for machine use. The drum is internally 9 -8 centimetres, and round the neck 6 '6 centimetres wide, and is set in motion by means of a toothed wheel. Both separators attain their maximum speed when the handle makes 40 revolutions per minute. We have to thank the Bergedoff Iron Works for the following details: Number of Separator. De Laval. Weight of the Drum with Spindle. Milk Contents of Drum in Motion. Number of Revolu- tions per Minute. Milk Separated in the Hour. The Cost Observations. of Sepa- rator. of Gearing. Kg. Kg. Kg. Marks. Marks. A I 20-5 6-0 7000 400 550 100 Machine-driven. All 25-0 8-2 7000 600 800 100 > E I 20-5 6'() 7000 400 1100 Steam-turbine. E II 25-0 8'2 7000 600 1500 JJ K 4-5 1-6 7000 150 550 Hand -use (hori- zontal drum). Baby 3'5 0-8 6400 50 260 Hand-use (verti- cal drum). (c) Alpha Separators for Machine Use. These have been known in Germany since 1890, and at present three different sorts are manufactured, viz. Nos. (1), (2), and the Alpha pony (fig. 35). (d) Alpha Separator for Hand Use. These at present in use are of three numbers: Alpha K with horizontal, and Alpha B, as well as Alpha S or Baby, with perpendicular steel drum (figs. 36, 37, and 38). The drums of these three machines attain their most favour- able speed when the handles make forty revolutions per minute. 64. The Separators of Burmeister & Wain. As early as the year 1872, the well-known chemist, Storch, of Copenhagen, drew the attention of Danish agriculturists to experiments carried out by 134 SCIENCE AND PRACTICE OF DAIRYING. THE SEPARATORS OF BURMEISTER AND WAIN. 135 136 SCIENCE AND PRACTICE OF DAIRYING. Antonine Prandtl in Munich, regarding the separation of cream from milk by centrifugal force. In consequence of this, in 1873, experi- ments were conducted with the Eimer centrifugal separator, and an engineer, Mr. P. J. Winstrup, undertook the construction of a milk-separator. He made experiments in 1878 with a separator constructed by himself in the dairy of States- Councillor Valentine in Jeddesdal, and in 1878 brought out a workable separator, which, however, was not largely adopted in practice. In the mean- time, several other en- gineers, particularly L. C. Nielsen, had been occupying themselves with the construction of milk-separators. In the year 1878, there had been set up on a farm near Copenhagen a separator for regular work, Kongen's Ny torf separator No. 10, de- vised by L. C. Nielsen, and made in the manu- factory of Peterson Brothers in Magle- kilde, near Roskilde. In the course of a year it was distinctly im- proved, and in the year 1879 it was changed into the form which it at present possesses, and quickly became known under the name of Nielsen & Peterson's patent separator. In the year 1881, the Engineering and Ship-building Co. of Burmeister & Wain bought the patent of 1878, and since that time the separator has been known as Burmeister & Wain's separator (fig. 39). It has been extensively used, especially in Denmark itself. It is warranted, and Fig. 40. Hand-separator (Burmeister & Wain). THE SEPARATORS OF BURMEISTER AND WAIN. 137 can be unreservedly recommended. At present four other separators are used or made, the bowl-separators (A) and (B) for machine use, the separators (X 1), (A), and (X 2) for hand use (figs. 40 and 41). The separators of Burmeister & Wain are characterized by their elegant construction and their smoothness of working. They allow the quantity of cream to be regulated during the revolution of the drum, und alone among separa- tors offer the extremely and uni- versally valuable advantage, that it is possible, if desired, to pump up the cream and the skim -milk several metres in the ascending tubes. Cream and skim -milk gush out at the end of the exit tubes more strongly than is the case with other separators. Owing partly to their fine construction, they require to be carefully and intelligently handled. They are provided with a self- acting security arrangement, which prevents an increase of the speed above the regulated degree. It may be added that these separators may be used in the simplest manner for pre- paring emulsions of oil and skiin-milk for calf feeding. The following are the dimen- sions of a number of separators made by Burmeister & Wain: Fig. 41. Burmeister & Wain's Hand-power Separator. (Perpendicular Section.) 1 dumber of Separator. Burmeister & Wain. Weight of the Drum without Spindle. Milk Contents of Drum in Motion. Number of Revolu- tions per Minute. Milk Separated per Hour. Cost of Separator. Observations. A Kg. 120 Kg. 58-0 Kg- 2700 Kk. 1400 Marks. 835 Marks. 425 A A 120 58-0 2700 1400 835 425 B 54 16-5 4000 -700 467 288 XI 3-25 1-25 7200 150 285 X2 3-75 1'66 7200 200 400 138 SCIENCE AND PRACTICE OF DAIRYING. 65. The Victoria Separators. These are made in the works of Messrs. Watson, Laidlaw, & Co., Glasgow, and have been known since the end of the year 1879. Six different sizes of these separators, Fig. 42. Victoria Hand-power Cream Separator. known as (1), (2), (3), (4), (5), (6), have been used in Germany (figs. 42 and 43). The first three are for hand use, the last three for machine use. Up till now these separators lack an arrangement for regulat- THE VICTORIA SEPARATORS. 139 Fig. 43. Sectional View of Victoria Hand-power Cream Separator. 140 SCIENCE AND PRACTICE OF DAIRYING. ing the amount of cream to be obtained from an equal flow of milk. 1 66. The Balance Separators. The discoverer and first patentee of this separator, which was made known at the beginning of 1888, was a Dane, whose nom de plume was Musician. In February, 1888, a similar separator under the name of the Nil son separator was made by the firm of Mot & Co. of Paris, and in the same month a balance separator supplied by the Carl Peter Co. was used on the estate of Emken Dorf in Holstein. The construction of the balance separators has undergone, up to the present time, a number of changes, but they have been compara- tively little tried in practice. The Carl Peter Co., which lias acquired the patent, makes these separators of six different sizes, three for machine use, with drums made of hardened steel, and three for hand use, with drums made of hard hammered copper (fig. 44). 67. The Separators in Use at Present in Germany. The separ- ators at present in use in Germany are of seven types those of Lefeldt, De Laval, Burmeister and Wain, Alpha separators, Victoria separators, Balance separators, and Dr. O. Brown's separators. The first six types include several large separators of different sizes for 1 Messrs. Watson, Laidlaw & Co. point out, on the other hand, that in their machine the proportionate yield of cream is altered by increasing or diminishing the supply of milk, which can be done without stopping the machine. They claim that this method of obtaining thick or thin cream is advantageous, as it obviates the necessity for having any special arrangement in the drum for this purpose. English Editors. Fig. 44. Section of the Balance Separator. THE BEST SEPARATORS. 141 power use, as well also as for hand use. The separators of Dr. O. Brown are hand-separators. Altogether there are used in German dairying 41 separators, 22 for power use and 19 for hand use. The separators of De Laval and Burmeister and Wain are war- ranted. Their merit is established. The Alpha separators have also been proved to be satisfactory, from the results of many exhaustive experiments which have been carried out on them. As to the capa- city of the remaining separators, further reliable experiments and tests are required to enable a correct judgment to be formed, and to prove their practical value. 68. The Best Separators. The value of a separator is determined chiefly, though not exclusively, by its capacity for work. This is best measured by the quantity of milk which it can cream in an economical manner, at a uniform rate of speed, and at a fixed cost per hour, when fed with a regular supply of warm milk at 30 C., the skim -milk to contain an average percentage of fat of '25 per cent. A separator possesses, therefore, the largest capacity for work which creams in an hour, under the above conditions, the largest quantity of milk. Which is the best separator at the present time it is impossible exactly to say. In the middle of the eighties, one might assert that the three at that time most in use differed very little from one another. Among the six different separators for power use which are at present used, much difference, however, exists, since a new advance would appear to have been made in the perfecting of separators, which in time may permit us to await again a certain settlement in the capacity of the different separators. The most efficient separators are not always the best. The best separators may be described as those that are best suited, from a technical and economical point of view, for the special conditions under which they are to be used. Whether a separator will ever be found which will prove to be the best under all conditions, it is impossible to say. It is also very questionable whether circumstances may not exist in which, where very slight differences in their capacities exist, the less capable of two separators may not be preferable, since it may possess certain advantages and conveniences which, although they appear to be of little importance, have yet a material value in the circumstances in which they are used. 69. The Cream-raising Coefficient in connection with the Use of Separators. As has already been mentioned in 53, the extent to which cream has been separated from milk by centrifugal 142 SCIENCE AND PRACTICE OF DAIRYING. force is best ascertained by the percentage of fat in the skim-milk obtained. Considering the efficiency with which separators at present do their work, one is justified in demanding that in dairies where separators are in use the coefficient of cream-raising should be such that a percentage of *2 to '3 on an average '25 of fat is obtained in the skim-milk. It is only under very exceptional circumstances that the skim-milk obtained by separators contains as little as ! per cent of fat. Just as in the case of whole-milk which has been evaporated down to dryness, the fat is less easily extracted by ether, so it is found that, in the gravimetric determination of fat in skim-milk, if not done with care, the percentage of fat may quite easily be placed too low. Examples of skim-milk obtained by separators under ordinary conditions containing less than '15 per cent, or much less than ! per cent of fat, are, therefore, to be viewed with suspicion. 70. The Conditions which Influence the Cream-raising Coefficient in connection with Separators. The coefficient of cream-raising ob- tained with milk-separators depends on the following conditions: (1) On the strength of the centrifugal force used to separate the milk, or on the rapidity of the revolutions of the drum. As has already been pointed out, the centrifugal force increases with the square of the number of revolutions made by the drum in a minute. If the drum of a separator does not revolve quickly enough, or up to the required speed, much fat will remain behind in the skim-milk, which might, with greater care, be easily obtained in the cream. (2) On the time during which the milk is submitted to centri- fugal force, or on the quantity of milk which is creamed per hour. The more milk that is creamed in a given time, the less favourable will the coefficient of cream-raising be. (3) On the temperature at which cream-raising takes place. The warmer the milk the better does it cream. From 5 to 25 C. upwards, the percentage of fat in the skim-rnilk rapidly decreases, and from that temperature always more and more slowly up to the boiling point of milk. These three conditions are of enormous importance, and since they are always under control, it may be said that the success of cream-raising depends on the art and method in which separators are worked. It is further influenced by (4) The construction and nature of the separator. For example, CREAM-RAISING COEFFICIENT. 143 whether the milk-ring in the drum is more or less strong, whether the drum works regularly and quietly, and whether the machine can be conveniently and simply worked. (5) On the special properties of the milk which is to be separated. Under ordinary conditions, milk brought from a dis- tance, or lazy milk, or boiled milk, is less easily creamed than fresh milk of ordinary properties. Perhaps also milk, very rich in fat, is less perfectly creamed than milk containing an average percentage of fat. These conditions are insignificant, and hardly possess any importance in practice. They have a perceptible influence in properly regulated separators only if the creaming takes place at a temperature under 20 C. The numerous experiments carried out during the years 1877-1885 at Raden, with different separators, were the first which distinctly showed that creaming is more effective the quicker the separator-drum revolves, and the warmer the milk is which is to be creamed, and the smaller the quantity of milk that passes through the drum in a given time. They showed, however, that between the percentage of fat (/) in the skim-milk on the one hand, the rapidity (u) of the drum which determined, on the other hand, the quantity of milk (m) creamed in an hour, and the temperature of creaming (t), a certain regular relation existed. Numerous detailed calculations, which the author has made on the basis of a large number of single experiments, show that the truth is very nearly obtained by assuming that the percentage of fat in skim-milk (/) is inversely proportional to the square of the number (u), denoting the revolutionary speed, and directly proportional to the square root of the number (m), denoting the quantity of milk creamed in an hour. The relation of the number (/) to the temperature of cream -raising (t) was found, if (/), denoting the fat percentage of skim-milk at 40 C., lay between the limits of 13 and 40 C. by the equation /-/i-x and this yields also (c) indicates a constant factor, which has been obtained for each separator by means of exact experiments. If the value of this factor has been care- fully fixed for a definite separator, it is easy, as has been elsewhere shown, by the author, to find the exact value of (/) for all values of (u) between J (u') and 2 into (u'\ for all values of (ra) between (J m') and (2 into, ra'), and for all values of (t) between 20 and 40 C. In the case of some 144 SCIENCE AND PRACTICE OF DAIRYING. separators, the author obtained better results if he substituted, in the above formula, for the square root of (m), simply (m). The above formula was well suited for the three separators, which were almost exclusively used up till 1888. As to whether it also suits the Alpha, the Balance, and the Victoria separators in their present form, the author has not yet been able to make investigations. In order always to obtain satisfactory results, the following points have to be carefully observed in practice : (1) That the drum should always revolve at the prescribed rate; to permit it to revolve more quickly may be dangerous (see 60), and if it does not revolve sufficiently quickly there may be a considerable loss. (2) That the milk to be creamed every day should be of suitable quantity, and should enter at as uniform a rate as is possible per hour. (3) That the milk during the whole period of creaming should possess the proper temperature. (4) That the separator should always be in good order, and should be carefully lubricated with good oil. 71. The Supervision of the Revolving Rate of the Drum. For- merly the rate of revolution of the drum was shown by an indicator, which was either in permanent connection with the well of the drum, or was pressed against the head of the well from time to time, in order to show if the drum were revolving at the prescribed rate. This indicator showed how many revolutions per minute the drum made during the time of observation. For ordinary use, how- ever, it is unnecessary always to know the exact number of revolu- tions per minute. It is sufficient to know whether the drum is revolving at the prescribed speed, or whether the speed is increasing or diminishing. This is shown by the new indicator, devised by Dr. O. Brown, of Berlin, which may be directly or indirectly placed in all separators in a very simple way. As the success of creaming is influenced, to a large extent, by the rate at which the separator drum revolves, work should never be carried on without an indi- cator. In the case of hand-separators, it is often sufficient to regard the revolution of the handle as an indication of the prescribed number of revolutions per minute. This may be effected without using an indicator by utilizing the swing of a swinging pendulum, the number of swings of which per minute correspond exactly with the desired number of the revolutions of the handle. No doubt it is certain, in the case of hand-separators, that the drum assumes the QUANTITY OF MILK CREAMED PER HOUR. 145 proper revolving rate only where the handle is properly turned. The hand-separators whose drum is turned by means of friction (the hand-separators with falling drums, the Arnold, De Laval, and the Alpha hand-separator K) should not be used without an indicator. For exact scientific experiments indicators are necessary, such as those of Schaffer and Budenberg indicators which record exactly the number of revolutions made by the separator-drum throughout a comparatively long period. 72. The Supervision of the Quantity of Milk Creamed per Hour. Very different quantities of milk may be creamed per hour, in different separators, and variable quantities of skim-milk, containing different percentages of fat, may similarly be obtained. In a well-ordered dairy the aim is to obtain daily an equal quantity, viz. the largest possible quantity of fat. In order to obtain this, the milk has to be poured into the drum at an equable rate ; and secondly, the quantity of milk creamed should be creamed in such a way that the desired coefficient of cream-raising should be obtained. The first condition can be satisfied, at any rate approximately, by the use of vessels with floats. A good vessel should also be arranged in such a way that one can limit the rate at which the milk runs out, so as to be able to increase or diminish the quantity running out in the course of an hour. The measure of the rate at which milk runs out is discovered by estimating the amount of milk which is daily creamed per hour. The percentage of fat in the skim-milk is also determined. Should it be found that the coefficient of creaming is unsatisfactory, the rate at which the milk runs in ought to be diminished, until the skim-milk flowing away shows a percentage of fat of about '25. The amount of milk creamed per hour is determined as follows: When the drum has obtained its full speed, and creaming is ready to be started, the hour, minute, and second are noted, at which the cock of the warmer or of the collecting vessel is opened ; and again, the time at which the last of the milk passes through the cock. The interval is that during which the whole quantity of milk runs through the drum. For example, if from 6-17 till 9*32 that is, 3 hours 15 minutes, or 195 minutes, 260 kilos, exactly of milk passed through the drum of the separator, the amount of milk which would be creamed in an hour would be 2600 x 60 QAA , ., = 800 kilos. 195 (M175) K 146 SCIENCE AND PRACTICE OF DAIRYING. In order to obtain a regular flow of milk into the drum of a separator, one may use a feeding vessel (floating) such as that made at the works of Lefeldt and Lentsch. It was first exhibited at the second German Dairy Exhibition in Munich, in October, 1884, and is used in many dairies. 73. The Regulation of the Temperature in the Separation of Milk. As the percentage of fat in the skim-milk is very largely influenced by the temperature at which the creaming of the milk is effected, it is quite inadmissible to cream milk at the changing temperatures which it possesses from day to day. Creaming should rather be effected at a temperature at which it will be maintained throughout the whole year. This temperature practical experience has shown to be between 25 and 35 C., on an average 30 C. In the event of one wishing to cream the milk at 70 to 80 C., for the sake of steril- izing it, if a definite temperature has been determined, it ought to be rigorously maintained; and that it varies as little as possible during creaming should be determined by frequently testing it with the thermometer. In order to warm milk to the right temperature warmers are used, which are placed between the milk-collecting and milk-feeding vessels, and these are best heated with steam. The cylindrical warmer containing a simple stirrer without brushes, or warmers in which the milk is allowed to flow over a hot, ribbed surface, have been found in practice to be successful. Good warmers should be arranged, as they generally are, so that the milk may quickly gain the desired temperature, and when this is done the milk should be conducted without any unnecessary delay into the drum. The shorter the time required to raise the milk from 25 to 35 C., the more certainly can a cream and skim-milk of good keeping quality be relied on. If it be desired, in order to avoid the cooling of cream and skim -milk, to cream the milk at 15 C., the flow of the milk must be correspondingly diminished, and the separation of the milk carried on for from 5 to 8 minutes longer. The increased expense by such treatment in dairies where steam is used, is generally more than that incurred in warming the milk, and in cooling the cream and skim-milk. R. Backhaus, the director of the dairy in Fulda and Lau'terbach, has recently recommended that the sterilizing of the milk should be combined with separating it in such a way, that the milk, at a temperature of 70 to 80 C., coming out of the sterilizer, is immediately conducted into the separator-drum. Backhaus has been working for a year already at this process, and he affirms that it gives the best results. This process has also been in operation in Kleinhof-Tapiau since the middle of February, REGULATION OF CREAM AND SKIM-MILK IN SEPARATORS. 147 1892. If a percentage of fat in the skim-milk of '25 per cent be regarded as satisfactory, certainly distinctly more milk can be creamed per hour at these high temperatures than at 30 C., and in this fact another advantage is to be found. 74. The Regulation of the Relative Quantity of Cream and Skim- milk in the Use of Separators. With all separators a larger or smaller quantity of cream in proportion to the skim-milk can be obtained at the will of the worker. All that has to be done is to increase or diminish the amount of the flow of the milk to the drum. In this, however, the degree of creaming varies, a thing that ought not to be permitted in well-regulated work. For this reason, the quantity of cream obtained from an equal supply of milk ought to be able to be regulated at will. In the drums of all separators, with the exception of the Victoria separator, the neces- sary apparatus is supplied. In the separators of Burmeister and Wain, arranged for power use, the regulation is effected during the flow, and in the other separators such precautions as are necessary must be taken while the drum is at rest, in most cases before the commencement of the creaming. If the speed of the flow of milk does not change, it does not exercise the slightest influence on the percentage of fat in the skim-milk, whether 15, 20, or 25, or still higher percentages of cream be taken. It is only when the quantity of cream is less than 10 per cent of the total weight of the milk, that the cream is imperfectly separated in the case of some separators. The cream is obtained thicker and richer in fat the smaller the quantity. It is not to be recommended to take less than 10 per cent of the weight of milk, while over 20 per cent should only be taken if there is some special object, since skim-milk would be lost. As a rule it is desirable to obtain 15 per cent to 20 per cent of cream. If there be indicated by (/) and (/j) the percentage composition of the fat of milk and skim-milk, and by (r) and (b) the relative proportions of cream and butter obtained from 100 parts of milk, the percentage of fat in the cream (a) will be exactly found by the following equation: 100 x (/-.ft)- ~~ + " and approximately by the equation: *=* B 148 SCIENCE AND PRACTICE OF DAIRYING. If milk containing 3*3 per cent of fat be creamed at 30 C., the cream will contain, according as it forms 15 or 20 per cent of the milk, 19 to 20 per cent, or 14 to 15 per cent of fat. 75. Condition of Cream and Skim-milk from Milk -separators. When the work is carried out intelligently, the creaming of milk by centrifugal force exercises a favourable action on the condition of the cream and skim-milk; and it has long been proved that it is easy to obtain butter which comes perfectly up to all requirements from cream obtained by means of separators. The very small loss in material which milk suffers in cream- ing, by a small portion of the nitrogenous matter pass- ing into the so-called sepa- rator mud, is, it would seem, in every respect, and espe- cially so far as the condition of the skim-milk is concerned, quite unimportant. The ob- taining of fine butter is de- pendent upon the fulfilment of the necessary condition, that the cream, coming out of the separator-drum, should be cooled down as quickly as possible, to 5 C., by the application of ice. If the cream be exposed for any length of time at the temperature at which it leaves the drum its condition suffers, as does that also of the butter into which it is made. Experience has shown that it is not sufficient only to cool the cream partially to 12 C. For cooling, cream-coolers of different construction may be used. Refrigerators which have been largely used and tested are the Lawrence coolers (fig. 45) coolers in which the cream is cooled by being slowly passed over ribbed and comparatively large metal surfaces in a thin stream, and the Laval cream -cooler (fig. 46). Skim-milk, unless for use, ought to be cooled down, after its removal from the drum, to at least 10 to 14 C. It is admirably suited for use as human food, or for feeding calves and pigs. As it is very poor in fat, however, it forms only a one-sided kind of food. Fig. 45. Lawrence's Refrigerator. WORKING OF CENTRIFUGAL MACHINES IN DAIRIES. 149 Skim-milk, containing only '25 per cent of fat, is not, as a rule, adapted for making into skim-milk cheese. Nothing is easier, where there is a demand for skim-milk cheese, than to so regulate creaming that a skim-milk is obtained with the desired higher percentage of fat. Skim-milk, when Pasteurized, no longer possesses the property of yielding a coherent coagulation under the action of rennet. There can hardly be any dairies in which throughout the whole year there will be a supply of such cold water at command that the requisite quantity can be safely enough pro- vided. For that reason ice cannot be dispensed with in dairies, and the necessary supply must be provided. Fig. 46. Laval Cream-cooler. The precaution of cooling the cream quickly and thoroughly is one which is apt to be least recognized in practice, although it is known by thousands of observations that cream at warm tem- peratures quickly loses its pure taste. It is only by a happy chance that cream, which has been kept for some time at a high temperature, yields good butter. If creaming be effected at 30 C., it will be sufficiently near the necessary quantity to give, for every litre of milk which passes through the drum, "2 to -3 kilograms of ice. 76. The Proper Working of Centrifugal Machines in Dairies. Success in dairy management requires that there should be no failure to provide sufficient and well-arranged rooms, and that the staff on the one hand are not overworked, and, on the other hand, that they observe the greatest care and punctuality. In every good and well-regulated dairy, separators are used, and in those in which cheese is not made there should be at least ten rooms. First, a room for the milk samples; second, for cleaning the vessels and utensils; third, for separators and their necessary gear; fourth, for keeping milk, skim-milk, and cream, with an arrangement for cooling; fifth, for butter- casks; sixth, for cream-souring and the working of butter; seventh, for the storage of ice; eighth, for coal storage; ninth, for steam-engines; and tenth, 150 SCIENCE AND PRACTICE OF DAIRYING. for keeping butter for sale. If space be deficient, and if it be required to limit the room, it may be necessary to unite the milk samples' room and the room in which the cleaning of the vessels goes on, and to put the butter-casks and the separators in one room; but the room for the separators and butter-casks must be large and roomy. Especial care should be exercised in the choosing of the situations of the rooms for keeping the milk, skim-milk, and cream, and for cream-souring and the working up of the butter. The last-mentioned room must be capable of being heated. Before creaming is begun, the separators should be examined daily to see that they are in good working order. During creaming, the supply of milk, and its temperature, as well as the rate at which the drum revolves, should be carefully observed for five minutes. It is sufficient to steam the drums of the separators, along with the other apparatus, once a day, and to rinse them out with hot and cold water. Furthermore, they should be treated at least twice a week with a warm dilute solution of soda. The following points ought to be carefully observed : (1) If a separator is not in good working order it ought on no account to be set in working motion. (2) The drums of separators should be slowly and gradually brought up to the required revolving speed. (3) When, during motion, the driving-belts slip off the wheel, no attempt ought to be made, under any conditions, to put them on while the wheel is in motion. The engine must be stopped before the belt can be put right. (4) During the time the machine is in motion the hand ought not to be laid on it, and the drum should not be touched. This habit may be very easily acquired in the case of some separators. In using the separators of Burmeister and Wain, no attempt ought to be made to remove or to replace a dish while the machine is in motion. (5) If, during the motion of the machine, anything unusual happens, the driving power ought to be at once stopped, and the same ought to be done if the drum stops. (6) Great care ought to be taken when the machine is in motion not to come near the running belt. In most dairies in which separators are used the separators are only used once a day, and the morning and evening milk are creamed together, perhaps also the forenoon's milk of the previous day, which has been kept overnight in a special room at a temperature of under 10 C. Practical experience has shown that the necessary attention can no longer be paid if the creaming takes more than four hours daily. For this reason the WORKING OF CENTRIFUGAL MACHINES IN DAIRIES. 151 I ^ s : jo 3 f,- g^ 2 I JHOH 2 I? 8UUX oo do t~ os os o CN oo CO OS x os i>- O-HCO 5 . O O 00 05 CO O CO ficial and very unsatisfactory idea of the composition of cheese. In these analyses, what is designated as fat is the entire amount of body which has been extracted by ether or other fat solvent, regardless of whether it consists wholly of fat or not. The percentage of protein, or caseous matter, is generally expressed by a number obtained by multiplying the percentage of nitrogen found with a constant factor, viz. 6*25, which in the case of caseous matter is probably not once right. A determination of this kind is of little value, even CHEMICAL COMPOSITION AND ANALYSIS OF CHEESES. 273 although it be correctly carried out, because ripe cheeses contain, in addition to unaltered nitrogenous matter, quite a number of pro- ducts of the decomposition of nitrogenous bodies, which do not belong to the group of albuminoids. The investigation of fresh cheese is much simpler, since, in its case, the individual constituents of the milk, although they have partly undergone change, are yet in a condition which does not offer especial difficulty in their separation and determination. In the investigation of fresh cheese the following method may be pur- sued : (1) Determination of Water and Fat. The sample of cheese to be investigated is cut into small square pieces, of which 2*5 to 5 grams exactly are weighed out, and carefully warmed to 40 C. They are then brought, in an open glass capsule, under the receiver of a hand air-pump, the air from which is pumped out. It is left for some time standing, again warmed, and this is again repeated, until no further loss in weight is observed. It is then digested several times with cold ether, removed from the capsule, and pressed in a dish. It is then brought on to a weighed filter; the capsule and the dish being rinsed with ether. The cheese is then extracted on the filter with warm ether, the different washings being all brought together. The cheese, from which the fat has thus been extracted, is dried at from 100 to 110 C., cooled, and is weighed on the filter, the weight of which is deducted. After the ether has been distilled off from the ether extract, the fat remaining behind is dried carefully at from 100 to 105 C., cooled, weighed, and the percentage of fat of the cheese thus estimated. By subtracting the sum of the weight of the cheese from which the fat has been extracted, and which has been dried, and of the fat, from the weight of the cheese originally taken, the percentage of water in the cheese is obtained. If the largest part of the water has not been removed before its treatment with ether, it may happen that in the extraction process small quantities of mineral salts, which are soluble in water, and perhaps also small quantities of milk- sugar, may go into the extract, and render the determination inexact. In the investigation of sour-milk cheeses, it must be remembered that the lactic acid present is soluble in ether. On this account the determination of fat must be carried out in a specially prepared sample, which has been rendered weakly alkaline with soda, and then carefully dried. (2) Determination of Nitrogenous Matter. This is determined in another quantity of the cheese, or in that portion from which the fat and the water have been separated, either volumetrically, by Dumas' method, or by the Kjeldahl process, the nitrogen obtained being multiplied by the (M175) S 274 SCIENCE AND PRACTICE OF DAIRYING. factor 6 -39, on the assumption that the albuminoid matter of the milk contains 15 '65 per cent of nitrogen. (3) Determination of Ash. This may be carried out in a special sample of the cheese, or on the portion which has been used for the determination of water, observing the precautions which are necessary in this process. The ash is determined by burning a small portion. (4) The Determination of Milk-sugar. The percentage of milk-sugar may be determined in perfectly fresh cheese by difference, if all the remain- ing determinations have been carried out in duplicate with great care. If it be desired to determine the milk-sugar directly, this may be done in a water extract, obtained by taking a portion of the cheese dried under the air-pump, rubbing it up thoroughly with pure sea-sand, and boiling it repeatedly with pure water. In order to separate the albumin from this water extract before treating it with the copper solution, it is necessary to acidify it with acetic acid, boil, and then filter. In a perfectly exact analysis of fresh cheese, it must be assumed that the fat of the milk contains lecithin, and that, therefore, small quantities of nitrogen will be found in the fat of the cheese. In the investigation of ripe cheeses there is no method which can be recommended as suitable or trustworthy. Manetti and Musso recommend the following: Determination of the percentage of water and bodies volatile at 115 C. ; preparation of a carbon bisulphide extract; prepara- tion of an alcoholic extract; preparation of a watery extract; determination of the quantity of bodies insoluble in bisulphide of carbon, alcohol, and water; determination of the ash; determination of ammonia; determina- tion of the sum of the acids present; determination of the nitrogen; and finally, the determination of the nitrogen and ash in the different extracts, as well as the determination of the nitrogen and ash in the residues of the different extracts. As an example of the chemical composition of certain kinds of fresh cheese, and of products resembling cheese, the following figures may be given : Neufchatel Limburg (Double Fat (Fat Soft Cheese). Soft Cheese). Emmenthaler Backstein Raden Olmlitzer (Fat (Skim-milk (Skim-milk (Sour-milk Hard Cheese). Soft Cheese). Hard Cheese). Cheese). Water, 34-5 357 36-1 73-1 57'3 44-6 Fat, ... 41-9 34-2 29-5 2-8 3-5 3-4 Nitrogenous j matter, ... ) Non-nitrogen- ) ous matter, \ 13-0 7-0 .24-2 3-0 28-0 3-3 19-8 2-2 33-0 2-9 41-1 Ash, 3-6 2-9 3-1 2-1 3-3 10-9 100-0 100-0 100-0 100-0 100-0 100-0 CHEMICAL COMPOSITION AND ANALYSIS OF CHEESES. 275 Ziger. Mysost. Water, 68'5 23'6 Fat 3-1 16-3 Nitrogenous matter, .. 22'1 8 '9 Milk-sugar, 3'2 37'3 Lactic acid, 0'8 I'l Remaining constituents, ... ... 8'1 Ash, 2'3 47 100-0 100-0 A study of the history of the manufacture of cheese, as carried out in different countries, shows that in three countries, viz., in Swit- zerland, in Holland, and in England, special kinds of preparation methods for the manufacture of hard cheeses have been in use from a very early period. In South German hill districts, in Austro- Hungary, and over Italy, the Swiss method has been followed; in Schleswig-Holstein, in the Rhine Province, and over the whole of North Germany, the Dutch method has been adopted; and in the United States of America the English method has been preferred. France produces the finest and the most popular of soft table cheeses, Switzerland the best of hard cheeses, and Upper Italy the highly-prized Reib cheese. In Switzerland the manufacture of cheese is much more extensive than the manufacture of butter; the contrary is the case throughout Scandinavia, that is, in Denmark, Sweden, and Norway, as well as in Finland, in the Russian East Sea Provinces, in the whole of North Germany, and in a large part of France. The manufacture of butter, as well as of cheese, is carried on in North America, Great Britain, Holland, a part of France, South Germany, and over Italy. In Austro-Hungary, the manufacture of cheese, indeed the whole business of dairying, has up till the present time not received the amount of attention which has been devoted to it in most other countries. CHAPTEE VI. PREPARATION OF KEEPING MILK, FERMENTED MILK, AND THE BYE-PRODUCTS OF MILK. 129. Keeping Milk. By keeping milk, is understood milk which by heating, or by heating and other suitable treatment, possesses the property of being able to keep, without becoming decomposed, for a longer time than ordinary milk. As long as milk stands boiling without coagulation, and possesses no other foreign flavour than a slight taste of cooked milk, it may be regarded as a good keeping milk. The keeping qualities of milk, on the other hand, may be increased to such an extent, that it will keep for days, or months, or for a much longer period. In such cases the milk may possess its original percentage of water, or it may lose a portion of it by becoming thick. 130. Pasteurized Milk. By such milk is meant that which has been heated, for a shorter or longer period, to a temperature under the boiling point of water, but high enough, as experience has shown, to kill most of the microscopic fungi. The temperature which meets these conditions, and which is consequently commonly used in Pasteurizing, lies between 56 and 80 C. Within these limits, the higher the temperature, the shorter is the period in which a distinct effect is produced. It would be very extraordinary, indeed, if milk were rendered free from spores by Pasteurizing. Since Pasteurized milk is scarcely ever kept free from spores, it possesses only, as a rule, a slightly increased keeping property. This is explained by the fact that the lasting spores of certain kinds of bacteria, which are not uncommonly present in milk, can withstand for a long time the application of such heat as is applied in Pasteur- izing, and that there are bacteria which only begin to develop at temperatures over 50 C. ; indeed, there are some which even rapidly increase at temperatures of from 70 C. to 75 C. Fortunately such bacteria as agree with these high temperatures are generally uncommon, and are only very rarely found in milk. Experiments have shown that in Pasteurizing, the vegetative forms of nearly all bacteria, and especially, also, of the most dangerous pathogenic germs, 276 PASTEURIZED MILK. 277 such as cholera, typhoid, and tubercle bacilli, are killed. This, and this alone, is what is effected by Pasteurizing, and should always be effected by it. On this account, milk which has been so strongly and so long heated that the above results have been safely obtained, or milk in which the lasting forms, and the forms of such bacteria as prefer unusually high temperatures can alone be present, is named correctly Pasteurized milk. Correctly speaking, Pasteurized milk is, for example, milk which has been heated for 15 minutes at 75 C. or for ^f 30 minutes at 68 C. The action effected by Pasteur- izing is the more perfectly brought about the more carefully the operation is carried out. If it be de- sired to take every pos- sible precaution, attention must be paid to having the milk contaminated as little as possible in the process of milking. The Pasteurizing appar- atus should be cleaned for fifteen minutes before use, and the cooling of the Pas- teurized milk should be carried out as quickly as possible in a cooler, which should also have been previously steamed. The cooled milk should then be put in steamed vessels, and care taken that it should not be left to stand for any time in uncovered receptacles. Properly Pasteurized milk keeps at ordinary animal heat for 20 to 24 hours at 20 C.; about 60 hours at 12 to 15 C.; 72 hours, and often even longer at lower temperatures, in a con- dition which admits of its being boiled without coagulation. It only possesses a flavour slightly suggestive of boiled milk, and may be converted into cheese, since its susceptibility to rennet has only been weakened to a very slight extent. In spontaneous coagu- lation it forms a comparatively spongy coagulum. Occasionally it is not lactic bacteria which induce, after a lapse of time, coagula- Fig. 78. Laval Milk Scalder. 278 SCIENCE AND PRACTICE OF DAIRYING. tion of Pasteurized milk, but rennet and butyric acid bacteria. In such cases the coagulated milk exhibits only a slightly weak acid reaction, and shows near the surface a thin whey-like layer. If the creaming be effected, as is now beginning to be customary, by centrifugal force at 75 C., and the milk be kept fifteen minutes at this temperature, the cream is obtained, as well as the skim -milk, in the same condition as ordinary Pas- teurized milk. If the creaming operation be followed at the tempera- ture which is now cus- tomary, of 25 to 35 C., the skim-milk is often Pasteurized (fig. 78) in order to impart the neces- sary keeping qualities to it, and to permit of its regular transport to other places. Cream for butter- making should only be slightly Pasteurized if it be intended to be kept for a few hours only, or if it be intended to be soured with a pure culture of lactic ferment for the purpose of being made into butter. Fig. 79. Pasteurizing Apparatus (Burmeister re traces of the muscle substances are contained in the fat, even trichiniae, may be introduced into the margarine. This is all the more important, since in the preparation of oleomargarine a temperature of at most 65 C. is employed, a temperature which cannot be regarded as invariably effecting the destruction of the above-mentioned organisms. Although up to the present no case of illness has been proved to be directly due to the partaking of mar- garine, this does not guarantee that serious outbreaks of illness might not suddenly arise, due to the use of bad margarine. The use of plant fats in the preparation of margarine is also open to objection. Plant fats consist of different mixtures of fats from that MARGARINE. 319 of animals, and are, as common experience has shown, less easily digested than the latter. It goes without saying, that attempts have been made, in order to promote its sale, to make margarine as attractive as possible. There is no reason, however, on this account, for rendering the new fat similar in external appearance to butter, or for bringing it on the market in a similar form and packed in the same way as butter. The great resemblance of the prepared animal fats to butter has always this disadvantage, that it opens the way to fraudulent practices, and has thus a tendency to destroy the honest character of the sale. The possibility of fraud was formerly increased by the universal practice of calling margarine by the name of butterine; that is, by a title which was only justified by the appearance of the margarine, but which was otherwise strained on account of the fact that not only was the chemical behaviour of the margarine, but also its mechanical texture and fundamental condition, different from that of butter. Of more importance still than the use of the word butterine, was the manufacture of mixtures of margarine and butter, and the manufacture of mixed butters, which were commonly used in the years 1884 and 1885. These different titles indicated, clearly enough, the fraudulent intention which underlay them. It is hardly neces- sary to add that no improvement in the food is effected by the mixing of margarine with good butter. The mixture of butter with foreign fat is practised solely for the purpose of increasing the value of the very cheapest fat by the addition of good butter, so that it may take the place of butter to a large extent, and that at a relatively higher price; or for the purpose of passing it off in the market as butter. For these reasons this practice must be regarded as an attempt to create a new and lucrative industry, at the expense of the dairy industry, and of the less wealthy portion of the public. Thus, in the course of time, the manufacture of margarine has departed more and more from the healthy basis on which it was started in 1870, and has threatened to become, to a serious extent, a parasitic industry. It has placed the manufacture of butter at a disadvantage, given an impetus to the perpetration of fraud, and has thrown on the market a large quantity of food, the origin of which is a mystery, and which everyone has a right to regard with distrust. About ten years ago measures were adopted in most countries where dairying was in an advanced state, Holland excepted, to free the 320 SCIENCE AND PRACTICE OF DAIRYING. new industry from its unhealthy accretions, and to place it in its former position. German agricultural interests effected, not with- out much trouble, the passing, on July 12th, 1887, of a law dealing with the sale of butter substitutes. This law came into force in October, 1887. If it did not entirely meet all the necessities of the case, it nevertheless furnished, when stringently and watchfully carried out, and in combination with the law of 14th May, 1879, dealing with the consumption of foods and condiments, and the conditions of their use, an important protection to agriculture and to the public. With regard to the development of the margarine industry in the United States of North America, little is known to the author of a detailed and definite nature. It would seem that the manu- facture of margarine, since its commencement, has been carried on with less care than in Europe. In the latter case the manufacture was carried on practically according to the process of Mege-Mouries, and according to a process patented by Mr. Paraf on April 8th, 1873, after Hortiny's specifications. The new food was not called margarine but butterine. Soon after the discovery was made by Mege-Mouries, attempts were made in various quarters, at first with little success, to intro- duce the manufacture of margarine into Austria-Hungary. The first attempt originated with an American, Benford, who came to Vienna in 1871, and who there exhibited samples of margarine, which were discovered to consist for the most part of butter. Subsequently a Belgian, RonstorfF, general consul for the republic of Uruguay, exhibited at the first dairying exhibition held at Vienna in 1872 on the 13th to 17th December, several samples of margarine which, according to his representations, were prepared from ox fat and milk. His attempts to start the manufacture of margarine on a commercial scale also failed. The first to introduce the manufacture successfully into Vienna was Mr. Sarg, the owner of the world-renowned soap factory at Leising. He built in Leising in 1873, with the help of a French engineer, a factory, which was opened in 1874, after the municipal authorities of Vienna had granted permission to sell the new fat under the name of prima Wiener sparbutter. The factory of Sarg was one of the first and best arranged of the large margarine factories started in Europe outside of France. It supplied margarine which had been prepared from fresh ox tallow, and which was prepared in an appetizing form. Among the many forms of MARGARINE. 321 margarine which the author has had an opportunity of examining in the course of time, the prima Wiener sparbutter was the best. In Holland, so far as the author is aware, no margarine is made, or, at any rate, sold as such. In that country the preparation of mixed butter, since the year 1870, has been developed to an extent which is found nowhere else. As long as the Dutch butter market is in existence, there will be no lack of dealers to mix the superior and the inferior kinds of butter, and produce an average saleable article, and thus make profit. Against the method of mixing, which is still carried on elsewhere, it is impossible to do anything. Butter has, however, been mixed with all sorts of fats, a condition of affairs which formerly only very rarely occurred. At the time of the Franco-German war, when the demand for butter became greater and greater in Holland, inferior butter, Galician, Russian, and Finnish butter, at first mixed with milk and starch solution, and subsequently also with fats and oils of different kinds, were all worked together by a butter-worker and sold as butter or mixed butter. The discovery of Mege-Mouries, which was either not at all, or only to a very slight extent, utilized in Holland, merely helped to further develop the mixed butter industry, by furnishing it with acceptable raw material. From the use of butter-workers the business advanced to the manufacture on a factory scale, and fac- tories were erected to mix butter with fats, oils, milks, and colouring matter in large butter- vats, at temperatures at which the fats in use melted. The proportions in which these raw materials were mixed were as follows: 15 to 35 of milk, 40 to 70 of margarine, 13 to 35 of oil, and from to '5 of butter. The better sorts contained, indeed, an addition of from 10 to 20 per cent of the best butter. The de- sired oily condition was imparted to the product by the addition of a considerable quantity of oil, according as it was desired to produce an article possessing a dull opaque substance, more of the nature of a salve, or a transparent wax-like material. This difference in the preparation accounts for the fact that the Dutch so-called artificial butter, which, both in a salted and unsalted condition, is placed on the market like butter, possesses no uniform chemical composition. From the above short description, it will be seen that the preparation of good margarine from fresh animal fat, obtained from healthy animals, and without the addition of milk, cream, or butter, is a useful and beneficial discovery. It has had the effect of utilizing animal fats, and of rendering them capable of manifold application, ( M 175 ) X 322 SCIENCE AND PRACTICE OF DAIRYING. and has permitted of their being used for the middle and lower classes as a cheap cooking fat, and a good substitute for butter. Good margarine is quite capable of entering into successful compe- tition with poor kinds of butter, but not with first-class butter, so that there can be no talk of a serious blow being dealt to the butter trade or to dairying through its use. Nothing can be objected against the preparation of margarine, as long as it is manu- factured in such a way that the product is of an appetizing nature, and free from all unhealthy adulterants. Its manufacture is wholly justifiable, and no sensible man will deny the economic importance it possesses, in so far as it supplies a want, and furnishes a valuable public food. The following paragraph gives the chemical composition of margarine and mixed butters of different sources : French American **J 1 5 amburg *S* ^^ 3rd Alir.rnririo "Riif-f orina VVienCr ISt ZllCl 6TQ. Margarine. Buttenne. Sparbutter . Quali ty. Quality. Quality. Water, ...... 12-56 11-25 10-69 10-25 9-61 8'08 Fat, ......... 86-24 87'15 87-45 85-88 86-26 84-15 Other organic matter, ) ,. 20 ,. 60 (0'46 1'75 1'62 2-14 ash and salt, ... j ( 1-40 2-12 2-51 5-63 100-00 100-00 100-00 100-00 100-00 100-00 The percentage of insoluble fatty acids in the Wiener sparbutter, and in the Hamburg mixed butter, amount respectively to 95-59, 92-47, 93-58, and 93-96. In the investigation according to the Reichert method, the quantity used for the three Hamburg mixed butters was respectively 5-3, 2*8, and -9 c.c. of the tenth normal alkali solution, and the specific gravity of the pure fat of the three samples of Hamburg mixed butter at 100 C. was respectively -8618, -8605, -8601. The Wiener sparbutter was analysed by the author in 1887, and the others in 1886. 148. Margarine Cheese. Margarine cheese was formerly known as melted cheese, oleomargarine cheese, and artificial cheese. It is now known as the kind of cheese which it imitates. While it was possible to say of the preparation of margarine that it originated in a proper idea, as was pointed out previously, and that it might be regarded as a beneficial discovery, so long as there existed a want that it could supply, and that it thereby justified its existence, it was difficult to say the same of the preparation of margarine cheese. No one can deny that the demand for butter exceeds that for cheese, and that it is a benefit for the poorer section of the people, who are MARGARINE CHEESE. 323 not able to buy the higher-priced butters, to have at their disposal, instead of bad butter, a good, healthy, and cheap substitute. But the demand for cheeses is, on the whole, by no means very great, and the already limited area for the manufacture of cheeses abundantly suffices for it. The demand for the finer kinds of cheeses is still comparatively brisk, but it is not so for cheeses of the medium and poorer kinds, such as skim-milk cheeses. In connection with the consumption of cheese, the taste of the individual is an important factor, and in large districts of Germany cheese is no longer a popular food. The reason of this is not due to the fact that there is a lack of good skim-milk cheeses, and that good cheeses have not been successfully prepared from milk which has been skimmed by means of centrifugal force. Where skill is not awanting, it is possible to make good skim-milk cheese possessing a piquant flavour. That this art has not yet become widely known cannot be doubted, especially in Middle and North Germany, but as the demand increases it will certainly be rapidly developed. In dis- tricts in which a taste for cheese is awanting, or where the people have not become accustomed to eating cheese, no market would be found for margarine cheese, even although which is a doubtful point margarine cheese excelled milk cheese in flavour. Nor can the small use of skim-milk cheeses be explained on the ground that they are too dear, since there have been times when the J kilo, of skim-milk cheese of good quality was, owing to a scarcity of demand, to be had for 15 to 20 pfennig, a price at which a similar weight of appetizing margarine cheese could not be supplied. It cannot therefore be asserted that the preparation of margarine cheese meets a pressing demand for public food, and that it has proved a benefit to the working classes. It must be noted that cheese in which nitrogenous matter ip present, along with a considerable amount of fat, is more easily digested than a skim-milk cheese poor in fat. This is certainly true, but it does not mean that margarine is required in order to increase the digestibility of skim-milk cheese. Whoever desires to render this cheese more digestible, through the addition of fat, would be better to do so by adding to his piece of cheese a piece of good bacon fat, and eating this along with it, than by buying it in margarine of a dubious origin. Therefore it is not to be understood, after all that has been said, that the preparation of margarine cheese can be economically 324 SCIENCE AND PRACTICE OF DAIRYING. justified. Still less justifiable is the opinion that this branch of dairying can supply a want. It has been further claimed that the utilization of skim-milk, which is found in some places to be very difficult to effect, would be greatly assisted by the manufacture of margarine cheese. If this be of any benefit, it can only be so in the same way as brandy is given to a person who has fainted, in order to bring him again to his senses. Margarine cheese manufacture is far more dangerous to the manufacture of cheese than the manufacture of margarine is to the production of butter, and there can be no greater example of short- sightedness than to expect assistance to the dairy industry, in its time of need, from the help of a manufacture which utterly destroys the cheese industry, and thereby strikes a blow at the entire dairy industry. On the side of the dairies which have already entered into contracts, it is asserted that the maximum value on an average is not reached, and that the margarine cheese industry threatens many results which would be highly disastrous to them. The disadvantages consist in that the whey assumes, in the course of a few hours, a very disagreeable smell, which is disadvantageous to butter, that on this account it loses much of its value as a food, and that it is not available for margarine manufacturing purposes, and that it is capable of inflicting a deleterious influence on the sale of butter. If more attention were given to the preparation of skim- milk cheeses, the value of skim-milk would be much more consider- ably increased than by the manufacture of margarine cheese. 100 kilos, of skim-milk will yield 10 kilos, of fresh skim-milk brick-shaped cheeses, and, at the same time, 87 kilos, of sweet whey, leaving a loss from the total weight of 3 per cent. If the cheese lose before its sale 25 per cent in weight, so that only 7'5 kilos, of cheese are sold, and if the kilo, of ripe cheese only fetches 36 pfennig, there is obtained from the cheese, 7'5 x *36 = 2*7 marks. The manufacturers of margarine cheese, naturally enough, oppose the attempt to apply to the article the title of oleomargarine, or fatted cheese, nor are such titles convenient for the public. For this reason, there has been nothing to prevent the artificial products in common use from appearing under the names of the different kinds of cheeses of which they are the imitation. The buyer is then no longer certain of procuring what he desires to purchase. Fraud is easily perpe- trated and the whole cheese industry decays. It is for these reasons, without doubt, the case that this new department of dairying is of no MARGARINE CHEESE. 325 use, but on the other hand is only likely to do harm, and to render all attempts made to improve the skim-milk industry abortive. It has been said, finally, that margarine cheese is neither intended nor will enter into competition with ordinary cheese, but constitutes a new food, and is perfectly independent of the dairy industry. The conception, which supports the opinion that an industry which has for its object the imitation of one of the chief products of dairying, will in no way effect dairying, is so obviously absurd, that it needs no further consideration. The preparation of margarine cheese, or, as it was formerly called, artificial cheese, was introduced from the United States of North America. Artificial cheese was already made in that country as far back as 1878, from skim-milk which, after melted margarine or other fat had been incorporated with it by special apparatus, was manufactured into cheese, special precautions being taken on account of the unstable state of the emulsion. This artificial cheese was, from the very first, a source of annoyance to the American farmer, and met with very little support from the public. In the course of time the attempt was made to develop the industry, and to introduce it into Europe, where the manufacture was begun in many countries, especially in Denmark. In Germany it was first undertaken by A. M. Mohr, of Barnfeld in Ottensted in Holstein, who took the matter up, and who has during recent years made great attempts to set the margarine trade into active motion. As has already been pointed out, A. M. Mohr did not buy skim-milk cheese, but had the product manufactured in dairies in which were the necessary utensils. The apparatus for the incorporation of fat into the skim-milk were the emulsion machines, which have been very much improved in the last few years, so that it is possible to obtain a fineness of the fat division not even exceeded by that of the butter-fat in milk itself. The most extensively used of these machines are the Danish, and those of Dr. De Laval. Both machines are centrifugal machines, and respectively make 4500 and 7000 revolutions per minute. By means of these machines, there is made in the manufacture of margarine cheese, from a definite proportion of skim-milk and mar- garine, an emulsion which is known to the manufacturer by the name of artificial cream, and which is added to the skim-milk which it is desired to manufacture into cheese, in such a proportion, that for every 100 kilos, of skim-milk there are about 3 kilos, of mar- garine. Despite the extraordinary fineness of the division of the fat, 326 SCIENCE AND PRACTICE OF DAIRYING. so long as it is melted, it rises very quickly to the surface of the cheese- vat, so that even when the coagulation-time is of the shortest possible duration, there is always a small portion of the melted fat lost to the margarine cheese. It is, of course, obvious that the best kind of fat, such as is employed in the preparation of butter substi- tutes, is not used, but inferior fat and refuse from the margarine factories. This fact is admitted by the manufacturer. In conse- quence of the fact that the fat, during the process of emulsification, is submitted to the high temperature of 60 C., and that it offers an enormously large surface to the action of the oxygen of the air, it is further deteriorated. The result is, as is often noticed in the manu- facture of cheese in this way, that the whey remaining behind often after a few hours gives off a highly disagreeable smell. The manufacture of margarine cheese is far more troublesome than the manufacture of genuine cheese, and its value depends to a large extent on the quantity and condition of the fat added to the skim- milk. The author has formerly had many opportunities of testing and examining American cheeses, although he has never seen the Mohr products. According to reports in the dairy newspapers, they do not possess good keeping properties, and are very liable to mould. They are prepared usually according to the Cheddar method, but also according to the method employed in the making of Limburg, Gouda, and Edam cheeses, and even after the method of the Stilton. With regard to their flavour nothing can be said. In margarine bad fat can be very easily detected. In ripe margarine cheeses it is less easily detected. Anyone with a good appetite may enjoy this kind of cheese, but it is not a common taste. It is not suited for the tables of the rich. The manufacturers of margarine cheese must therefore find an outlet for their cheese chiefly among the poorer classes, and it is this portion of the public who must pay for the whole industry, without obtaining any advantage. Neither in Germany nor elsewhere is margarine cheese popular. Whether this is due to its quality, or to a healthy instinctive feeling on the part of the public, is doubtful. A careful consideration of all the conditions of the trade proves the margarine cheese industry to be of a purely parasitic character. It benefits no one except itself, and grows rich at the expense of the poorer classes and the dairy industry. That there should be dairies which do not scruple to work in the interests of this industry, is as difficult to understand as it is lamentable. CHAPTER IX. EXPLANATION OF THE APPENDED TABLES. 149. In the preceding paragraphs different works and calcula- tions have been referred to in the sections describing dairying, to illustrate which, calculation tables are either necessary or extremely desirable in the interests of economy of time. The number of tables which have been devised in the interests of dairying have in the course of time become so greatly increased, that it is impossible to publish all of them in a text-book. The author will consequently only give a few which are most frequently required for use. Those given here are as follows: Table I. Comparison of Fahrenheit, Centigrade, and Reaumur Thermometric Scales. The temperature can be converted from one scale into the other by the following formulae: n F.=f (n-32) C. = t (n-32) K. = -555 (n - 32) C. = -444 (n - 32) R. n C. = | n R = (f n + 32) F. n R. = (| n + 32) F. = n C. = (2-25 n + 32) F. = l-25 n C. To convert a given temperature on the Fahrenheit scale to degrees Centigrade, subtract 32 and multiply by -jj, when the answer will be the required temperature on the Centigrade scale. The following is an example: 173 Fahr. = 173 - 32 x | = 78'33 C. To convert a given temperature on the Centigrade scale to the Fahrenheit, multiply by -- and add 32. The following is an example: 60 C. = 60 x f + 32 = 140 Fahr. The space between boiling point and freezing in Reaumur is divided into 80, in the Centigrade or Celsius into 100, and in the Fahrenheit into 180 equal divisions. The boiling point is respec- tively indicated by 80, 100, and 212, and the freezing point by 0, and 32. On the Fahrenheit scale under the freezing point there are 32 degrees. Tables II. and III. are arranged for the correction of the specific 327 328 SCIENCE AND PRACTICE OF DAIRYING. gravity of milk and skim-milk (observed at temperatures from and 30 C.), to 15 C. All comparisons are made at that tempera- ture, for the sake of simplicity in practice. When the specific gravity of milk is stated, the first two figures, along with the point, are removed. Thus, for example, a sample of milk having a specific gravity of 1*03175 at 15 C., is spoken of as having a specific gravity of 3175. For example, if the specific gravity of milk at 24 C. has been found to be 2970; at 15 C., therefore, it will be 31-2 + -1 X 7, equal to 31'9. There is found on Table II. the numbers 31'2 and 32'2 for 29 and 30 respectively, at 24 C. The difference for one degree amounts to 1, for a tenth of a degree *1, and for seven-tenths 7. The specific gravity of milk may be stated in different ways. It may be stated in comparison to distilled water at 15 C., and weighed in air, or it may be stated in comparison with water at 4 C., and weighed in air or water at 4 C., and calculated in vacuum. According to the method of comparison, the numbers will naturally differ. If, for example, the specific gravity of a sample of milk has been determined by the pyknometer at 15 C. and compared with distilled water at the same temperature, and weighed in air, and found to be T0315, and if it be desired to convert this number into comparison with water at 4 C., taking the density of water at 15 C. at -99916, then the figure will be found by multiplying 1-0315 by '99916, that is, T03063. The difference amounts to 1-0315 -1-03063 = -00087. If it be desired to calculate this in vacuum, it will be found by multiplying T0315 into ('99916 00119) + -00119, that is, T03060. The figures, then, for specific gravities are as follows: Weighed in air and compared with water at 15 C., equal to 1-03150. 4C, 1-03063. in vacuum 4 C.j 1-03060. As it is sufficient for practical and scientific purposes to know the specific gravity to four places of decimals, it will make little difference whether it is calculated to water at 4 C., or whether it is weighed in vacuum or not. On the other hand, it is not the same whether the specific gravity be taken with reference to water at 15 C. or at 4 C. As a rule, the specific gravity of milk is calcu- lated at 15 C., and compared with distilled water at the same temperature. AN EXPLANATION OF THE APPENDED TABLES. 329 Table IV A. and IV B. serve for the calculation of total solids (t) when the specific gravity (s) at 15 C. and the percentage of fat (/) are known. Both tables are based on the following formula: In the above formula (ri) equals the specific gravity of the solids not fat at 15 C. This amount, as has already been pointed out, is very nearly constant. It may be worth while to calculate its value in those districts in which the above formula will be used. This can be done by the following formula: in which (s 1 ) is the specific gravity of the butter -fat at 15 C. compared with water at a similar temperature. If 1-600734 be taken for the value of (ri), as stated in formula (1), the following will be the result. Substituting for the figures 10()xs-100 = d: (3) *=1. and from this we obtain the following: *=. 833 x <- 2-22 x-^, and 100C 1000-3-75 (t-l-2xf) If, for example, it had been calculated that (s) = 1*0321 and (/) = 3*456 per cent, from Table IV A. for 1-2 x/= 4*147 per cent, and from Table IV B. 2*665 x^ = 8*288 per cent; therefore (Q = 12*435 per cent. Both tables can be used for the calculation of (/), if (s) and (t) are given, for from equation (3) it follows that If, therefore, (t) equals 12*435 and (s) 1*0321 from Table IVB., its value would be 2*665x^ = 8*288. If we take this number from 12*435, the figure 4*147 is found, a number which, by division with 1'2, gives the percentage of fat at 3*456 per cent. 330 SCIENCE AND PRACTICE OF DAIRYING. Table V. serves for calculating the specific gravity (m) of the total solids of milk at 15 C., compared with water at like temperature. In many cases where the question arises as to whether milk has been adulterated or not, as has already been pointed out in 31, page 69, the value of m can be obtained from the formula, in which (f) equals 12*435 per cent, and (s) equals 1*0321. From Table V. we obtain for - =3*110. If one subtracts this number and divides 12*435 by the remainder, 9*325, we obtain (m) equal to 1*333. Table VI., calculated by J. Nisius, gives the relation of the percentage of fat (p) and specific gravity of the total solids (m) of milk. In order to distinguish among several samples of milk the compositions of those which are known to be comparatively rich in fat, that is, in comparison with the non-fatty solids, the composition of all the samples must be calculated to a similar percentage of total solids. Formerly, in such a comparison, the percentage 12 or 12*5 was generally chosen. It appeared to the author to be more suitable to calculate the percentage of the amount of fat in the dry substance. (ra) can easily be calculated if (p) is given, or (p) if (m) is given. By the formula 2665 the following is obtained: For (p) 27*792 per cent, for example, (m) equals -Vy- equals 1*334, and where (m) equals 1*334 (p) will be 27*80 per cent. TABLE I. 331 TABLE I. Comparison of Fahrenheit and Centigrade Thermometric Scales. F. C. F. C. F. C. F. C. F. C. 32 o-oo 69 20-56 106 41-11 143 61-67 180 82-22 33 0-56 70 21-11 107 41-67 144 62-22 181 82-78 34 I'll 71 21-67 108 42-22 145 62-78 182 83-33 35 1-67 72 22-22 109 42-78 146 63-33 183 83-89 36 2-22 73 22-78 110 43-33 147 63-89 184 84-44 37 278 74 23-33 111 43-89 148 64-44 185 85-00 38 333 75 23-89 112 44-44 149 65-00 186 85-56 39 3-89 76 24-44 113 45-00 150 65-56 187 86-11 40 4.44 77 25-00 114 45-56 151 66-11 188 86-67 41 5-00 78 25-56 115 46-11 152 66-67 189 87-22 42 5-56 79 26-11 116 46-67 153 67-22 190 87-78 43 6*11 80 26-67 117 47-22 154 67-78 191 88-33 44 6-67 81 27-22 118 47-78 155 68-33 192 88-89 45 7-22 82 27-78 119 48-33 156 68-89 193 89-44 46 778 83 28-33 120 48-89 157 69-44 194 90-00 47 8-33 84 28-89 121 49-44 158 70-00 195 90-56 48 8-89 85 29-44 122 50-00 159 70-56 196 91-11 49 9'44 86 30-00 123 50-56 160 71-11 197 91-67 50 10-00 87 30-56 124 51-11 161 71-67 198 92-22 51 10-56 88 31-11 125 51-67 162 72-22 199 92-78 52 11-11 89 31-67 126 52-22 163 72-78 200 93-33 53 11-67 90 32-22 127 52-78 164 73-33 201 93-89 54 12-22 91 32-78 128 53-33 165 73-89 202 94-44 5$ 12-78 92 33-33 129 53-89 166 74-44 203 95-00 56 13-33 93 33-89 130 54-44 167 75-00 204 95-56 57 13-89 94 34-44 131 55-00 168 75-56 205 96-11 58 14-44 95 35-00 132 55-56 169 76-11 206 96-67 59 15-00 96 35-56 133 56-11 170 76-67 207 97-22 60 15-56 97 36-11 134 56-67 171 77-22 208 97-78 61 16-11 98 36-67 135 57-22 172 77-78 209 98-33 62 16-67 99 37-22 136 57-78 173 78-33 210 98-89 63 17-22 100 37-78 137 58-33 174 78-89 211 99-44 64 17-78 101 38-33 138 58-89 175 79-44 212 100-00 65 18-33 102 38-89 139 59-44 176 80-00 66 18-89 103 39-44 140 60-00 177 80-56 67 19-44 104 40-00 141 60-56 178 81-11 68 20-00 105 40-56 142 61-11 179 81-67 co r- oo os o CM CM CM CM CO COCOCOCOCOCOCOCOC^COCOCOCOCOCOCOCOCOCOCOCOCOCOCO w cococococococococococococoeooscococococococococorc w cococococococococococococococococococococoeococococococow 00 CNCMCMcocococococococococococococococococococococoro CO i 8 oo --N J- ^ CNCNCN<>CNCNCNCNCN(NCN<*ICMC*IC^ ^ ' ^ CNS^CNCNCNCNCNCNCNCNCNCNCNCNCNciqCNCNScMCN^cSc^CNC^^C^ 3 ' CN COOOOOOr-I^H^Hr-ir-i^^H-^01fNCNfNrNCOCOCOCOCOTt1CNCNCNCNCMCNCN ^p^^^^^^CNCNCN^^C^CNCN^CNCNCN^CMCNCNC^ O5 00 CM CN 1 cB CN 1> HI 10 ^-, t'j t'j vw ~^r "^r ^r "^r ^r ^r "^r ^r ^^ ' s ^' ^r "^x 1 .j -w w.^ .w ^^ **-w v^' >^* >^ >^^ >^* j.^- j.^" DIRECTIONS FOB USE. Suppose the specific gravity found at 18 C., to be T030, this is represented in the Table, on the horizontal line at the top, by the last two figures, viz. 30. Under the figure 30, the number corresponding to the temperature 18 C. (in the vertical column at the sides of the table) is found, which in this case is 30'6, and represents the specific gravity at 15 C. 332 p o ^ ^ ^ cococococococoebcocococococococococococococococococococo^^^ $ CO CO CO CO CO CO CO CO CO CO CO CO CO COCOCOCOCOCOCOCO^T^T^T^T^T^T^ioOiOiCOCOCOCOCDCOt^t^I^QOGOGO COCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCO Q CM G^l G*l G^ (*^l G^l G^l CO CO CO CO CO CO CO CO "^ ^ "^ "^ Tf *O O *O *O *O CO CO CO CO t^* 1T^* CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO 00 CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO '""' 1 ~"^ "" ' 1 " 1 r ~^ i~^ CM Q^ G^J CM C^l G^l G^ CM CM CO CO CO CO CO "^t* COMCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOCOW 00 cococooococococowcowcocococococococococo co 0505 0505 05 g; o p 6 6 6 6 6 6 6 -^ ^- -^ ^ r^ lJ(^lCN(^C>J(N(^<>J^<^(>l(^CNCNC^ ---------- Qq Qq (jq (jq Qi(^Qq(>i(jq(^i^cqtjqcocOCOCOCOCOCOTtl(N(>lG^C?l^(^<^CNCqc>l(>IGqCNCN(Nl(^ CM C. CO O 6 19 1-428 69 2-028 19 2-628 69 3-228 19 3-828 1-20 1-440 1-70 2-040 220 2-640 2-70 3-240 320 3-840 21 22 1-452 1-464 71 72 2-052 2-064 21 22 2-652 2-664 71 72 3-252 3-264 21 22 3-852 3-864 o 23 24 25 26 27 1-476 1-488 1-500 1-512 1-524 73 74 75 76 77 2-076 2-088 2-100 2-112 2-124 23 24 25 26 27 2-676 2-688 2700 2-712 2-724 73 74 75 76 77 3-276 3-288 3-300 3-312 3-324 23 24 25 26 27 3-876 3-888 3-900 3-912 3-924 6 28 29 1-536 1-548 78 79 2-136 2-148 28 29 2-736 2-748 78 79 3-336 3-348 28 29 3-936 3-948 s 1-30 1-560 180 2-160 2-30 2-760 2-80 3-360 330 3-960 31 1-572 81 2-172 31 2-772 81 3-372 31 3-972 32 33 34 35 36 37 38 39 1*584 1-596 1-608 1-620 1-632 1-644 1-656 1-668 82 83 84 85 86 87 88 89 2-184 2-196 2-208 2-220 2-232 2-244 2-256 2-2(58 32 33 34 35 36 37 38 39 2-784 2-796 2-808 2-820 2*832 2-844 2-856 2-868 82 83 84 85 86 87 88 89 3-384 3-396 3-408 3-420 3-432 3-444 3-456 3-468 32 33 34 35 36 37 38 39 3-984 3-996 4-008 4-020 4-032 4-044 4-056 4-068 CN M 8 ~! 1-40 1-680 190 2-2*0 2-40 2-880 2-90 3-480 340 4-080 41 42 43 44 45 46 47 48 49 1-692 1-704 1-716 1-728 1-740 1-752 1-764 1-776 1-788 91 92 93 94 95 96 97 98 99 2-292 2-304 2-316 2-328 2-340 2-352 2-364 2-376 2-388 41 42 43 44 45 46 47 48 49 2-892 2-904 2-916 2-928 2-940 2-952 2-964 2-976 2-988 91 92 93 94 95 96 97 98 99 3-492 3-504 3-516 3-528 3-540 3-552 3-564 3-576 3-588 41 42 43 44 45 46 47 48 49 4-092 4-104 4-116 4-128 4-140 4-152 4-164 4-176 4-188 ""or thousandths of / add, :. 150 1-800 2-00 2'40() 250 3-000 | 300 3-600 350 4-200 TABLE IVA. (Continued). f 1-2 x/ / 1-2 xf / 1-2 x/ / 1-2 x/ / 1-2 x/ 350 4-200 4-00 4-800 4-50 5-400 5-00 6-000 5-50 6-600 51 52 53 54 4-212 4-224 4-236 4-248 01 02 03 04 4-812 4-824 4-836 4-848 51 52 53 54 5-412 5-424 5-436 5-448 01 02 03 04 6-012 6-024 6-036 6-048 51 52 53 54 6-612 6-624 6-636 6-648 osp 55 56 57 58 59 4-260 4-272 4-284 4-296 4-308 05 06 07 08 09 4-860 4-872 4-884 4-896 4-908 55 56 57 58 59 5-460 5-472 5-484 5-496 5-508 05 06 07 08 09 6*060 6-072 6-084 6-096 6-108 55 56 57 58 59 6-660 6-672 6-684 6-696 6-708 o 00 360 4-320 4-10 4-920 4-60 5-520 5-10 6-120 5-60 6-720 61 62 63 4-332 4-344 4-356 11 12 13 4-932 4-944 4-956 61 62 63 5-532 5-544 5-556 11 12 13 6-132 6-144 6-156 61 62 63 6-732 6-744 6-756 J>- O 6 64 65 66 67 68 4-368 4-380 4-392 4-404 4-416 14 15 16 17 18 4*968 4-980 4-992 5-004 5-016 64 65 66 67 68 5-568 5-580 5-592 5-604 5-616 14 15 16 17 18 6-168 6-180 6-192 6-204 6-216 64 65 66 67 68 6-768 6-780 6-792 6-804 6-816 CO O 6 69 4-428 19 5-028 69 5-628 19 6-228 69 6-828 3-70 4-440 4-20 5-040 4-70 5-640 5-20 6-240 5-70 6-840 71 72 4-452 4-464 21 22 5-052 5-064 71 72 5-652 5-664 21 22 6-252 6-264 71 72 6-852 6-864 o 73 74 75 76 77 4-476 4-488 4-500 4-512 23 24 25 26 5-076 5-088 5-100 5-112 73 74 75 76 5-676 5-688 5-700 5-712 23 24 25 26 6-276 6-288 6-300 6-312 73 74 75 76 6-876 6-888 6-900 6-912 TJ< o o / / 78 79 4 OSM 4-536 4-548 Zi 28 29 1Z4 5-136 5-148 n 78 79 /!z4 5-736 5-748 27 28 29 b o!a4 6-336 6-348 77 78 79 o 924 6-936 6-948 .2 - *|* CD S J, g| . fe *> bo * be - 8 .5 OJ 5 2 " C *2 1*1 2 "S -S ~ 11 S .a 1 * 21-0 5-481 260 6-753 31-0 8-013 36-0 9-261 1 2 3 4 5 6 7 8 9 5-507 5-532 5-558 5-584 5-609 5-635 5-660 5-686 5-711 1 2 3 4 5 6 7 8 9 6-779 6-804 6-829 6-855 6-880 6-905 6-930 6-956 6-981 1 2 3 4 5 6 7 8 9 8-038 8-063 8-088 8-113 8-138 8-163 8-188 8-213 8-239 1 2 3 4 5 6 7 8 9 9-285 9-310 9-335 9-360 9-385 9-409 9-434 9-459 9-484 220 5-737 27-0 7-006 32-0 8-264 37-0 609 M o ~ 1 1 I i t 1 | 3 1 2 3 4 5 6 7 8 9 5-762 5788 5-813 5-839 5-864 5-890 5-915 5-941 5-966 1 2 3 4 5 6 7 8 9 7032 7O57 7-082 7-107 7-133 7-158 7-183 7-208 7-234 1. 2 3 4 5 6 7 8 9 8-289 8-314 8-339 8-364 8-389 8-414 8-439 8-464 8-489 1 2 3 4 5 6 7 8 9 9-533 9-558 9-583 9-608 9-632 9-657 9-682 9-707 9-732 230 5-992 28-0 7-259 330 8-514 380 9-756 1 2 3 4 5 6 7 8 9 6-017 6-042 6068 6-093 6-119 6144 6-170 6-195 6221 1 2 3 4 5 6 7 8 9 7-284 7-309 7-334 7-360 7-385 7-410 7-435 7-460 7-485 1 2 3 4 5 6 7 8 9 8-539 8-563 8-588 8-613 8-638 8-663 8-688 8-713 8-738 1 2 3 4 5 6 7 8 9 9-781 9-806 9-830 9-855 9-880 9-904 9-929 9-954 9-979 240 6-246 290 | 7-511 340 8-763 39-0 10-003 TABLE V. For calculating Specific Gravity of the Total Solids of Milk m, from the Specific Gravity s, and the percentage of Total Solids t. 5 Thou- sandth 4 s 5 Thou- sandths e3 &| 3 j3 4a 21-0 2-057 26-0 2-534 31-0 3-007 36-0 3-475 S rrt a> co 1 2 3 4 5 6 7 8 9 2-066 2-076 2-086 2-095 2-105 2114 2-124 2-133 2-143 1 2 3 4 5 6 7 8 9 2-544 2-553 2-563 2-572 2-582 2-591 2-601 2-610 2-620 1 2 3 4 5 6 7 8 9 3-016 3-026 3-035 3-044 3-054 3-063 3-073 3-082 3-091 1 2 3 4 5 6 7 8 9 3-484 3-494 3*503 3-512 3-521 3-531 3-540 3-549 3-559 5| 11 f* (0 & |.s 1-1 CO s : > ^ *H rH ^ 03 1 t O "** 1C H3 11 v .2 - T T3 J. 22-0 2-153 27-0 2-629 32-0 3-101 37-0 3-568 - - D * bJ , 2 s 1 2 3 4 5 6 7 8 9 2-162 2-172 2-181 2-191 2-200 2-210 2-220 2-229 2-239 1 2 3 4 5 6 7 8 9 2-638 2-648 2-657 2-667 2-676 2-686 2-695 2-705 2-714 1 2 3 4 5 6 7 8 9 3-110 3-120 3-129 3-138 3-148 3-157 3-166 3-176 3-185 1 2 3 4 5 6 7 8 9 3-577 3-587 3-596 3-605 3-614 3-624 3-633 3-642 3-652 ll s > a- o| o a j r* Q) M & 1 S s s -a .3 1 s ^ 3 5 - i f e 2 bfi 23-0 2-248 28-0 2-724 330 3-195 380 3-661 tsy g c 1 2 3 4 5 6 7 8 9 2-258 2-267 2-277 2-286 2-296 2-306 2-315 2-325 2-334 1 2 3 4 5 6 7 8 9 2-733 2-743 2-752 2-762 2-771 2-780 2-790 2-799 2-809 1 2 3 4 5 6 7 8 9 3-204 3-213 3-223 3-232 3-241 3-251 3-260 3-269 3-279 1 2 3 4 5 6 7 8 9 3-670 3*679 3-689 3-698 3-707 3-717 3726 3-735 3-744 s t* is i i y M rt 3 SI 8 1 1 .2 Q) e * . *& J r- 1 CO T< Oi CO II .S ei = 24-0 2-344 290 2-818 34-0 3-288 39-0 3-754 (M175) 337 TABLE VI. Showing the relation bet>rtoi the percentage of Fat p, and the Specific Gravity ' of the Total Solids m of Milk. Directions for use, see p. 30. P m P M P M P m P m 1-601 10 1-493 20 1-399 30 1-316 40 1-242 1 1-589 11 1-483 21 1-390 31 1-308 41 1-236 2 578 12 1-473 22 1-382 32 1-301 42 1-229 3 567 13 1-463 23 1-373 33 1-293 43 1-222 4 556 14 1-454 24 1-365 34 1-286 44 1-215 5 545 15 1-444 25 1-356 35 1-278 45 1-209 6 534 16 1-435 26 1-348 36 1-271 46 1-202 7 1-524 17 1-426 27 1-340 37 1-264 47 1-196 8 1-513 18 1-417 28 1-332 38 1-256 48 1-189 9 1-503 19 1-408 29 1-324 39 1-249 49 1-183 10 1-493 20 ' 1-399 30 1-316 40 1-242 50 1-177 COMPARISON OF THE METRICAL WITH THE COMMON MEASURES. MEASURES OF LENGTH. In English Inches. In English Feet = 12 Inches. In English Yards =3 Feet. In English Fathoms =6 Feet. In English Miles = 1760 Yards. Millimeter, . 0-03937 0-0032809 0-0010936 0-0005468 0-0000006 Centimeter, 0-39371 0-0328090 0-0109363 0-0054682 0-0000062 Decimeter, . 3-93708 0-3280899 0-1093633 0-0546816 0-0000621 Meter, . . 39-37079 3-2808992 1-0936331 0-5468165 0-0006214 1 Inch =2-539944 Centimeters. 1 Foot =3-0479449 Decimeters. 1 Yard = 0-91438348 Meter. 1 Mile =1-6093140 Kilometers. 1 Square Inch =6-4515669 Square Centimeters. 1 Square Foot =9-2899683 Square Centimeters. 1 Square Yard = 0-83609715 Square Meter or Centiare. 1 Acre =0-404671021 Hectare. MEASURES OF CAPACITY. In Cubic Inches. In Cubic Feet = 1728 Cub. Inches. In Pints = 3465923 Cub. Inches. In Gallons = 8 Pints = 277-27384 Cubic Inches. In Bushels =8 Gallons = 221819075 Cubic Inches. Milliliter or cub. centimeter, Centiliter or 10 cu. centim., Deciliter or 100 cu. centim., Liter or cubic decimeter, ... 0-061027 0-610271 6-102705 61-027052 0-0000353 0-0003532 0-0035317 0-0353166 0-001761 0-017608 0-176077 1-760773 0-00022010 0-00220097 0-02200967 0-22009668 0-000027512 0-000275121 0-002751208 0-027512085 1 Cubic Inch =16-3861759 Cubic Centimeters. 1 Cubic Foot =28 '3153119 Cubic Decimeters. 1 Gallon = 4 -543457969 Liters. MEASURES OF WEIGHT. In English Grains. In Troy Ounces = 480 Grains. In Avoir- dupois Lbs. = 7000 Grains. In Cwts. =11 2 Lbs. = 734,000 Grains. In Tons = 20Cwts. = 15,020,000 Grains. Milligram 0-015432 0-000032 0-0000022 0-00000002 o-ooooooooi Centigram 0-154323 0-000322 0-0000220 0-00000020 o-oooooooio Decigram, 1-543235 0-003215 0-0002205 0-00000197 0-000000098 (Jr; nil, 15-432349 0-032151 0-0022046 0-00001968 0-000000984 Decagram , 154-323488 0-321507 0-0220462 0-00019684 0-000009842 Hectogram, 1543-234880 3-215073 0-2204621 0-00196841 0-000098421 Kilogram.... 15432-348800 32-150727 2-2046213 0-01968412 0-000984206 1 Grain = 0*06479895 Gram. 1 Troy oz. =31-103496 Grams. 1 Lb. Avd. = 0-45359265 Kilogr. 1 Cwt. =50-80237689 Kilogr. OF THE UNIVERSITY INDEX. Acarus siro, 232. Acid generator, preparation of, 99. Acidity of milk, determination of, 204. Acids, coagulation of milk by, 201. Adams' fat estimation method, 83-84. Adulteration of, butter, 195; milk, 65-74. Aerobic bacteria, 95. Aerometric estimation of milk-fat, 70. Age of cows, value of knowledge of, 40. Albuminoids of milk, 15-19. Albuminose, 16. Alcohol, preparation of, from whey, 270. Alexandria cream-separator, 121. Alpha separators, 129, 131-132, 133, 134. Alveoli, 2. American butterine, composition of, 322. American Cheddar cheese, 249. Ammonia in milk, 30. Amphoteric reaction of milk, 11-12. Anaerobic bacteria, 95. Analysis of, butter, 195-199; cheese, 272-275; milk, 80-88. Annatto colouring matter, 177. Antiquity of cheese-making, 243. Arnoldt's hand separator, 128. Aroma of milk, 190. Ash of, butter, composition of, 195 ; cheese, 274; milk, determination of, 86; whey, composition of, 270. Baby separators, 132, 133, 134. Bacillus, cyanogenus, 101 ; diatrypeticus casei, 260; synxanthus, 101. Backstein cheese, 274. Bacteria of milk, 89-105; development of, 93; different forms of, 91, 93; forms and life conditions of, 93; injurious action of, in milk, 89. Bacteriology and dairying, 89-105; practical application of, 105. Balance separator, 140. Bavarian Algau, 258. Beastings, 35. Beating churns, 161, 162. Benzoic acid in milk, detection of, 88. Bergedoff's Iron Co.'s separators, 129, 133. Bicarbonate of soda in milk, detection of, 87. Bitter butter, 192. Boiled milk, detection of, 88. Books for dairy, keeping of, 305-310. Boracic acid ; in milk, detection of, 87; in rennet, 208. Box churns, 162. Budding fungi, 91. Buffalo milk, 57; cheese from, 265; composi- tion of, 57; properties of, 57; specific gravity of, 57; yield of, 57. Bulling, effect of, on milk, 40. Butter, 106, 169-199; analysis of, 195-199; appearance of, faults in, 192 ; chemical composition of, 193-195; colouring of, 177; defects in, 192; different kinds of, 185; faults of, 191-193; flavour and smell of, defects in, 192; fresh, 185; good, properties of, 191; influence of feeding on properties of, 191; investigation and testing of, 195- 199; methods in which made, 106; nature of, 159; Petersburg, 185; physical charac- teristics of, 191; preserved, 186; properties of, 169 ; salting of, 178 ; separation of, in churning, 160; specific gravity of, 194; water in, 169, 180, 193; working and knead- ing of, 179; yield of, 184. Butter-churns, 160-166. Butter colours, 177. Butter-extractors, 175-177. Butter-fat, properties of, 196. Butterine, 316-322. Butter-knife, 180. Butter-making, general remarks on, 159-161. Butter-milk, 160, 188-189; ash of, 189; com- position of, 189; uses of, 189. Butter-separator, 175-177. Butter-syringe, 180. Butter-trough, 182. Butter workers, 180-181. Butyric acid, 103. Bye-products of milk, 294. Byre, treatment of milk in, 60-61. Byre-butter, 186. Byre-test for milk, 72. Calculations for methods of milk utilization, 302-306. Calves, feeding of, with skim-milk, 157. Calves' stomachs, preparation of rennet from, 208. Calving time of cows, regulation of, 80. Capillary blood-vessels, 3. Carbonates in milk, detection of, 87. 339 340 SCIENCE AND PRACTICE OF DAIRYING. Carbonic acid in milk, 27, 30. Casein, composition of, 17, 202; heat equiva- lent of, 18; in milk, 15, 18; precipitation of, 18. Casein-gum, 295. Centrifugal acceleration, 125. Centrifugal force, 119, 125; value of, for creaming milk, 120. Centrifugal machines, proper working of, 149. Centrifugal separators, 120-153. Cheddar cheese, 249. Cheese, 200-275; analysis of, 272-275; art of making, 234-235; Cheddar, 249; buffalo- milk, 265; chemical composition of, 272; classification of, 243-246; colouring of, 213; defects of, 241; different kinds of, 243-246; Edam, 253; Emmenthaler, 256- 261; goat-milk, 265; hard, 248; hot-iron test of, 220; liquid residue of, 269; micro- organisms in, 102, 239-241; Neufchatel, 247; potato, 267; preparation of, for mar- ket, 242; pressing of, 223-227; reindeer- milk, 265; ripening of, 102-103, 231-233, 236-243; salting of, 227-231; shaping of, 221-223; sheep-milk, 261; soft, 246-247; sour-milk, 266-268; utensils for preparation of, 214; utilization of milk in manufacture of, 298, yield of, 270. Cheese-kettles, 215-218, 220. Cheese-knives, 218, 219. Cheese-ladles, 219. Cheese-milk, 269. Cheese refuse, products from, 268. Cheese-tubs, 214. Cheese-vats, 214-218, 224. Cheesy butter, 192. Cheshire curd-mill, 267. Cholera caused by germs, 95. Cholesterin in milk, 30. Churning, 159, 166-174; changes during, 168; conditions influencing, 170; definition of, 159; of milk, 173; preparation of milk for, 166; temperature for, 171. Churns, 160-166; beating, 161; description of, 161-166; horizontal barrel, 164; prac- tical value of, 166; qualifications of, 160- 161; of special construction, 165; swinging, cradle, or rocking, 162-164; varieties of, 161; vertical barrel, 165; working of, 161. Citric acid in milk, 29, 30. Cleanliness in relation to dairying, 89, 97. Coagulation of milk, 12, 200-203; by acids, 201; by bacteria, 89; by rennet, 210-213. Coagulum from milk, 200-203; preparation of, 210. Cold water cream-raising method, 114-115. Colostrum, 34-37; ash of, 36; composition of, 35, 36; corps granuleux in, 35; corpuscles, 36; properties of, 35; specific gravity of, 36. Coloured milk, 102. Colouring of, butter, 177; cheese, 213. Condensed milk, 282-286; composition of, 284, 285; preparation of, 283-284; proper- ties of, 284; specific gravity of, 285; un- sweetened, 285. Connective tissue, 1. Co-operative dairies, supervision of milk in, 77. Corps granuleux, 35. Cotswing churn, 162. Cow-dung, bacteria in, 293. Cows, age of, 40; feeding of, 41-48; treatment of, 80; working of, 40. Cradle-churns, 161, 163. Cream, 76, 154-156; ash of, 155; composition of, 155; condition of, 148; cooling of, 148; outflow of, from separator drum, 123; regu- lation of weight of, in separator, 124; ripen- ing of, for churning, 166; sour, churning of, 172; specific gravity of, 155; spontaneous souring of, 99-100; sweet, churning of, 172; utilization of, 155; valuation of, 156. Cream-butter, 185. Creaming by separators, supervision of, 145- 146. Cream -raising, 107-119; coefficient, 101; conditions necessary for, 108; methods of, 117; older methods of, 112; by separators, 119; Swartz method of, 113. Cream-souring, 166-168. Cream-yielding coefficient, 118. Curd from milk, 200-203; treatment of, be- fore moulding, 218-221. Curd-breaker, 219. Curd-knives, 219. Curd-mill, 266, 267. Curd-stirrer, 219, 266, 267. Curd-whey, 269. Currents in creaming, 178. Dairies, books for, 305-310; departments of, 149 ; model of, 315 ; proper working of separators in, 149-152; structure and arrangement of, 314; supervision of milk in, 77. Dairying, economic aspects of, 296-315; rela- tion of bacteriology to, 89-105. Danish separator, 135. Dead milk, 52. Definition of milk, 1-6. De Laval separators, 129-131, 132. Density of milk, 13. Devonshire cream-raising method, 109. Dialysis of milk, 14. Diaphragm churn, 163. Dishorning, 41. Disinfectants, 45. Distribution of milk, 61-62. Disturbances of milk, 100. Drum of separator, 122. Drying-rooms for cheese, 227. Dull butter, 192. INDEX. 341 Edam cheese, 253-256. Eimar centrifugal separator, 136. Emmenthaler cheese, composition of, 274; preparation of , 256-261; properties of , 260. Enzymes, 92, 100. Epithelial cells, 2. Erythrogenes bacteria lactis, 102. Eureka butter-worker, 180. Expansion of milk, coefficient of, 13. Extraction of milk, 58. Factors for calculating composition of milk, 32-34, 329-330. Fat, determination of, in butter, 198; in cheese, 273; in milk, 82-84. Fat cheese, conversion of milk into, 298. Fattening, value of milk for, 51-53. Faults of, butter, 191-193; cheese, 241; milk, 51-53. Feeding of cows, 41-48; influence of, on pro- perties of butter, 191. Fermentation processes, caused by bacteria, 90; nature of, 202; necessary for dairying, 90. Fermented milk, 286-291. Fibrin in milk, 30. Firmness of butter, 191; defects in, 192. Fission, 93. Fission fungi, 92, 93. Flat sugar, 293. Food, influence of, on milk secretion, 41-48; quantity of, to be given, 44-46. .Forces acting in separators, 152. Formation oi milk, 6-11. Formula? for calculating, composition of milk, 32-34, 329-330; yield of butter, 310. .French margarine, composition of, 322. Fresh butter, 185-186. Frost, action of, on bacteria, 94; on milk, 13. Fungi, distribution of, 93; functions of, 92. Galactose, 26. Gammelost, 269. Gland-basket, 2. Glarner green cheese, 266. Glasler, 260. Gleed cheese-press, 225. Globulin in milk, 15, 17. Goat, 54. Goats' milk, 53-55; amount of yield of, 54; cheese from, 265; composition of, 54; pro- perties of, 53; specific gravity of, 55. Grape-sugar, 293. Grass butter, 186. Gravity, influence of, on creaming, 119. Gruax de montagne, 269. Gruyere cheese, 256. Guaiacum, a test of milk, 12, 88. Gussander cream-raising method, 112. Hamburg mixed butter, composition of, 322. Hands, position of, in milking, 59. Hand separators, 121, 126, 128, 153. Hard cheeses, 248. Hardening of cheese-curd, 218. Heat, action of, on milk, 12. Heating of cheese-vats, 214-217. Heat units, 217. Hehner method for butter analysis, 197. Holstein butter-worker, 181. Holstein cream-raising method, 109, 112. Horizontal churns, 161, 164. Hot-air engines, 152. Hot-iron test for cheese, 220. Hydrolytic ferments, 203. Hygrometer, 231. Hypoxanthin in milk, 30. Ice, collection and storage of, 115-117; in- dispensable for dairying, 115; used in cream -raising, 113. Ice machines, 117. Indicator for separators, 128. Inertia of matter, 119. Inflation of cheese, 104. Inflow of milk into separator-drum, 123. Inorganic constituents of milk, 27-29. Inspection of milk-trade, 76-77. Intermittent sterilization, 96. Jaurt, 294. Karagrut, 294. Keeping milk, 276. Kephir, 104, 287-289; composition of, 289; grains, 287; nature of fermentation, 288; preparation of, 288; properties of, 287. Keschk, 294. Kircuma, 87. Kneading of butter, 179; temperature for, 182. Koettstorfer method for butter analysis, 197. Kongen's Nytorf separator, 136. Koumiss, 104, 289-290; composition of, 290; preparation of, 290; properties of, 289. Lactalbumin in milk, 15, 17. Lactarine, 295. Lactation periods, 39. Lactic acid, produced by bacteria, 99. Lactite, 295. Lactocaramel, 26. Lactocrit, 70, 78. Lactoprotein, 16, 18. Lange milch, 291. Lardy butter, 192. Latent heat, of milk, 13; of water, 117. Laval, cream-cooler, 149; milk-scalder, 277. Lawrence refrigerator, 148. Lazy milk, 52 Lecithin, 29, 30. 342 SCIENCE AND PRACTICE OF DAIRYING. Lefeldt, centrifugal butter - tester, 197; churns, 163; Pasteurizing apparatus, 279; separator, 126, 127, 129. Le reclage, 264. Le revirage, 204. Lever cheese- press, 226. Light, effect of milk on, 14. Limburg cheese, composition of, 274. Limits of variation in composition of rnilk, 73. Liquid residue from cheese manufacture, 269. Lobules, 2. Lower fungi, 90-93; distribution of, 93; functions of, 92. Mammary glands, 3. Mares' milk, 56-57; amount of yield of, 57; composition of, 57; properties of, 56; spe- cific gravity of, 57. Margarimeter, 196. Margarine, 316-322; composition of, 322; discovery of, 316 ; oils used for, 318 ; pre- paration of, 317; uses of, 318. Margarine cheese, 322-326; demand for, 323. Melted butter, 188. Metabiosis, 103. Micrococcus prodigiosus, 101. Micro-organisms, 89-105; destruction of, 105; discovery of, 90; forms of, 91; in cheese, 102, 239-241 ; in milk, 89-105. Milk, 1-105; adulteration of, 65-74; analysis of, 80-88; churning of, 173; coagulation of, 12, 200; coefficient of expansion of, 13; composition of, 30-32; definition of, 1; density of, 13; dialysis of, 14; difficult to churn, 53; distribution of, 61-63; factors for calculating composition of, 32-34, 329- 330; fat in, determination of, 82-84; for- mation of, 6-12; freezing of, 13; heating of, 12; lazy or dead, 52; latent heat of, 13; light, action of, on, 14; limits of variation in, 73; micro-organisms in, 89-105; mineral matter of, 27-29; minor constituents of, 29-30; nitrogenous matter of, 15-19; pre- cipitation of, 16; properties of, 11-14; pur- chase of, 77; reaction of, 11-12; refractive point of, 14; relation between specific gravity and percentage of fat and total solids, 32-34; sale of, 63-64; sandy, 53; secretion of, in udder, 37-39; influence of food on, 42-44; specific gravity of, 11, 16, 31, 32; spontaneous coagulation of, 99-100; sterilization of, 95-99; testing of, 66-74; total solids of, composition of, 31, deter- mination of, 81 ; treatment of, after milking, 60-61; utilization of, 296-315; value of, as an article of sale, 63, for fattening pur- poses, 62-63; yields, 48-51. Milk businesses, 64-65. Milk-butter, 185. Milk-cakes, 282. Milk-cisterns, 3, 4. Milk-cows, 63. Milk-diseases, 100-102. Milk-fat, 19-24; composition of, 22; condition of, 20; decomposition of, 23; determination of, 82-84; globules in milk, number of, 21, size of, 19; percentage of, in milk, 19; pro- perties of, 22 ; specific gravity of, 20, 23; solubility of, 24. Milk-faults, 51-53; causes influencing, 52. Milk-fehler, 100. Milking, 58-60. Milking machines, 58. Milking periods, 38-39. Milk-ivory, 295. Milk-production, supervision of, 79. Milk-records, 308. Milk-scalder, 277. Milk-sugar, 24-27, 294 ; composition of, 25, 294; decomposition of, 24; determination of, in butter, 199, in cheese, 274, in milk, 85-86; effect of heat on, 25; preparation of, 293; uses of, 291. Milk-testing, 66-74. Milk-trade, supervision of, 74-77. Milk-warmers, 146. Milk-yielding capacity of cows, 49-51; arti- ficial development of, 49; conditions in- fluencing, 49; determination of, 50; external characteristics of, 50. Milk-yields, 48-51; conditions influencing, 48. Mineral adulterants of milk, 87. Mineral matter of milk, 27-29. Minor constituents of milk, 29-30. Model of dairy, 315. Molkensich, 259. Moulding of cheese, 222-223. Moulds, 92. Multiplex separator, 126. Musty butter, 193. Mysost, 268; composition of, 275. Neufchatel cheese, composition of, 274; pre- paration of, 247. Niszler, 260. Nitrogen in milk, 30. Nitrogenous matter, of cheese, determination of, 273; of milk, determination of, 84-85; lost in separation of milk, 154. Nuclein, 15, 30. Nucleo-albumin, 17. Nutritive ratio, 45. Nutritive value of skim-milk, 159. Nytorf separator, 136. Oil-cakes, influence of, on milk production, 47. Oily butter, 192. Olmiitzer cheese, 274. Oneida cheese-vat, 217. Osmotic action of salt, 179, 227. Ox-flesh, protein in, 159. Oxygen in milk, 30. INDEX. 343 Ozone reaction for boiled milk, 88. Paracasein, 202, 236. Paris butter, 185. Pasteurized milk, 276-280; properties of, 277. Pasteurizing apparatus, 278. Pasteurizing of milk, 61, 95; effects of, 276. Pathogenic germs, 95, 276. Payment of milk by weight and composition, 311-313. Pegot, 264. Percentage composition of cows' milk, 30-32. Petersburg butter, 185. Petersen separator, 135. Petroleum engines, 152. Pigs, feeding of, with skim-milk, 157. Piophila casei, 232. Potato cheese, preparation of, 267. Pottkass, 256. Power separators, 131. Preservatives, for butter, 199; for milk, 60. Preserved butter, 186. Preserved milk, 282-286. Pressing of butter, 182. Pressing of rennet cheese, 223-227. Prima weinar sparbutter, 320; composition of, 323. Profits from utilization of milk by different methods, 302-305. Properties of milk, 11-14. Prophet's grains, 287. Proteids, determination of, in butter, 198; in milk, 84-85. Protein, 15. Ptomaines, 92. Puffiness in cheese, 261. Pultost, 269. Putrefaction, caused by bacteria, 90. Raden cheese, composition of, 274. Eancid butter, 192. Reaction of milk, 11-12. Recuit, 268. Refractive point of milk, 14. Refrigerators, 148. Reib cheese, 275. Reichert method for butter analysis, 197. Reimer creaming method, 112. Reindeer-milk cheese, 265. Rennet, 203-213; application of, in practice, 210-213; coagulation of milk by, 201-206; conditions favourable for action of, 204; determination of strength of, 206; forms used in, 206; preparation of, 208; proper- ties of, 205, 208; sources of, 203; tempera- ture for coagulating by, 205; testing of, 206. Rennet cheeses, shaping of, 221 ; from sheeps' milk, 261; hard, 248; pressing of, 223-227; salting of, 227; soft, 246. Rennet powder, 206. Eennet test for milk, 79. Resistance to rising of fatty globules, 107. Reverum, 264. Ribarbe blanche, 264. Ricotta, 268. Ripe milk, 166. Ripening of cheese, 102-103, 236 -243; changes in, 236; effected by micro-organisms, 102; products of, 239. Ripening of cream for churning, 166. Ripening rooms for cheese, 231-233. Rocking churns, 161, 163. Ropy milk, 101, 287, 291. Roquefort cheese, preparation of, 262-265. Sale of milk, 63, 296. Salicylic acid in milk, detection of, 87. Salt, 178. Salting of, butter, 178, 181; cheese, 227. Sampling of milk, 68. Sandy milk, 53. Saprophytic germs, 95. Sarcina, 102. Schottensicht, 268. Scoops for cheese-making, 218, 219. Secretion of milk in udder, 37-39; influence of food on, 42-44. Separator butter, 185. Separator drum, 122; inflow of milk into, 123; milk in, 122; outflow of cream and skim- milk from, 123; reliability of, 124; super- vision of revolving rate of, 145. Separator residue, 153-154; bacteria it, 98; composition of, 154. Separators, 120-153; Alpha, 131-134; bal- ance, 140; best, 141; Burmeister& Wain's, 134-137; cream-raising coefficient in, 141; De Laval, 129-131; forces acting in, 152; hand, 121, 126, 128, 132, 137; invention of, 120; Lefeldt, 126; multiplex, 126; power, 126-127; presently used, 126, 140; proper working of, in dairies, 149-152; value of, 141; regulation of weight of cream and skim-milk in, 124; Victoria, 138. Shaping of cheese, 221-223. Sheep, 55. Sheep's milk, 55-56; amount of yield of, 55; composition of, 56; properties of, 55; speci- fic gravity of, 56. Siberian butter, 188. Skim-milk, 76, 156-159; ash of, 158; composi- tion of, 158 ; fattening power of, 114 ; nutritive value of, 159; outflow of, from separator drum, 133; properties of, 156; regulation of weight of, in separator, 124: separator, fat in, 142; specific gravity of, 76, 156 ; uses of, 157; value of, 158. Skim-milk cheese, 275. Skimming- tubes, 124. Slimy milk, 101. Soapy butter, 193. Soft cheeses, 246. 344 SCIENCE AND PRACTICE OF DAIRYING. Sourers, 167. Souring liquid, preparation of, 99, 167. Sour-milk, 188-189. Sour-milk cheese, 266-268; composition of, 275. Soxhlet's fat estimation method, 70. Spaltpilz, 101. Specific gravity of butter, 194. Specific gravity of milk, 11, 16, 31, 72, 76; determination of, 68; relation between, and percentage of total solids and fat, 32-34, 329. Specific heat, of milk, 13; of water, 117. Spontaneous coagulation of milk, 99-100. Spontaneous souring of cream, 99-100. Spores, 94. Starch in milk, detection of, 88. Steam for separators, 152. Sterilization of milk, 95-99; effects of, 95; intermittent, 96; temperature for, 96. Sterilized unthickened milk, 280-282. Sterilizing apparatus, 281. Stirrers for cheese-making, 218, 219. Structure and arrangement of dairies, 314. Stubble butter, 186. Sugar-sand, 293. Sulphates in milk, 30. Sulphocyanates in milk, 30. Summer butter, 186. Supervision of milk-trade in towns, 74-77. Surprim, 269. Swartz's cream-raising method, 113. Sweet-cream churning, 160, 172. Sweet- milk churning, 160. Swinging churns, 161, 163. Swiss butter-worker, 180. Swiss lever-press, 275. Symbiosis. 101. Table butter, 185. Tables for, calculating, total solids from per- centage of fat and specific gravity, 334-336; specific gravity of total solids of milk, 337; correcting temperature, 331; regulating separation of milk, 157. Tallowy butter, 192. Tea butter, 185. Teats of cows, 4-7. Temperature for, churning, 171-172; cream- raising, 108, 111; milk separation, 146. Testing of milk, 66-74. Thickened milk, 284. Thranen cheese, 256. Tin-foil for cheese packing, 243. Total solids of milk, 31-32; composition of, 31; determination of, 81; specific gravity of, 12. Toxalbumin, 92. Treatment of milk after milking, 60-61. Trimethylamine, 102. Tuberculosis caused by germs, 95. Tunica propria, 3. Two-in-one double cheese-press, 224. Typhus, caused by germs, 95. Tyrothrix, 100. Udder, 1-5; secretion of milk in, 37-39. Unit of heat, 117. Unsweetened condensed milk, 285; composi- tion of, 286. Unthickened sterilized milk, 280-282. Urea in milk, 30. Utensils necessary for cheese preparation, 214. Utilization of milk, 296-315. Vacuum-pan for condensing milk, 283. Vegetative cells, 93. Vertical churns, 161, 165. Vessels for, cream-raising, 112; milk, 62, 105. Victoria churns, 163, 164. Victoria separators, 138-139. Vinegar from whey, 270. Volatile fatty acids in butter, 196. Vorbruch, 187, 269. Warmers for milk separators, 146. Water, determination of, in butter, 197; cheese, 273; milk, 81. Weighing of milk, machine for, 306, 307. Whey, 269-270; composition of, 269. Whey butter, 187, 258, 269. Whey champagne, 270. Whey cream, 258. Whey protein, 202. Whey punch, 270. Winches for dairies, 152-153. Winter butter, 186. Woody butter, 192. Working of, butter, 179, 182-183; cows, 40. Yeasts, 92. Yield of, butter, 184; cheese, 270; milk, 48- 51 ; conditions influencing, 48. Ziger, 268; composition of, 275. Ziger cheese, 258, 268. Zoogloa bacteria, 101. UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. 2 JAN 1948 LD 21-100m-9,'47(A5702sl6)476 YD CMF