Lib. v '. V.A -~~*- TO THE MEMORY of MY FATHER This Volume is Dedicated COPYRIGHT, 191S O. F. HUNZIKER CONDENSED MILK and MILK POWDER SECOND ED ITION AND ENLARGED PREPARED FOR THE USE OF Milk Condenseries, Dairy Students and Pure Food Departments By OTTO F. HUNZIKER, B. S. A., M. S. A. \ \ Formerly Professor of Dairy Husbandry, Purdue University and Chief of the Dairy Department of the Indiana Agricultural Experiment Station LaFayette, Indiana Now Manager Manufacturing Department and Director Research Laboratory Blue Valley Creamery Co. Chicago Published by the Author La Grange. Illinois 1918 I L <"? H . DEPT, PREFACE This book treats of the various phases of the condensed milk and powdered milk industry. It discusses every step in the process of manufacture, following the milk from the farmer's door to the finished product in the pantry of the consumer. The processes of condensing and desiccating milk, skim milk, buttermilk and whey are given special attention and the defects of the product, their causes and prevention are explained in detail. The inception of this publication is the result of innumerable and persistent calls for definite and reliable information on the sub- ject of condensed milk and milk powder, from manufacturers in this country and in foreign lands ; from parties contemplating embarking in the business ; from national and state experiment stations which are oftentimes called upon to investigate condensed milk defects; from dairy schools desiring to give instruction on the subject ; from national and state pure food, departments, seeking information con- cerning the possibilities and limitations of manufacture, in their efforts to formulate and enforce standards and laws ; and from com- mercial chemists in need of reliable methods of analyses of these special dairy products. The information contained in this volume represents the author's experience, covering a period of twelve years, in the prac- tical manufacture of condensed milk, as expert advisor to milk condensing concerns in the United States, Canada and Australia, and as visitor of condensed milk and milk powder factories in this country and in Europe. It is the author's hope that the information contained herein may serve as a guide to manufacturers, investigators, teachers and food authorities, alike ; that it may assist in a better understanding and wider dissemination of the principles, phenomena and facts involved in the processes of manufacture; and that it may lift the obstructing veil of unnecessary secrecy which has hovered over these industries since their beginning, curtailing their development and depriving them of much of the light of advanced science to which they are justly entitled and which they need for their greatest development for the lasting benefit of the producer, manufacturer and consumer alike. O. F. HUNZIKER. Purdue University, March, 1914. PREFACE FOR SECOND EDITION Since the issuance of the First Edition of this treatise many changes have taken place in the various phases of the Condensed Milk Industry. Old processes have been modified and improved, new processes have been invented, the equipment used for manu- facture has undergone changes, new tests have been devised for the determination of the composition of the finished products and the entire status of the industry has yielded to an unexpected, unfore- seen and important evolution. Of the most outstanding new features in this edition may be mentioned the chapters on the Continuous Concentrator, the Stand- ardization of Condensed Milk and Milk Powder, Malted Milk, the Mojonnier Test, Bacteriological Analyses. Important additions have also been made to the chapters on History of the Industry, Volume of Output, Markets, Exports, Imports, Cost of Manufac- ture and the various processes of manufacture of Condensed Milk, Condensed Buttermilk and Milk Powder. In preparing the Second Edition, the author has endeavored to completely revise the old edition, incorporating in the revised edition the many changes which the tooth of time has wrought and to bring this treatise in all its important phases up-to-date. O. F. HUNZIKEX Chicago, 111., July, 1918. CONTENTS PART I CONDENSED MILK Chapter I Definition History and Development of Industry Invention of process; develop- ment of industry; output of condensed milk in the United States; 1899 to 1917 Pages 17-27 Chapter II Essentials of Suitable Locations for Milk Condensing Factories Milk supply; water supply; transportation facilities; other conditions. Building and Equipment Material of construction; drainage; general plan of factory; list of equipment; economic arrangement of machinery; sanitary arrangement of machinery Pages 28-41 Chapter III Milk Supply Basis of buying milk; quality; control of quality; in- spection of milk at the condensery; tests for purity of milk. Factory Sanitation Effect on patrons; effect on wholesomeness of product; effect on marketable property of product; how to keep factory in sanitary condition; care of milk in factory prior to manufacture Pages 41-53 PART II MANUFACTURE OF SWEETENED CONDENSED MILK Chapter IV Definition Heating Purpose; temperature; manner; advantages and disadvan- tages of different methods. Addition of Sugar Kinds; quality; amount; mixing the sugar. Pages 54-62 Chapter V Condensing Description of the vacuum pan. The Condenser Surface condenser; barometric condenser; wet- vacuum spray condenser; care of the condenser. The Expansion Tank, Catch-All, or Milk Trap. The Vacuum Pump. Science and Practice of Condensing in Vacuo Object; relation of pressure to boiling point; relation of altitude to atmospheric pressure; relation of steam pressure in jacket and coils, water in condenser, temperature in pan, and vacuum, to rapidity of evaporation. Starting the Pan. Operating the Pan. Prevention of Accidents Pages 62-87 X CoNDl^NvSED MlLK AND MlI^K POWDER Chapter VI Striking or Finishing the Batch Definition; ratio of concentration; methods of striking. Use of the Beaume hydrometer; correction of Beaume reading for temperature variations; specific gravity of sweetened con- densed milk of different Beaume degrees; sampling the batch. Drawing off the condensed milk. Cooling the Condensed Milk Pages 87-97 Chapter VII Filling Filling in barrels; filling in cans. Sealing Kinds of seals; soldering devices and machinery; solder; soldering flux; gas supply, gas generators Pages 97-103 PART III MANUFACTURE OF UNSWEETENED CONDENSED MILK EVAPORATED MILK Chapter VIII Definition. Quality of Fresh Milk. Heating the Milk. Condensing. Striking Use of the Beaume hydrometer; correction of Beaume read- ing at temperatures other than 60 F.; calculation of specific gravity from Beaume reading 104-110 Chapter IX Homogenizing Purpose; principle of the homogenizer; kinds of homogenizers; operation of the homogenizer; effect on casein. Pages 110-114 Chapter X Cooling. Filling, Filling Machines. Sealing, Sealing Machines Pages 114-120 Chapter XI Sterilizing Purpose of sterilization; sterilizers; loading the sterilizer; uniform distribution of heat; temperature and time of exposure; qualifications of processor; rapid and uniform cooling; fractional sterilization. Shaking Methods of shaking; speed of the shaker; efficiency of dif- ferent types of shakers; formation of curd not desirable nor necessary. Incubating Pages 120-129 Chapter XII Plain Condensed Bulk Milk Definition; quality of fresh milk; heating of fresh milk; condensing; superheating; striking; ratio of con- centration; cooling Pages 129-132 CONDENSED MILK AND MILK POWDER XI Chapter XIII Concentrated Milk Definition; apparatus needed; operation of Camp- bell process; advantages and disadvantages of Campbell process. Pages 132-133 Chapter XIV Condensing by Continuous Process Buflovak rapid circulation evap- orator, construction, operation; continuous concentrator, descrip- tion, speed of agitator, operation, possibilities Pages 133-141 Chapter XV Condensed Buttermilk Manufacture, separation of curd by gravity, evaporation in vacuo, evaporation by hot air blast, evaporation by continuous concentrator, evaporation by centrifugal separa- tion; packing; composition; uses. Condensed Whey, Myseost, or Primost Pages 141-146 PART IV FROM FACTORY TO CONSUMER Chapter XVI Stamping. Inspecting Checking the work of the sealers; disposition of leaky cans; importance of inspection. Labeling Labeling machines; principle of labeling machines; wrin- kles and rust spots on labels. Packing Marking the cases; packing condensed milk for export. Pages 146-152 Chapter XVII Storage Purpose of storing; effect of storage temperature; advisabil- ity of storing. Transportation Pages 152-155 Chapter XVIII Markets Market prices of condensed milk; effect of World-War on prices; commercial stock Jan. 1, 1918; exports and imports, 1911 to 1918 Pages 155-161 Chapter XIX Chemical Composition of Condensed Milk Sweetened condensed milk; evaporated milk; plain condensed bulk milk; concentrated milk. Pages 162-172 Chapter XX Sanitary Purity. Dietetic Value of Condensed Milk. Growth-Promoting and Curative Properties Pages 173-178 Chapter XXI Condensed Milk Standards and Laws Federal standards for; sweet- ened condensed milk; evaporated milk. Modified standard; difficulties of meeting standard; putting com- position of evaporated milk on label. XII CONDENSED MILK AND MILK POWDER Condensed Skim Milk. Explanatory Notes Concerning Legality of Federal Standards. Requirements of Composition for War Contracts Pages 178-186 Chapter XXII Cost of Manufacture General Discussion. Cost of sweetened condensed milk per case. Cost of evaporated milk per case Pages 186-190 PART V CONDENSED MILK DEFECTS, THEIR CAUSES AND PREVENTIONS Chapter XXIII Classification of Defects. Defective Sweetened Condensed Milk Sandy, rough or gritty; settled; thickened and cheesy; lumpy; fermented; rancid; putrid; metallic; brown Pages 190-215 Chapter XXIV Defective Evaporated Milk and Plain Condensed Bulk Milk Curdy; grainy; separated and churned; fermented, acid curd, bitter curd, gassy fermentation. Swelled cans due to freezing; swelled cans due to chemical action; brown; gritty; metallic Pages 215-229 Chapter XXV Adulterations of Condensed Milk Skimming; addition of artificial fats; addition of commercial glucose; addition of bi-carbonate of soda, ammonium hydroxide, lime water and other alkali; addition of cream of tartar-; addition of starch Pages 229-233 PARRT VI MANUFACTURE OF MILK POWDER Chapter XXVI Definition. Kinds. History and Development of Industry. Quality of Fresh Milk. Description of Principal Processes; Wimmer process; Just-Hatmaker process; Ekenberg process; Buflovak process; Campbell process: Merrell-Gere process .Pages 234-245 Chapter XXVII Packing for Market. Composition. Defects of Milk Powders High water content; insoluble milk pow- ders; non-miscible milk powders; rancid milk powders. Markets; commercial stocks of dried milk Pages 245-248 CONDENSED MILK AND MILK POWDER XIII Chapter XXVIII Dried Buttermilk and Dried Whey Manufacture of; composition of buttermilk powders Malted milk. Federal Standards for Milk Powders and Malted Milk. . .Pages 248-252 Chapter XXIX Standardization Standardizing fluid milk for fat and milk solids; standardizing condensed milk for fat, solids not fat and total solids Pages 253-258 Chapter XXX Practical Methods of Systematic Examination of Product for Market- able Properties Number of samples needed; frequency of exam- ination; technique of examination; interpretation of results; systematic examination a necessary factor of economic manu- facture Pages 258-260 Chapter XXXI Chemical Tests and Analyses Milk specific gravity total solids ash total nitrogen casein and albumin lactose butterfat. Sweetened Condensed Milk Preparation of sample specific grav- ity total solids ash proteids lactose butterfat sucrose milk solids. Evaporated Milk Preparation of sample specific gravity total solids tables showing total solids, when Beaume reading and per cent fat are known ash proteids lactose butterfat. Milk Powders Total solids ash proteids lactose sucrose butter fat Pages 261-283 Chapter XXXII Mojonnier Test for Fat and Solids List of equipment; directions for operating; fresh milk, skim milk, whey and buttermilk; sweetened condensed milk, evaporated milk and plain condensed bulk milk; powdered milks and malted milk Pages 283-294 Chapter XXXIII Detection of Adulterants and Preservatives Extraneous water; skim- ming; extraneous water and skimming; artificial coloring; sucrose of lime; lime; gelatin; formaldehyde; boric acid; benzoic acid; salicylic acid; hydrogen peroxide Pages 295-305 Chapter XXXIV Bacteriological Analysis Sampling, dilutions, preparation of media, plating, incubation, making counts, qualitative determinations. Table Showing Legal Standards of Dairy Products by States Pages 307-311 ACKNOWLEDGMENTS The author desires to express his high appreciation and grat- itude to Mr. A. W. Milburn, president Borden's Condensed Milk Co., for cuts for illustration of Gail Borden and of the first milk condensing factory in the United States ; to Messrs. Louis Latzer, president Helvetia Condensed Milk Co., J. P. Meyenberg, vice- president Alpine Evaporated Cream Co-, and to John F. Mont- gomery, president John Wildi Evaporated Milk Co., for valuable biographic data concerning the early history of the evaporated milk industry ; to Messrs. D. A. Yoder, president, and Howard S. Mellott, superintendent, of the Ohio Dairy Co., for gener- ous assistance in assembling data and information relating to the origin, construction and operation of the "Continuous Con- centrator"; to Mr. T. Mojonnier, president of the Mojonnier Bros. Co., for detailed directions for the operation of the Mojon- nier test and other phases of the condensed milk industry; to Mr. R. C. Horlick, president of Horlick's Condensed Milk Co., for valuable information on the malted milk industry; to Mr. S. R. Park, superintendent Interstate Milk Products Co., Sparta, Wis., for many valuable suggestions, particularly on standardization ; to Prof. A. C. Anderson, Michigan Agricultural College, for valuable data on war-time cost of manufacture; to Dr. C. L. Alsberg, chairman of Board of Editors, for permission to quote from the Journal of the A. O. A- C., and to the following manu- facturers of machinery and supplies related to the manufacture of condensed milk and milk powder for valuable cuts for illus- tration in the text and for their generous contributions of adver- tisements as shown at the conclusion of this volume, whose kindly and active co-operation made possible the issuance of this publi- cation; Alois Aufrichtig Copper & Sheet Iron Works; A. H. Barber Creamery Supply Co., Bausch & Lomb Optical Co., Buf- falo Foundry & Machine Co., By-Products Recovery Co., Cream- ery Package Manufacturing Co., Davis-Watkins Dairymen's Manufacturing Co., F. G. Dickerson Co., The Engineering Co., J. B. Ford Co-, General Laboratories, Geuder, Paeschke & Frey Co., Groen Manufacturing Co-, Hamilton Brass & Copper Works, Arthur Harris & Co., Jalco Motor Co., Jensen Creamery Machin- ery Co., Mojonnier Bros. Co., Louis F. Nafis, Inc., The Pfaudler Co., C. E. Rogers, E. H. Sargent & Co., Schaefer Mfg. Co., The Sharpies Separator Co., The Simpson-Doeller Co., L. Sonneborn Sons, Inc., Stevenson Cold Storage Door Co., Sturges & Burn Mfg. Co., C. J. Tagliabue Mfg. Co., Torsion Balance Co-, The Vulcan Detinning Co. Complete Milk Condensing Unit for Dairy Schools and Experimental Laboratories The dairy school is the manufactory of dairy knowledge, the clearing house of dairy thought, and the distributor y of the dairy gospel. PART I. CONDENSED MILK CHAPTER I. DEFINITION Condensed milk is cow's fresh milk from which a considerable portion of the water has been evaporated and to which sucrose may or may not have been added. There are chiefly two classes of condensed milk, namely, sweet- ened and unsweetened. Both reach the market in hermetically sealed tin cans intended for direct consumption, and in bulk, in- tended for bakers, confectioners and ice cream manufacturers. A portion of the condensed milk on the market is made from the chief by-products of milk, skim milk and buttermilk. Condensed skim milk supplies the same markets as condensed whole milk sold in bulk. Condensed buttermilk furnishes a valuable chicken feed. It has, also, been recommended for medicinal purposes. HISTORY AND DEVELOPMENT OF INDUSTRY Invention of Process. Condensed milk is the child of the nineteenth century. Its origin does not date back far, and its innovation and rapid development stand in sharp contrast to those of the manufacture of butter and cheese, industries to which reference is made in the Old Testament 1 and the evolution of which has been very gradual. Notwithstanding the newness of this product, its manufacture has assumed such proportions that today it occupies a prominent place am6ng the leading branches of dairy manufactures. The condensed milk industry was introduced at about the same time as the factory system of the butter and cheese industry ; al- though, for many years before the invention of a successful process of condensing milk, methods had been sought to preserve milk. 1 Book of Genesis, C. 18, V. 8: "And he took butter and milk and the calf he had dressed and set it before them." Book of Job, C. 10, V. 10. "Hast thou not poured me out lik milk and curdled me like cheese." 18 : . V" : / HSTORY AND .iJ- Borden, the inventor of the manufacture of condensed milk, is said to have experimented some ten years before he finally decided that a semi-fluid state, produced by evap- oration in vacuo, was the best form of preservation. He first applied for a patent in 1853, but it was not until three years later that the Patent Office appreciated the originality and value of his Fig. 2. Gail Borden claim sufficiently to grant him a patent. In August, 1856, he was awarded a patent on his process both by the United States and by England. In his application Mr. Borden says i 1 "I am aware that sugar, and various extracts, have been and are now concentrated in vacuo under a low degree of heat, to pre- vent discoloration or burning. I do not claim concentrating milk in a vacuum pan for such a purpose, my object being to exclude the air from the beginning of the process to the end, to prevent incipient decomposition. This is important and I claim the discovery." * "A Brief Sketch of Gail Borden" by S. L. Goodale, Secretary Maine State Board of Agriculture, 1872. Courtesy of Borden's Condensed Milk Company. HISTORY AND DEVELOPMENT 19 The claim, United States Patent, August, 1856, is in the fol- lowing words: "Producing concentrated sweet milk by evaporation in vacuo, substantially as set forth, the same having no sugar or other foreign matter mixed with it." Since the introduction of the process of milk condensing, in- vented and patented by Borden, numerous modifications of the process, as well as entirely different processes, have been invented in this country and abroad. The most characteristic among these are: condensation by refrigeration, by centrifugal force, by boiling under atmospheric pressure, by passing hot air through milk, etc. Most of these new processes have not proved commercially satis- factory, with the result that the principle of the process, originally invented by Gail Borden, and which consists of condensing the milk in vacuo to a semi-fluid liquid, is still made use of in the manufacture of the great bulk of condensed milk produced, both in this country and abroad. While the claim of the patent granted Gail Borden was that of "producing concentrated sweet milk by evaporation in vacuo without the admixture of sugar or other foreign matter," records show that Gail Borden manufactured sweetened condensed milk, sold under the famous Eagle Brand label as early as 1856. The first adver- tisement by Borden of unsweetened condensed milk was recorded in Leslie's Weekly, May 22, 1858. It reads as follows : "BORDEN'S CONDENSED MILK. Prepared in Litchfield County, Conn., is the only milk ever concentrated without the admixture of sugar or some other substance and remaining easily soluble in water. It is simply Fresh Country Milk, from which the water is nearly all evaporated, and nothing added. The Committee of the Academy of Medicine recommend it as 'an article, that, for purity, durability and economy, is hitherto unequalled in the annals of the milk trade.' "One quart, by the addition of water, makes two and a half quarts, equal of cream, five quarts rich milk and seven quarts good milk. "For sale at 173 Canal Street, or delivered at dwellings in New York or Brooklyn at 25 cents per quart." Development of Industry. The beginning was small, the process crude and the product imperfect. Not until the strenuous years of the war of Secession did the value and usefulness of con- 20 HISTORY AND Fig 3. The first condensed milk factory In America, Wolcottville, Conn. densed milk as a commodity become fully recognized. During the Civil War there was a great demand for this product and from that time on the industry grew with great rapid- ity. The first factory was operated by Gail Borden in Wolcottville, Litchfield county, Connecticut, in the summer of 1856, but disap- pointed in not obtaining means, nothing was accomplished. A sec- ond attempt was made at Burrville, five miles distant, in 1857, by a company consisting of the owners of the patent. A small quantity of milk was here successfully con- densed and its introduction into New York began. Although admitted by all to be superior to any before made, it was slow in meeting with sales proportional in magnitude to the expenses in- curred. Yielding to the monetary revulsion of that year the company suspended operations, leaving Mr. Borden liable for bills drawn, on which he was sued. It was not until February, 1858, when Mr. Borden (with the other owners of the patent) associated himself with Jeremiah Mil- bank, Esq., who advanced money to revive the business, that he could be said to enjoy adequate means to develop his invention and at which time the New York Condensed Milk Company was formed. Abandoning Burrville, the new company established work on a more extensive scale in Wassaic, Duchess county, New York, in 1860. In 1865, extensive works were erected at Elgin, Illinois. Borden's Condensed Milk factories today number upwards of fifty, extending from Maine to Washington State as well as into Canada. The New York Condensed Milk Company was incorporated in New Jersey in 1860 and in New York in 1870. This company was succeeded by Borden's Condensed Milk Company which was incor- porated in New Jersey in 1899. In the sixties of the last century, the Anglo- Swiss Condensed Milk Company was organized in Switzerland under the leadership of Charles A. Page, then United States Consul at Zurich, Switzer- land, and his brother George H. Page, and with the assistance of HISTORY AND DEVELOPMENT 21 Swiss and English capital. The first factory of that company was built and operated in 1866 at Cham, Lake Zug, Switzerland, under the direction of George H. Page, who was its president until 1898, when he died. This company prospered and grew rapidly in Europe. In the eighties of the last century it invaded the United States, where it built and operated several large factories in New York, Wisconsin and Illinois. The American factories were managed by David Page and William B. Page, brothers of George H. Page. In 1902 the Anglo-Swiss Condensed Milk Company sold its entire American I BKMSCaid iSsss Morey Gondensery, North Prairie, Wis. interests, factories and business, to Borden's Condensed Milk Com- pany. In 1904 the Anglo-Swiss Condensed Milk Company consoli- dated with Henry Nestle, of Vevey, Lake Geneva, Switzerland, an- other successful manufacturer of condensed milk. The company which is now known as the Nestle-Cham Condensed Milk Company, is operating some twenty large condensed milk factories in European countries, with headquarters at Cham, Switzerland. Up to the early eighties of the last century, sweetened con- densed milk was the only condensed milk that was put on the market and sold in hermetically sealed cans, while unsweetened condensed milk was manufactured and sold open, largely direct to the con- sumer, in a similar way as market milk. The purity and keeping quality of this unsweetened condensed milk, however, were greatly superior to market milk. Early in 1885 the Helvetia Milk Condensing Company was organized at Highland, Illinois. This company confined its efforts exclusively to the manufacture of evaporated milk (unsweetened 22 HISTORY AND DEVELOPMENT condensed milk, sterilized by heat and sold in hermetically sealed cans). While, for several years before the organization of this company, the possibilities of producing a sterile unsweetened con- densed milk were essayed in laboratory investigations by scientists, and while simultaneously with the commencement of operations of this company, several other companies also experimented on this form of condensed milk, the Helvetia Milk Condensing Company was the first organization that succeeded in producing a marketable unsweetened condensed milk that was sterile and would keep in- definitely. Fig. 5. John B. Meyenberg The rudiments of the process of evaporated, sterilized milk were introduced by Mr. John B. Meyenberg, a native of Switzer- land, who formerly was operator in the mother plant of the Anglo- Swiss Condensed Milk Co. at Cham, Switzerland. Mr. Meyenberg, being a man with an inventive turn of mind, experimented on the evaporation and sterilization of milk, during the years 1880 to 1883. As the result of these experiments he decided that it was possible to preserve milk, without the aid of sugar. Migrating to this country, he applied for, and was granted a patent on his idea of preserving milk by sterilization, by the United States Government in 1884 (Patent No. 308,422), and again in 1887 (Patent No. 358,213). Mr. Meyenberg was also granted patent rights (Patent No. 308,421) on apparatus for preserving milk. HISTORY AND DEVELOPMENT 23 Attracted to Highland, Illinois, by reason of its large Swiss population, on the representations of Mr. A. J. Pagan, a leading Highland citizen, who brought Mr. Meyenberg to Highland and introduced him to the community, Mr. Meyenberg associated himself with Mr. John Wildi, then a merchant of Highland, who at once took a leading part in the organization of the Helvetia Milk Con- densing Co., early in the year 1885. Mr. Meyenberg served as the technical manager for the first year, after which he severed his connections with this company and became engaged in the promo- tion of other evaporated milk factories in the middle west, and on the Pacific Coast. Mr. Meyenberg died in 1914. During the first year of its existence, operations of the Helvetia Milk Condensing Company were suspended a number of times, both on account of difficulties encountered in the technique of successful manufacture and also for financial reasons. In an endeavor to place the company on a technically and commercially successful basis, the board of directors took charge of the work with Mr. Louis Latzer as technical manager, and the first half of the second year was mostly devoted to experimental work. During the third year, inter- ruptions in the operations were only slight and after that the com- pany operated continuously and successfully until the panic of 1893, which marked the last suspension of business and which was due to the strained commercial conditions that prevailed throughout the country. The first board of directors of this company was composed of Dr. Knoebel, John Wildi, George Roth, Fred Kaeser and Louis Latzer, with Dr. Knoebel as president and Mr. Wildi as secretary and treasurer, and business manager. In 1888 Mr. Latzer became president, which position he is holding to the present day. In 1907 Mr. Wildi severed his connection and organized the John Wildi Evaporated Milk Co. with headquarters in Columbus, Ohio. Mr. Wildi died in 1910. The early development and the vicissitudes through which this pioneer company in the evaporated milk business passed are most instructively expressed by its president, Mr. Latzer : "Very little of the product turned out the first two years would now pass as standard goods. About the third year, after more knowledge of the physical and chemical properties of milk and after the introduction of the practice of fractional sterilization, had 24 HISTORY AND solved the keeping properties and had improved the physical condi- tion of the product, we felt that the industry had come to stay. After we had gained more knowledge and experience, and a lower standard of the product was adopted by the industry, the practice of fractional sterilization was abandoned for economic reasons. "The commercial part of the business also had its trials and tribulations in introducing a new and comparatively inferior product of comparatively high cost, and to overcome the prejudices of both the trade and the medical profession. "The problem thus confronting the company was to improve the product, decrease its cost and improve selling methods at the least possible cost." At first this unsweetened condensed milk, of relatively thin consistency and pregnant with the cooked flavor resulting from its exposure to high sterilizing temperatures, failed to appeal to the public, who had become accustomed to the use of the sweet, thick and semi-fluid sweetened condensed. But of late years the demand for, and the manufacture of this product, evaporated milk, has increased rapidly, until today, in this country, its output by far exceeds that of sweetened condensed milk. Originally this unsweetened sterilized condensed milk was labeled and sold under the name of "Evaporated Cream." The Federal Food & Drugs Act of 1906 caused the name "Evaporated Cream" to be changed to "Evaporated Milk." A further important step in the development of the manufac- ture of condensed milk occurred with the introduction of the Con- tinuous Concentrator, which machine was developed by the By- Products Recovery Co., of Toledo, Ohio. This company was or- ganized in 1913 and their machine and process are covered by numerous United States patents. The principle upon which the Continuous Concentrator is constructed and operates is as follows: "To rapidly move a film in layer formation within a cylinder having a heated surface, having means for escaping vapors and means for keeping the surface bright and clean, circumferentially and from the point of inlet to the point of outlet." The Continuous Concentrator in its present improved form has reached a state of perfection that renders this machine applicable for the commercial manufacture of the diverse forms of condensed milk and milk by-products. HISTORY AND 25 The simplicity and economy of the equipment involved, the simplicity and rapidity of the process and the fact that no water is required for condensing the escaping vapors, are decided advan- tages over the condensation in vacuo. Already the demand for these concentrators among condenseries and ice cream factories is very great. This process lends itself admirably to the establishment and operation of small local condenseries and milk shipping stations where milk is condensed and then shipped for packing and steriliza- tion to concentration plants. In this country, as well as in Canada and Europe, the condensed milk industry grew rapidly. Every succeeding decade marked the organization of new companies and the erection of new factories until today, there are milk condensing factories in nearly every civilized country within the dairy belt. ANNUAL OUTPUT OF CONDENSED MILK IN THE UNITED STATES 1899-1917, INCLUSIVE Years Total condensed milk Sweetened condensed Milk Unsweetened condensed Milk 1899 Pounds 1 186,921,787 (5) (5) Dollars 1 ..... 11,888,792 (5) (5) 1904- Pounds 1 308,485,182 198,355,189 110,129,993 Dollars 1 1909 Pounds 1 20,149,282 494,796,544 13,478,376 214,518,310 6,670,906 280,278,234 Dollars 1 33,563,129 17,345,278 16,217,851 1914 Pounds 2 883,112,901 (5) (5) Dollars 3 58,011,677 (5) (5) 1917- Pounds 2 Dollars 4 .. . 975,000,000 106,000,000 (5) (5) (5) (5) 1 United States Census Report for 1910. 2 United States Dairy Division, by Correspondence. 3 Value estimated at $3.40 per case. * Value estimated at $5.50 per case. 5 Not reported separately. 26 HISTORY AND DEVELOPMENT The above figures serve to emphasize the rapid growth which the condensed milk industry has enjoyed during the last decade. The total output of condensed milk in 1917 was 975,000,000 pounds, estimated at a value of $106,000,000.00. Calculating the ratio of concentration at 2.5 to 1, this output represents the utilization of 2,437,000,000 pounds of fluid milk for the condensed milk industry. The total production of fluid milk in the United States in 1917 was 84,611,350,000 pounds, of which 2.9 per cent were manufactured into condensed nxilk. The above figures largely represent canned condensed milk only. Within recent years, the manufacture of condensed milk sold in bulk, especially to the ice cream trade, has increased enor- mously. If this bulk condensed milk were included in the above figures, the amount shown for the total output would be materially augmented. A new and unprecedented impetus was given the condensed milk industry in America by the advent of the World War. The concentration of the product, its wholesomeness and high food value, the serviceableness of its package and its great keeping quality render it indispensable as a food for the army and navy as well as for the civilian population of the warring nations in its dire need for food. In this great crisis in which the food supply of the nations of the earth is playing a most important role, con- densed milk has proved its worth and the demand for this com- modity has increased to tremendous proportions. This demand has been readily responded to by the industry on the American con- tinent and has resulted in a vast increase of the output of condensed milk and in the erection of many new and large factories within the short span of the war. In 1899, there were in operation in this country about fifty factories manufacturing condensed milk, distributed over fourteen different states, New York and Illinois leading the list by over 50 per cent. In 1904, the Government estimated the total number of condenseries in operation at eighty-seven. In 1914, there were in the United States over two hundred milk condensing factories, distributed over twenty-three different states, as shown on the following page : HISTORY AND DEVELOPMENT 27 DISTRIBUTION OF MILK CONDENSING FACTORIES IN UNITED STATES IN 1914 States Number of Factories Arizona 1 California 7 Colorado 1 Illinois 39 Indiana 9 Iowa 3 Kansas 4 Kentucky 1 Maine 1 Maryland 3 Massachusetts 1 Michigan 12 Missouri 2 New Jersey 6 New York 54 North Dakota 1 Ohio 19 Oregon 6 Pennsylvania 20 Utah 6 Vermont 4 Washington . 14 Wisconsin 26 Total 23 240 The above distribution of milk condenseries has undergone con- siderable change since the beginning of the war. In many states new factories have been erected and in numerous instances cream- eries and cheese factories have been converted into condenseries. In the State of Wisconsin alone the number of condenseries has risen from 26 in 1914 to 52 in 1918. Other countries in which the condensed milk industry has made rapid progress are : Canada, Australia, New Zealand, Switzerland, Germany, England, Ireland, Holland, Sweden, Norway, Austria, Russia, Japan and India. 28 ESSENTIALS OF SUITABLE LOCATIONS CHAPTER II. ESSENTIALS OF SUITABLE LOCATIONS FOR MILK CONDENSING FACTORIES Unlike the establishment of creameries and cheese factories, the building of condenseries and the installing of the necessary ma- chinery involve the investment of large capital. There is need of a substantial building and of expensive machinery. The supplies are numerous and must be purchased in larger quantities before the returns from the sale of the manufactured product are avail- able. It is estimated that it takes from three to six months before the condensed milk reaches the consumer. This holds true espec- ially in the case of canned goods. The fixed expenses also are com- paratively heavy, and do not materially change with a decrease or increase in the milk supply. All of these facts emphasize the importance of locating the factory in a territory most suitable for economic manufacture, to guard against heavy loss which would naturally result in localities unfavorable to the industry. The chief factors to be considered in this connection are: Milk supply Water supply Transportation facilities. Other conditions. Milk Supply. A large supply of milk with possibilities for extending the milk supply territory is the first essential. The con- densery must have milk to do business. The locality in which it is located must be adapted for the production of large quantities of milk; it must be a dairy country where reasonably large herds are kept. Other things being equal, the larger the milk supply, the lower the cost of manufacture. Where the milk supply drops be- low fifteen thousand pounds of milk daily, profitable manufacture becomes difficult. Territories of gathered cream creameries are usually not very desirable. The farmers generally have small herds and are not inclined to haul their milk daily. They prefer to take their cream to the creamery once or twice per week, or whenever it is convenient for them to do so. Again, they appreciate the feed- ing value of the skim milk and depend on the skim milk to raise ESSENTIALS OF SUITABLE; LOCATIONS 29 their young stock and pigs. When they take their milk to the con- densery, there is no skim milk nor buttermilk left for feeding pur- poses. The presence of whole milk creameries and cheese factories renders a locality most attractive for the establishment of milk condenseries. The farmers usually have reasonably large herds, they are accustomed to take reasonable care of their milk and to haul it to the factory daily, and the condensery prices are generally high enough above the creamery or cheese factory prices to induce the fanners to patronize the condensing factory. Territories in close proximity of large consuming centers, though dairying may have reached a high state of development, are not desirable, owing to the continuous and growing demand for fresh milk. Competition of this kind means high prices, which no business tactics are capable of modifying. Water Supply. The value to the milk condensing plant of a generous and never-failing supply of clean, cool water cannot be overestimated. The folly of erecting condenseries without first ascertaining the water supply has in some instances compelled milk condensing companies to abandon new plants, merely because of lack of water. In addition to the water used in the boilers and for washing purposes, large amounts of water are necessary for condensing and for cooling the condensed milk. It is estimated that the condensa- tion of one pound of fresh milk requires about three gallons of water. The water must be pure. In spite of all precautions, it will come in contact, more or less, with the milk. Though all apparatus and utensils holding and conveying milk and condensed milk may be thoroughly steamed after rinsing with water, there are untold channels through which the milk may become contaminated with polluted water. Frequently, while the milk is condensing, the vac- uum pump accidentally stops. If the processor fails to immediately shut off the water supplying the condenser, water will pour back from the condenser into the milk in the vacuum pan. In the case of filthy, polluted water, the entire batch may be ruined. Again, the pan is usually rinsed between batches and, if the water used is unclean, it will contaminate the milk of the succeeding batch. 30 ESSENTIALS OF SUITABLE LOCATIONS Finally, when the heavy 40-quart cans filled with condensed milk are set into the cooling tank, water frequently splashes over into the cans. Here again the quality of the condensed milk is jeopar- dized, unless the water used is pure. The water must be cold. The colder the water the more sat- isfactory is the operation of the vacuum pan. If the temperature of the "water used in the condenser rises much above 65 degrees F., the process of condensing becomes difficult. Cold water is essen- tial, also, for the prompt and proper cooling of the condensed milk. Transportation Facilities. It is essential that the factory have access to one or more railway lines. While, for reasons discussed under "Milk Supply," it is not advisable to erect a factory in too close proximity to large consum- ing or railway centers, it is equally undesirable to choose a conden- sery site where transportation facilities are poor. Where access to one railroad only can be had, the factory is at the mercy of that road. Experience has shown that monopoly of transportation usually means a low standard of efficiency of service and high freight rates. 1 On the other hand, competition in- volves a struggle for the survival of the fittest, and it offers the public all the inducements that business ingenuity and enterprise can produce. Where two or more transportation companies are after the business of the same manufacturing concern, they will generally leave nothing undone in the way of accommodations and low rates to please the manufacturer. The result is that the man- ufacturer enjoys the advantages of efficient service, good accom- modations and reasonable freight rates. 1 This is a factor which the condensery cannot afford to over- look, as the freight charges are a very conspicuous item in the ex- pense account of the milk condensing business. A part of the fresh milk may have to be shipped to the factory by rail, all the finished product must leave the factory by rail and the condensery is de- pendent on the railway for its raw materials and supplies, such as sugar, tinplate, solder, box shooks, barrels, labels, oil, rosin, gaso- line, coal, etc. Prompt and efficient transportation is essential. 1 The matter of freight rates is now largely regulated by the Federal De- partment of Transportation. BUILDING AND EQUIPMENT 31 Undue delays may cause the condensery serious inconvenience and loss, and may result in the cancelling of important orders. Other Conditions. The removal of the sewage of the factory is important. It may be possible for the factory to connect with the town or city sewer, in which case the problem is easily solved. Where this is not possible, a site along a creek, river, pond or lake may offer effective means to take care of the condensery sewage. Where no such natural depository is-available, the elevation of the site should be sufficient to carry off the sewage far enough from the factory to insure the plant against foul odors and unsanitary conditions. In the absence of all of these avenues for the disposal of the sewage, a properly laid-out system of septic tanks with effi- cient filter beds may serve the purpose. Where possible, it is advisable to take advantage of hillsides, affording natural means to arrange and operate the factory on the gravity plan. , BUILDING AND EQUIPMENT Material of Construction. Since the establishment of a milk condensing factory involves the investment of considerable capital, those willing to invest must have faith in the permanency of the business. For a permanent business, a building substantially con- structed is the most economical. Most of the factories belonging to the most reputable concerns are built very substantially. How- ever, there are in this country condensing factories in the construc- tion of which cheapness was the governing factor. Many of these cheap factories are the work. of unscrupulous promoters, whose ambition it is to convince men of wealth or farmnig communities of the "enormous" profits possible in the manufacture of condensed milk, and to induce them to invest large sums of money in the con- densed milk industry. By skillful manipulation these promoters frequently secure "fat rake-offs" on every purchase of machinery and on every contract of labor, occasionally on every sale of the product. Their victims pay exorbitant prices for a first class build- ing and most up-to-date equipment, and often receive a shack barely strong enough to stand up under its own weight, and equipment of inadequate capacity. 32 BUILDING AND EQUIPMENT & & c^ Da. ^3 6ft i Is m m rCh K> BUliI I l! t 0bnlz] {K Jfl f^Ec ! Iff! Q. O- W 14 ' Vacuum pan and condenser Courtesy of C. E. Rogers increases the speed of evapora- tion. The t coils -vary in diameter from about three to five inches. The upper and outer coils are the larger ones. The diameter and length of the coils necessarily vary with and are limited by the capacity of the pan. The greater the total heating surface, consistent with easy access to all parts of the jacket and coils, the better. Other things being equal, the more square feet of heating surface, the less steam pressure, by the gauge, is required to furnish the necessary heat for maximum evaporation. This is important because high steam pressure in the jacket and coils means exposure of the milk to high temperature, which is undesirable. The heating surface should be sufficient to make possible the complete con- densation of the steam in the jacket and coils. If the heating surface is inadequate, more steam has to be turned into the jacket and coils, in order to secure the necessary heat for rapid evapora- 66 D CONDENSED MILK CONDENSING r Fig. 15. Covering and insulation for vacuum pans Courtesy of Arthur Harris & Co. tion, than will condense; free steam will blow through and out of the coils, resulting in uneconomic and wasteful use of fuel, and jeopardizing the quality of the product. A properly constructed six-foot pan usually has not less than one hundred twenty to one hundred thirty square feet of heating surface. In the latest improvement in coils each independent coil makes only one turn in the pan and the inner and outer coils have the same inlet and dis- charge and are placed on the same level. This permits of the installation of a larger number of independent coils, each placed at a different level. In this manner the coils can be utilized to better advantage. This is especially significant when the volume of milk Fig. 16. Steam coils Courtesy of Arthur Harris & Co. SWEETENED CONDENSED MILK CONDENSING 67 in the pan is very small, making possible the operation of the lower coils independent of the upper coils and thereby avoiding the danger of burning the milk, which inevitably occurs when the heated coils are not completely submerged. This arrangement increases the heating efficiency of the pan, heat can be turned on the lowest coil almost immediately after starting operation, and toward the end of the batch, when the milk again boils low, some of the coils are still covered and can be used. The shorter length of these coils from inlet to exhaust also makes possible the simultaneous utilization of a greater volume of steam. These combined features materially increase the rapidity of evaporation and augment the capacity of the pan. These improved coils have the further advantage that their exhausts do not have to be carried through the jacket, but pass through the body of the pan. Jacket and coils are connected independently with the direct steam main from the boiler. Each connection at the pan should carry a valve and a steam gauge on the pan-side of the valve. The main steam line and connections leading to pan should be properly insulated by proper pipe coverings, in order to supply the pan with as dry steam as possible. The drips or discharge ends of the jacket and coils are con- nected with the boiler feed water tank. If the pan has sufficient heating surface and is operated properly, the drip ends of the jacket and coils should discharge warm water only, and not free steam. The jacket and coils should be free at the drip or discharge ends so that all condensation water may be quickly and continuously removed. This is necessary in order to make the most economical use of the steam and to secure high efficiency of evaporation. In order to guard against back pressure the drips may be equipped with suitable check valves. Through the walls of the body of the pan also enters the milk draw pipe. This pipe connects with the hot well and through it the milk rushes into the pan. Immediately outside of the pan the milk pipe should be equipped with a valve to regulate the inflow. The size of the milk draw pipe and valve is governed by the capacity of the pan ; usually two to three inches in diameter. Inside of the pan the milk pipe should be turned down. If this provision is not made, the milk shoots straight across the pan atomizing into a dense spray, which is partly drawn over into the condenser, causing loss of milk. 68 D CONDENSED MILK CONDENSING THE DOME: rests on top of the body of the pan. It is equipped with a manhole, manhole cover, thermometer, vacuum gauge, sight glasses, lights and blow-down valve, or vacuum breaker. The manhole measures about fourteen to eighteen inches in diameter. It is closed by a solid brass cover with a well-fitting, ground surface flange. The cover carries a five-inch eye- glass or sight-glass through which the operator watches the boiling milk in the pan. The stem of the thermometer is enclosed in a brass casing and reaches to near the bot- tom of .the pan. Some processors prefer a short thermometer which Fig . 17 . vacuum gauge registers the temperature of the va- courtesy of Arthur Harris & Co. pors instead of that of the milk. As both, the milk and the vapors are subjected to the same pressure, their respective temperatures are the same. The long-stem thermometer, the bulb of which is submerged in the milk, however, is more sensitive and registers changes in temperature more rapidly, because the milk is a better conductor of heat than the vapors. The vacuum gauge connects with the interior of the pan, and indicates the number of inches of vacuum. A mercury column may be used in the place of the vacuum gauge. In the rear of the dome there are two sight glasses. Through these the interior of the pan is illuminated by means of lamps, gas or electric lights. The "blow-down" valve, or vacuum breaker, serves to admit air into the pan in order to "break" the vacuum. This is Fig. 18. necessary for readily drawing off the finished con- Thermometer densed milk. It is further needed to prevent the for vacuum pan Courtesy of contents of the vacuum pan from being drawn over Arth & r c? arriS * nto tne conQl enser, whenever the milk rises above a safe level. A further accessory of the dome may be an automatic milk sampler. The sampler tube is carried through the wall of the dome and extends to near the bottom inside of the pan. Where this tube SWEETENED CONDENSED MILK CONDENSING 69 projects through the dome it is equipped with motor, pump, piston, striking cup and hydrometer. The striking cup at its upper end terminates in a small chamber equipped with a sight-glass through which the operator notes the position of the hydrometer. The Condenser. The condenser is that portion of the condensing ap- paratus in which the vapors, rising from the boiling milk in the pan, are condensed to water. The condenser is attached to the dome of the^ pan. There are three types of condensers in use, the surface condenser, the baro- metric condenser and the wet-vacuum spray condenser. Fig. 19. Vacuum breaker or blow- down valve Courtesy Arthur Harris & Co. THE SURFACE CONDENSER consists of a tube cylinder filled with brass tubes, mounted on a receiver. The water used for cooling circulates out- side of the tubes and the vapors pass through the tubes, where they are chilled and condensed. This conden- ser has the advantage of enabling the operator to note the amount of con- densation and to measure the amount of water actually condensed. The re- ceiver at the bottom of the condenser should be so arranged that it can be drained at will and without interfer- ing with or retarding the operation of the pan. THE BAROMETRIC CONDENSER con- Fig. 20. The surface condenser sists of a vertical cylinder of iron or Courte JLch chine 70 SWEETENED CONDENSED MILK CONDENSING brass, equipped with a spray jet, through which the cooling water enters the condenser. The vapors being drawn over from the vio- lently boiling milk in the pan, are condensed by passing through this spray of cold water. This condenser discharges its water into a Fig. 21, Vacuum pan with dry vacuum barometric condenser Courtesy of Arthur Harris & Co. tight cistern in the ground. The condenser is placed so that its bot- tom flange is about thirty-five feet above the water level of the cis- tern in which the discharge pipe from the condenser terminates. The height of the condenser depends on the barometric pressure of the location where it is installed- The lower the altitude and, therefore, the higher the atmospheric pressure, the higher must the condenser SWEETENED CONDENSED Miuc CONDENSING 71 be above the cistern. At the sea level, the atmospheric pressure sus- tains a water column about thirty-four feet high. This water column in the discharge pipe seals the vacuum and at the same time permits the water from the .spray and the condensation water to escape auto- matically. The cistern in which the water column terminates should be of sufficient size to hold about one-third more water than the ca- pacity of the entire length of the discharge pipe calls for and should have a large overflow into the sewer. When the pan is in operation and a uniform vacuum is maintained, the level of the water column remains constant and the excess water from the condenser over- flows from the cistern into the sewer. Fig. 22. The wet-vacuum spray condenser Courtesy of Arthur Harris & Co. THE WET- VACUUM SPRAY CONDENSER consists of a huge hol- low cylinder of brass or iron, usually, but not necessarily, horizontal. The horizontal spray condensers are usually equipped with a perforated spray pipe, placed lengthwise in the cylinder. This spray pipe should run close to the top side of the cylinder, so as to give the spray that escapes from the holes on the upper side of the spray pipe a chance to strike the top of the horizontal cylinder with force and to become atomized. The spray pipe connects at the end nearest the pan with the pipe supplying the cooling water. When the pan is in operation, a shower of cold water issues forth from the per- forations of the spray pipe as the result of the reduced pressure in pan and condenser. The force with which the water escapes these perforations is further augmented by the fact that in most cases the water supply tank is located higher than the condenser. The hot vapors arising from the boiling milk in the pan are drawn over into the condenser, where they come in contact with the cold water spray and are condensed. The bottom of the condenser cylinder, at the end farthest from the pan is connected with the suction end 72 SWEETENED CONDENSED MILK CONDENSING of the vacuum pump through which the water and the condensed vapors in the condenser escape. In the vertical spray condenser the condenser cylinder is up- right, located either on top of the pan or at some distance, as is the case, for instance, where a catch-all is installed between pan and condenser. The interior arrangement of the vertical condenser varies somewhat with the different makes. The vertical condenser most widely used in American condenseries consists of a double insulated vapor tube setting on top of the pan. This insulated tube is surrounded by and connects with a spray chamber, which termi- nates at its top in a perforated metal plate and which has an open- ing in the side near the bottom that connects with the vacuum pump supplying the suction and that permits the escape of the condensed vapors and cooling water. The cooling water enters at the top of the condenser. Immediately underneath the water inlet it strikes a metal cone or disc which prevents the water from running into the vapor tube, and distributes it evenly over the perforated spray plate. The vapor rises into the vapor tube of the condenser and is drawn over into the spray chamber surrounding it, where the vapor is condensed by the spray of water issuing from the per- forated spray plate which tops the spray chamber and which con- tains a large number of very small holes. As the water falls through these openings by gravity, the spray is uniform and con- stant and does not depend on the amount of water used, nor does it require water pressure on the condenser. The chief difference between the wet-vacuum condenser and the barometric condenser is that in the wet-vacuum condenser the water from the condenser passes through the vacuum pump, while in the barometric condenser the water does not pass through the vacuum pump, but goes direct into the sewer and the vacuum is sealed by the barometric water column. So far as practical experi- ence has shown, there is no material difference in the efficiency be- tween these two types of condensers. The water column of the barometric condenser helps somewhat to maintain a uniform vacuum. It necessitates, however, the installation of the pan inconveniently high and requires somewhat more expensive machinery than is the case with the wet-vacuum condenser. The chief difference between SWEETENED CONDENSED MILK CONDENSING 73 both of these systems and the surface condenser is that, in the wet- vacuum and barometric condensers the condensed vapors mix with the cooling water, while in the surface condenser the condensed va- pors are collected and carried off separately and without mixing with the cooling water. In the case of condensing liquids, the vapors of which are of commercial value, the surface condenser must be used. The surface condenser, however, is of relatively small ca- pacity and the cooling water cannot be utilized as economically as in the case of the other systems. Where large quantities of vapors are to be handled and the vapors have no commercial value, as is the case in condensing milk, the barometric and wet-vacuum con- densers are best suited ; their operation utilizes the cooling water most economically. CARE OF THE CONDENSER. In the operation of the spray and jet condenser, special attention should be paid to the condition of the spray pipe, or spray plate. Especially, when the water used con- tains much organic matter, as is the case with water from a creek, pond or lake, there is a tendency of the spray pipe becoming filled and coated with slimy organic matter, causing the perforations to clog. This renders the distribution of the spray irregular and the control of the pan difficult. It causes great waste of water because much of the water is discharged from the condenser and lost without coming into direct contact with the vapors. The water is, therefore, not utilized economically and the difference between the temperature of the vapors and the discharge of the condenser is excessive. In order to avoid this the condenser should be cleaned out thoroughly at least once a week, or oftener if necessary, to keep the pores of the spray pipe free from obstructions. It is advisable to install con- densers equipped with a manhole on top or at the end, otherwise access to the spray pipe is not sufficiently convenient to insure fre- quent inspection and thorough cleaning by the average operator. The Expansion Tank, Catch- All, or Milk Trap. T his is a tank frequently installed between the dome of the pan and the con- denser. Its purpose is to collect and reclaim any milk that may be carried over from the pan and to prevent its escape and loss through the condenser. 74 SWEETENED CONDENSED MILK CONDENSING Fig. 23. Vacuum pan with milk trap Courtesy of Arthur Harris & Co. If the pipe through which the milk enters the pan is turned down and its end is carried to near the bottom of the pan, so as to avoid the formation of excessive milk spray, if the pan is operated carefully and if the milk is kept at a reasonably low level, there is very little danger of milk being carried over into the condenser in quantities sufficient to be of any consequence. Under these conditions the installa- tion of a special milk trap between the pan and the condenser for the purpose of collecting the escaping milk spray and carrying it back to the pan is, therefore, an unnecessary expense. If the pan is small in comparison to the amount of milk to be condensed, and if it is forced beyond its intended capacity so that the milk boils up high, there usually is considerable loss of milk, as indicated by the foaminess and milky color of the exhaust of the vacuum pump. In such cases the mechanical loss of an average size batch may amount to several hundred pounds of milk. In order to not lose this milk, a milk-trap or catch-all may be installed between the pan and the condenser. The vapors loaded with the milk spray enter the trap near the top. The spray drops to the bot- tom of the trap, while the vapors are drawn over into the condenser, where they are condensed as usual. This trap may be constructed of sufficient size so as to serve as a reservoir to collect all the milk that is carried over, and at the conclusion of the process the con- tents of the trap are drawn from the bottom and are condensed with the next batch ; or the bottom of the trap may be connected with the pan so that the milk thus carried over flows back into the pan auto- matically. In this case a small trap only is necessary. It should be understood that the milk trap is only a remedy and not a preventive. Where the capacity of the pan is in proportion to the amount of milk to be condensed, as it should be, and where the pan is operated properly, the trap is unnecessary. The trap is an additional piece of apparatus to be kept clean. Unless it is so constructed that access can be had to all parts of its interior and CONDENSED MILK CONDENSING 75 unless it really is kept clean at all times, it may become a serious source of contamination. The Vacuum Pump. The vacuum pump is, strictly speaking, not a part of the vacuum pan, but its intimate connection with the pan makes it necessary to briefly consider it at this point. The suction end of the vacuum pump is connected with the end of the condenser farthest from the pan. The vacuum pump exhausts the pan, forming a partial vacuum. There are prin- cipally two types of vacuum pumps used in the milk con- densery, the dry-vacuum pump and the wet-vacuum pump. The dry-vacuum pump is used in the factories with the dry-vacuum system, i. e., where the cooling water and the condensation water escape to the sewer direct and without passing through the vacuum pump, as is the case with the surface condenser and the barometric condenser. The wet-vacuum pumps are used with the wet-vacuum system, where the cooling water and the condensation water pass through the cylinder of the pump. The dry-vacuum pumps have the advantage of permitting the operation of the machine at a higher piston speed than the wet-vacuum pumps in which the water must be displaced at the end of each stroke. The cylinders of the dry- vacuum pump are cooled by water jackets. The initial cost of the dry-vacuum pumps, however, is greater than that of the wet- vacuum pumps. The efficiency of the vacuum apparatus depends very largely on the vacuum pump. Rapid evaporation at a relatively low tem- perature necessitates the maintenance of a high vacuum. The type, material, construction, workmanship, installation and operation of the vacuum pump should be such as to insure the maximum effic- iency. The pump should be placed on a good foundation and as near the vacuum pan as practicable in order that the full benefit of the vacuum may be realized. The suction pipe and all connections must be tight. The suction pipe must be of the size directed by the man- 76 SWEETENED CONDENSED MILK CONDENSING ufacturer, as short as possible and with few and easy bends. The grade of the suction pipe should be uniform in order to avoid air pockets. Fig. 25. Dry-vacuum pump Courtesy of Buffalo Foundry & Machine Company The water should be turned into the condenser before the vacuum pump is started. The pump should not run at a higher speed than is necessary to secure the required vacuum. Excessive speed means high steam consumption and heavy wear and tear on the pump. The amount of water supplied to the condenser should be regulated to suit the requirements. Ordinarily, and with a vacuum of twenty-five to twenty-six inches, the temperature of the condenser discharge should be about 110 degrees F. A lower tem- perature would cause excessive and uneconomic use of water. The basin on the vacuum cylinder should be kept filled with water to prevent admission of air to the cylinder through the stuffing box, and the spray pipe or jet in the condenser should be inspected often to make sure that the perforations are not clogged. The stuffing box of the cylinder should be well packed with a good quality of packing and the steam cylinder well oiled. Start the pump slowly. Belt-driven pumps, especially those equipped with a fly-wheel, insure greater uniformity of speed than direct-acting, steam-driven pumps. Steam-driven pumps should be furnished with a high grade gov- ernor. The vacuum pump should have a capacity proportionate to the size of the vacuum pan, amount of heating surface, steam pres- sure and temperature of condensing water. Science and Practice of Evaporating in Vacuo. PURPOSE OF CONDENSING IN VACUO. The important advantages gained by evap- SWEETENED CONDENSED MILK CONDENSING 77 orating milk under reduced pressure, or in vacuo, are : economy of evaporation, rapidity of evaporation, low temperature and large capacity of apparatus. All of these features are essential in the suc- cessful condensing of milk. Rapid evaporation cannot take place until the milk is brought to the boiling point and is kept there until evaporation is completed. Under atmospheric pressure and at the seal level, the boiling point of water is 212 degrees F., the boiling point of milk is very slightly higher, about 214 degrees F. Evaporating of milk under atmos- pheric pressure in an open kettle, however, is a relatively slow process, requiring a long time, much fuel and large apparatus. Fur- thermore, exposure of the milk to 212 to 214 degrees F. long enough to complete evaporation would render the product unsuitable for market. The properties of some of its ingredients are altered, the product would assume a dark color and a marked cooked flavor as the result of the effect of heat. All of these objections are mini- mized and partly avoided by lowering the boiling point of milk. These objections, however, do not apply to evaporation under atmos- pheric pressure by film treatment, as is the case with the Continuous Concentrator described in Chapter XIV, page 133. RELATION OF PRESSURE TO BOILING POINT. The temperature at which milk boils depends on the pressure to which it is exposed. 78 SWIFTENED CONDENSED MILK CONDENSING The table below shows the boiling point of water at pressures ranging from atmospheric pressure at the sea level (14.72 pounds per square inch) to a complete vacuum. BOILING POINTS OF WATER AT DIFFERENT VACUA. Absolute pres- sure per square inch Vacuum inches of mercury column Vacuum milli- meters of mercury column Temperatures of boiling point of water, F. Temperatures of boiling point of water, C. 14.720 0.00 00 212.00 100.00 14.010 1.42 36 209.55 98.5 13.015 3.45 88 205.87 96.8 12.015 5.49 139 201.96 94.3 11.020 7.52 191 197.75 91.9 10.020 9.56 243 193.22 89.5 9.020 11.60 295 188.27 86.75 8.024 13.63 346 182.86 83.7 7.024 15.67 398 176.85 80.5 6.024 17.70 450 170.06 76.8 5.029 19.74 502 162.28 72.5 4.029 21.78 553 153.01 67.2 3.034 23.81 605 141.52 60.8 2.034 25.85 657 126.15 52.3 1.040 27.88 708 101.83 38.7 .980 28.00 712 100.00 37.8 .735 28.50 724 90.00 32.2 .544 28.89 734 80.00 26.7 .402 29.18 741 70.00 21.1 .294 29.40 747 60.00 15.6 .216 29.56 751 50.00 10.0 .162 29.67 754 40.00 4.4 .127 29.74 756 32.00 1 By courtesy of the Buffalo Foundry & Machine Company. CONDENSED MILK CONDENSING 79 The pressure or, correctly speaking, the vacuum, is expressed in terms of inches of mercury which the atmospheric pressure sus- tains. The mercury column is not a direct measure of the pres- sure, but it shows the difference between the atmospheric pressure and the absolute pressure in the vacuum chamber. The atmospheric pressure at the sea level is 14.7 pounds per square inch. It sus- tains a mercury column in an absolute vacuum of 30 inches at 62 degrees F., and of 29.922 inches at 32 degrees F. The absolute vacuum may be calculated by multiplying the atmospheric pressure by the factor 2.04. In case there is only a partial vacuum the mercury column sustained is lowered to the extent of the absolute pressure in the vacuum pan. The absolute pressure may be calcu- lated as follows : AV = Absolute vacuum which is thirty inches at the sea level. V == Actual vacuum. P = Atmospheric pressure which is 14.7 pounds at the sea level. AP = Absolute pressure. Example: The actual vacuum in the pan is 25 inches at the sea level. What is the absolute pressure? PX (AV V) 14. 7 X (30 25) ; = = 2.45 pounds of absolute pressure per sq. inch. RELATION OF ALTITUDE TO ATMOSPHERIC PRESSURE. At alti- tudes higher than the sea level, the atmospheric pressure is reduced and the mercury column is lowered, though the absolute pressure in the vacuum pan may be the same. Therefore, in factories lo- cated at high altitudes the mercury column will show fewer inches of vacuum at a given temperature and with a given absolute pressure. The following table shows the barometric reading in inches of mercury column and the atmospheric pressure in pounds per square inch at different altitudes: 80 SWEETENED CONDENSED MILK CONDENSING 1 BAROMETRIC READING CORRESPONDING WITH DIFFERENT ALTITUDES. Barometric reading in inches of mercury Atmospheric pressure in pounds per square inch Altitude above sea level in feet Barometric reading in inches of mercury Atmospheric pressure in pounds per square inch Altitude above sea level in feet 30.0 14.72 23.5 11.54 6412 29.7 14.60 264 23.0 11.30 6977 29.5 14.47 441 22.5 11.05 7554 29.2 14.35 710 22.0 10.80 8144 29.0 14.23 890 21.5 10.56 8747 28.7 14.11 1163 21.0 10.31 9366 28.5 13.98 1347 20.0 9.81 10648 28.2 13.86 1625 19.0 9.32 11994 28.0 13.74 1812 18.0 8.82 13413 27.5 13.50 2285 17.0 8.33 14914 27.0 13.26 2767 16.0 7.84 16506 26.5 13.02 3257 15.0 7.35 18201 26.0 12.77 3758 14.0 6.86 19996 25.5 12.53 4268 13.0 6.37 21891 25.0 12.27 4787 12.0 5.88 23886 24.5 12.03 5318 11.0 5.39 25981 24.0 11.78 5859 1 By courtesy of the Buffalo Foundry & Machine Company. SWEETENED CONDENSED MILK CONDENSING 81 In the following table may be found the altitudes of various cities in the United States: ALTITUDE IN FEET OF VARIOUS CITIES IN THE UNITED STATES. By Courtesy of United States Department of Agriculture. Akron, Ohio 940 Albany, N. Y 22 Atlanta, Ga 1032 Baltimore, Md 92 Birmingham, Ala 600 Boston, Mass 16 Buffalo, N. Y 583 Burlington, Vt 112 Butte, Mont 5555 Charleston, S. C 12 Chattanooga, Tenn 672 Chester, Pa 22 Chicago, 111 590 Cincinnati, Ohio 490 Cleveland, Ohio 582 Dayton, Ohio 740 Denver, Colo 5183 Dallas, Tex 430 Des Moines, Iowa 805 Detroit, Mich 588 Duluth, Minn 609 Houston, Tex 46 Indianapolis, Ind 708 Ithaca, N. Y 411 Kansas City, Mo 750 Knoxville, Tenn 890 Lexington, Ky 955 Little Rock, Ark 264 Los Angeles, Cal 267 Louisville, Ky 453 Memphis, Tenn 256 Milwaukee, Wis 593 Minneapolis, Minn 812 New Haven, Conn 10 New Orleans, La 6 New York City . , . . 54 Oklahoma City, Okla 1197 Omaha, Neb 1016 Philadelphia, Pa 42 Phoenix, Ariz 1082 Pittsburgh, Pa 743 Providence, R. 1 11 Richmond, Va 51 Rochester, N. Y 510 St. Louis, Mo 455 Salt Lake City, Utah 4238 San Francisco, Cal 15 Santa Fe, N. M 6952 Seattle, Wash 10 South Bend, Ind 717 Spokane, Wash 1908 Tampa, Fla 15 Washington, D. C 25 Wichita, Kan 1294 Vicksburg, Miss 1% 82 SWEETENED CONDENSED MILK CONDENSING According to Kent x the relation of altitude to atmospheric pressure per square inch is as follows : Pounds Pressure Altitude Per Square Inch At sea level - 14.7 Y^ mile above sea level - 14.02 J/2 mile above sea level - 13.33 % mile above sea level - 12.66 1 mile above sea level - 12.02 1 Y^ miles above sea level - -11.42 \y 2 miles above sea level - - 10.88 2 miles above sea level - 9.80 "For a rough approximation we may assume that the pressure decreases one-half pound per square inch for every 1,000 feet of ascent." The absolute pressure in the pan of a factory located at Omaha, Neb., with an altitude of 1,016 feet above sea level, and condensing in an actual vacuum of twenty-five inches, would then be as fol- lows : Atmospheric pressure 14.7 .5 = 14.2 pounds per square inch. Absolute vacuum = 14.2 X 2.04 = 28.97 inches. 14. 2 X (28.97 25) Absolute pressure n>7 1.95 pounds ^o. y/ per square inch. RELATION OF STEAM PRESSURE IN JACKET AND COILS, WATER IN CONDENSER, TEMPERATURE IN PAN AND VACUUM, TO RAPIDITY OF EVAPORATION. The temperature of the vapors in the vacuum pan depends directly upon the pressure or vacuum under which they are generated. The more nearly complete the vacuum and, therefore, the lower the pressure, the lower the temperature, and, other conditions being the same, the more rapid the evaporation. The pressure in turn is governed by the capacity of the vacuum pump, the tightness of the joints, the steam pressure in jacket and coils and the amount and temperature of the water in the con- denser. 1 Mechanical Engineer's Pocket-Book, p. 581. NED CONDENSED MILK CONDENSING 83 With a low capacity vacuum pump, or a pump running irreg- ularly, or too slow, or too fast, and with leaky joints, the vacuum will always be low, and the pressure and temperature relatively high. Under these conditions the pan is difficult to operate and evapora- tion is slow. With the above conditions under control and properly adjusted, the temperature and the rapidity of evaporation depend on the steam pressure in the jacket and coils and on the amount and temperature of the water used in the condenser. Twenty-five pounds of steam pressure in the jacket and coils has been found to be about the maximum that can safely be used. With this steam pressure the milk coming in direct contact with the heating surface is exposed to about 267 degrees F. and there is a tendency for some of it to bake or burn on, which is undesirable. The walls of the jacket and coils are also subjected to considerable strain, since they are surrounded by an almost complete vacuum. Then again, if the pan has the proper amount of heating surface the capacity of the condenser and the water supply are in most cases insufficient to take care of and condense the vapors arising from the boiling milk in the pan, when the steam pressure in jacket and coils approaches or exceeds twenty-five pounds.. Most con- denseries operate their pans with twelve to twenty pounds of steam pressure in jacket and coils. In the operation of some pans not more than about five pounds steam pressure can be used economically in jacket and coils, because the use of more steam causes the steam to blow through and out of the coils. This may be due to relatively large heating surface, or small evaporating capacity due to a small capacity pump or limited water supply to condenser. The capacity of the condenser used in milk condenseries is very largely dependent on the water supply. Whenever the con- denser is forced beyond its capacity, by using excessive steam in jacket and coils, the vacuum drops, the temperature rises and the process of evaporation is retarded. The higher the vacuum the more rapid the evaporation. A rise in the steam pressure in the jacket and coils increases the rapidity, 84 SWEETENED CONDENSED MII^K CONDENSING of evaporation only as long as enough water passes through the con- denser to maintain a high vacuum. As soon as the steam pressure in the jacket and coils reaches the point where the water in the con- denser fails to promptly reduce the vapors, the vacuum drops, the temperature in the pan rises and evaporation is checked. The condensing of milk requires immense quantities of water ; experience has shown that it takes from two to three gallons of water to condense one pound of fresh milk. The water supply is one of the weakest links in most condenseries, so that economy of water is one of the important factors to be considered. The steam pressure in the jacket and coils should, therefore, be so regulated as to make it possible to maintain the maximum vacuum consistent with reasonably economic use of water. The experience of the best pan operators is that about fifteen pounds of steam pressure in the jacket and coils and a vacuum of twenty-five inches is practic- ally the maximum that can be maintained under average conditions without taxing the usual water supply beyond its capacity. With a vacuum of twenty-five inches the temperature in the pan is about 135 degrees F., the temperature varying somewhat with the altitude of the factory. In some condenseries the temperature of the pan is kept at 150 degrees F. This practice may economize the water a trifle better, but the rapidity of evaporation is considerably lower. Condensing at temperatures lower than 130 degrees F., without reducing the steam pressure in the jacket and coils, increases the rapidity of evaporation, but taxes the water supply beyond the reach of most condenseries. So much water has to be used in the con- denser that it is not used economically, as is shown by the relatively low temperature of the water discharging from the condenser. The temperature of the condenser discharge bears a direct relation to the temperature of the vapors in the pan. Observations made in various factories and under different conditions by Hunziker and others showed that the condenser discharge was anywhere from 5 to 25 degrees F. lower in temperature than the vapors in the pan, the difference averaging about 15 degrees F. The smaller the difference in temperature between the con- denser discharge and the vapors in the pan, the more economic is SWEETENED CONDENSED MILK CONDENSING 85 the use of the water and vice versa. It is not advisable under aver- age conditions to so operate the pan that the temperature of the condenser discharge drops below 110 degrees F., because of the wasteful use of water under such conditions. The condensing of one pound of milk requires about one pound of steam and eighteen to twenty-five pounds of water. The quan- tity of heating steam used for condensing in vacuum is practically the same as that required by evaporating in open pans. In order to use the steam economically the pan should be so operated as to make possible its complete condensation by the time it leaves the jacket and coils. Whenever so much steam is used that it blows through and out of the jacket and coils without being condensed, there is great waste of fuel. For further details on this point see "Descrip- tion of the Vacuum Pan." Starting the Pan. Before drawing the milk into the pan, the pan should be thoroughly rinsed with water, then steamed until the temperature rises to about 180 degrees F. or above. Then the man- hole cover is put in place, all the air valves are closed, water is turned into the condenser and the vacuum pump is started. When the vacuum gauge shows over twenty inches of vacuum, the pan is ready for the milk. Operating the Pan. The valve of the milk pipe leading to the pan is now partly opened. The milk enters the pan automatically as the result of the reduced pressure in the pan. When the milk covers the jacket, steam is gradually turned into the jacket. As each coil becomes submerged in milk, the coils are charged with steam. At no time should steam be turned on the jacket and coils when they are not completely covered with milk, as such action would cause the milk to stick to and burn on the heating surface, the milk would assume a burnt flavor, it would become permeated with black specks and the evaporation would be retarded. On the start, but a few pounds of steam pressure should be used in the jacket and coils, to avoid burning, owing to the presence in the milk of considerable air. As the milk becomes more concentrated and settles down to uniform boiling, the steam pressure may be grad- ually increased until it reaches the maximum. The maximum pres- 86 SWEETENED CONDENSED MILK CONDENSING sure permissible must be governed by the amount of heating sur- face, the capacity of the vacuum pump and the temperature and amount of water available for use in the condenser. Under aver- age conditions about fifteen pounds of steam pressure may be safely used. During the early stages of the process, when the milk is of low density, the evaporative duty is high, probably about twenty- five to thirty-five pounds per square foot of heating surface with ten pounds of steam pressure. This gradually decreases and is lowest toward the end of the process. When enough milk is in the pan to completely cover the jacket and coils, the milk intake should be reduced and regulated in ac- cordance with the rate of evaporation. The milk is drawn into the pan continuously, but only as fast as it evaporates. It should be kept as much as possible at a constant level, and this level is prefer- ably as low as is consistent with complete covering of the upper coil. In order to secure maximum rapidity of evaporation, the vacuum pump should run at the proper speed and its operation should be uniform, a uniform vacuum and temperature should be maintained and the milk should be prevented from rising to an ab- normally high level in the pan. Prevention of Accidents. The operator should pay strict at- tention to the pan in order to avoid loss of milk due to accidents. He should watch the water supply and govern its use accordingly. If the water supply becomes exhausted, air is liable to be drawn into the pan through the condenser. This will cause the milk to drop suddenly and then rise in a body, threatening to escape through the condenser. Whenever air in considerable quantities is allowed to enter the pan while in operation, be it as the result of lack of water, or through any other cause, or when the vacuum pump is allowed to stop and live steam is turned into the milk in the pan, as is the case when the milk is superheated, the escape of milk may be avoided by immediately shutting the steam inlet to the jacket and coils, by clos- ing the milk intake and by slightly opening the blow-down valve whenever the milk rises dangerously high. By skillful manipulation of the blow-down valve until the milk again settles down to uniform CONDENSED MILK STRIKING 87 boiling, loss can be avoided and the process can be continued in the normal way. By the time all the milk is in the pan, condensation is nearly completed, and from ten to twenty minutes further boiling usually gives the milk the desired density. Toward the end of the process the steam pressure in jacket and coils should be reduced to about five pounds or less. When the milk approaches the desired density, it is comparatively heavy and viscous and boils less vigorously. It therefore is more directly exposed to the heating surface. In the case of excessive steam pressure, its quality is jeopardized. If the batch is small so that the level of the milk drops below some of the coils, steam to the exposed coils should be turned off entirely. CHAPTER VI. STRIKING OR FINISHING THE BATCH Definition. When the boiling milk in the vacuum pan ap- proaches the desired degree of concentration, the batch is "struck." The term "striking" is applied to the operation of sampling the con- densed milk and testing the sample for density. This term very probably referred, originally, to the meaning of "striking the batch right," that is, stopping the process at the proper time, or when the milk is neither too thick nor too thin. It then expressed the result of the operation, while now it is used to mean the operation itself. Ratio of Concentration, Sweetened condensed milk intended for canned goods has a specific gravity of 1.28 to 1.30. This den- sity is reached usually when the ratio of concentration is about 2.5 :1, i. e., 2.5 parts of fresh milk are condensed to one part of con- densed milk, assuming that about sixteen pounds of sucrose have been added to every one hundred pounds of fresh milk. Occasionally the ratio of concentration is based on the propor- tion of water evaporated, in which case it is obviously much higher than when based on the amount of milk required to make one pound of condensed milk, because the added cane sugar takes the place of 88 SWEETENED CONDENSED MII.K STRIKING its own weight of water, and thereby acts as a diluent of the con- densed milk. Thus let us assume that 16 pounds of cane sugar are added to every 100 pounds of fresh milk and that it takes 250 pounds of fresh milk to make 100 pounds of sweetened condensed milk., 100 pounds of sweetened condensed milk, therefore, contain 16 X 2.5 =40 pounds of cane sugar. Using the sugar-free fin- ished product as the basis for calculation, then, the ratio of concen- tration would be: (1QQ-40) = 4 ' 17 to L Instead of giving the ratio of concentration, this basis of calcu- lation determines the ratio of evaporation only. The results are. therefore, erroneous and misleading. It does not materially matter whether the diluent in the condensed milk is water or cane sugar, or both; the really important factor is the per cent milk solids in the condensed milk as compared with the per cent solids in the original fresh milk, and this relation is solely determined by the amount of fluid milk required to make one pound of condensed milk, or by the true and actual ratio of concentration. If it takes 2^ pounds of fresh milk for every pound of condensed milk, then the ratio of concentration is obviously 2.5 to 1 and not 4.17 to 1. Methods. To know just when the proper degree of concen- tration has been reached is difficult and requires patience. It is here where the processor can easily make or lose his wages. There are various indications reminding the observant processor that the milk in the retort is nearly "done," viz., time consumed for con- densing, time elapsed since all the milk has been "drawn up," amount of condensed milk left in the pan and, most of all, the ap- pearance and behavior of the boiling milk itself. Milk that has been sufficiently condensed assumes a glossy, glistening lustre, it boils over from the periphery towards the center, forming a small nucleus or puddle of foam in the center of the pan. An experienced and observant operator knows within a few minutes when the milk is condensed enough. This does not mean, however, that he should wait until the last minute before he "strikes" the batch, for even the most skillful and experienced processors are easily deceived by the mere appearance of the condensed milk through the sight glass. SWEETENED CONDENSED Miuc STRIKING 89 The degree of concentration may be more accurately determ- ined by taking a sample from the pan and testing it by various methods, such as by weighing a definite quantity of condensed milk on a sensitive scale, by the use of a resistance apparatus, or by the use of a specially constructed hydrometer. Of these the Beaume hydrometer has been found the most suitable to use under average factory conditions. Mechanical devices and methods, such as the above, can be de- pended upon, when all the conditions influencing the specific gravity of the liquid are under control, and when there is plenty of time for their manipulation. When the boiling and rapidly evaporating milk in the retort is approaching the proper density, however, quick action is essential. One minute over- or under-condensing may cause the milk to be either too thick or too thin for the market and may necessitate the "re-running" of the entire batch. These instru- ments are, therefore, often inadequate at the time they are needed most. There is not time to carefully measure and weigh out a sample of sweetened condensed milk, nor can the processor al- ways wait until the hydrometer has found its equilibrium in as viscous a fluid as sweetened condensed milk. Again, the density or specific gravity of the finished product depends, outside of the de- gree of concentration, on many and fluctuating conditions, such as amount of heat applied toward the end of the process, the tem- perature of the sample when drawn and the per cent of fat and cane sugar in the condensed milk. It is for these reasons that arbi- trary mechanical instruments and methods are not uniformly satis- factory and are liable to yield misleading results ; while they are very desirable to use as a check, the experienced eye and good judgment of the processor are all essential. The following factory methods have been found satisfactory and reasonably reliable : Draw a sample from the pan into a tin dipper, lower the dipper into a pail of ice water or snow. Stir the condensed milk with a metal-back thermometer until the condensed milk is cooled to 70 degrees F. Note the thickness of it. Or, finish the batch at a con- stant temperature, say 120 degrees F. Draw a sample into a tin cup and note the thickness by examining the milk when pouring 90 SWEETENED CONDENSED MILK STRIKING from a teaspoon. The transparency of the milk when thus held against the light and the manner in which the milk piles up in the cup furnish a practical index to its density. The last method is preferable because of its greater rapidity. USE OF BEAUME HYDROMETER. Beginners and inexperienced operators do well to take numerous sam- ples from the batch in the operating pan and to start sampling early, so as to avoid over-condensing. The use of a Beaume hydrometer, especially constructed for sweetened condensed milk, graduated from 30 to 37 degrees B. and with subdivisions of one-tenth de- grees, is an additional safeguard to insure accuracy and uniformity of thickness. No definite figure at which the Beaume hydrometer should be read can be stated that would show the proper density under all conditions. The Beaume reading of sweetened con- densed milk of the proper concentration varies with such factors as per cent of fat, per cent of sucrose and per cent solids, ratio of concentration and tem- perature of the condensed milk when the reading is taken. However, for general guidance, it may be stated that condensed milk of proper density, made from fresh milk of average richness and containing sucrose at the ratio of sixteen pounds of sugar per one hundred pounds of fresh milk, will show a Beaume reading of about 33.5 degrees B. at 60 degrees F., or about 32 degrees B. at 120 degrees F. Sweetened con- densed skim milk containing approximately 40 per cent sucrose will show a Beaume reading at 60 de- grees F. of about 37 degrees B., or about 35.5 degrees B. at 120 degrees F. CORRECTION OF HYDROMETER READING FOR TEM- PERATURE. The Beaume hydrometers used in Ameri- can condenseries are graduated to give correct read- ings at 60 degrees F. If the readings are to be correct, c - JHK Fig. 26. Beaume hy- drometer for sweetened condensed milk Courtesy CONDENSED MILK STRIKING 91 or if it is desirable to convert them into specific gravity, the con- densed milk should have a temperature of 60 degrees F. Where this is not convenient, the observation may be made at any tem- perature convenient and the reading corrected as follows : When the temperature is above 60 degrees F. multiply the dif- ference between the observed temperature and 60 degrees F. by the factor .025 and add the product to the observed reading of the Beaume hydrometer. When the temperature of the observed read- ing is below 60 degrees F. the corresponding product is deducted. Example: Beaume reading at 120 degrees F. is 31.2. Cor- rected reading is 31.2 + [.025 X (120 60)] = 32.7. The specific gravity may be calculated when the Beaume read- ing is known, by using the following formula : 144 3 Specific gravity = J^ ; B. = Beaume reading Example: Beaume reading, at 60 degrees F. is 33.1. 144 -* Specific gravity = m 3 _ 33 t = 1.2976 In the following table are assembled figures showing the spe- cific gravity of sweetened condensed milk of different Beaume degrees, varying from 28 degrees B. to 37.8 degrees B. 92 SWEETENED CONDENSED MII B = Beaume reading at 60 degrees F. Example: Beaume reading at 60 degrees F. is 8 degrees B. What is the specific gravity? 145 5 Specific gravity = = 1.0582 CHAPTER IX. HOMOGENIZING Purpose. The introduction of the homogenizer in milk con- densing factories is a comparatively recent innovation. The ob- ject of its use is to avoid the separation of the butter fat in the evaporated milk after manufacture. The butter fat is present in milk in the form of minute globules. These fat globules are lighter than the rest of the ingredients of the milk. They, therefore, show a strong tendency to rise to the surface and to form a layer of thick cream in the cans. When these cans are subsequently subjected to agitation, as is the case in transportation, this cream churns, forming lumps of butter. This tendency of evaporated milk to separate in stor- age and churn in transportation is especially noticeable with milk rich in fat und in Avhich the large fat globules predominate. In Jersey and Guernsey localities, it is more difficult, therefore, to manufacture evaporated milk that does not separate, than in Holstein and Ayrshire localities. While separated and churned evaporated milk is perfectly sound and in every way as valuable as a food, as it would be without this separation, it does not sell in this condition. It is rejected on the market. This tendency toward fat separation can be minimized and frequently entirely prevented by increasing the viscosity of the evaporated milk. This can be accomplished by superheating the milk in the pan or after it leaves the pan, and by prolonging the sterilizing process, raising the heat very slowly or stopping the reel of the sterilizer at certain stages of the process. How- EVAPORATED MILK HOMOGENIZING 111 ever, there are conditions when even these precautions do not permanently avoid separation of the fat. In such cases, the proper use of the homogenizer furnishes a reliable means to guard against this difficulty. Principle of the Homogenizer. The principle of the homo- genizer is to force the milk under high pressure through exceed- ingly small, microscopic openings. By so doing the fat globules are broken up so finely that they fail to respond to the gravity force, they cannot rise to the surface and therefore remain in homogeneous emulsion. The value of the homogenizer lies in removing the fundamental cause of this separation. It reduces the fat globules to such small size that their buoyancy, or grav- ity force, is not great enough to overcome the resistance of the surrounding liquid. The tendency of fat globules to separate out in homogenized evaporated milk is further reduced by the fact that the homogen- izer also alters the physical condition of the casein, making it more viscous and thereby increasing the resistance which the fat globules must overcome in their upward 'passage. Kinds of Homogenizers. There are at this time two makes of homogenizers in use in this country, namely, the "Gaulin" and the " Progress" homogenizer. In the Gaulin 'homogenizer, the milk is forced, by means of single- acting pumps, a- gainst an agate valve which pres- ses against a ground valve seat. The milk has to pass between the I ^^ B^ ground surfaces of this v a 1 v e and valve seat. This causes the fat Fig. 38. The Progress homogenizer HobuleS to be di- Courtesy of Davis-Watkins Dairymen's Supply Company 5 112 EVAPORATED MI^K HOMOGENIZING vided very minutely. This type of homogenizer has not been used much as yet in the manufacture of evaporated milk and but little is known concerning its effect on this product. In the Progress homogenizer the homogenizing principle consists of forcing the milk, by means of single acting pumps, between a series of discs with ground surfaces. The discs lay flat one upon the other, they are enclosed in a cylinder and are Fig. 39. The Gaulin homogenizer Courtesy of Creamery Package Mfg. Company held in place by a rod running through their center. The discs are pressed against each other by a heavy spiral screw, which regulates the pressure to which the milk is subjected. The milk passes from the center to the periphery of the discs. While being forced through the discs the fat globules are split up very finely. The discs used in this machine are of two types. One type has very fine irregular grooves. The milk shoots through these grooves against hard shoulders. The other type of discs has smooth surfaces but their area of contact is narrow. The milk passes through between these smooth surfaces. EVAPORATKD MilyK HOMOGENIZING 113 The Progress homogenizer is used in numerous evaporated milk factories in this country and, where operated properly, it overcomes fat separation very satisfactorily, without damaging the other ingredients of milk. Operation of the Homogenizer. In order to avoid fat separation it is necessary to subject the milk to enough pressure to reduce the fat globules to about one-third their original size. If enough pressure is applied to divide the fat globules into much smaller units there is a tendency to also change the prop- erties of the casein to such an extent as to cause it to give rise to copious precipitation, when the evaporated milk is sterilized, and making the finished product curdy and unmarketable. In this case the cure would be more disastrous than the original defect. Great care must, therefore, be exercised, guarding against the use of excessive pressure that would injure the casein. Experiments have shown that a pressure of between one thousand and fifteen hundred pounds per square inch is sufficient to prevent fat separation and is practically harmless as far as its objectionable effect on the casein in the evaporated milk is concerned. The evaporated milk is run through the homogenizer hot, just as it comes from the vacuum pan or standardizing tank. The first pailful of milk passing through the machine should be re- turned to the supply tank, as on the start, the pressure is not uniform and homogenization is incomplete. The pistons, cylinders, valves and pipes of the homogenizer should be kept in sanitary condition. They are difficult to clean. After homogenizing, the machine should be kept in operation, running water through it, until most of the remnants of evap- orated milk are rinsed out; then hot water containing some active alkali should be pumped through ; this should be followed by clean hot water and steam. Unless this machine is kept scrupulously clean, it may become a dangerous source of con- tamination, infecting the evaporated milk with spore forms that are exceedingly resistant and which are liable to pass into the finished product alive, in spite of the sterilizing process, causing the goods to be a complete loss, due to subsequent fermenta- tion. 314 EVAPORATED MILK COOLING CHAPTER X. COOLING In the cooling of the evaporated milk, no attention need be paid to sugar crystallization. In this class of goods there is plenty of water to keep the milk sugar in ready solution. The evaporated milk can, therefore, be cooled as rapidly as facilities permit. The cooling- may be accomplished in similar ways as are used for cooling fresh milk. From the homogenizer the evaporated milk is run over a surface cooler, or cooling coil. It is advisable to cover the coils with a jacket of gal- vanized iron, tin or copper, so as to avoid undue contamination of the milk from dust, flies, and other Undesirable agents. F '9- ^Q. Surface cooler for evaporated milk In SO-me COndenS- Courtesy of Davls-Watkins Dairymen's Supply Co. cries the hot evap- orated milk is forced through double pipes, cold water passing between the inner and outer pipe, or the coils through which the milk passes are submerged in a tank of cold water. The only objection to this system is that the pipes are more difficult to clean than in the case of an open surface cooler. Where this system is used, the pipes should be equipped with sanitary fit- tings so that they can be readily swabbed out from both ends. In other factories, the same cooling equipment is used as for sweetened condensed milk, with the exception that cold water is run into the cooling tank at once. In still other factories the cooling is done in vats or tanks by means of revolving coils which carry the cooling medium. If the evaporated milk is not EVAPORATED MILK COOLING 115 homogenized it should be cooled as soon as it leaves the vacuum pan. Holding in tanks. The establishment and enforcement of a Government standard of composition and the tendency of the manufacturer, in the face of increasingly keen competition which narrows down the margin of profit and demands more exacting attention to the cost of manufacture, to reduce his output to a uniform composition that complies with the Government standard but does not exceed it, have resulted in the adoption, especially among the larger condenseries of the practice of standardizing or unifying each day's output by mixing together all the batches of evaporated milk of one and the same day's make. This practice necessitates the use of one or more large tanks with facilities for refrigeration of their contents. This need has been and is being admirably met by the installa- tion of jacketed glass enameled cir- cular tanks, ranging in capacity from about 15,000 to 60,000 pounds. These tanks are equipped with one or more propellers which serve to agitate the evaporated milk, mix- ing it and hastening the cooling. The propellers in the latest im- proved holding and cooling tanks are located near the side or periphery of the tank and are driven by in- dependent motor, or by belt power. It has been found that the thus ex- centrically placed propeller, when set at the proper angle, is more efficient in its agitation and in bringing all portions of the evaporated milk in direct contact with the cooling jacket than is the case with the centrally located vertical agitator, which merely gives the contents of the tank a circular motion. In factories where these large glass tanks are installed, each successive batch of evaporated milk is transferred, at the con- clusion of the process of evaporation and homogenization, to Fig. 42. Holding tank for evaporated milk Courtesy of The Pfaudler Co. 116 EVAPORATED MII.K FUSING this large holding and cooling tank, where all the batches of the same days' make are cooled, mixed and held until the last batch is in the tank. The mixture is then standardized to the desired composition by the addition of distilled water, skim milk, or cream, according to needs. The evaporated milk in this tank is usually cooled to and held at 40 to 45 degrees. F. until next morning, when the filling into tins commences. See also "Stan- dardization," Chapter XXXIX, page 253. It should be understood that, at this stage of the process the evaporated milk is not sterile, nor does it con- tain cane sugar to preserve it, neither is it sufficiently concentrated to be preserved because of the absence ot moisture. If exposed to heat, such as summerheat, or even room temperature, its acidity will increase rapidly thereby rendering the subsequent sterilizing process difficult. Fig ' 41 " Hand Sl' e n d 9 k chlne for evap ' Therefore, Unless it is Courtesy of Arthur Harris & Co. canned and sterilized im- mediately after it leaves the vacuum pan, or the homogenizer in case it is homogenized, it should be cooled promptly to a tem- perature low enough to check bacterial development, 40 to 45 F., or below. In the absence of holding tanks or vats with refrigerat- ing facilities as described above, the cooled evaporated milk may be drawn into 40 quart milk cans, and set in the cold room, or these cans may be submerged in a tank of ice water. FILLING The cooled evaporated milk is filled into tin cans ranging in size from eight ounces to one gallon. The gallon cans are usually filled by hand. The filling of the smaller cans is done by auto- matic filling machines. Of late years much progress has been made in the con- struction of different types of filling machines for evaporated EVAPORATED MILK FILLING 117 milk. The opening's in the cans through which the cans are filled range from the San- itary can, which is filled with the top of the can entirely removed, to the venthole can with an opening of not more than one-eighth inch in dia- meter. The filling ma- chines are constructed to fill by gravity, under pres- sure, or in vacuo. These filling machines should be thoroughly washed and freed from all remnants of evaporated milk adhering to the valves and other parts after each use. Remnants of milk left in any part of the filling machine decompose readily and impair the wholesomeness and marketable properties of the product. This is an important point and one too often neglected. Much of the spoiled evap- orated milk may be the result of the use of unsanitary and unclean filling machines. The fact, that the evap- orated milk is sterilized after it leaves the filling machine, is no excuse for unclean filling machines. The operator should bear in mind that the milk run- ning through an unclean filling ma- chine becomes contaminated with mil- lions of bacteria. The more bacteria it contains, the more difficult it is to render it perfectly sterile. Furthermore, sporeforms are prone to develop in Fig. 44. venthole can the decaying remnants of milk; these F G Dickerson Company Fig. 43. Venthole filling machine Courtesy of F. G. Dickerson Company 118 EVAPORATED MILK SEALING spores are very resistant and require excessively high sterilizing temperatures to be destroyed. In the filling of the venthole cans the foaming of the evapo- . rated milk frequently causes serious annoyance. This can be avoided by having the milk at the proper temperature at the time of filling. Experience has shown that warm milk and milk excessively cold are most apt to foam profusely. Under average conditions, milk at a temperature of 60 to 70 F. generates the least amount of foam and at this temperature the filling is ac- complished most readily. SEALING The filled cans should be capped and sealed at once. The seal must be hermetical and strong enough to withstand the strain of the subsequent sterilizing process. With the exception of the " Sanitary can," seals without solder have so far proven unsatisfactory in the canning of evaporated milk. They are prone to weaken in the sterilizer and cause "leakers." Most of the cans on the market containing evaporated milk are, therefore, sealed with solder. Sealing evaporated milk cans with solder is by far the safest method. For details of methods of sealing see Chapter VII. For the sealing or tipping of the venthole cans an automatic tipper is usually attached to the filling machine, so that when the cans leave the filling machine, they have also been sealed. It is exceedingly important that the sealing be done per- fectly, because the minutests leaks cause the evaporated milk in the cans to become contaminated causing spoilage. In order to detect cans with imperfect seals all the cans, as they come from the filling and sealing machine, are carefully inspected for leaks. This may be done by the use of a test bath consisting of a narrow oblong trough, filled with hot water and through which the cans pass on an endless chain. In the case of leaky cans, the heat ol the hot waterbath expands the air in the cans and causes it to escape through the leak in the seal and perculate upward in the water in the form of air bubbles. The operator standing over EVAPORATED MILK SEAUNG 119 the test trough picks the cans which expel air bubbles out so that the defective seals can be mended. Most condenseries manufacturing evaporated milk are now using a hot water bath for testing the sealed cans. But experience has shown that the hot water baths built on the continuous chain principle often fails to give the desired efficiency. This is not the fault of the machine, but it is due to the fact that it becomes very tiresome for the inspector to watch the moving line of cans in the water bath and he soon becomes careless and his work inefficient. It has been found that baths constructed and operated on the principle of submerging a whole tray full of cans, (usually 24 cans) at a time, give more satisfactory re- sults, relieving the monotony and preserving more successfully the keenness of observation of the inspector. The venthole filler is simple in construction, economical in operation and easily cleaned and kept in sanitary condition. The milk, from the time it comes within the range of the filler, is no longer exposed to contaminating influences, such as the hands of employes, insects, etc. The cans are uniformly filled to within one gram of the guaranteed weight and the vents or pin holes are automatically sealed with the minimum amount of solder. While the quantity of solder must necessarily vary with operating conditions, it is possible to limit the average amount of solder, under proper conditions, to 5 ounces per 1000 cans. The fact that the vent hole or pin hole filler operates by gravity, as to both, the empty cans and the inflowing evaporated milk, reduces the human and mechanical error to the minimum, once the machine is set for operation. The acknowledged advantages of the venthole filler have made its general adoption and use rapid and it is estimated that today over 90 per cent of the evaporated milk is being canned by this type of filling machine. 120 EVAPORATED MILK STERILIZING CHAPTER XL STERILIZING The sealed cans are now ready for the sterilizer. If they cannot be sterilized within an hour or two they should be sub- merged in ice water or placed in a refrigerating room until the sterilizer is ready for them. This precaution is especially ad- visable in summer. Purpose of Sterilization. The chief purpose of subjecting the evaporated milk to the sterilizing process is to kill all germ life and, therefore preserve the product permanently. When the hermetically sealed cans come from the sealing room, their contents are not sterile. The only means to preserve this milk is to subject it to temperatures high enough to kill all forms of ferments, organized and unorganized, vegetative cells and spores. The success of the manufacture of this product depends to a large extent on the process of sterilization. Aside from this, the manufacturer aims to gain another com- mercially important condition, namely, to prevent the separation of the butter fat. Before sterilization, there is nothing to prevent the fat from separating out in the evaporated milk and from churning in transportation, unless the evaporated milk was homogenized. This is a highly undesirable characteristic, mak- ing the goods unmarketable. The sterilizing process helps to so change the physical properties of the milk, that this tendency of the fat to separate is greatly minimized. The sterilizing temperatures used, further lend to the evaporated milk a creamy consistency and yellowish color, giving the product a semblance of richness. Sterilizers. The predomi- nating apparatus used for ster- ilizing is a huge, boiler-like, hollow, iron cylinder or box. It opens either at one end or on the side. Its interior is equipped with a revolving framework, steam inlet and ex- haust, a water distributing pipe running the entire length of EVAPORATKD MILK STERILIZING 121 the sterilizer and a water exhaust. The sterilizer carries on its exterior a steam gauge, a vacuum gauge, a water gauge, a blow- off valve and a high-temperature thermometer (registering to about 280 degrees F.). In some makes of sterilizers the interior frame-work does not revolve on its axis, but moves back and forth by means of a direct-act- ing, steam- driven piston, attached to the back end of the sterilizer. The purpose of keeping the cans in motion while heat is applied, is to heat the coti- tents rapidly and unifonn|ly, and to prevent the evaporated milk from bak- ing onto the sides of the cans. A still other form of sterilizer is the continuous sterilizer in which the unsterilized cans pass into and the sterilized cans escape from the heating chamber in continuous procession. Loading the Batch-Sterilizer. The sealed tin cans are placed in heavy iron trays, usually holding twenty-four 16-ounce cans or six 1-gallon cans. The loaded trays are slid and locked into the framework in the interior of the sterilizer. The sterilizer is closed with heavy iron doors and the frameAvork is put in motion. In some makes of sterilizers the interior consists of a large per- forated iron box revolving on its axis. In this case the cans are simply piled into this box; no trays being used. Uniform Distribution of Heat. Where no water is used in the sterilizer during the sterilizing process, it is important that Fig. 46. Sterilizer for evaporated milk Courtesy of The Engineering Company 122 EVAPORATED MILK STERILIZING there be a free air space between every two layers of cans, so as to allow the steam to circulate freely and to come in direct con- tact with every can. When the cans are piled into the sterilizer six to twelve layers deep without any free air space between layers, the cans in the center do not receive as much heat as those at the sides, ends, top and bottom. This causes irregular heating and imperfect sterilization. A satisfactory means of insuring even distribution of heat is to fill the sterilizer about one-thirdful of water, so that, when the sterilizer is in operation the cans pass through this water, with each revolution of the frame work. Water distributes the heat uniformly, rapidly and there is no danger of the formation of air pockets between the cans. Since the heat is applied by steam under pressure the temperature of the water is equal to that of the steam in the sterilizer. This precaution is especially necessary in the case of baby-size cans (eight ounces) which are usually piled in stacks more than two deep. When sterilizing in the absence of water there is danger of lack of uniformity of the amount of heat they receive. Temperature and Time of Exposure. When the sterilizer is filled with the cans and closed, the frame work is set in motion and steam is turned into the sterilizer. In order to hasten the heating and expel all the air, the exhaust and safety should be left open until the temperature has risen to 212 degrees F. This temperature is usually reached in about ten to fifteen minutes. The exhaust and safety are then closed. From this point on, the process must depend on locality, season of year and condition, properties and concentration of the milk. No formula can be laid down which can be depended on to give uniformly satisfactory results under all conditions. Nor does the proper sterilization depend on one particular formula. There are numerous ratios of temperature, time of exposure and extent of agitation, which when adjusted to local conditions may give satisfactory results. The temperature should be high enough and the duration of exposure long enough to insure absolute sterility of the product and to give the milk sufficient body to prevent the separation of the butter fat in subsequent storage. The temperature should not be so high nor the duration of ex- EVAPORATED MILK STERILIZING 123 posure so long, as to cause the formation of a hard, unshakable curd and dark color. Some processors use a very short process with high tempera- tures, others raise the heat gradually and not to quite so high a degree. The more gradual heating is preferable, as it gives the product a better body and more viscosity, which is necessary to keep the fat from separating in storage. The author's judgment in this matter is, that it is not safe to raise the temperature to less than 230 degrees F. and it is advisable to heat the milk to 234 to 236 degrees F., provided that the milk is in condition to stand this heat without the formation of too firm a curd. Where the maximum temperature to which the milk is raised in the sterilizer is 230 degrees F. or thereabout, the raise of the last ten degrees should occupy from thirty-five to forty-five minutes, and this time should be about evenly distributed over the last ten degrees. Of recent years, the practice of stopping the reel of the sterilizer, either at intervals or when the maximum temperature has been reached, has been. adopted by some of the manufacturers. In this case, the temperature usually is rapidly raised to about 240 F., and after keeping the reel running at this temperature for a few minutes (about two minutes) the reel is stopped and this temperature is maintained for from 15 to 20 minutes, with the cans laying still. When the "hold" is completed, the cooling proceeds in the usual way. Some condenseries stop the reel for several minutes once or twice when the temperature has been lowered and before it has dropped to below 212 F. This method of sterilizing, by stopping the reel, has the advantage of developing in the cans a soft, custard-like coagu- lum, giving the product a very heavy consistency and making it appear rich and creamy. It represents a form of superheating, however, which if not done with great care, may prove disastrous, causing the evaporated milk to spontaneously thicken and become cheesy in consistency upon storage. In his efforts to insure complete sterility the operator should understand that the size of the cans may influence the sterilizing efficiency. It takes more time and agitation to sterilize gallon cans than small cans. At a time of the year when the milk con- tains micro-organisms of relatively high resistance to heat, as 124 EVAPORATED MILK STERILIZING is often the case especially in fall and winter, the per cent loss of gallon cans due to "swell heads" may become disastrously large, unless the manufacturer makes a special effort to adjust his process for gallon cans. The installation and efficient use of automatic temperature controllers and recorders is of material assistance for securing uniform results of sterilization. These accessories are made use of in numerous factories, and have proven to be of valuable help to the manufacturer. Aside from the fact tha-t they actually do facilitate the temperature control, they automatically make for increased efficiency of the operator. The knowledge of the Fig. 47. Pilot sterilizer Courtesy of The Engineering Company operator that his work is permanently recorded and checked up exerts a beneficial effect on his performance. The operation of an experimental or pilot sterilizer also has proven a great help in the accurate determination of the amount of heat which the evaporated milk of any batch requires, to produce the desired viscosity, body and color and that it will stand without becoming hopelessly curdy. These machines are of small size, accomodating only a feAv cans. A few sample cans of each batch are placed in the pilot sterilizer and run through the process. Thus the proper process EVAPORATED MILK STERILIZING 125 to be used for the entire batch in the large sterilizer may be adjusted according to the behavior of the contents of the sample cans in the pilot sterilizer. Qualifications of the Processer. The operator, or the person directing the sterilizing process, should thoroughly appreciate the complexity of the product, understand the cause and effect of the many influencing factors, study the ever-changing condi- tions and modify the process in accordance with prevailing con- ditions. He should know that during the exceedingly hot sum- mer days, when the cows suffer from heat and are pestered with flies, the milk will not stand as much heat without badly curdling in the sterilizer as under more favorable conditions. He should know that toward and during the fall months the organisms normally present in milk are more resistant and require higher heat to be destroyed, than earlier in the season. Rapid and Uniform Cooling. As soon as the required heat has been given the milk in the sterilizer, the steam should be turned off and the exhaust and drain should be opened. When the temperature has dropped to about 220 degrees F., cold water should be turned into the sterilizer while the cans are constantly in motion, until the cans are cool enough to handle. There should be enough cold water available to reduce the temperature to 70 or 80 degrees F. in twenty minutes for gallons and in ten to fifteen minutes for small size cans. The water pipe should be so arranged as to distribute the water uniformly over the entire length of the sterilizer. If the process is to be sucessful, the processor must have as nearly perfect control of the heat as possible. This means espe- cially, that there must be plenty of water available to insure rapid cooling and the water must be distributed over the cans uniformly. Insufficient water supply and uneven distribution of the water in the sterilizer, means that some of the cans are exposed to the sterilizing heat longer than others, causing lack of uniformity in the smoothness and color of the milk of different cans of the same batch. Delayed cooling, owing to insufficient water supply, has the further disadvantage of causing the cans to bulge badly, owing to the difference in pressure between the interior and exterior of the cans. This is especially noticeable in gallon-size cans, the ends of which may become badly dis- 126 EVAPORATED MILK SHAKING torted, present an unsightly appearance and their seams and seals may be weakened to the extent of producing "leakers." Fractional Sterilization. In the early days of the manu- facture of evaporated milk the product was sterilized by frac- tional sterilization. This method has now been largely abandoned, but is occasionally used when the milk happens to be in very abnormal condition. The milk is heated in the sterilizer to con- siderably lower temperatures than those stated above, and this heating is repeated on two or three successive days. The prin- ciple of this process is to kill all vegetative forms of bacteria during the first heating. This gives the spores a chance to develop into vegetative forms by the second and third days, which forms are then destroyed during subsequent heating. This system of sterilization is not practical for general use. It is too great a tax on the capacity of the average factory and increases the cost of manufacture. It should, therefore, be made use of only in exceptional cases, when it is known that a certain batch of milk could not be put through the higher sterilizing tem- peratures without causing the product to become permanently curdy. SHAKING Purpose. The purpose of shaking the evaporated milk is to mechanically break down the curd that may have been formed in the process of sterilization and to give the contents of the cans a smooth and homogeneous body. The high temperatures to which the evaporated milk is sub- jected in the sterilizer have a tendency to coagulate the casein. In the case of normal, fresh milk the casein coagulates at a tem- perature of 269 degrees F. In the evaporated milk, made from perfectly normal and sweet, fresh milk the casein curdles at much lower temperatures, and the higher the ratio of concentration, the lower the temperature required to precipitate the casein. It seems that the concentration of the milk intensifies the properties of milk to coagulate when subjected to heat. This factor is probably largely, though not necessarily, wholly due to the in- crease of the per cent of lactic acid in the evaporated milk, due to the concentration.* If the fresh milk contains .17 per cent EVAPORATED MILK SHAKING 127 lactic acid, a concentration of two and one-fourth parts of fresh milk to one part of evaporated milk causes the evaporated milk to contain .17 X 2.25 = .38 per cent lactic acid. With this amount of acid acting on the casein, it is not difficult to understand why a coagulum is often formed in the sterilizer. While the forma- tion of this coagulum may be partly avoided, under certain conditions it appears in every factory and there are more batches, especially in summer, Fig. 48. shaker that come from the sterilizer courtesy of Arthur Harris & Co. coagulated than otherwise. In this condition the product is not marketable. Some means must be provided, therefore, to break up this curd and reduce the contents of the cans to a smooth, homogeneous and creamy body. For this purpose a mechanical shaker is used. Fig. 49. Shaker Courtesy of The Engineering Company Method of Shaking. The shaker consists of one or more heavy iron boxes or boxes made of black iron pipes. These boxes are attached to an eccentric. The trays filled with evapo- rated milk cans are firmly wedged into these boxres. When the shaker is in operation, the cans are shaken back and forth violent- ly, causing the curd in the cans to be broken up. Speed of the Shaker. If the shaker is to perform its work properly, it must have long enough a stroke and run fast enough to cause most vigorous agitation. The stroke should be not less than about two and one-half inches and the eccentric should re- 128 EVAPORATED MILK INCUBATING volve not less than three hundred to four hundred times per minute. In order to accomplish this without wrecking the ma- chine, the shaker must be fastened securely to a solid foundation. From one-fourth to two minutes' shaking is usually suffi- cient to completely break down a soft curd. When shaking for five minutes does not produce a smooth milk, the product is usually hopelessly curdy and no amount of additional shaking will remedy the defect. In some cases it has been possible, however, to improve the curdy product by shaking again after a day or two. Under cer- tain conditions, age seems to have a slight mellowing effect on the curd. Efficiency of Different Types of Shakers. Some shakers have a straight, horizontal, back and forth motion. Others have a rotary or elliptical motion; the latter are not considered as effective in their work as the former. Some of the sterilizers in which the interior frame holding the cans, moves back and forth, are advertised to shake the milk as well as sterilize it. Ex- perience has shown, however, that the shaking performed by these sterilizer-shakers is not sufficient and that the use of a separate shaker is necessary. Formation of Curd not Desirable nor Necessary. It should be understood that the processor should aim to get only a very slight and soft curd in his product, that can be shaken out in the shaker in one-fourth to one-half minute. When the curd prod- uced is firm, even prolonged shaking will not prevent the appear- ance in the finished product of specks and small lumps of curd. Such milk is rejected on the market. The formation of curd during the sterilizing process is not desirable and is not necessary as far as the marketable properties of the evaporated milk is concerned. It is unavoidable, however, under many conditions and as long as it can be confined to a soft curd that readily shakes out, no harm is done. INCUBATING From the shaker, the cans are transferred to the incubating room. This is a room with a temperature of 70 degrees to 90 degrees F. The evaporated milk remains there ten to thirty days. PLAIN CONDENSED BULK MILK 129 The purpose of incubation is to detect defective milk and de- fective cans before they leave the factory. If the contents of any of the cans have not been completely sterilized, or if any cans have the minutest leak, the evaporated milk therein will spoil within the time of incubation. Such milk either sours, curdles or becomes solid, or it undergoes gaseous fermentation, causing the appearance of "swell heads." The more nearly perfect the process of sterilization and the better the construction and seal of the cans, the fewer are the spoiled cans. This incubation process is strictly a preventative measure. It is omitted in many factories where the cans are labeled, packed and shipped to their destination at once, or put in ordinary storage in the factory. CHAPTER XII. PLAIN CONDENSED BULK MILK Definition. This is an unsweetened condensed milk made from whole milk, or partly, or wholly skimmed milk, condensed in vacuo at the ratio of about three or four parts of fluid milk to one part of condensed milk. It is usually superheated to swell and thicken it, and it has the consistency of rich cream. It is sold in 10-gallon milk cans to ice cream factories and in milk bottles to the direct consumer. Plain condensed bulk milk is not sterile, nor is it preserved by sucrose. Its keeping quality is similar to that of a high quality pasteurized milk. Quality of Fresh Milk. The sweeter and purer the fresh milk or skim milk, the better will be the quality of this product. Old milk, or skim milk in which the acid development has made considerable headway, tends to form a lumpy, plain condensed bulk milk. However, since this milk is not subjected to steriliz- ing temperatures and is used up quickly after manufacture, the quality of the fresh milk from which it is made, is not of such magnitude as in the case of evaporated milk. Heating. In the manufacture of plain condensed bulk milk the heating is accomplished much in the same manner as in the case of sweetened condensed milk and evaporated milk. The milk is usually heated by turning steam direct into it ; though 130 PLAIN CONDENSED BULK MILK many of the more efficient types of milk and cream pasteurizers could be used to excellent advantage for this purpose. It is advisable, however, to heat this milk only to about 150 to 160 degrees F. in order to secure a nice "liver" (coagulum), when it is superheated in the pan. If the milk is heated to the boiling point in the forewarmers, it does not respond to the super- heating in the pan as satisfactorily. Condensing. The condensing of plain condensed bulk milk is done in the vacuum in a similar manner as described under evaporated milk, except that the evaporation is carried farther. See also Chapter XIV on "The Continuous Concentrator," pages 133 to 141. Superheating. When the condensation is nearly completed the milk in the pan is superheated. This is accomplished by shutting off the steam to the jacket and coils, closing the valve that regulates the water supply of the condenser, stopping the vacuum pump and blowing steam direct into the milk in the pan, for the purpose of swelling and thickening it. During this process the temperature rises to between 180 and 200 degrees F. When the milk has become sufficiently thick or, in the lan- guage of the processor, has produced the "proper liver" (coagu- lum) the steam is shut off, water is again turned into the con- denser and the vacuum pump is started up. As soon as the vacuum has risen to from twenty-five to twenty-six inches and the temperature has dropped to about 130 degr. F. the process is complete, the vacuum is released and the condensed milk is drawn off. The superheating usually occupies about twenty-five to thirty minutes. The completion of the superheating, or the point when the superheating should cease, may also readily be detected by the examination of a sample of the product. As soon as the con- densed milk begins to show a flaky condition of the curd, the purpose of superheating has been accomplished. The amount of superheating necessary and that the milk will stand, will largely depend, aside from the sweetness of the original milk, on the extent of the concentration. The higher the ratio of concentra- tion, the less superheating is required to secure the desired results. PLAIN CONDENSED BULK MILK 131 Striking. The striking-, or sampling and testing for gravity is done with a Beaume hydrometer, the same, or a similar one, as is used for evaporated milk. The scale should extend to 15 degrees Beaume. The batch should be struck before and after superheating. Factories which standardize their product to a certain established density, usually condense the milk to a point slightly beyond that desired. Then, after superheating, they determine the amount of water required to reduce the finished product, and then add the required amount of water before the condensed milk is cooled. It is advisable to use distilled water for this purpose. Ratio of Concentration. The ratio of concentration varies largely with the fat content of the milk, although the locality and season of year are also influencing factors. Whole milk is condensed at the ratio of about three parts of milk to one part of condensed milk, while the ratio of concentration for skim milk is about 4 to 1. The proper density varies somewhat with locality and season of year. Roughly speaking, whole milk has reached the proper density when the Beaume reading at 120 degrees F. is about 10 degrees B. and skim milk has reached about the proper density when the Beaume reading at 120 degrees F. is about 14 degrees B. When the ratio of concentration exceeds 4 to 1, there is danger of gritty condensed milk due to the pre- cipitation, in this concentrated product, of crystals of milk sugar. Cooling. The plain condensed bulk milk is usually drawn into 40 quart milk cans, placed in cooling tanks containing re- volving cogwheels, as described in Chapter VI, under "Cooling Sweetened Condensed Milk," and is cooled to as near the freezing point as facilities permit. Recently this crude and laborious method of cooling has been superseded in many of the larger condenseries by more modern ways. While the plain condensed bulk milk becomes too thick and sluggish during the process of cooling to make possible the use of surface coolers, and internal-tube coolers, it can be readily cooled in vats equipped with revolving discs, or in horizontal coil vats especially constructed for this purpose and in which the lower part of the vat is constricted and the coil sets very low in this constricted part, so as to agitate the milk vigorously and at the same time prevent the incorporation of air, 132 CONCENTRATED MILK by being completely submerged, or in circular vats equipped with a vertically suspended coil. The vertical coil vat has the further advantage in that it eliminates from the milk, all bear- ings and glands and it expells, rather than incorporates air, from the condensed milk. When cooled the condensed milk is ready for the market. If held in the factory, it should be placed in a cold room or should be otherwise protected against temperatures sufficiently high to cause it to sour. When kept at 40 F. or below the danger from souring is largely eliminated. If transported long distances during warm weather, it should be shipped in refrigerator cars. CHAPTER XIII. CONCENTRATED MILK Definition. Concentrated milk is cow's milk, either whole milk, or partly or wholly skimmed milk, condensed at the ratio of three to four parts of fresh milk to one part of concentrated milk. It is not condensed in vacuo, but in open vats by passing currents of hot air through the milk. It is sold largely in pint and quart bottles for direct consumption. It is not sterile and therefore keeps for a limited time only. Its keeping quality is similar to that of a high grade of properly pasteurized milk. The process by which the concentrated milk is manufactured is known as the "Campbell Process." This process was invented by J. H. Campbell of New York City, in 1900 and patented in 1901. Apparatus Needed. The principal parts are : the evap- orating vat with hot water jacket and coils, and air blast registers or nozzles near the bottom of the vat ; an air blower which fxirnishes the air blast; an air heater through which the air blast passes and from which the heated air is conducted into the milk; a water pump circulating hot water through the jacket and coils ; an auxiliary evaporating tank for completing the evapora- tion ; and a spray pump which throws the spray of milk drawn from the bottom of the main evaporating vat into the auxiliary tank and for transferring the partly condensed milk from tank 1 to tank 2. Operation of Campbell Process. The milk is heated to about 100 degrees F. and allowed to flow into evaporating tank 1 CONTINUOUS PROCESS EVAPORATORS 133 Water at temperatures ranging- from 100 to 125 degrees F. is forced through the coils and jacket. Hot air is then passed into the milk. The temperature of the air is regulated so as to keep the temperature of the evaporating milk down to 120 degrees F. on the start, and to finish the evaporation between 90 and 100 degrees F. The air blast is so introduced as to keep the milk along the heating surface of the jacket and coils in circulation and, therefore, prevent largely the baking of the milk on the heating surface. After the milk has been evaporated to a certain degree of concentration, say 2:1, it is transferred to the auxiliary evaporating tank where the condensation- is completed. This transfer is not necessary, but is resorted to solely as a conven- ience, in order to continue treatment of the reduced bulk of material in a smaller tank and leave the larger tank free for treating a fresh batch of milk, and further, because there are no obstructing coils in the auxiliary tank, interfering with the drawing off of the finished and thick condensed milk. In this pro- cess, as now used, the milk is usually first separated and the skim milk only is condensed. The cream is subsequently added, to the condensed skim milk. Advantages and Disadvantages of Campbell Process. The initial cost of installing the necessary machinery is much less than where vacuum evaporation is practiced. The low heat applied makes it possible for the finished product to retain the properties of raw milk, leaving the albumenoids and lime salts in their original and easily digestible form. This process is applicable only in the manufacture of un- sweetened condensed milk. Unless subsequently sterilized, the product will fceep for a short time only. This process has at the present time only very limited use. It can hardly be considered as an important branch of the condensed milk industry. CHAPTER XIV. CONDENSING MILK BY CONTINUOUS PROCESS The processes of condensing milk described in preceding chapters, are exclusively confined to the intermittent or batch- principle of evaporation. That is in the case of the vacuum pan. the fresh milk runs into the pan until the capacity of the pan is reached and no condensed milk leaves the pan until the condensa- 134 CONTINUOUS PROCESS EVAPORATORS tion of the entire batch is completed. Then the pan must be emptied before more milk can be drawn in. In a similar man- ner, in the Campbell process, evaporation of the entire batch must be completed before any of the finished product leaves the evaporating vat or tank. The operation in either case is inter- mittent and not continuous. Of more recent years, equipment and processes have been developed that make possible continuous operation. That is the fresh milk enters the machine and the condensed milk leaves it simultaneously and continuously. So far two types of continuous machines have been perfected sufficiently to make them com- mercially practical and usable, namely the Buflovak Rapid Cir- culation Evaporator, invented and manufactured by the Buffalo Foundry and Machine Co.. Buffalo, N. Y., and the Continuous Concentrator, invented by the By-Products Recovery Co., To- ledo, Ohio, and manufactured by the Creamery Package Manu- facturing Co., Chicago. BUFLOVAK RAPID CIRCULATION EVAPORATOR This type of Evaporator has been developed from the standard return-flue tubular boiler and adopted for the spe- cial purpose of hand- ling foamy and del- icate liquors. Construction. The Buflovak Rapid Circulation Evapora- tor consists of a horizontal cylindric- al vapor body. To this is bolted an in- c 1 i n e d cylindrical steam-chest. The vapor body is ennirmed with a F '9- 50 - Tne Buflovak rapid circulation evaporator equipped Wit Courtesy of Buffalo Foundry & Machine Co. CONTINUOUS PROCESS EVAPORATORS 135 baffle plate which extends across its cylindrical part and leaves opening's at both ends of the vapor body for the vapors to escape, the ends or heads of the vapor body being dished outward. The vapor body also carries the milk inlet, vapor outlet and spy glasses. The steam chest which is attached to the lower part of the vapor body, is divided by a solid partition into two compart- ments. The upper and larger compartment is filled with tubes which are expanded in the flue-sheets, closing both ends. The tubes themselves are open at both ends. They are two inches in diameter and from six to eight feet long. The lower and small compartment, called the downtake, is entirely open at both ends. The steam chest is equipped with a steam inlet, a liquor outlet and a condensation outlet or drip. The steam is around the tubes and the milk is inside the tubes. Operation.- This machine is operated under vacuum of from 26 to 28 inches mercury column, the vapor outlet being connected with a condenser and vacuum pump. . The fluid milk enters the vapor body and flows down into the bottom of the downtake of the steam chest, from where it rises in the tubes and finds its level. The level of the milk in the tubes " is kept low, the co- efficient of the heat transmission being highest when the milk level in the tubes is about one-third of the tube length above the lower flue- plate, and it is regulated by automatic float controls in the larger machines. The steam that is turned into the steam chest, causes the milk in the tubes to boil. The vapor thus arising from the milk, together with a portion of the milk rises and passes through 5ECTIOH Fig. 51. Cross section of Buflovak rapid circulation evaporator Courtesy of Buffalo Foundry & Machine Co. 136 CONTINUOUS PROCESS EVAPORATORS the upper part of the tubes at a very high speed, and is thrown with great force against the ribs of the baffle plate which extends across the Avhole cylindrical length of the vapor body. The liquid or condensed milk returns through the down- take to the lower part of the steam chest where it escapes from the machine. The vapor passes at both ends of the baffle plate into the vapor space above and from there through the entrain- ment separator for reclaiming escaping milk, and then to the condenser attached to the outlet of the vapor body. The upper part of the tubes becomes covered with a climbing film of milk. This together with the high speed of the milk in the tubes (100 feet per second or more) increases the capacity of the heating surface, and the small amount of milk in circulation, together with the low level of the milk in the tubes, reduces the possibility of foaming, confining the foam to and breaking it up in the upper part of the tubes where film evaporation takes place. The escape of the condensed milk is continuous and the degree of concentration is controlled by a valve regulating the outlet. The condensed milk runs by gravity from the steam chest into a reservoir located under the evaporator. In this case the reservoir must be under the same vacuum as the evaporator. In some cases it is recommended to have an intermediate storage tank removing the condensed milk from the evaporator by a spe- cially constructed steam pump. THE CONTINUOUS CONCENTRATOR The inflow of the fluid milk and the outflow of the condensed milk are continuous. The milk is condensed under atmospheric pressure at 212 F. A rapidly revolving agitator throws the milk in a thin film against the steam-heated and continuously polished periphery of a jacketed copper drum. By keeping the heating surface clean and bright, and the milk rapidly moving, the power of the milk to absorb and utilize heat is greatly augmented and the rapidity of evaporation increased. CONTINUOUS PROCESS EVAPORATORS 137 Description of Continuous Concentrator. The continuous concentrator consists of a hollow copper drum. The copper shell is surrounded by a steam jacket which is insulated. The space between inner shell and jacket is about one inch. This drum carries in its interior, a re- volving dasher with four or more blades, according to the size of the machine, and similar to an ice cream freezer or a flash pas- teurizer. The edge of these blades comes in direct contact with the inner surface of the shell which is the heat- ing surface, so that when revolving, each blade constantly re- moves from the heating surface any milk that adheres to it. The blades are pres- sed against the heating surface by the centri- fugal force that is generated when the machine is in motion. The arms to which the blades are attached are equipped with stops that control their pressure against the heating surface so as to insure con- tinuous and uniform pressure. The shaft which carries the dasher passes through the front and rear heads of the concen- trator and carries a pulley back of the rear head, to which the power is transmitted. The rear of the concentrator terminates in the exhaust chamber of the condensed milk vapors, which escape through a galvanized iron flue to the outside. The vapors are not condensed by water, but escape into the atmosphere. The rear wall is equipped with the intake of the fluid milk. In order to permit Fig. 52. The continuous concentrator Courtesy of The Creamery Package Mfg. Co. 138 CONTINUOUS PROCESS EVAPORATORS the milk to feed the concentrator by gravity, without necessitat- ing inconveniently high elevation of the forewarmer, the intake is located at the bottom. In the front head, in close proximity to the periphery of the concentrator is located the outlet of the condensed milk. Its distance from the inside wall of the concentrator determines the thickness of the film of condensed milk that is allowed to form on the heating surface, and the amount of milk that is retained in the concentrator. According to the amount of superheating intended, this film may vary from J to ^ inch in thickness and the amount of milk retained in the machine may vary from 6 to 12 quarts. The front head is equipped with a cover which is fastened to the rim with screw bolts and which carries a spy glass through which the operator may watch the process. At the conclusion of the operation this cover is removed and the dasher and blades are taken out, so that both the shell and the dasher can be readily washed. Over the top of the concentrator extends the steam line, a 3 inch pipe, with H inch laterals, supplying the steam jacket, and insuring uniform distribution of heat. The steam line is also equipped with regulator and steam gauge. At the bottom of the concentrator is located the exhaust and regulating drip valve. The continuous concentrator is constructed of diverse sizes and capacities, the most common of these sizes are the following: Capacity when Boiler Capacity Diameter Length Concentrating required at the ratio H. P. of 3:1 3 feet 4 feet 4000 Ibs. 100 H. P. 3 feet 3 feet 3000 Ibs. 80 H. P. 3 feet 2 feet 2000 Ibs. 40 H. P. Speed of Agitator. The proper speed of the continuous concentrator is expressed in terms of rim speed, that is the distance which the blades travel per minute. It has been found that the rim speed which is sufficient to move the film CONTINUOUS PROCESS EVAPORATORS 139 of milk in the machine properly, is about 2500 feet per minute. In order to insure a rim speed of 2500 feet per minute, the blades 2500 in a 3 feet diameter machine must revolve . . t . = 265 times 3x3.14 per minute. In a six foot diameter wheel, the same rim speed 2500 would require 7 -. / =133 revolutions per minute of the spider. OXO.l'T Again it has been found that the blades should be not more than about 2\ feet apart. A three foot diameter concentrator, therefore, requires four blades while concentrators with larger diameter require a larger number of blades in order to keep the distance between blades within the limit of two and one-half feet. Operation of Continuous Concentrator. The operation of the continuous concentrator is simple and the ratio of concentra- tion of the product can be regulated as desired. Heating of Milk. Similar as in case of evaporation in vacuo, it is desirable, if not necessary, to heat the milk before it enters the concentrator. This not only increases the capacity of the machine, but it also prepares the casein in the milk for the superheating to which the milk is subjected in the concentrator. Any method of forewarming or preheating may be used for this purpose, but since the milk flows to and through the concen- trator, in a continuous stream, it is preferable to also use a fore- warmer of the continuous type. The milk should be heated to about 185 to 200 F. and the forewarming should be so arranged that the milk is exposed to this temperature for 5 to 10 minutes before it enters the concentrator. Condensing. The concentrator is steamed, the parts of the agitator are assembled and installed in their proper place, the cover is securely bolted over the opening in the front head and the machine is ready for operation. Before starting the agitator a small amount of milk is permitted to flow into the concentrator so as to avoid the blades from running over the dry heating sur- face, cutting the copper. Simultaneously with the starting of the 140 CONTINUOUS PROCESS EVAPORATORS agitator the steam is turned into the jacket and then the milk intake valve is opened. The steam pressure on the jacket is kept uniform, preferably at 40 to 50 Ibs. of steam. This machine evaporates the milk at atmospheric pressure. The temperature of the milk in the con- centrator therefore, is practically the same as that of boiling water 212 F. at the sea level and varies only with the altitude of the location. The ratio of concentration is regulated by the rate of the milk inflow. As the milk inflow is increased, the ratio of concentration is reduced, because the amount of evaporation being constant, a smaller proportion of the water is taken out of the milk. The density is determined by the use of the Beaume hydro- meter. If the density is greater than desired, more milk is allowed to flow into the machine. If the density is lower than desired the inflow of milk is reduced. Cooling of Condensed Milk. From the discharge spout the condensed milk is run over a continuous cooler from which it escapes ready for packing in whatever form it is intended for. The disc continuous cooler has proven very suitable for this purpose. No subsequent superheating of the concentrated milk is necessary. This product can be made of any consistency desired, regardless of concentration, according to the thickness of the film that is allowed to form in the concentrator, and this in turn depends on the distance of the discharge from the periphery of the machine. Type of Products that can be made by the Use of the Con- tinuous Concentrator. The continuous concentrator can be used for the manufacture .of all types of unsweetened condensed milk, such as plain condensed bulk milk, evaporated milk, condensed buttermilk, condensed whey. For sweetened condensed milk, it would be necessary to delay the addition of the sugar until after condensing, in which case the sugar would have to be added in the form of a syrup. This phase has not as yet been worked out on a practical scale, and demands further investigation before definite directions can be given. CONDENSED BUTTERMILK 141 When properly operated, the continuous concentrator yields a product of excellent flavor and good quality. Contrary to popular assumption, that milk exposed to so hot a heating surface (40 to 50 Ibs. steam pressure which equals a temperature of about 260 F. to 280. F., develops a pronounced cooked flavor, this product is remarkably free from this off-flavor, its solubility is- not materially affected, and its body is smooth. CHAPTER XV. CONDENSED BUTTERMILK The value of buttermilk as a chicken feed is rapidly gaining recognition. Buttermilk, similar to skim milk and whole milk, is a highly satisfactory feed for fattening chickens. Its value is enhanced by the superior quality of the meat from buttermilk- fed chickens and by increased egg production of laying hens. For similar reasons buttermilk which is the foundation of a good hog, is becoming a more and more indispensable part of the ration fed to pigs and hogs. Since the great bulk of butter is manufactured during the summer season the main supply of buttermilk is confined to the summer months. In summer the output of buttermilk far exceeds the demand for this product and much of it goes to waste for lack of a suitable market for it. In winter, on the other hand, the output of buttermilk is small and insufficient to supply the demand. In order to stop this waste of buttermilk in summer, to utilize it economically and profitably and to equalize the supply throughout the year, some of the large creameries of the country have found it practicable and profitable to condense the surplus buttermilk. Information from chicken feeders and hog feeders shows that, when re-diluted to the consistency of the original buttermilk, this condensed buttermilk gives equally as satis- factory results as the fresh buttermilk. Manufacture. There are many methods whereby butter- milk can be and is being reduced in .volume. The most common ones are: Separation of whey by gravity, evaporation in vacuo. evaporation by blowing hot air through it, evaporation by the continuous concentrator, centrifugal separation. 142 CONDENSED BUTTERMILK Separation of Whey by Gravity. Much of the so-called condensed buttermilk that reaches the market is not the result of evaporation of a portion of the water contained in the butter- milk, but is produced by permitting the curd to settle by gravity and then drawing off and rejecting the whey. In this case the fluid buttermilk is pumped into a wooden tank, either a horizontal vat or a vertical stave tank. The tank usually contains several outlets with gates, located at different heights, to facilitate the removal of the whey. The tank may or may not be equipped with steam pipes for heating. The butter- milk is heated to boiling point in these tanks either by blowing live steam into it, or by running steam through the pipes installed in the tank. This heat is maintained for several hours. This causes the casein to contract and settle to the bottom in the form of fine particles of curd, leaving on top a clear whey. This whey is drawn off through the gates located above the stratum of curd. The residue, consisting largely of casein, water and some lactic acid and milk sugar, represents the condensed buttermilk. The concentration, or more correctly speaking, the reduction in volume thus effected, is at the ratio of about 4 to 5 parts of fluid buttermilk to one part of condensed buttermilk. It is obvious that in this form of concentration all of the valuable food elements of the buttermilk are not reclaimed. Most of the milk sugar and much of the lactic acid escape in the whey and are lost. However, the equipment required for this process is very simple and in- expensive and the process requires no special knowledge on the part of the creamery personnel. Evaporation in Vacuo. This is accomplished in a similar manner as is the case in the manufacture of sweetened condensed milk. The buttermilk is condensed in the vacuum pan. Earlier trials of this method did not prove entirely satisfactory, especial- ly because of the tendency of the curd in the buttermilk to stick to the coils and the sides of the pan. Another objection was the relatively high initial cost of equipment the vacuum pan and pump. In order to avoid the sticking of the curd, attempts have been made to neutralize the buttermilk before evaporation by the ad- ' dition to it of such alkalies and alkaline earths as sodium carbon- CONDENSED BUTTERMILK 143 ate, sodium bi-carbonate, milk of lime, ammonium hydrate, and ammonium carbonate. Since one of the virtues, for which buttermilk is of special value for feeding purposes, is its relatively high content of lactic acid, it is obvious that by neutralization the manufacturer is robbing the condensed buttermilk of the very ingredient thai renders it most wholesome and dietetically valuable. Furthermore, while, with the exception of milk of lime, these alkalies add nothing to the product that is of acknowledged bene- fit as a food, the addition of caustic alkalies in quantities suffi- cient to reduce the precipitation of the curd and to prevent its sticking on to the pan, is detrimental to the wholesomeness of the finished product. There are now several firms in this country who claim to have perfected a method of condensing buttermilk in vacuo, that eliminates most of the difficulties formerly encountered and the expensive copper pan is being replaced for this purpose by one of cheaper material. Evaporation by Blowing Hot Air through the Buttermilk. This refers to the Campbell process of making concentrated milk as described on page 132. This method has not come into general use and its practicability for concentrating buttermilk is as yet untried. Evaporation by the "Continuous Concentrator." There is every reason to believe that the use of the "Continuous Concen- trator" for condensing buttermilk is a commercially practical proposition. Experiments have demonstrated that a condensed buttermilk of very good quality can be made by this process and a very high degree of concentration can be accomplished. It is probable that the future will see many of these machines installed in creameries for the purpose of condensing buttermilk. See also "Condensing Milk by the Continuous Process," pages 133-141. Concentration by Centrifugal Separation. For many years, efforts have been made to remove the water from the buttermilk by centrifugal separation. Machines are now on the market and in use, in which the curd of the buttermilk collects on the walls of a revolving basket while the whey is centrifuged out. These machines are similar in principal to the well-known laundry centrifuge. They have been successfully used by creameries that 144 CONDENSED BUTTERMILK are engaged in the manufacture of buttermilk cheese. Their operation, however, is intermittent only. When the basket fills up with the curd, the machine must be stopped and the curd removed. For the purpose of handling large volumes of buttermilk daily these centrifuges are obviously not well adapted. They are too limited in capacity and in speed and in volume of perform- ance. Efforts to devise a centrifuge for continuous operation, similar to the cream separator, have so far failed. The specific gravity of the curd in the buttermilk is so nearly like that of the whey, that the centrifugal separator refuses to discharge a liquid rich in curd and one of practically clear whey. Experiments by the author have demonstrated that, no matter how the outlets of the discharges are adjusted, both liquids have practically the same composition. Packing Condensed Buttermilk. Condensed buttermilk is usually filled in wooden barrels, similar to glucose barrels. On account of its high lactic acid content it keeps without spoiling for a considerable length of time. For prolonged storage, it should be held in the cold. Its keeping quality naturally depends largely on the method of condensation, the degree of concentra- tion and the amount of acid present. Condensed milk produced by evaporation of a portion of its water contains more lactic acid than that which is the result of gravity separation. Evaporated condensed buttermilk may keep for months at ordinary tempera- ture. Wheyed-off condensed buttermilk will spoil in a few weeks, if held at ordinary temperatures. Chemical Composition of Condensed Buttermilk. The com- position of condensed buttermilk naturally varies with the compo- sition of the original buttermilk and the nature and the degree of concentration. Since these three factors are not constant, the composition of the finished product may vary within compara- tively wide limits. The following analyses show the composition of two samples of buttermilk condensed in a vacuum pan. CONDENSED WHEY 145 Composition of Condensed Buttermilk Not Partly neutralized by neutralized ammonium hydroxide Total solids 51.48 40.90 Moisture 48.52 59.10 Ash 3.93 3.70 Curd 18.93 15.38 Lactose 26.30 . 15.76 Lactic acid 3.60 2.52 Ammonium hydroxide .00 .88 Total 101.28 97.34 Uses of Condensed Buttermilk. Most of the condensed but- termilk is sold to chicken feeders. It brings from about four to six cents per pound. Condensed buttermilk has also found a limited demand as human food. It is claimed to be a most wholesome, readily digestible, nutritious and palatable food. Its wholesomeness and digestibility are attributed to its high lactic acid content. It is best put on the market in glass bottles. Its keeping quality is enhanced by the high per cent of lactic acid it contains. CONDENSED WHEY, MYSEOST, OR PRIMOST The condensing of whey is a practice which originated in vScandinavia. The original process consisted of straining the whey into a kettle or large open pan over a fire. "The albuminous material that precipitates and rises to the surface is skimmed off." 1 The whey is evaporated as rapidly as possible with con- stant and thorough stirring. When it has reached about one- fourth of its original volume the albumin previously skimmed off is returned and stirred thoroughly to break up all possible lumps. When the whey has attained the consistency of thick- ened milk it is poured quickly into a wooden trough and stirred with a paddle until cool, to prevent the formation of large. sugar crystals. It can then be molded into the desired form for market. 1 United States Department of Agriculture, Bureau of Animal Industry, Bul- letin No. 105. 146 CONDENSED WHEY A more rapid method of making primost is to evaporate the whey in the vacuum pan. When the syrup has reached the desired density it is drawn off, allowed to cool and pressed into bricks. The product has a yellowish-brown color, gritty texture and sweetish taste. The evaporation of whey in vacuo is as yet a rare practice and the demand for the finished product is very limited. Experiments with the " Continuous Concentrator" have demonstrated that condensed whey of good quality can readily be prepared with this machine. The concentration can be carried as far as 15 to 1 ; whey so condensed escapes from the concen- trator still in liquid form, but changes to a solid upon cooling, the milk sugar in this supersaturated solution crystallizing com- pletely. If made of sour whey, the product thus obtained has a splendid clean and sharp acid flavor. This product promises to have excellent dietetic properties, and also to lend itself admirably for cooking purposes. PART IV. FROM FACTORY TO CONSUMER CHAPTER XVI. STAMPING Every well regulated condensing factory, selling condensed milk in hermetically sealed tin cans, employs some system of marking the cans. This is important for future reference. When defective condensed milk is returned to the factory, the marks on the cans tell the manufacturer the date of manu- facture, and his own record on file in the factory shows the con- ditions under which the defective milk was made. In this way defects can usually be traced to their causes and the recurrence of similar trouble can be avoided. In some factories the batches of condensed milk are num- bered from one up, and the cans are stamped with the respective batch number. This method is simple but may prove undesirable, since it informs the competitors also of the date of manufacture of competing brands. In most factories a code of letters and figures is used, designating the factory, the date, and the number of the batch of each day. Thus for instance : a concern has three factories, A, B and C. X stands for the current year, the letters E, F, G, H, I, J, K, L, M, N, O, P indicate the twelve months of the year, respectively, the figures 1, 2, 3, 4, etc., represent the day of the month and also the batches of condensed milk made in one day. Example : A can of condensed milk belongs to the second batch made April 9, 1918, at factory B. The can would be stamped as follows : B 9 H X 2. The cans are usually stamped on the bottom, that is, on the end which carries the cap. The stamping is done by the sealer. Small interchangeable rubber letters and figures are used. The stamping ink should contain a drier and be waterproof. In small factories the stamping is done by hand. It can be done very 148 INSPECTION OF CANS rapidly. In large factories an automatic stamping- outfit is at- tached to the filling, sealing or labeling machine and the cans are stamped automatically while they are being filled, sealed, or labeled. INSPECTING The sealed and stamped cans are placed, with caps down, in wooden trays holding twenty-four medium-sized cans. All trays of one batch are stacked together. A card indicating number and date of batch and number of cans in the batch is attached to the stack and a copy of the same is filed in the office. The cans are placed with their caps down in order to detect " leakers" (cans with defective seals). Before labeling, the trays should be taken down, the cans turned over and examined for leaky seals. Unless the factory is behind in filling orders the cans will have been in stock at least twenty-four hours or usually longer. In the case of sweeetened condensed milk, if any seals are de- fective, a little condensed milk will have oozed out by that time. Inexperienced sealers are prone to cause a high percentage of leaky cans. A careful sealer may reduce the number of leakers to .1 per cent. Checking the Work of the Sealers. In order to regulate and improve the Avork of the sealers and to locate those doing poor work, it is advisable to number the sealers and supply each with small tin tag's bearing his or her respective number. Each sealer drops one tag into each tray of cans sealed by him. The inspectors record the number of leakers found in each tray. Thus each sealer is charged up with the leakers he made. Disposition of Leaky Cans. Small leaks, in the case of sweetened condensed milk, can usually be soldered over success- fully and the mended cans are returned to their respective batches. In the case of very defective seals, attempts at mending generally cause the milk in the can to burn, forming a brown crust on the cap, which spoils the can for the market. The con- tents have a burnt taste and smell, and upon stirring, brown and black specks of burnt milk appear. It is best to cut bad leakers open and pour the contents into the succeeding batch of milk. LABELING CANS 149 Importance of Inspection. The above description of inspec- tion refers to sweetened condensed milk. This work is neglected in many factories, though it is very important. It may save labels and boxes, as well as much unnecessary labor in unpacking cases with leaky cans, and washing, relabeling and repacking them in new, clean cases. In the case of evaporated milk (unsweetened, sterilized) all cans coming from the incubating room should be individually shaken by hand. All cans showing no signs of bulging, and the contents of which shake with the characteristic sound and be- havior of a liquid, pass inspection. If the ends of the cans are bulging or the contents do not respond to the shaking with the characteristic sound of normal milk, they are rejected, as the evaporated milk in them has either undergone gaseous or curd- ling fermentation, and is spoiled. LABELING Labeling Machines. In the early days of the milk condens- ing industry, the labeling of the cans was done by hand, involving much time and considerable expense. Today, especially con- structed labeling machines are almost exclusively used for this purpose. The efficiency of these machines is such, that they have become a permanent fixture in practically every condensery selling canned goods. They are adjustable to various sizes of cans and can be operated by hand, motor, or belt power. Principle of Labeling Machines. The cans are placed into a chute from which they roll into the machine by gravity. They are caught by two endless belts which draw them through the machine. They first pass over the paste box, which contains an automatically revolving \vheel covered with a thick layer of felt. The felt is saturated with paste or glue from the paste box. Each can comes in contact with the paste wheel and receives a touch of paste. Then the cans pass over the label box containing a stack of labels, face down. Each can picks up one label which is automatically wrapped around the can as it runs through the machine. The label box is equipped with an automatic feeder which pushes the labels up as fast as they are being used. The 150 PACKING IN CASES labeled cans leave the machine over a chute which slants from it. As they are removed they are packed directly into cases. Wrinkles and Rust Spots on Labels. The attractiveness of the package depends, largely, on the neatness of the label. The use of too thin, too thick, or too much paste causes the labels to wrinkle on the cans. The paste should have the consistency of heavy dough and the paste wheel should be so adjusted that it barely touches the passing cans. Frequently the labels of the cans show stains and spots. This is especially true in the case of old goods, and is due either to a poor quality of paper, the use of sour paste or the storing of the labeled goods in damp places. Sour paste corrodes the cans and causes them to rust. The rust penetrates the label and spoils the appearance of the package. Trouble of this kind can be avoided by preparing fresh paste every day. Paste saved from the previous day is prone to sour and should not be used. The storing of the labeled goods in damp places also often causes rust spots as well as moulds on the labels. Thin and soft paper labels more easily than thick, stiff and glossy paper. In the latest types of labeling machines the use of ordinary paste has been largely superseded by that of specially prepared glue, which removes most of the objectionable features of the ordinary paste, does not damage the label apd makes a neater package. PACKING The labeled cans are packed in cases holding from six to ninety-six cans, according to the size of the cans. (One case holds six 1-gallon cans; forty-eight 14-, 15-, 16-, and 20-ounce cans; or seventy-two to ninety-six 8-ounce cans). The sides, bottom and top of the cases should be of material about three-eights of an inch to one-half inch thick, the ends three-fourths of an inch to seven-eights of an inch thick. The cases are usually bought in the ''knock-down" shape and are made up in the factory. Sixpenny cement-coated wire nails are most suitable for this purpose. The cases are most economically nailed by the use of nailing machines, which nail one entire side or one side and one end simultaneously. The cans are usually PACKING IN CASES 151 placed into the cases direct from the labeling machine. In some factories, packing- machines, which pack twenty-four medium- size cans in one operation, are used. Formerly condensed milk cans were packed exclusively in wooden cases. Within the last few years the use of paste-board and fibre boxes has been adopted in many condenseries. These boxes are proving very serviceable for domestic trade, and prior to the price advance on paper ma- terial caused by the world war, they made possible a considerable saving in the cost of the package. Marking the Cases. One end of each case is stenciled with the number of the batch ; over the other end is pasted a case label, representing, enlarged, the brand of the label on the cans within. In the place of the case label, the respective brand may be printed on or burnt into the wood. The burnt stencilling is usually done by the manufacturer of the shocks. One side of each case is usually marked "Condensed Milk" or "Evaporated Milk," as the case may be; the other "Keep in cool, dry place." [f sweetened condensed milk is exposed to excessive heat for a considerable length .of time, as is often the case in storehouses or in the hold of steamers, where the cases may be stowed against the boiler room, it becomes brown, thickens rapidly and develops a stale flavor. Evaporated milk also darkens when exposed to heat and depreciates in flavor. It should, therefore, be kept in a cool place. The humidity of the storage room has no effect on the condensed milk proper, the cans being hermetically sealed. Prolonged exposure to dampness, however, will moisten the paste under the labels. This causes the labels to wrinkle and the paste to become sour and musty. The sour paste corrodes the cans and rust spots penetrate the labels. Such cans also may soon become coated with mildew. Packing Condensed Milk for Export. In the case of con- densed milk bought by the United States Government, the. cans are dipped in a solution of shellac before they are labeled, or the tin plate or empty cans are bought by the manufacturer already lacquered. Cans for export trade and in many instance for the home market, are wrapped into heavy, soft paper, bearing on the outside a copy of the respective brand. This wrapping paper takes up the space between the cans and prevents the cans from being damaged on their long journey and by rough usage. This wrap- 152 STORAGE; ping is usually done by hand. Some makes of labeling machines, however, have an attachment for wrapping the cans so that when the cans leave the machine they are wrapped as well as labeled. The cases are reinforced with a band of strap iron around each end. Where the cases have to be loaded and unloaded numerous times, as is the case with export shipments, they are in danger of being torn to pieces, unless such special precautions are taken. CHAPTER XVII. STORAGE Purpose of Storing. The purpose of storing condensed rnilk is largely the same as that of storing butter and other produce, namely, to keep the product from the time of large supply and low prices, to the time of small supply and high prices. In sum- mer time, the market is usually flooded with condensed milk throughout the country, the demand for it is at ebb tide and the prices are low. In winter, there is usually a great shortage of condensed milk, the demand far exceeds the supply and prices soar high. The storing of summer milk may be necessary, also, in order to enable the manufacturer to fill his contracts and supply his trade in winter. This is especially true where the factories of a concern are located in new territories where the patrons produce an excessively small amount of winter milk. Plain condensed milk and concentrated milk which are not sterile and contain no cane sugar to preserve them, keep but a few days at ordinary temperatures and should, therefore, be sold arid used as soon as possible after manufacture. If their storage is unavoidable, they should be held as near the freezing point as possible. For prolonged storage it might be advantageous to freeze them. However, reliable data on this phase of the industry are lacking. Evaporated milk, sold in hermetically sealed cans, is supposed to be entirey sterile, and, if made properly, will keep indefinitely, There is a constant tendency, however, for the fat to separate out, which naturally is augmented by prolonged storage. Again, the lactic acid in the evaporated milk gradually acts on the can, causing the tinplate to become dull and the contents to aquire a disagreeable metallic flavor. When stored for an excessively long time this chemical action may be sufficient to cause the evolution of considerable quantities of hydrogen gas, swelling the cans. STORAGE 153 Sweetened condensed milk which is preserved by about 40 per cent, of sucrose, will keep apparently unchanged for a con- siderable length of time. It is best, however, when fresh. Bac- teriological examinations have shown that, while moderate age does not change the outward appearance of this condensed milk, the bacteria in it gradually increase and the milk gradually de- velops a stale flavor. White and yellow "buttons," lumps, or nodules of a cheesy texture and flavor, probably due to some fungus growth, are also prone to appear in the condensed milk. Age, also, causes it to become darker in color. These defects are especially apparent in old milk which has not been kept at a low temperature. Again, sweetened condensed milk made in May and June has a strong tendency to thicken with age and to become entirely solid. In some cases a part of the sweetened condensed milk made during the summer months is stored in large cylindrical wooden or iron tanks sunk into the ground, or installed in the basement of the factory, where the condensed milk remains at an even tem- perature. As the demand for the product increases and the supply of fresh milk decreases, condensed milk is drawn from these tanks to fill the increasing orders. Effect of Storage Temperature. Most, if not all the changes which condensed milk is prone to undergo in storage are retarded, if not entirely prevented, when stored at the proper temperature. Temperatures of 60 degrees F. or above are too high for satisfactory storage for a prolonged period of time and the higher the temperature the greater the resulting defect. Temperatures below the freezing point of water are also undesirable. The evaporated milk freezes and while so doing it expands sufficiently to swell the cans. Although this swelling disappears when the contents of the cans dissolve again, yet the swelling action tends to weaken the cans and may give rise to subsequent leakers. Again the melted evaporated milk is prone to be grainy as the result of freezing. This is due to the fact that when freezing, the watery portion separates from the curd and the latter contracts. When the milk thaws up the curd remains contracted and fails to form a smooth emulsion with the remainder of the milk. 154 STORAGE; The sweetened condensed milk does not freeze, because it contains so concentrated a sugar solution that its freezing point is usually far below the refriger- ating temperature. If it is packed in solder-sealed cans there is usually no bad effect .from cold storage. However, when packed in cans sealed with the friction cap or the burr cap, difficulties may arise. These seals are not air-tight. Excessively low storage tem- peratures cause the contents to shrink appreciably. Suction is formed and air is drawn in through the seal. When these F|g . 53 . The stevenson co|d storage door cans again warm up, the vis- Courtesy of stevenson GO. cous milk in the cans seals the microscopic openings, the air and the liquid expand but the air finds no exit. This causes the cans to swell. While the quality of the milk in these cans is not impaired in the least, the swelled cans suggest gaseous fer- mentation, which means spoiled milk and which is invariably rejected on the market. The temperatures at which condensed milk can be stored with least objectionable results, range between 32 and 50 de- grees F. Advisability of Storing. A heavy stock of condensed milk is a severe drain on the working capital of the condensery in- volving the cost of the fresh milk, cane sugar, tinplate, boxes, solder, labels, coal and labor. Unless the manufacturer has successfully overcome and mas- tered all of the principal condensed milk defects, and, unless his experience justifies him in believing that his goods will stand the trials of storage, he will find it advisable not to manufacture more than he can promptly dispose of. Even at best, the con- densed milk will be from three to six months old before it is all consumed, and, if it is at all subject to deterioration, the sooner it is consumed the better. But even if the condensed milk comes out of storage in good MARKETS 155 condition, the condition of the market may be such that the goods cannot be sold at a profit, and if the market happens to take a demoralizing slump at the time the goods are ready to leave the storage, the manufacturer may suffer heavy loss. This condi- tion has occurred repeatedly within the last ten yars. TRANSPORTATION The plain condensed bulk milk and concentrated milk are highly perishable products. If shipped considerable distances they should be placed in refrigerator cars. The evaporated milk and sweetened condensed milk in her- metically sealed cans, and the latter also in barrels, can safely be shipped in ordinary box cars. The cases weigh from fifty to sixty-five pounds, and the barrels from three hundred to seven hundred pounds. Care should be taken that the cars used for this purpose are clean and did not previously carry goods with strong and obnoxious odors, such as fertilizers, as these odors are prone to follow the condensed milk to its destination. Strong box cars, in good repair only, should be used. Even at best, the cases and cans suffer more or less damage in transportation. Cars with leaky roofs should be condemned, as transportation in them may cause the package to suffer in appearance. If shipped on steamboats, it should be specified to stow the cases away from the boiler room, as prolonged exppsure to high temperatures causes the condensed milk to deteriorate. CHAPTER XVIII. MARKETS A large proportion of the canned condensed milk, both sweetened and unsweetened, supplies localities, territories and countries where the dairy industry is yet in its infancy, or where geographic and climatic conditions bar the profitable husbandry of the dairy cow. Thus, we find some of the best condensed milk markets in the tropics, in the arctic regions, in the army and navy, on ocean liners and in mining and lumber camps. In these markets condensed milk has, in many cases, become as great a necessity as fresh milk is to the inhabitants within the temperature zone. The consumption of canned con- 156 MARKETS densed milk in our home markets has, also, been increasing rapidly within recent years, and is today assuming astonishing proportions. The rapid growth of the ice cream industry has further developed a splendid and ever-increasing market for plain condensed bulk milk. It is estimated that the canned condensed milk is from three to six months old before it reaches the consumer. It is usually sold through the medium of a jobber or broker and not direct from manufacturer to retailer. In its transit to the distant markets, it is subjected to many delays; first, by its storage in the factory, then the time in transportation, next, the delay in the warehouse of the jobber, broker or wholesale dealer. From there it gradually finds its way to the shelves of the retailer, where there is again considerable delay before it reaches the pantry of the consumer. Market Prices of Condensed Milk. The price of condensed milk is not controlled by the general market of dairy products, nor by any board of trade ; there is no consistent uniformity of price throughout the country as is the case of butter and cheese. The price of condensed milk does not necessarily follow the rise and fall of the butter and cheese markets, but in the long run it is usually affected by abrupt fluctuations of prices of these other dairy products, largely on account of the influence of such fluctuations on the supply to the condensery of fresh milk. It is chiefly governed by local conditions of supply and demand, composition of product and reputation of the individual brand. Condensed milk is sold under hundreds of different brands or labels. While one and the same concern may sell scores of different brands, the brand itself has very little, if anything, to do with the quality or composition of the contents of the can. Each brand usually sells at its own special price, although the various brands put on the market by the same concern often contain the same quality of milk and may be filled with con- densed milk from one and the same batch. It is customary in most factories to fill the cans before they are labeled and the orders for different brands of condensed milk are filled from the same general stock. The brands serve largely as an in- strument to increase the sales and "dodge" competitors. MARKETS 157 Sweetened condensed milk, packed in hermetically sealed cans, sells from about $3.25 to $5 per case of 48 sixteen-ounce cans and the cans retail at from 5 to 20 cents each, according to the size of the cans and market conditions. Evaporated milk, unsweetened condensed milk in hermetic- ally sealed cans, sells from $2.25 to $4.00 per case, according to the size of the cans and market conditions. Bulk milk, both sweetened and unsweetened, goes direct from the manufacturer to the purchaser who uses it at prices agreed upon by the contracting parties. The sweetened con- densed milk is sold in barrels holding from three hundred to seven hundred pounds (usually about six hundred pounds) to candy and caramel factories, bakeries and confectioners. The price varies from four to ten cents per pound according to the per cent, of fat, demand und supply. When there is a general "epidemic" of bad canned condensed milk, as is often the case in years when the price of sugar is high, due to failure of the sugar cane crop, and many manufacturers are tempted to use inferior cane sugar, which they buy at a comparatively low cost, this spoiled condensed milk is usually turned into candy shops and bakeries, where it is sold for "a song." This condition has always a depressing influence on the price of sweetened con- densed bulk milk, which, during such seasons, may have to be sold at a loss. Some milk condensing concerns operate their own candy shops which take care of the condensed milk that is re- jected on the market. Plain or unsweetened condensed milk is sold in 1 -gallon to 10-gallon cans to ice cream factories, the price varying from twenty-five to ninety cents per gallon, according to fat content, concentration and market conditions. The market for this class of goods is not very constant, but the profits are generally high. It reaches ebbtide in winter when the demand for ice cream is small. Limited quantities of plain condensed bulk milk are also sold in milk and cream bottles for direct consumption. The concentrated milk finds the same markets as the plain con- densed bulk milk. The above range of prices of the several types of condensed milk refers to the market conditions which prevailed while the industry was protected against competition with goods from 158 MARKETS abroad by an import tariff of 2c per pound or $1.00 per case of condensed milk, and to conditions prior to the advent of the European war in 1914. In 1913, the United States, by Act of Congress, removed the import tariff, placing condensed milk on the free list. This Act became effective in the fall of the same year. Its immediate effect was a rapid increase in the importation of European con- densed milk, which was offered for sale at relatively low prices, decreased the sale of domestic goods and caused the holdings of condensed milk to accumulate in large quantities. Condensed milk prices depreciated rapidly throughout 1914 and reached the bottom in the fall of that year when financial limitations compelled many concerns to move their goods at any price. At that time the bottom prices of condensed milk were approxim- ately as follows : Sweetened condensed milk per case $2.50 Evaporated milk per case 1.90 The losses suffered by this slump in the condensed milk market, caused by the influx of cheap foreign goods in the absence of a protective tariff, were enormous and caused bank- ruptcy of numerous of the financially limited concerns. The outlook for the future of the industry looked very uninviting at best, but the situation was saved and market conditions reversed by the urgent food requirements of the Allied nations in the European war, and after the entrance of the United States into the World War, by large orders for the American army and navy. The extraordinary and very urgent demand for condensed milk by the U. S. Government and by its allies boosted the prices of this product to a level not attained since the Civil war. The profits per case were augmented manyfold of those of normal periods and the prices paid the farmer in some localities rose to as high as $3.50 per hundred weight and 75 cent per pound of butterfat. This situation naturally made it easy for the milk condensing factories to encroach on the milk and cream supply territory of the creameries and cheese factories, whose products experienced only a relatively moderate increase in price, and not at all proportionate with the soaring of condensed milk prices. MARKETS 159 In the summer of 1917, the Federal Food Administration, in an effort to control the prices and profits of condensed milk, ruled that the profits on condensed milk shall not exceed 30 cents per case on an average for the year, this being- considered the average pre-war profit. This did not mean that the govern- ment guaranteed a profit of 30 cents per case, it merely meant that 30 cents per case was the maximum profit the condenseries were allowed to make. This ruling applied only to condensed milk sold to the government, it did not refer to the goods sold to the domestic trade nor to export contracts. The national committee of condensed milk men who met with the Federal Food Administration Committee, however, agreed to apply the same ruling to their product sold to the domestic trade. Profits on condensed milk supplied to the allied nations, however, were in excess of this figure, partly because of high prices payed for this export milk and partly because of the greatly reduced cost of selling and distributing. The following figures show wholesale condensed milk prices in 1916 and 1917: January June 1916 1917 per case, per case. Sweetened condensed milk, per case $6.50 $8.75 Evaporated milk, per case 3.85 5.75 Early in 1918, this condensed milk boom suffered an abrupt check from the fact that the transatlantic bottoms available proved entirely inadequate to handle the vast stores of goods which were intended to be shipped to the Allies and to the Amer- ican forces in France. Thus, the Allied Provision Export Com- mission was forced to reduce its orders for shipment of condensed milk from this country to one fourth the regular monthly amount and the American government ceased ordering additional supplies of condensed milk for its overseas forces. In the meantime, the condensed milk firms in this country had contracted for an increased supply of fluid milk at high prices with their farmers, many new factories had been erected and the output of the old factories was vastly increased. With the sudden reduction of orders from the Allies and the complete 160 EXPORTS AND IMPORTS absence of orders from the U. S. Government, large quantities of condensed milk, produced at high cost began to stack up in our factories, causing serious fianancial embarassment to the condensed milk concerns and placing many of the financially limited companies on the brink of disaster. The outlook for a rapid increase in the ocean-going bottoms during the summer of 1918 promises to permanently relieve this temporarily embarass- ing situation of the condensed milk industry. Commercial Stocks of Condensed Milk. Bulletin No. 7 of the United States Food Surveys 1 shows that the total condensed milk stocks January 1, 1918, amounted to 310,881,660 pounds. Of this total the milk condenseries held 22.8 per cent ; the storage warehouses, 7.7 per cent; the wholesale dealers, 35.4 per. cent; and the retail dealers, 27.2 per cent. The remainder, amounting to 6.9 per cent was held by a miscellaneous group of firms. Stocks of Condensed Milk Reported for January 1, 1918, with Comparative Figures for Jan. 1, 1917, by Classes of Business. Class of Business. Total Stocks Reported for Jan. 1, 1918. Pounds. Comparative Figures from Firms Reporting for both 1918 and 1917 1918 Stocks. 1917 Stocks. Pounds. Pounds. Per Cent of 1917. Total 310,881,660 252,477,297 143.3 176,233,345 Milk Condenseries. Storage Ware- houses 70,825,746 23,864,774 4,502,077 19,362,697 110,198,428 91,377,772 11,220,326 7,600,330 84,575,145 54,011,146 29,791,437 772,562 21,417,567 68,446,813 10,769,896 3,365,032 7,404,864 98,317,135 82,642,228 9,741,702 5,933,205 63,227,472 39,980,275 22,739,673 507,524 11,715,981 252.8 204.6 668.6 155.6 121.9 108.1 368.4 390.4 110.5 108.8 113.1 128.9 194.9 27,073,128 5,262,791 503,280 4,759,511 80,648,372 76,484,205 2,644,461 1,519,706 57,238,147 36,746,660 20,097,645 393,842 6,010,907 Col^ Storages Warehouses Wholesale Dealers. Wholesale Grocers Meat Packers... Other Wholesale Dealers Retail Dealers Retail Grocers... General Stores. . . Other Retail Dealers Miscellaneous 1 Food Surveys, Bureau of Markets, U. S. Department of Agriculture, Vol. 1, No. 7. Special issue, June, 1918. EXPORTS AND IMPORTS 161 Exports and Imports. Canned condensed milk only need be considered here. The United States Bureau of Statistics reports the following imports and exports of condensed milk for the years 1911 to 1917 inclusive : Exports and Imports of Condensed Milk for the Years 1911 to 1917, inclusive. 1 Exports Imports. Years . Pounds Dollars Pounds Dollars 1911 1912 1913 1914 1915 1916 1917 12,180,445 20,642,738 16,525,918 16,209,082 37,235,627 159,577,620 259,102,213 936,105 1,651,879 1,432,848 1,341,140 3,066,642 12,712,952 25,129,983 630,308 698,176 1,778,044 14,599,339 33,624,189 18,174,505 18,375,698 46,088 61,671 135,724 1,089,440 2,556,787 1,515,354 1^46,446 Prior to 1914 the United States exported condensed milk chiefly to North America, Oceanica and Asia, small quantities were also exported to South America, Africa and Europe. About 60 per cent, of all the export condensed milk went to countries of the North American Continent, Canada and Panama being the leading- markets. During the last few years, immediately preceding the world war, our exports to Canada had fallen off very rapidly. In 1911 the exports to Canada amounted to only about 15 per cent, of the total exports of condensed milk to the same country in 1908. The rapid development of the milk con- densing industry in Canada, within the last decade was largely responsible for this situation. From 1907 to 1911 there was an annual decrease in the total exports of the United States. In 1907 they amounted to $2,191,000.00 as against $936,105.00 in 1911. Prior to 1913, the imports of condensed milk into the United States were likewise very limited. This was largely due to the protective tariff on imported goods, which was an effective agent to exclude foreign brands from American markets. 1 United States Department of Commerce and Labor, Bureau of Statistics for 1911 to 1917. 162 CHEMICAL COMPOSITION In the fall of 1913, Condensed Milk was placed on the "free list." This resulted in an immediate and rapidly growing in- flux of condensed milk from European countries, such as Switzer- land, Denmark, Holland, Sweden, Norway, Germany and Eng- land. At first the bulk of the influx consisted of sweetened con- densed milk, but later evaporated milk also arrived in increasingly large quantities, causing havoc in our domestic markets, and almost unprecedented depression in the industry in the Fall of 1914. At the same time, the exports further decreased and ceased almost entirely. In 1915 the food shortage in the allied countries and their need of condensed milk for their armies and navies began to counteract the effect of the removal of the protective tariff. Imports rapidly decreased and finally ceased almost entirely, while large and repeated contracts for exports to the Allies brought about an unprecedented growth of our export trade of condensed milk at attractive prices. Our exports were further increased by the fact that the war deprived non-combatant countries in South America, Asia and Africa of their usual imports of this commodity from the now warring countries, opening up the world markets to the United States. These events have resulted in partial elimination of foreign condensed milk from our domestic markets and in a fifteen fold increase of our exports of condensed milk in 1917 over 1914. CHAPTER XIX. CHEMICAL COMPOSITION OF CONDENSED MILK Sweetened Condensed Milk. Sweetened condensed milk contains all the constituents of fresh milk and considerable but varying quantities of sucrose. Its composition, therefore, de- pends on such factors as : composition of the fresh milk from which it is made; the degree of condensation and per cent, of cane sugar added. As all of these factors vary in milk from different localities, and in milk of the same factory at different seasons of the year, no hard and fast rule can be given. The following figures merely show the average composition of sweet- CHEMICAL COMPOSITION 163 ened condensed milk as obtained from the results of analyses of a large number of different brands. Average Composition of Sweetened Condensed Milk Water 26.5 per cent, rfat 9.0 per cent.^ 7V/r ,, 1 ,.j I proteids 8.5 per cent. 00 ,. Milk solids. < no > 32.6 P er cent - | milk sugar 13.3 per cent. C (^ash 1.8 per cent.J Cane sugar 40.9 per cent. Total 100.0 per cent. Water. The water content is largely governed by the de- gree of condensation and the per cent, of cane sugar. American brands average from 24 per cent to 28 per cent water. In ex- ceptional cases milk has been found to contain as low as 21 per cent, and as high as 34 per cent, water. Milk Solids. The per cent, of milk solids is largely governed by the per cent, of milk solids in fresh milk and the degree of condensation. In the majority of brands the solids fluctuate be- tween 30 and 34 per cent. ; in extreme cases analyses have shown as low as 28 per cent, and as high as 40 per cent, milk solids. The relative proportion in which the various solid constituents are present is the same as that in the fresh milk from which the condensed milk is made, provided that the fresh milk was not skimmed previous to condensing. Butterfat. The butter fat in sweetened condensed whole milk fluctuates from about 8 to 12 per cent., according to locality, season of year and degree of condensation. Sweetened con- densed milk sold in barrels is usually partly or wholly skimmed and is, therefore, low in fat. It has been suggested that a small portion of the milk fat is lost during the process of condensation, and this theory is frequently resorted to by condensed milk men to explain why their milk is low in fat. It has been claimed by some that the volatile fats (volatile fatty acids) are lost during the process of condensation. This claim is not well founded, since 164 CHEMICAI, COMPOSITION repeated experiments 1 have conclusively demonstrated that con- densed milk contains the normal amount of volatile fatty acids. It has f.urther been experimentally proven that the condensed milk, when made properly and from whole milk, contains fat equal in amount to that found in the fresh milk used. A reason- able allowance should be made, however, for loss of milk due to spilling and wasting in pipes and retainers. Experience has shown that this loss amounts to about fifty to one hundred pounds of milk per average batch under normal conditions. Proteids. The per cent, of proteids in the condensed milk varies with the per cent of proteids in the original milk and the degree of concentration. It fluctuates usually between 7.5 and 9 per cent. The heating previous to condensing coagul- ates a portion of the milk albumin and alters the casein to the extent that it is not precipitated in the normal way, when rennet is added to the diluted condensed milk. In early spring when the majority of the cows supplying the condensery freshen, there is a tendency of the jacket and coils in the vacuum pan to become coated more or less heavily with a layer of semi-solid milk. This very probably is due to the relatively high per cent, of albumin which sticks to the heating surface. This thickened milk, when mixed with and stirred in water, usually dissolves without much difficulty. See also "Defects of Sweetened Con- densed Milk," page 202. While, in most analyses of sweetened condensed milk, the per cent, of proteids nearly equals that found in the fresh milk multiplied by the degree of concentration, there is a tendency toward a slight loss of this constituent due to precipitation in the forewarmers. Milk Sugar. Sweetened condensed milk contains from about 12.5 to 15 per cent, of milk sugar, the amount varying according to the degree of concentration and per cent, of milk sugar in the fresh milk. The milk sugar is not known to undergo any material changes as the result of the condensing process. If condensed milk is recondensed, it assumes a darker color which is largely due to the caramelizing of a part of the milk sugar, caused by the action of prolonged exposure to heat. The milk 1 Hunziker and Spitzer, Indiana Agricultural Experiment Station Bulletin No. 134, 1909. CHEMICAL COMPOSITION 165 sugar in condensed milk crystallizes very readily and causes the condensed milk to become sandy and settled. Chemical ana- lyses of this sugar sediment show that it consists principally of milk sugar. The primary cause of this property lies in the fact that sweetened condensed milk contains so little water (about 26.5 per cent.) that the milk sugar is present in the form of a supersaturated solution ; therefore, any condition which favors sugar crystallization will tend to produce this defect. 1 Milk sugar requires from five to six times its weight of water at ordinary temperatures for complete solution. In sweetened condensed milk the milk sugar has access to only about twice its weight of water (12.5 to 15 per cent lactose to 25 to 27 per cent, water). Ash. The per cent, of ash is largely dependent on the degree of condensation. It usually varies from 1.5 to 2 per cent. It is quite constant in fresh milk (normal fresh milk contains uniformly about .7 per cent. ash). The per cent, of ash in sweetened condensed milk may serve, therefore, as a reason- ably reliable factor in determining the degree of condensation. The heating of milk, before condensing, precipitates and renders insoluble a portion of the mineral solids, principally the lime salts. Sucrose. The purpose of the presence of sucrose in this product is to preserve it. Most of the sweetened condensed milk on the market contains from 37 to 43 per cent, sucrose, or cane sugar. Wider variations, however, are not infrequent. In some cases analyses showed as low as 30 per cent, and in others as high as 48 per cent, cane sugar. Cane sugar dissolves in one half its weight of water, so that under normal conditions there is sufficient water in the condensed milk to keep the sucrose in solution. The amount of sucrose in milk does not appreciably affect the power of the milk to dissolve milk sugar, nor does the per cent of lactose present materially affect the power of the milk to dissolve sucrose. Specific Gravity. The specific gravity of sweetened con- densed milk falls within the limits of 1.24 to 1.35. Foreign 1 For further details on causes of settled sweetened condensed milk see Chapter XXIII, page 196. 166 CHKMICAI, COMPOSITION brands average higher in specific gravity than American brands. The specific gravity of sweetened condensed milk is controlled by the degree of condensation, the per cent, of fat and the per cent, of cane sugar. Milk condensed at the ratio of about 2.5 parts of fresh milk to 1 part of condensed milk and contain- ing about 9 per cent fat and 40 per cent cane sugar, has a specific gravity of about from 1.28 to 1.29. The specific gravity of sweet- ened condensed skim milk may go as high as 1.35, and, if it con- tains an excess of cane sugar, it may be still higher. Chemical Analyses of Sweetened Condensed Milk of Eighteen Different Brands Brand Milk solids per cent. Water per cent. Pat per cent. Pro- teids per cent. Lac- tose per. cent. Ash per cent. Sucrose per cent. 1 "Silver Spoon" Hires' Condensed Milk Oo . 31 90 28 68 8 40 9 12 12 56 1 91 40 38 3 "Eagle" Borden's Condensed Milk Co 2 "Reindeer* Truro Condensefd Milk Co _. "Tip Top" Bordens' Condensed Milk Co. 31.08 31.23 36.57 25.99 27.33 21.67 8.72 9.56 10.07 8.15 8.32 9 35 12.35 13.42 15 00 1.83 1.80 2 15 42.93 41.44 41 76 a "Challenge" Borden's Condensed Milk Co r _ 3 "Sweet Clover" Mohawk Condensed Milk Co. . . . 31.74 32.84 24.84 24.07 8.23 9.31 8.57 871 13.C2 12 95 1.92 1 87 43,42 43 09 3 "Arrow" Wisconsin Condensed Milk Co 3 "Blue Bell" American Condensed Milk Co\ 3 "Red Cross" Mohawk Condensed Milk Co. 31.15 35.56 34 78 26,83 26.50 27 14 8.00 9.31 11 07 8.49 9.50 7 92 12.87 14.80 14 0** 1.79 1.95 1 7fl 42.02 37.94 00 BC4 3 "Rose" Borden's Condensed Milk Co 30.82 24 76 8 88 8 06 12 07 1 81 Af) Qf 8 "Magnolia" Borden's Condensed Milk Co. 31 98 26 32 8 64 7 84 13 50 200 An AA 3 "Rustic" Michigan Condensed Milk Co 30 00 27 63 8 60 7\07 10 fjT) 1*0 2 "^ilk "Maid" Anglo-Swiss Condensed Milk Co B "Jubilee" The Manitoba Dairy Co 2 "Export" Baldwin Condensed Milk Co. _ 35.69 29.40 32 24 25.65 32.15 26 69 9.65 9.62 11 50 8.78 8.61 8 50 15.17 11.30 12 35 2.09 1.85 1 Aft 38.66 33.45 4.1 Cfl a o w i Canada Milk Condensing Co _. 2 "Nestle" Henry Nestle fc . 31.61 32 91 30.84 28 04 10.61 8 06 8.47 7 68" 12.40 15 28 1.81 104 37.55 OQ O5 3 "Upper Ten" U. S. Condensed Milk Co... 33.65 27.88 8.80 8.34 14.66 1.85 3847 1 Spitzer, Indiana Agricultural Experiment Station, 1910. 2 McGill, Inland Rev. Dept., Ottawa, Bulletin No. 144, 1908. 8 Cochran, Special Report of Analysis of Condensed Milks and Infants' Foods, Pennsylvania Department of Agriculture, 1905. CHEMICAI, COMPOSITION 167 Evaporated Milk. The same factors which control the chemical composition of sweetened condensed milk, also govern that of the unsweetened product, with the exception that the cane sugar is absent. The following figures represent, in round numbers, the average composition of evaporated milk as obtained from analyses of a large number of American brands. Water Milk solids Average Composition of evaporated milk fat 8.3 per cent proteids 7.5 per cent lactose 9.7 per cent ash 1.5 per cent 73 per cent. 27 per cent. 100 per cent. The chemical and physical properties of the various ingredi- ents in unsweetened condensed milk are affected to a greater extent than in the case of sweetened condensed milk. This is largely due to exposure of the evaporated milk to high tempera- tures in the sterilizer. Water and Solids are governed by the degree of concentra- tion and the relative per cent of the same constituents in the fresh milk. The per cent of solids admissible in evaporated milk is largely dependent on the chemical and physical properties of the milk and the sterilizing temperatures employed. Excess in solids in this product jeopardizes its marketable properties, owing to the tendency of the proteids to form hard lumps of curd during the sterilizing process. Evaporated milk very low in solids tends toward the separation of its butter fat in storage. Analyses show a range of from 23 to 31 per cent solids. Since the per cent of solids necessary and possible to be contained in marketable evaporated milk, largely depends on the properties of milk, and, since these properties again are principally con- trolled by locality, season of year, crop, feed and weather con- ditions and the quality of the fresh milk, the solids in milk from any given season of the year may vary very considerably. In 168 CHEMICAL COMPOSITION some localities and at certain times of the year the best results may be obtained with evaporated milk containing 28 per cent solids. In other localities it may be difficult at certain seasons of the year, to incorporate more than 24 per cent solids without injuring or destroying the marketable properties of the product. 1 Butterfat. The fat varies with the per cent of fat in the fresh milk and with the degree of concentration. No fat is lost during the process of condensing and sterilizing. 2 It has been claimed by some that in the process of manufacture, the volatile fatty acids escape and that the evaporated milk therefore con- tains less fat than the fresh milk from which it is made, times the degree of concentration. If this were true the loss of fat in the evaporated milk would not exceed .25 of 1 per cent. But analyses show that the fat in the evaporated milk is entirely normal in composition and contains the same proportion of volatile fatty acids as the fat in the fresh milk. The Composition of Milk Fats in Evaporated Milk 2 Date of Manufacture Reichert Meissl number Iodine number Melting point of mixed fats Melting point of insoluble fatty acids \ugust 1908 28 48 33 64 33 3 degrees C 41 degrees C November, 1908 29.52 33.60 33^4 degrees C. 41.2 degrees C. In the evaporated milk there is a strong tendency for the fat to separate out during storage and to churn in transportation. This is largely avoided by the proper adjustment of the steriliz- ing process and by use of the homogenizer. Proteids. (The proteids vary with the per cent of total proteids in the fresh milk and the degree of concentration. Similar to the case of sweetened condensed milk there is a tendency of a slight loss of proteids in evaporated milk due to mechanical adhesion of a part of the precipitated curd to the heating surfaces in the forewarmers and in the vacuum pan. Most of the coagulable milk albbumin is precipitated. Fresh milk contains about .16 per cent of albumin that is not coagu- lable by heat. 3 The relation of soluble and insoluble curd is 1 Hunziker, Indiana Agricultural Experiment Station, Twenty- first Annual eP r Hunziker and Spitzer, Indiana Agricultural Experiment Station, Bulletin ' 8 Hunziker, Indiana Agricultural Experiment Station, Bulletin No. 143. CHEMICAL COMPOSITION 169 shown in the following table which represents analyses of dif- ferent brands of evaporated milk. Soluble and Insoluble Curd in Evaporated Milk 1 Brand Insoluble curd per cent Soluble albumin per cent Total proteids per cent Gold Milk 844 .46 8.90 Columbine 7.41 .49 7.90 Every Day 7.54 .46 8.0 Gold Milk 737 33 770 Star 786 .30 8.16 Morning 1 Glory 828 .34 8.62 Carnation 6.49 * .52 6.91 Beauty 8.39 .39 8.78 Van Camp's 7.52 .42 7.94 Monarch 6.77 .52 7.29 Diadem 7.06 .42 7.48 Reindeer 6.88 .52 7.40 Wilson's . . . 6.89 .49 7.38 Dundee 7.21 .44 7.65 Average 7.436 .429 7.865 The above figures show that, in the evaporated milk, prac- tically all of the coagulable albumin is changed to insoluble curd. The brands analyzed contained evaporated milk condensed at the ratio of 2 to 2.4 parts of fresh milk to 1 part of evaporated milk. The soluble albumin found corresponds with the albumin not coagulable by heat, normally found in fresh milk, times the ratio of concentration. The casein is largely precipitated by the sterilizing heat, but is present in the form of very finely divided particles. This is due to the mechanical shaking to which the evaporated milk is subjected in the sterilizer and in the shaker. In many batches of evaporated milk the precipitation of the casein during sterili- zation is so fine that the product is perfectly smooth without 143. Hunziker, Indiana Agricultural Experiment Station, Bulletins No. 134 and 170 CHEMICAI, COMPOSITION shaking. The casein in evaporated milk does not respond to the action of rennet as does the casein in fresh milk. Milk Sugar. The milk sugar is present in per cent corre- sponding with that of the original milk, times the degree of con- centration. A portion of it has undergone oxidation (carameliza- tion) due to the high sterilizing temperatures. It gives to the evaporated milk a yellow to light brown color. The higher the sterilizing temperature and the longer the exposure of the evapo- rated milk to this heat, the darker is its color. Ash. The mineral constituents also are present in nearly the same proportion to the other solids, as in fresh milk. They are largely rendered insoluble by the sterilizing process. The lime constituents frequently are found in the bottom of the cans in the form of hard, whitish, insoluble granules. Since the ash in normal fresh milk is practically constant, averaging about .70 per cent, the per cent of ash in the evapo- rated rnilk is frequently used as a factor in determining the degree of concentration. The results may, however, be very misleading, since, when the ash is precipitated in the form of granules, it is practically impossible to mix it back into the milk in order to obtain a representative sample for analysis. The Specific Gravity ranges from 1.05 to 1.08, according to the degree of concentration and the specific gravity of the original milk. It averages about 1.065. Plain condensed bulk milk is of very varying composition, depending largely on the degree of concentration and the per cent of fat present. It is usually made from partly or wholly skimmed milk and is condensed at the ratio of 3 to 4 parts of fresh milk to 1 part of condensed milk. The same fact applies to the composition of concentrated milk. CHEMICAL COMPOSITION 171 Chemical Analyses of Twenty-four Different Brands of Evapo- rated Milk 1 Brand Solids Water Eat Curd Lac- tose Ash Total Gold Milk 29.25 7075 942 844 975 1 54 9990 Columbine .... Every Day... . Gold Milk Star 24.63 26.20 27.18 2904 75.37 73.80 72.82 7090 7.45 8.07 9.07 835 7.41 7.54 7.39 786 8.56 9.10 9.23 1037 1.36 1.47 1.49 1 62 99.98 100.15 100.00 99 16 Morning Glory Carnation .... Beauty 31.08 23.81 28.38 68.92 76.19 7162 10.48 8.05 847 8.26 6.49 839 10.47 7.55 994 1.67 1.24 1 56 99.82 99.49 9998 Van Camp's. .. Wilson's 27.89 25.23 72.11 74.77 8.69 870 7.52 653 9.66 868 1.54 1 37 99.52 10005 Monarch 26.70 73.30 8.09 677 1035 1 44 9995 Diadem 2496 7504 816 706 792 1 33 9951 Reindeer 26.66 73.34 8.08 688 10.21 145 9996 Dundee 27.04 7296 873 721 936 1 48 9974 Sundry samples 1 28.02 71.98 8.93 768 986 1 61 10006 2 31.99 68.01 9.68 849 1.1.88 1 69 9975 3 26.01 73.99 8.18 6.77 924 1 46 9964 4 2733 7267 904 693 942 1 51 9957 5 2937 7063 971 734 1052 1 56 9976 6 21 12 7888 7.30 578 678 1 12 9986 7 2325 76.75 798 619 7.96 1 25 100.13 8 25.48 74.52 8.68 6.34 8.67 1 35 99.56 9 26.62 73.38 9.20 7.00 9.18 1.37 100.13 i Hunziker and Spitzer, Indiana Agricultural Experiment Station, Bulletin No. 134, 1909. 172 SANITARY PURITY CHAPTER XX. SANITARY PURITY AND DIETETIC VALUE OF CONDENSED MILK Sanitary Purity. From the point of view of freedom from pathogenic and other harmful micro-organisms, all forms of con- densed milk are superior to the average market milk. In the first place, the manufacture of a marketable condensed milk makes essential eternal vigilance in the control of the quality of the fresh milk. It is safe to state that in no milk plants does the quality of the fresh milk accepted, receive more careful atten- tion and average higher than in the milk condensery. The foun- dation of the condensed product, the fresh milk, therefore, is of a relatively high standard of purity. Again, the temperature to which the milk is subjected is suf- ficiently high to destroy the germs of practically all milk-borne diseases; so that, unless the condensed milk becomes infected with pathogenic germs after condensing and before the tin cans are hermetically sealed, practically all danger from disease germs is eliminated. In the case of evaporated milk the marketable product is free from all forms of germ life. The only exception to this rule would apply to concentrated milk, in the manufacture of which the milk is not heated to temperatures detrimental to the life of bacteria. Dietetic Value. The dietetic value of condensed milk is largely dependent on the effect of heated milk on its nutritive value and on digestion. As far as condensed milk is concerned, there are no available data that would throw any light on this subject. The results of feeding experiments with heated, pas- teurized or sterilized milk vs. raw milk, however, may furnish a logical guide as to the dietetic effect of condensed milk. Milk pas- teurized at Jiigh temperatures, or sterilized, may be considered comparable, as far as the effect of heat is concerned, to condensed milk. Doane and Price 1 report the following experimental results : "Raw milk is more easily digested when fed to calves than either 1 Doane and Price, Maryland Agricultural Experiment Station, Bulletin No. 77, 1901. DIETETIC VALUE 173 pasteurized, or cooked milk. Contrary to theory, cooked milk, when fed to the calves used in these experiments, caused violent scouring- in the majority of trials. A majority of physicians in charge of children's hospitals corresponded with, favored the use of raw milk for infants when the milk is known to be in perfect condition, but favored pasteurized milk under ordinary condi- tions. With one exception all the physicians corresponded with, discouraged the use of cooked, or sterilized milk for infant feeding." Rosenau* states that "Comparative observations upon in- fants under the same conditions show that they flourish quite as well upon heated milk as upon raw milk. Laboratory experi- ments as well as chemical observations coincide with the view, that heated milk is quite as digestible as raw milk. In fact it is now claimed to be more so. Metabolism experiments indicate that the utilization of calcium and iron in the body is more com- plete in children fed upon boiled cow's milk, than in those fed upon raw cow's milk." Stutzer 1 who conducted experiments of artificial digestion reports in favor of boiled milk, while similar investigations made by Ellenberger and Hofmeister 2 showed no difference in the digestibility between raw and cooked milk. Rodet 3 who experimented with dogs noticed a slight dif- ference in favor of boiled milk. Bruning 4 fed dogs, pigs, rabbits, and guinea pigs with raw and sterilized milk and reports that all results were in favor of the sterilized milk. Bruckler's 5 ex- periments with dogs showed that the animals gained more in weight on sterilized milk than on raw milk, but that their general health, vigor and vitality was better when fed raw milk. Variot observed no difference in the effect on infants between raw and boiled milk. Peiper and Eichloff made post mortem examinations on num- erous dogs which had been fed for prolonged periods on raw * Rosenau, United States Department of Agriculture, Bureau of Animal In- dustry, Circular No. 153, 1910. 1 Stutzer, Landw. Versuchs-Stationen, 40, p. 307. 2 Ellenberger & Hofmeister, Bericht ueber das Veterinarwesen Koenigreich Sachsen, 1890. 3 Rodet, Compt. rend. soc. biol., 48, p. 555. 4 Bruning, Muenchner Mediz., Wochenschrift, No. 8, 1905. * Bruning, Zeitschrift fuer Tiermed, 10, p. 110, 1906. 6 Bruckler, Jahrbuch fuer Kinderheilk, 66, p. 343, 1907. 6 Variot, Comp. rend., 139, p. 1002, 1904. 174 DIETETIC VALUE and boiled milk, respectively. In the dogs fed on boiled milk the marrow of the bones was highly anaemic, the articulation of the bony structure looser, the ash content of the bones and the blood lower, and there was more sodium chloride and less fibrin in the blood than in the case of the dogs fed on raw milk. Storck* and others attribute such infantile diseases as rickets and scurvy to the feeding of boiled milk. It is generally assumed that, because the lime and phosphoric acid of milk become largely insoluble when milk is heated to sterilizing temperatures, these elements in sterilized milk are not sufficiently available to supply the needs of the growing organism. In experiments with dogs Aron and Frese** found that the utilization of the lime is not affected by heating the milk and that, as far as the assimilation of the lime by the growing organism is concerned, it is immaterial in what form the lime is present. Even when fed in difficultly soluble form, as tertiary lime phosphate, the lime was utilized as well as the lime of normal raw milk. The fact that the phosphorus (phosphoric acid), needed for the building up of the bony structure, and which is present in milk largely in organic combination as casein and as lecithin, is changed by heat to inorganic combinations, the lecithin phos- phorus by saponification, and the casein phosphorus by changes in the casein molecule, suggests a poorer retention of the in- organic phosphorus by the animal body. Cronheim and Mueller 1 who studied this phase of nutrition could detect no appreciable difference as to the assimilation of phosphorus by feeding ste- rilized and raw milk, respectively. Their results were rather in favor of sterilized milk. Grimmer 2 holds that digestive and intestinal disorders in in- fants are possibly largely due to biological disturbances, modify- ing the bacterial flora of .the intestines, and to the absence of lecithin and unorganized ferments in heated milk. He reports that the addition to boiled milk of substances rich in lecithin, such as the yolk of egg, also ferments, such as pepsin, trypsin, and emulsin produce a marked improvement in such cases. * Storck, zit. n. Knusel, Studien ueber die sog. sterilisierte Milch des Han- dels. Diss., Luzern, 1908. ** Aron and Frese, Grimmer Chemie u. Physiologic der Milch, 1910. 1 Cronheim and Mueller, Jahrbuch fuer Kinderheilk, 57, p. 45, 1903. 2 Grimmer, Chemie and Physiologic der Milch, 1910. DIETETIC VAUJE 175 The foregoing citations suggest that our knowledge of the dietetic effect of heated or boiled milk is exceedingly limited and that the results obtained and conclusions drawn by the various investigators are at variance. In experiments with the living organism, and confined to so few specimen as seems to have been the case in the work reported, the factors of individuality and environment are a constant stumbling block, magnifying the limit of experimental error and weakening the conclusiveness of the results. On the basis of our present knowledge it seems reasonable to conclude that, as far as the digestibility of its inherent ingredients is concerned, condensed milk, when con- sumed in properly diluted form, varies but little, if any, from raw milk. The absence in condensed milk of ferments, such as en-zymes, which are destroyed in the process and which may assist digestion, may be considered the most important defect of condensed milk from the dietetic point of view. In the case of sweetened condensed milk, however, the nutri- tive ratio of the normal milk is decisively disturbed by the pre- sence of large quantities of sucrose. Even when diluted to far beyond the composition of normal and original fluid milk, the per cent, of cane sugar is still high, causing the nutritive ratio of such milk to be abnormally wide and unbalanced. The carbo- hydrates are present far in excess of the protein, fat and ash. If fed to infants exclusively and for a prolonged period of time, the growing organism is bound to suffer from malnutrition and at the expense of muscular development. Furthermore, it is conceded by the medical profession that sucrose is not a suitable form of carbohydrates for infants. It js not as digestible as lactose, it changes the bacterial flora of the intestines, enhancing the development of butyric acid and other gas-forming and putrefactive germs at the expense of Bacillus bifidus, which is the natural inhabitant of the intestine in normal, milk-fed babies. vSweetened condensed milk is generally highly advertised by the manufacturer as a suitable food for babies; it is frequently recommended by physicians and in some instances, it is claimed to have agreed with babies who were unable to take care of milk in any other form. It is not improbable that in these extremely isolated cases of baby feeding, when all other feeds failed, the 176 GROWTH-PROMOTING AND CURATIVE: PROPERTIES true virtue attributed to the sweetened condensed milk, lay in the fact that the mothers carefully followed the directions on the label for dilution. The directions specify that the condensed milk be diluted with ten to sixteen parts of water. The majority of cases of digestive disorders in bottle-fed babies are un- doubtedly the result of the natural tendency of the mother to feed her child too much milk or too rich milk. When we con- sider that the ratio of concentration in sw r eetened condensed milk is only about 2.5 to 1, it is obvious that a dilution of 10 or 16 to 1 is a great relief to the over-taxed digestive organs of infants, previously fed on milk too rich for normal digestion. The im- mediate change of the health and disposition of these babies for the better, as the result of turning from a prolonged siege of too rich food to the very dilute condensed milk, is therefore not surprising. The manufacturer of sweetened condensed milk in this country is inclined to load his product excessively with sucrose. He does this largely in an effort to increase the keeping quality and to guard against the development of fermentations in the finished article that ruin the goods for the market. While a certain amount of sucrose is necessary to preserve this milk, yet, if the product is manufactured from a good quality of fresh milk, as it should be, and when the proper sanitary conditions are maintained in all departments of the factory, sixteen pounds of cane sugar per. one hundred pounds of fresh milk is entirely sufficient. He should bear in mind that sweetened condensed milk is used and accepted by the consumer as a substitute for market milk, and it is the manufacturer's moral duty to retain in this substitute the normal properties and composition of the product which it is supposed to replace, as nearly as is consistent with the production of a wholesome and marketable product. Growth-Promoting and Curative Properties. 1 Recent dis- coveries by Hart of the University of Wisconsin, McCollum and Davis, formerly of the University of Wisconsin and now at John Hopkins University. Osborne & Mendell of Yale University and other eminent nutrition experts have demon- strated, that before complete growth can occur in a young animal, or for prolonged maintenance, or for the preven- i Journal of Biological Chemistry 1913 to 1917. GROWTH-PROMOTING AND CURATIVE PROPERTIES 177 tion of certain diseases, the diet, besides being adequate as regards its content of proteins, carbohydrates, fats and salts, must contain certain, at present unidentified accessory sub- stances. These substances are of two classes, namely those that are fat-soluble, and those that are water-soluble. The absence in the diet of either or both of these accessory substances causes stunting of growth and the development of certain characteristic diseases. In the absence of the fat-soluble accessory substance the diet produces certain diseases of which sore eyes and ultimate blindness are characteristic. In the absence of the water-soluble accessory substance, the diet gives rise to the disease of beriberi. In either case, normal growth is not obtained, the whole organism is stunted, and the cycle of life is abbreviated. The fat-soluble substance for man is most readily available in the butterfat of milk, in egg fat, and in cod liver oil. It is not contained in the ordinary animal fats such as lard nor in any of the vegetable fats. It is also found in the leaves of plants, but these are not consumed in the normal diet of man in sufficient quantities to supply the necessary amount of the fat-soluble accessory substances. The water-soluble accessory substances are present in a larger variety of foods and are known to constitute a part of the skim milk portion of milk. It is obvious from the above that milk furnishes not only the required protein, carbohydrates, fats, and salts, but it also supplies these fat- and water-soluble accessory substances, which are so indispensible to the normal and full development of the young, which make for full stature of the adult and which keep the individual and the race in healthy condition. Condensed milk made from whole milk is in no way robbed of these accessory elements. The heat to which the condensed milk is subjected in the process of manufacture neither destroys nor weakens them so far as experimental data now available show. This is true of all kinds of condensed milk and evaporated milk made from whole milk. From the standpoint of these growth-promoting and curative properties, all forms of condensed milk are, therefore, equally desirable for infant feeding, for child- ren and for the adult, as is whole milk. 178 CONDENSED MILK STANDARDS AND LAWS On the other hand, skim condensed milk is not a satisfactory food for the growing young. It lacks the indispensible fat- soluble accessory and unless supplemented by egg yolk, cod liver oil, or butter, its consumption by the young in the place of whole milk, or in the place of condensed milk made from whole milk, will prove disastrous to the growth and well-being of those who are restricted to such a diet. Nor does imitation condensed milk, such as the "Hebe" product, in which the butterfat has been replaced by a vegetable fat, supplement the lacking fat-soluble accessory substance. The public should clearly understand that in milk or condensed milk, there is no substitute for butterfat and when the butterfat is removed the product no longer can take the place of milk. See also "Addition of Artificial Fats," page 230. CHAPTER XXL CONDENSED MILK STANDARDS AND LAWS The Federal Food and Drugs Act, passed June, 1906, and which went in force January 1, 1907, has raised the standard of excellence of condensed milk to no small degree. It has served as a purifier of the entire industry putting a premium on the product of the honest manufacturer and insuring the public against condensed milk of inferior food value. Prior to the enforcement of this act, three states only had definite standards and laws regulating the composition of con- densed milk. In the absence of a federal law, car loads of con- densed skim milk were unloaded and sold as condensed milk in states and cities which had no laws or ordinances prohibiting the sale of condensed skim milk, labeled condensed milk. The Federal Food and Drugs Act. executed through the offices of the Interstate Commerce Department, put a stop to this fraud, protecting the public from these inferior goods, eliminating the manufacture, traffic and competition of an unlawful product, enhancing the business of legitimate manufacture and raising the standard and integrity of the industry. Federal Standards. 1 The Federal Standards for sweetened i United States Department of Agriculture, Circular No. 19; also Indiana Agricultural Experiment Station Bulletin No, 143. CONDENSED MILK STANDARDS AND LAWS 179 condensed milk and evaporated milk which went into force January 1, 1907, are as follows: "Sweetened Condensed Milk is milk from which a consider- able portion of water has been evaporated and to which sugar (sucrose) has been added and contains not less than 28 (twenty- eight) per cent of milk solids, of which not less than 27.5 (twenty- seven and five-tenths) per cent is milk fat." This standard for milk solids in sweetened condensed milk is reasonable, just, adequate and attainable under all normal conditions. Sweetened condensed milk in hermetically sealed tin cans averages about 32 per cent milk solids, and the per cent of milk solids can be increased considerably above this average without injuring the marketable properties of the product. Manu- facturers of sweetened condensed milk well know from costly experience, that it would not do to drop the per cent of milk solids to or below 28 per cent. Such milk would be too thin to hold the. sugar in suspension, the sugar would tend to settle to the bottom of the cans, rendering the product unsalable, though not necessarily unwholesome. Again, this thin milk does not keep well, it is prone to undergo fermentation. The manu- facture of a good quality of salable sweetened condensed milk requires that the fresh milk be condensed at the ratio of about 2:1. With this ratio of concentration it is obvious that it is not difficult to incorporate 28 per cent, or over, of milk solids in sweetened condensed milk at all times. The Federal requirement of butterfat in sweetened con- densed milk, i. e. that not less than 27.5 per cent of the total milk solids be milk fat, is also, in most cases attainable. In localities, however, where the factory is supplied almost exclusively w r ith low-testing milk, such as Holstein milk, there is danger of the product falling below the above standard in butterfat content at times. Eckles 1 reports that the butterfat in milk from Hol- stein cows kept by American Experiment Stations averaged 28 per cent of the total solids. This fact can leave no doubt that, while some of the Holstein milk shows a higher ratio of fat, a considerable portion of the Holstein milk produced must neces- sarily contain considerably less than 28 per cent of fat in the 1 Eckles Dairy Cattle and Milk Production, P. 33, 1911. 180 CONDENSED MILK STANDARDS AND LAWS total solids. In such cases, therefore, it would be necessary, in order to meet the above fat standard, to reinforce the natural milk, as produced by the cow, by the addition of cream or butter. From the standpoint of the ready and efficient enforcement, such a standard again has its difficulty. In order to determine accurately whether the fat content in the finished product repre- sents 27.5 per cent of the total milk solids, it is necessary to also determine accurately the per cent of milk solids, and this in turn means the determination of the per cent sucrose. But experience has amply demonstrated that in sweetened condensed milk, con- taining both lactose and sucrose, it is exceedingly difficult to correctly separate these sugars for accurate quantitative analysis. For these reasons, therefore, the author, 1 in. 1910, recom- mended that the standard for sweetened condensed milk be changed to 28 per cent milk solids and 8 percent fat; and this change became effective in 1917, as per Food Inspection Decision 170, 2 which reads as follows: "Sweetened condensed milk, sweetened evaporated milk, sweetened concentrated milk, is the product resulting from the evaporation of a considerable portion of the water from the whole, fresh, clean, lacteal secretion obtained by the complete milking of one or more healthy cows, properly fed and kept, ex- cluding that obtained within fifteen days before and ten days after calving, to which sugar (sucrose) has been added. It con- tains, all tolerances being allowed for, not less than twenty-eight per cent (28%) of total milk solids, and not less than eight per cent (8%) of milk fat. The Federal Standard for Evaporated Milk which went in force January 1, 1907, reads as follows: "Evaporated Milk is milk from which a considerable portion of water has been evaporated and contains not less than 28 (twenty-eight) per cent milk solids, of which not less than 27.5 (twenty-seven and five-tenths) per cent is milk fat." Unfortunately, for the moral effect of the law and for the progress of the condensing industry, the standard of evaporated milk was made so high, evaporated milk shall contain 28 per cent solids, that it was found to be beyond the reach of the manu- 1 Hunziker, Indiana Agricultural Experiment Station Bulletin No. 143, 1910. 2 U. S. Dept. of Agr. Food Inspection Decision 170, March 31, 1917. CONDENSED MILK STANDARDS AND LAWS 181 facturer to comply with it under most conditions without im- pairing the marketable properties of the product. The results of this error have confronted many an honest manufacturer with unsurmountable difficulties. He was compelled to choose be- tween two equally unsatisfactory alternatives, i. e., either to manufacture a product below standard, violating the law, or to close his factory. Modified Evaporated Milk Standard. The unreasonableness of the Federal Standard for evaporated milk was experimentally demonstrated by results of investigations conducted at the Indiana Agricultural Experiment Station. 1 Further extensive investigations were made by the United States Bureau of Chemistry. 2 Finally, in March, 191 1, 3 the standard was modified to read as follows : "1. Evaporated milk should be prepared by evaporating fresh, pure whole milk of healthy cows, obtained by complete milking and excluding all milkings within fifteen days before calving and seven days after calving, provided that at the end of this seven day period the animals are in a perfectly normal condition. "2. It should contain such percentages of total solids and of fat that the sum of the two shall be not less than 34.3 and the percentage of fat shall be not less than 7.8 per cent. "3. It should contain no added butter or butter oil incor- porated either with whole milk or skimmed milk or with the evaporated milk at any stage of manufacture." This modified standard was an improvement over the origi- nal standard which it superseded. However, the requirements of solids were still too high. Difficulties of Meeting These Standards for Evaporated Milk. While these standards can be complied with in some localities and under certain favorable conditions, they are beyond the reach of the manufacturer in other localities and under less favorable conditions. The manufacturer is compelled, in order to produce a marketable product, to use sufficiently high tem- 1 Hunziker, Indiana Agricultural Experiment Station Bulletin No. 143, 1910. 2 Results not published. 3 United States Department of Agriculture, Food Inspection Decision No. 131, 1911. 182 CONDENSED MII,K STANDARDS AND LAWS peratures in the sterilizer to render the milk absolutely sterile. This he must accomplish without causing the product to become curdy. The degree of concentration of the evaporated milk directly controls its curdling properties. The higher the degree of con- centration, the greater is the danger of a curdy product. Unfortu- nately, many of the agents which regulate the ease with which milk curdles, are not under the control of the operator. They have to do with breed, period of lactation, condition, care and feed of the cows, season of year, climatic and weather conditions and the care and chemical, physical and physiological properties of the milk on the farm. It so happens that in localities, where dairying has not as yet reached a high state of development, where cows are exposed to inclement weather, or in the southern tier of the dairy belt, where the cows suffer from the sweltering heat of the summer months and are pestered with flies, and where the available water for cooling the milk on the farm is not very cold, the milk is more prone to curdle, than in highly developed dairy countries, or in localities of the cooler regions of the dairy belt, etc. The properties of milk to curdle, whatever the agents caus- ing them may be, are intensified by the degree of concentration. It is, therefore, necessary for the successful manufacture of a salable product to regulate this. A further objection to both, the original and the modified standard for evaporated milk is that, where milk is bought and paid for on the basis of butterfat contained therein, as it should be, the factory receiving high-testing milk, labors financially under a distinct disadvantage. The reason for this is that in high-testing milk, such as Jersey and Guernsey milk, the butter- fat constitutes about 34 per cent of the total solids, while in low- testing milk, such as Holstein milk, the butterfat constitutes only about 28 per cent of the total solids. In order to meet the require- ments for milk solids, more butterfat has to be put into the evaporated milk per case, where high-testing milk is condensed than in the case of low-testing milk. Consequently, the cost per case, of the manufacture of such milk is greater than that of low- testing milk. These standards, therefore, discriminate in favor CONDENSED MILK STANDARDS AND LAWS 183 of manufacturers and breeds of low-testing milk, such as milk from Holsteins and Ayrshires, and against manufacturers and breeds of high-testing milk, such as milk from Jerseys and Guernseys. Putting the Composition of the Evaporated Milk on the Label. As the result of these difficulties, numerous manufacturers protested against these standards and succeeded in obtaining from the Government temporary concessions to the effect that "there would be no violation of the Food and Drugs Act if the percentage composition of the goods was plainly stated on the label in connection with the name of the substance, although this might be lower than that required by Food Inspection De- cision No. 131." This information was issued by the Government to the condenseries in the form of a circular letter. As the result of this concession, many condenseries, which experienced difficulties in complying with the original standard, adopted individual standards of composition in accordance with their local conditions and they stated on the label, in more or less legible type, the percentages of solids and fat below which their goods would not drop. Subsequent investigations by the Government, however, seemed to indicate that this form of labeling was misleading to the public and would, therefore, be in violation of the Food and Drugs Act. Consequently, the concession of permitting indi- vidual standards was then withdrawn. The Federal Board of Food Inspection continued to further consider the advisability of modifying the evaporated milk standard, and finally decided on the following standard for evapo- rated milk, which is now in force and which became effective April 2, 191 5 : x Condensed milk, evaporated milk, concentrated milk, is the product resulting from the evaporation of a considerable portion of the water from the whole, fresh, clean, lacteal secretion ob- tained by the complete milking of one or more healthy cows, properly fed and kept, excluding that obtained within fifteen days before and ten days after calving, and contains, all tolerances being allowed for, not less than twenty-five and five-tenths per 1 United States Department of Agriculture, Food Inspection Decision 158 April 2, 1915. 184 CONDENSED MILK STANDARDS AND LAWS cent (25%) of total solids and not less than seven and eight- tenths per cent (7.8%) of milk fat. Condensed Skim Milk. The original standard for condensed skim milk 1 which went in effect January 1, 1907, was as follows: "Condensed skim milk is skim milk from which a consider- able portion of water has been evaporated." Subsequently this standard was superseded to more ade- quately control the manufacture and sale of condensed skim milk by % the following standard 2 which became effective March 31, 1917! Condensed skimmed milk, evaporated skimmed milk, con- centrated skimmed milk, is the product resulting from the evapo- ration of a considerable portion of the water from skimmed milk, and contains, all tolerances being allowed for, not less than twenty per cent (20.0%) of milk solids. Sweetened condensed skimmed milk, sweetened evaporated skimmed milk, sweetened concentrated skimmed milk, is the product resulting from the evaporation of a considerable portion of the water from skimmed milk to which sugar (sucrose) has been added. It contains, all tolerances being allowed for, not less than twenty-eight per cent (28.0%) of milk solids. Explanatory Notes Concerning the Federal Food and Drugs Act ; Its Relation to the Interstate Commerce Law, and to the Federal Standards of Purity for Food Products. 3 Any article of food entering into interstate commerce should conform to the requirements of the Federal Law (Pure Food and Drugs Act). If sold other than in the original package in the state re- ceived, it should conform with the laws of that state. The term "Original Packages" used in the act generally means the package in Avhich articles are transported in interstate commerce, as distinguished from the unit packages usually dis- played on the shelves of retailers. 1 United States Department of Agriculture, Circular No. 19, 1907. 2 United States Department of Agriculture, Food Inspection Decision 170, March 31, 1917. 3 Hunziker, Indiana Agricultural Experiment Station Bulletin No. 143, 1910. CONDENSED MILK STANDARDS AND LAWS 185 Section 9 of the act provides that parties who make a guar- antee that products are not adulterated or misbranded within the meaning of the Food and Drugs Act, shall be amenable to the prosecutions, fines and other penalties which would attach in due course to the dealer, if the products are found to be violative of the law. Under these provisions, prosecutions may be directed against manufacturers if they ship or deliver for shipment in interstate or foreign commerce adulterated or misbranded articles of food, or if they guarantee that such articles are not adulterated or mis- branded, consignees may be prosecuted if they sell, in original packages, adulterated or misbranded articles of food which they have received in interstate commerce. With respect to the "Standards of Purity for Food Products" it is not contended that these standards have the force of law. It is believed, however, that they represent fairly what are under- stood generally by reputable manufacturers, dealers, and con- sumers to be the ingredients of the products described therein. This test has been applied by the courts in cases tried under the Act where adulteration and misbranding have been charged of articles of food sold under names recognized in the "Standards," but which were found, on examination, not to conform thereto. It is apparent, therefore, that the safe course for manufacturers, jobbers, etc., engaged in interstate commerce who wish to have their products free from exceptions under the Food and Drugs Act, is to see to it that they conform to the standards described in Circular No. 19, U. S. Department of Agriculture, and as stated on pages 503 to 505 of this bulletin. 1 REQUIREMENTS OF COMPOSITION OF CONDENSED MILK FOR WAR CONTRACTS Requirements of condensed milk sold to the U. S. Govern- ment. The composition of condensed milk and evaporated milk must meet the Federal Standards as specified in Food Inspec- tion Decision 158 for evaporated milk and in Food Inspection 1 These explanations were secured through the courtesy of Geo. W. McCabe, Office of the Solicitor, U. S. Department of Agriculture, Washington, D. C., upon request by letter in 1910. They equally apply to the Food Inspection Decisions which superceeded Circular No. 19. 186 COST OF MANUFACTURE Decision 170 for sweetened condensed milk and condensed skim milk. Requirements of Condensed Milk for Export to the Allied Nations. Condensed milk shall contain not less than 9.2 per- cent butterfat. In order to meet the high butterfat requirement in con- densed milk furnished to the Allies, American condenseries which receive largely low-testing milk are compelled to rein- force their product with butterfat. This is done either by removing a portion of the skim milk, or by the addition to the milk of butterfat in the form of cream or unsalted butter. CHAPTER XXII. COST OF MANUFACTURE General Discussion. The cost of manufacture varies, in a general way, with the organization and size of the factory, capacity of machinery and the amount of the output. These variations are further modified by the cost of available labor, the price of milk, cane sugar, tin cans, box shooks, coal and other supplies, etc. In a properly organized plant the cost of manufacture per case of finished product decreases with the increase of the out- put, provided that the capaciy of the machinery is sufficient to take care of such increase. When the plant is forced beyond its capacity, the factory operates at a disadvantage, and the extra labor and possible waste and losses tend to increase the cost per case. When the output drops below 100 to 150 cases per day. profitable manufacture becomes difficult, the overhead expense is out of proportion with the business, the factory can- not take advantage of rebates in the purchase of supplies, the factory labor is relatively high, because skilled men have to do manual labor, and occasional losses due to spoiled goods devour the profits of a comparatively large portion of the entire output. The price of milk fluctuates with season and proximity and strength of competing markets. The fluctuations embrace a range from $1.00 to $2.00 per one hundred pounds of fluid milk, COST OF MANUFACTURE 187 or twenty-five cents to fifty cents per pound of butter fat. Maximum war-prices up to and including May 1918 were $3.50 per 100 pounds of milk and 75 cents per pound of butterfat. Cane sugar varies in price largely with the season and with the success or failure of the sugar cane crop. Sugar prices usually reach their climax in fall and their minimum price in late winter or early spring. The variations usually fall within the limits of $4.00 and $6.50 per one hundred pounds of sugar. Maximum war price was 7Jc per pound. Tin cans vary in price with style of can and whether made in the condensery or bought from a can-making concern. Some factories are paying more or less heavy royalties for the priv- ilege of using certain patents of cans. Cans intended to be sealed without the use of solder, but which are guaranteed to make a hermetical seal, are generally higher in price than those in the sealing of which solder is used. This difference in price, however, is offset, in part at least, by the cost of the solder and gasoline. Cans purchased from can-making concerns usually are more expensive than cans manufactured in the condensery. This holds true only where the tin-shop of the condensery is properly equipped and efficiently manned. The cost of cans bought from can-making concerns is about fifty-five cents per case, varying somewhat with size and style of can; when made in the condensery the price may be lowered from 10 to 20 per cent. Maximum war price was 90 cents per case. The cost of coal varies with quality and locality. Under average conditions, the condensing and packing of one pound of fluid milk requires about three-tenths of a pound of coal or thirty to forty pounds per case. A good quality of "mine run" can be laid down at the factory in states near the coal region, like Indiana and Illinois for about $2.50 per ton, or in northern states, like Wisconsin, for about $3.30 per ton. The cost of coal per case, therefore, may vary from about three and eight-tenths to six and a half cents per case. Where natural gas or refuse from lumber mills are available, the cost of fuel may be reduced materially by the use of these substitutes for coal. Maximum war price raised the cost of coal about 12c per case. Solder and gasoline for sealing the cans average about three and a half cents per case. The price of solder is about twenty- 188 COST OF MANUFACTURE seven cents per pound and the solder used per case of forty- eight cans, amounts to about one-tenth of a pound. Maximum war price raised it to about 7c per case. For venthole cans the amount of solder needed is from .3 to .5 of one ounce per case. The labels vary in price according to quality of paper, and elaborateness of printing. The average cost of labels is about four cents per case. Maximum war price about 8 cents per case. The box shooks and nails per case cost about eight to ten cents. Maximum war price raised this item to about 10 cents per case. The labor, including factory labor, the office personnel and the manager's salary is about twenty-five cents per case, varying obviously with the organization and output of the factory. War conditions practically doubled the cost of labor, making it about 50 cents per case. The interest on the investment and insurance amount to about two and a half to three cents per case. A factory manu- facturing two hundred cases of condensed milk per day requires an investment of about $25,000 for building and equipment and about $10,000 for operating capital. The expense of freight and other transportation ranges from about five to twenty cents per case, according to distance. It may average about twelve cents per case. War conditions raised the freight to about 15 cents per case. The selling expense varies considerably with the organiza- tion of the sales department and the type and extent of advertis- ing done. Under favorable conditions it may be held down to from fifteen to thirty cents per case. If premiums are awarded the cost is about ten cents extra. The introduction of new brands often incurs an expense as high as $1.00 per case. The average sales expense may be consistently placed at thirty to forty cents per case. War conditions increased the selling expense for domestic trade about 50 per cent. For convenience sake the cost per case may be grouped as follows : COST OF MANUFACTURE 189 SWEETENED CONDENSED MILK Cost per case of forty-eight cans containing forty-six and four tenths pounds of condensed milk, net. 116 pounds milk @ 1.50 18.6 pounds, using 16 Ibs. per 100 Ibs. milk, cane sugar @ 5c Tin cans Boxes Labels Solder and gasoline Coal Labor Interest on investment and insur- ance Freight Selling expense Total cost per case .. 1913. 1.74 .93 .45 .075 .04 .035 .045 .25 .03 .12 .30 4.015 *Increase due" 1917. to war conditions. 3.48 100% 1.35 45% .90 100% .10 33^% .08 100% .07 100% .12 150% .50 100% .03 No Increase .15 25% .45 50% 7.23 80% EVAPORATED MILK Cost per case of forty-eight tall-size cans containing fifty-four pounds of evaporated milk, net. 110 pounds milk @ 1.50 Tin cans Boxes Labels Solder and gasoline Coal Labor Interest on investment and insur- ance Freight Selling expense Total cost per case 1913. 1.65 .55 .075 .04 .02 .045 .25 .03 .12 .30 3.080 1917. 3.30 .96 .10 .08 .04 .12 .50 .03 .15 .45 5.73 Increase due to war conditions. 100% 75% 33^% 100% 100% 150% 100% No Increase 25% 50% * The figures showing per cent increase due to war condition were com- piled by Professor A. C. Anderson, Mich. Agr. College, who conducted an exten- sive study on cost of manufacture of sweetened condensed milk. PART V CONDENSED MILK DEFECTS, THEIR CAUSES AND PREVENTIONS CHAPTER XXIII. CLASSIFICATION OF DEFECTS If we recognize in fresh cow's milk an article of food, highly complex in composition, subject to many and complex changes and to rapid deterioration unless handled carefully and skillfully, then the successful manufacture of condensed milk, a product more complex in its composition and exposed to more diverse, more varying and, in most cases, more unfavorable conditions than fresh milk, must involve a knowledge that extends beyond the mere mechanical knack of heating, adding sugar, evap- orating, sterilizing, cooling, filling, sealing and packing. The simplicity of the process tends to belittle and hide the complexity of the product. Anybody can acquire the routine knowledge of condensing milk, but few can make a uniformly good quality of condensed milk. It, therefore, happens that defective condensed milk is made now and then in most, if not all condenseries, and that the output of a poor quality of con- densed milk is not necessarily always the exception but quite often the rule. Many are the defects which cause condensed milk to be rejected on the market and numerous are the avenues that may lead to the manufacture of defective milk. The milk faults may be of mechanical, physical, chemical, or bacteriological origin, or they may be due to a combination of two or more of these forces. In some instances the defects can be detected in milk during, or immediately after the process, in which case they may be remedied, or their recurrence prevented. But more often, several weeks may pass before abnormalities develop and before the manufacturer realizes that something is wrong with the milk. In the meantime, the conditions which originally produced the SWEETENED CONDENSED MILK DEFECTS 191 milk defect may have so changed, that it is exceedingly difficult to locate the seat of the original trouble. DEFECTIVE SWEETENED CONDENSED MILK The following are the chief and most common defects of sweetened condensed milk : 1. Sandy, rough or gritty 2. Settled 3. Thickened and cheesy 4. Lumpy, white or yellow buttons 5. Blown or fermented 6. Rancid 7. Putrid 8. Brown 9. Metallic. Sandy, Rough or Gritty Sweetened Condensed Milk General Description. This is condensed milk in which a portion of the milk sugar has been precipitated in the form of crystals, the size of the crystals depending on the conditions causing crystallization. First-class sweetened condensed milk is smooth and velvety. Such milk is not entirely free from sugar crystals, but they are so minute in size that they do not rob the condensed milk of its natural smoothness. In sandy or gritty condensed milk the crystals are very numerous and large enough to grind between the teeth, similar to salt crystals in gritty butter. The presence of these crystals is also noticeable to the naked eye ; the milk looks candied. Causes and Prevention. The sugar crystals which render the condensed milk rough and sandy consist largely of milk sugar. The solubility of milk sugar is relatively low. Milk sugar requires about six times its weight of water at ordinary temperature for complete solution. Condensed milk contains from 12.5 to 15 per cent, milk sugar and only about 26.5 per cent, water. The ratio of milk sugar to water in sweetened con- densed milk, therefore, is 1:2, while for complete solution it should be 1 : 6. The milk sugar in this product is present in a 192 SWEETENED CONDENSED MII.K supersaturated solution and any condition which favors sugar crystallization strongly tends to precipitate this milk sugar, because there is more of it present in the milk tiian the available water is capable of readily keeping in solution. The chief factor that prevents the milk sugar from precipitating very badly is the great viscosity of the condensed milk. This is largely due to the caseous matter and the cane sugar. Cane Sugar Content. It has been argued that the large amount of sucrose which sweetened condensed milk contains, is the principal cause of sandy milk and of sugar sediment in the bottom of the tin cans, and that a reduction in the amount of sucrose lessens the tendency of the sugar to crystallize and the milk to become sandy. This line of reasoning is erroneous. The presence, in water, of sucrose in solution does not materially lessen the power of the water to dissolve milk sugar, provided that the sucrose solution is not a saturated one. Sweetened condensed milk, contains about 35 to 45 per cent, sucrose and 24 to 28 per cent, water. Sucrose dissolves in one half its weight of water. The sweetened condensed milk does not, therefore, contain a saturated solution of sucrose. The chief factors causing milk sugar crystallization and sandy condensed milk are : incomplete solution of the sucrose, excessive chilling in the vacuum pan, superheating in the vacuum pan, improper cooling, excessive stirring, and warming up too cold condensed milk with the help of agitation. Incomplete Solution of Sucrose. If the finished product is to be smooth and free from sandiness, it is essential that the sucrose which is added to the hot, fresh milk be thoroughly dis- solved before the mixture reaches the vacuum pan. Undissolved sugar crystals in a medium as highly concentrated as sweetened condensed milk have much the same effect in a physical way, as have bacteria in fresh milk in a biological way; they multiply rapidly. Therefore, if all the sugar added to the fluid milk is not completely dissolved, the undissolved sugar crystals give rise to wholesale precipitation of the milk sug~ar in this product after manufacture. Complete solution of the cane sugar can best be accomplished by heating the liquid, milk or water, in which the sugar is to be dissolved, to the boiling point and by boiling the mixture for several minutes ; or by placing the sugar SWEETENED CONDENSED MILK DEFECTS 19,5 on a large wire mesh strainer (about eighty meshes to the inch) which stretches across the sugar well and allows hot milk to run over this sugar into the well below. In this way the sugar crystals must dissolve before they can reach the sugar well. One of the safest methods of insuring complete solution of the cane sugar is to dissolve it in a separate kettle in a sufficient quantitiy of boiling water (preferably distilled water) and boil- ing the syrup for five to fifteen minutes. If the syrup thus made is given a few minutes rest it should become perfectly clear; by its clearness, the purity of the sugar can also be observed. If a scum forms at the top it should be removed ; then the hot sugar syrup is drawn into the pan. Care should be taken that the milk already condensing in the pan has not become too con- centrated, otherwise sugar crystallization may set in. It is ad- visable to inject the sugar syrup gradually, rather than to wait until nearly all the milk is in the pan. Excessive Chilling in the Pan. The cause of grittiness of condensed milk may lie in the pan itself. Where the water used for condensing is very cold, and where one end of the spray pipe in the condenser is very close to the goose neck of the pan, as is the case with most of the vacuum pans in use, which are equipped with horizontal spray condenser the chilling of the vapors and of the spray of milk rising from the pan is so sudden, that sugar crystals are prone to form in the spray and along the walls of the pan. These crystals either stick to the side of the pan, or fall back into the milk where they later multiply and cause the milk to become sugary. Trouble from this source can be avoided by either raising the temperature of the water that goes to the condenser which is, however, not practical under most conditions, or by closing the holes in that portion of the spray pipe which is nearest the pan. This can easily be done by wrapping a piece of galvanized iron or tinplate around the portion of the spray pipe to be closed, or by filling the holes with solder, or by replacing the old spray pipe by a new and shorter one, properly constructed. Superheating at End of Batch. Sometimes the manufac- turer is persistently troubled with the appearance of crystals in the condensed milk of monstrous size, as large as rice kernels; this condition arrives usually very gradually. During the first i94 SWIFTENED CONDENSED MILK DEFECTS few days after manufacture, only a few of these large crystals may appear in some of the cans. In the course of a few weeks, all of the cans may contain specimen of these "rice crystals" which increase in number until the entire contents of the cans are one mass of "rice crystals," rendering the milk unsalable. The direct causes of this particular kind of sugar crystallization are excessive concentration of the condensed milk, the use of too much steam pressure in the coils and jacket when condensa- tion is near completion, delay in the drawing off of the condensed milk from the pan, and leaky steam valves in the pipes leading to jacket and coils. Taward the end of the condensing process the milk becomes heavy, thick and syrupy, and boils with much less violence. If, at this stage of the process, excessive steam pressure is used in the jacket and coils, the milk is superheated, often causing the precipitation of "rice crystals." Again, where the finished con- densed milk is drawn from the pan very slowly, either owing to too small an outlet in the bottom of the pan, or because the milk is forced to run through a strainer attached to the outlet, or because the finished condensed milk is retained in the pan as the result of an accident, in all of these cases there is danger of superheating, and therefore, of the production of these large crystals. This danger is especially great, where the valves of the steam pipes leading to the jacket and coils are leaking, as is often the case. The avoidance of excessive concentration and the removal of any conditions that tend to expose the finished or the nearly finished condensed milk to excessive heat will usually prevent further trouble of this sort. Improper Cooling. The method used for cooling the sweet- ened condensed milk after it leaves the vacuum pan is another important factor determining the smoothness or grittiness of the finished product. The chief principles involved here are the rapidity and extent of cooling and the amount of agitation to which the condensed milk is subjected. In order to fully appreciate the importance of strict atten- tion to details in the cooling process of sweetened condensed milk, it should be understood, that the formation of sugar crystals in concentrated solutions is enhanced by sudden chilling and by excessive agitation of these solutions. The sudden and irreg- SWEETENED CONDENSED MILK DEFECTS 195 ular chilling of a part or all of the sweetened condensed milk in the cooling- cans is the result of the use of badly dented cans, poorly fitting paddles, a warped condition of the pivots on which the cog wheels in the bottom of the cooling vat revolve, too cold water, and the application of too much cold water. The paddles must scrape all parts of the sides of the cans, from top to bottom. This is possible only when the cans are intact and their sides are smooth and free from indentations. The paddles must be adjusted properly so that their edges fit snugly against the sides of the cans, they must be firmly fastened to the cross bars and forced against the sides of the cans by springs. In order that the cans may run true they must properly fit into the rim of the cog wheels in the bottom of the cooling vat and the pivots on which the cog wheels revolve must be per- pendicular. If the pivots are warped, the cog wheels cannot run true and the cans wobble ; this causes uneven and incomplete scraping of the sides of cans by the paddles. The water in the cooling vat should not be cold, but have a temperature of about 90 degrees F. when the cans, filled with the hot condensed milk, are set into the vat. The cold water should flow into the vat slowly and be evenly distributed throughout the vat. This is best accomplished by the installa- tion of a perforated pipe running the entire length of the vat. The cooling must be gradual. Excessive Stirring. The cans should revolve slowly. Rapid revolution causes excessive agitation of the condensed milk, which stimulates the formation of crystals. About five revolu- tions per minute is satisfactory. In order to make more effective the proper scraping of the cans by the paddles when the cans revolve slowly, it is advisable to install two paddles in each can, touching the periphery of the can on opposite sides. When the milk has been cooled to between 60 and 70 de- grees F., the water should be drawn from the cooling vat, or the cans should be removed at once. For other methods of cool- ing see "Cooling," page 94. Warming Up of Too Cold Condensed Milk. Finally, if the condensed milk is cooled to too low a temperature, either by mistake, or as the result of the cans of cooled milk standing in 196 SWT#NE;D CONDENSED MILK a very cold room over night, so that the condensed milk is too thick to run through the filling machine, it is best to warm it up by simply allowing it to stand in a warm room. The prac- tice of setting the cans back into the cooling tank and revolving them in warm water is objectionable, since this stirring of the milk, while it is warming, seems invariably to produce whole- sale sugar crystallization, and therefore, causes the condensed milk to become very gritty. (See also Settled Condensed Milk). Settled Sweetened Condensed Milk. General Description. By the term "settled milk" the con- densed milk man refers to condensed milk which has precip- itated and thrown down a portion of its sugar, forming a deposit of sugar crystals in the bottom of the can or barrel. This deposit may vary in amount from a very thin layer to a layer an inch deep or more, according to the character and age of the milk. The nature of this sediment also differs in different cases of settled milk. It may be soft, and upon stirring may mix in and dissolve readily, or it may be very dry and hard, in which case it sticks to the bottom of the can with great tenacity, and can be removed and mixed into the milk with difficulty only. Like gritty milk, settled milk is a very common condensed milk defect. Though it does not render the product less wholesome, it is an undesirable characteristic. Such milk is usually rejected on the market and results in a partial loss to the manufacturer. Causes and Prevention. It is obvious, for reasons above referred to, that the conditions leading up to the production of settled milk, are closely related to those that cause milk to become gritty. Condensed milk cannot drop its milk sugar, unless the latter is present in the form of crystals. The absence of crystals then', means that condensed milk will not settle ; but experience has shown that it is a practical impossibility to manu- facture sweetened condensed milk which contains no sugar crystals Sugar crystals are always present in it, and the fact that the milk is not sandy or gritty, does not necessarily mean that it will not settle. Nevertheless, the removal of conditions con- ducive of sandy or gritty milk, diminishes the tendency of the formation of sugar sediment. The succesful and uniform pro- duction of condensed milk that does not settle, however, involves CONDENSED MILK DEFECTS 197 additional conditions that are not controlled by the factors causing gritty milk. Effect of Density on Sugar Sediment. One of the chief of these conditions is the density of the condensed milk. The thin- ner the condensed milk, the greater the difference between the specific gravity of the liquid portion and that of the sugar crys- tals; therefore, the more readily will the crystals sink to the bottom. The viscosity of thin condensed milk, also, is less than that of thick milk, offering less resistance to the force of gravity of the crystals. In the manufacture of sweetened condensed milk that has the proper density, about 2.5 to 2.8 parts of fresh milk are condensed into one part of condensed milk. If the evaporation is stopped sooner, so that the ratio is much less than 2.5 to 1, the condensed milk is usually too thin to hold its sugar crystals in suspension. Effect of Fat Content on Sugar Sediment. The per cent, of fat in milk, also, influences the specific gravity of the condensed milk, and therefore, has some effect on the settling of the sugar crystals, although to a relatively slight degree. Nevertheless, sweetened condensed skimmed milk will settle less readily than sweetened condensed whole milk. Effect of Cane Sugar Content on Sugar Sediment. The per cent, of cane sugar materially influences the specific gravity and viscosity of the condensed milk. Milk with a high per cent, of sucrose is heavier, more viscous and drops its sugar crystals less rapidly than milk with a low per cent, of sucrose. Turning the Cans to Prevent Sugar Sediment. Concerns who have been continually troubled with settled milk often resort to the practice of turning their cases daily, or at other regular intervals. This keeps the precipitated crystals in mo- tion, but it does not prevent the settling entirely. Moreover, milk destined to settle, as the result of defects in the process, cannot be prevented from dropping its crystals after it leaves the factory. Some concerns have stooped to printing on their labels statements similar to the following: "A sediment in the bottom of this can indicates that this condensed milk is absolutely pure and free from harmful ingredients." Advice of 198 SWEETENED CONDENSED MILK DEFECTS the above denomination is obviously ridiculous as well as un- true. Adding Powdered Milk Sugar. It has been explained that after the condensed milk is cooled it contains sugar crystals. If those crystals are large, their cubic content is relatively great in proportion to their surface. Their buoyancy is, therefore, sufficient to overcome the resistance of the surrounding liquid and they will drop to the bottom, forming a sediment. If these crystals are very small and fine they are not objectionable and they usually do not cause settled milk, because their gravity force is insufficient to overcome the resistance of the viscous syrup. It has been further shown that the size of the sugar crystals is largely determined by the size of the first crystals present. Experience has demonstrated that the addition to the condensed milk before cooling, of very fine sugar crystals, such as powdered milk sugar contains, encourages the formation of very small crystals and tends to guard against the development of large and coarse crystals during subsequent cooling. Hence sugar sediment may be greatly minimized, if not entirely pre- vented, by adding to the hot sweetened condensed milk, a small amount of powdered milk sugar, add at the rate of a teaspoon full of milk sugar per one hundred pounds of condensed milk. The milk sugar must be added as soon as the condensed milk comes from the pan, if the milk is allowed to cool before the milk sugar is added, its effectiveness is largely lost. In order to insure the full desired action of the added pow- dered milk sugar, this powder must be transferred to the con- densed milk in such a manner as to prevent its formation into lumps. It must be evenly and finely distributed over and in the condensed milk. The use of a flower sifter has been found most suitable for this purpose. Thickened and Cheesy Sweetened Condensed Milk General Description. The term "thickened and cheesy" condensed milk applies to condensed milk that thas become thick and in some cases solid. This is a very common trouble with miflt manufactured in late spring and early summer. The milk thickens soon after its manufacture and continues thicken- ing until it assumes the consistency of soft cheese, without the SWEETENED CONDENSED MILK DEFECTS 199 development of acid. In this condition it usually has a peculiar stale and cheesy flavor, disagreeable to the palate. Such milk is in- variably rejected on the market. Causes and Prevention : Effect of Colostrum on Thickening. It has been suggested that this spontaneous thickening is due to the presence in the fresh milk of colostrum milk, because this defect appears at a time when the majority of the cows supply- ing the condensery freshen. This explanation can hardly be considered correct and there is no experimental evidence avail- able substantiating it. If the presence of colostrum milk were the cause of it, the thickening would take place during the process, as the result of the action of heat on the albuminoids. This is not the case. This thickening begins some days and often some weeks after manufacture and increases as the milk grows older. Effect of Cow's Feed on Thickening. Again, the cause of this defect has been attributed to the change in feed, the cows being turned from dry to succulent feed at the time when this tendency of the condensed milk to thicken occurs. There is no reliable evidence, however, of how the succulent pasture grasses on which the cows feed can bring about this thickening action in the condensed milk. Effect of Bacteria on Thickening. A third and far more rea- sonable explanation is that this thickening is the result of a fermentation process. It is quite probable that the thickening of sw r eetened condensed milk is closely related to the sweet- curdling fermentation in fresh milk. The sweet-curdling of fresh milk is a fermentation characteristic of, and frequent dur- ing late spring and summer. It is caused by certain species of bacteria which are capable of producing a rennet-like enzyme, which has the power to curdle milk in the sweet state. These bacteria are known to be closely associated with dirt and filth, especially from the feces, and gain access to the milk usually on the farms where the production and handling of milk is not accomplished under most sanitary conditions. It is further known, as the result of analyses that, in spite of the large per cent, of cane sugar which sweetened condensed milk contains, the bacteria in it increase with the age of the 200 SWEETENED CONDENSED MILK DEFECTS milk. The thickening of the sweetened condensed milk in early summer, therefore, very probably is the result of a slow curdling of its casein, caused by enzymes which are produced by bacteria. It has further been demonstrated that condensed skim milk thickens more readily than condensed whole milk, which may be explained by the fact that condensed milk without butter fat represents a more favorable medium for bacterial growth. Fur- thermore, it has been conclusively demonstrated by the writer and others that the addition of cane sugar to condensed milk, in excess of that present in normal condensed milk, greatly retards thickening. This fact suggests that the higher per cent, of sucrose has an inhibiting effect on the enzyme-producing bac- teria, and perhaps, on the action of the enzyme itself. This condensed milk defect can be prevented entirely by using, during the summer months, eighteen pounds of sucrose per one hundred pounds of fresh milk, so that the condensed milk contains about 45 per cent, sucrose. Effect of Finishing in Pan With High Steam Pressure on Thickening. Abnormally thick condensed milk is also the result of overheating the condensed milk in the vacuum pan toward the close of the process. The batch should be finished with low steam pressure in the jacket and coils, not to exceed five pounds of pressure, and the milk should be drawn from the pan at once after condensation is completed. The superheating to which the condensed milk is subjected in the pan, when finishing with a high steam pressure in jacket and coils, or when the milk is not drawn from the pan promptly when the vacuum pump is stopped, or when an effort is made to condense to a very high degree of concentration, is almost sure to cause the finished product to spontaneously thicken with age and this tendency is especially pronounced in the spring and early summer. Effect of Age on Thickening. Finally, all sweetened con- densed milk has a tendency to thicken with age. Kxposure to high storage temperature (summer heat) hastens this action. The rapidity of thickening in storage increases with the increase in temperature. This tendency is very much reduced, therefore, by protecting the goods from high temperatures and by storing them below 60 degrees F. (See Chapter on "Storage," page 152.) SWEETENED CONDENSED MII.K DEFECTS 201 Lumpy Sweetened Condensed Milk General Description. Lumps of varying denominations are not infrequently found in sweetened condensed milk. They may be soft and permeate the contents of the can throughout, or may appear especially in the form of a "smear" along the seams of the can ; or again, they may float on the surface, in which case they are usually hard and cheesy, and either white or yellow in color. Their presence gives the contents of the can an unsightly appearance at best, and in many cases, they spoil its flavor. They naturally suggest to the consumer that something is wrong with the condensed milk, and cause him to reject the whole package. Causes and Prevention. The chief causes of lumpy con- densed milk are : poor quality of fresh milk, unclean pipes in fac- tory, milk from fresh cows, acid flux in tin cans, and unclean and contaminated tin cans. Poor Quality of Fresh Milk and Unclean Factory Conditions. Upon opening the can of condensed milk, even shortly after it is filled, the lid is covered with large and small lumps and specks sticking to the tin, presenting a very uninviting appearance. This condition can usually be traced back to a poor quality of fresh milk, containing too much acid. Very often, too, the cause lies in the factory itself, where it is due to lack of cleanliness. A thorough inspection of milk pipes and pumps generally shows accumulations of remnants of milk which get into the milk of the succeeding batch. Where this condition exists, it is notice- able that the first batch of the day contains more specks and lumps than the succeeding ones. These lumps do not, as a rule, grow larger in size nor increase in number with the age of the condensed milk, but they injure its appearance to the eye, and certainly cannot add to the wholesomeness of the milk. They might easily become the cause of the formation of ptomains. A more rigid inspection of all the fresh milk as it arrives at the factory and thorough scouring of all milk tanks and milk pumps, pipes and conveyors usually prevents the recurrence of this defect. Milk from Fresh Cows. During early spring there is a strong tendency of the jacket and coils in the vacuum pan to 202 SWIFTENED CONDENSED MILK become coated with a thick layer of gelatinous and lumpy milk. This is probably due to the fact that milk during these months comes largely from freshened cows and may contain some colos- trum milk which coagulates when subjected to heat, or that the proteids of milk from these fresh cows are abnormally sensitive to heat. This thickened material usually does not leave the pan until most of the condensed milk has been drawn off. It, therefore, appears in the last one or two cooling cans. If the milk in these cans is mixed with the rest of the condensed milk, the lumps will appear again in the tin cans. The last cans drawn from the pan should, therefore, be kept separate. The contents of these remnant cans may be redissolved in hot water and should be recondensed in a succeeding batch. In this way the manufacturer sustains practically no loss. In order to pre- vent these lumps from getting into the cooling cans, some fac- tories attach a strainer to the outlet of the pan. This practice is as unneccessary, as it is damaging to the milk in the pan. The straining greatly retards the removal of the milk from the pan, and the milk is held in the hot pan so long, as to cause partial superheating which is otherwise detrimental to its quality. Comparative Composition of Gelatinous Coating of the Jacket and Coils and of Normal Condensed Milk of the Same Batch, made April 23, 1908 Coating of jacket Normal condensed and coils milk Moisture 24.76 per cent. 30.34 per cent. Lactose 13.12 " 13.16 Fat 9.50 " 7.44 Curd 8.14 " 7.30 Ash 1.42 1.80 Acid .33 " .40 Sucrose 41.36 40.02 98.63 per cent. 100.46 per cent. The above analyses were made in order to determine the difference in chemical composition between that part of the batch SWEETENED CONDENSED MIUC DEFECTS 203 which, in the spring of the year, forms a gelatinous coating on the jacket and coils and that part which remains normal. The figures do not show as great a difference, as the physical com- parison of the two products would suggest. Possibly the most significant point these analyses show is that, while the proteids in the coating are higher, the ash is lower than in the normal condensed milk. A large portion of the ash of milk is present in chemical combination with the casein, which does not curdle by heat, while the albumin, which is coagulated by heat, contains only a very small amount of ash. Therefore, the fact that an increase in the proteids of this gelatinous coating is accompanied by a decrease in the ash content, would suggest that the proteids of the coating of the jacket and coils consist of more albumin and less casein than the proteids of the normal condensed milk of the same batch. Since this coating of the jacket and coils occurs only in the spring of the year, when most of the cows freshen, it is reasonable to assume that this coating is the result of the acceptance at the factory of milk too soon after calving and which contains excessive quantities of proteids and other sub- stances which are highly sensitive to heat, such as albumin, colostrum, etc. Excess of Acid in Condensed Milk and Acid Flux in Tin Cans. The presence in the condensed milk of organic and mineral acids, in excess of the amount which normal fresh milk contains, is conducive of the formation of lumps. Excessive amounts of acid in condensed milk may be the result of fermentations, usually due to a poor quality of sugar, or of the use of acid flux in the making and sealing of the tin cans. Condensed milk that shows acid or gaseous fermentation usually contains lumps. The acid which it develops as the result of the fermentation, curdles the casein with which it comes in contact. One of the most common channels through which condensed milk may become contaminated with acid mechanically, is the use of cans, in the manufacture and sealing of which acid flux was used. The acid flux generally used contains zinc chloride. The flux precedes the solder and some of it is bound to sweat through the 204 SWEETENED CONDENSED MII^K seams into the interior of the cans. Zinc chloride is a highly poi- sonous product and its use in the manufacture of tin cans, which are intended for receptacles of human food, should be prohibited by law. Aside from its injurious effect on the health and life of the consumer, its presence, even in small quantities in condensed milk, is a detriment to its market value. In such cans there accumulate, usually along the seams, lumps and smeary sub- stances which have been found to consist of casinate of zinc. Most commercial soldering fluxes consist largely of zinc chloride and are highly acid, although many of these are adver- tised as acid-free fluxes. In order to avoid condensed milk con- taining lumps from this source, cans should be used, in the manufacture of which a strictly acid-free flux is used and which are sealed with acid-free flux. Dry, powdered resin or resin dissolved in alcohol or gasoline are harmless in this respect and are just as effective fluxes, as acid flux. Unclean and Contaminated Tin Cans. Finally, there fre- quently appear in sweetened condensed milk, species of lumps which are firm and cheesy and which usually float on top of the milk in the can. These are called buttons. Some are white, others are yellow. These buttons appear in old milk more fre- quently than in milk that has been in storage for a short time only. They grow in size and sometimes one "button" covers the entire surface of the condensed milk in the can. Their origin is not well understood, but they are supposed to be the result of fungus growth. It is not improbable that they are produced by molds, the spores of which gain access to the condensed milk in the factory, or to the cans before they are filled. These "but- tons" appear in the canned goods and in the barrel goods. Their occurrence can be minimized by protecting the condensed milk and the empty cans from dust and other impurities, by steriliz- ing the cans immediately before use, and by paraffining and thoroughly steaming the barrels before filling. Blown, or Fermented Sweetened Condensed Milk General Description. One of the most disastrous troubles in the manufacture of sweetened condensed milk is the appear- ance of "swell heads." This term is applied to cans of condensed SWEETENED CONDENSED MILK DEFECTS 205 milk, the contents of which have undergone gaseous fermenta- tion, the resulting pressure causing the ends of the cans to bulge or swell, and frequently to burst open the seams. In the case of barrel goods, the pressure may cause the barrel head to blow out. This gaseous fermentation is usually, though not always, accompanied by the development of acid and the formation of lumps. This fermented milk is worthless for any purpose and means a total loss to the manufacturer. The loss is generally aug- mented by the fact that this trouble does not become noticeable at once; its development requires several weeks, so that large quantities of condensed milk may have been manufactured before it is apparent that the milk is defective. Some of the goods may have reached the market before the cans begin to swell, in which case the reputation of the respective brand is jeopardized. In some instances entire batches show this defect, while in others only a few cans or cases of each batch are blown. Causes and Prevention. This defect may be brought about through various channels. In most cases it is due to contamina- tion of the milk, on the farm or in the factory, with specific micro-organisms which are capable of fermenting one or more of its ingredients, in spite of the preservative action of the sucrose; or the condensed milk may contain highly fermentable substances such as glucose or invert sugar, so that the germs normally present in the condensed milk become active and pro- duce gas ; or the milk may not be condensed to a sufficient degree of concentration, or may not contain adequate quantities of sucrose, to render it immune to the bacteria normally present. The cans may also bulge without bacterial action, as the result of exposure to a w r ide range of temperatures, causing mechanical contraction and expansion of the contents. Contamination With Specific, Gas-Producing Bacteria and Yeast. This is by far the most common cause of blown milk. While the. micro-organisms which, under normally sanitary pro- duction of milk and factory conditions, gain access to the con- densed mik, are largely inhibited and do not ferment the sweet- ened condensed milk, there are certain specific forms of bacteria and yeast whose growth is not retarded by the concentrated 206 SWEETENED CONDENSED MILK sugar solution of this product. Contamination of the condensed milk with these specific organisms is usually the result of highly unsanitary conditions in the handling of the condensed milk. The products of fermentation depend on the particular type and species of micro-organisms involved. In most cases the sucrose is the chief constituent attacked, but the lactose, also, is capable of gaseous fermentation, though instances of lactose fermentation in sweetened condensed milk are not common. The gaseous fermentation, of lactose is largely caused by bacteria, yeast and molds which contain the lactose-splitting enzyme "lactase," which has the power of hydrolyzing the lac- tose. While the species of organisms which cause lactic acid fermentation from lactose are very numerous, those containing the enzyme lactase and thereby causing gaseous fermentation from lactose, are less frequent, at least, as far as their access to milk and condensed milk is concerned. It is generally under- stood, though not experimentally proven, that species of micro- organisms which do not contain the enzyme lactase have no gas- producing action on lactose. The great majority of cases of gaseous fermentation of sweetened condensed milk are the result of the action of micro- organisms on the sucrose, especially tho>se which contain the enzyme "invertase." The majority of yeasts secrete invertase and ferment sucrose, producing alcohol and carbon dioxide to the same extent as in the case of glucose fermentations. The process is considerably slower, however, especially at the start, owing to the fact that inversion of the sucrose must precede fermentation. For this reason gaseous fermentations of sweet- ened condensed milk do not become noticeable until the product is one or several weeks old. Contamination With Yeast on the Farm. In most cases of yeast fermentations of sweetened condensed milk, the source of contamination lies in the factory. While such contamination may and often does occur on the farm, the yeast cells, though they may be spore-bearing, are destroyed by the heat to which the fresh milk is subjected in the forewarmers and before it reaches the vacuum pan. The thermal death point of all forms of yeast which have come to the attention of the writer in con- CONDENSED MlLK DEFECTS 207 nection with a vast number of investigations of fermented con- densed milk was below 180 degrees F. If all the milk is properly heated in the forewarmers to 190 degrees F. or over, there is, therefore, little danger of fermented milk, caused by contamina- tion of the fresh milk on the farm with yeast. If, however, the heating is incomplete, or if some of the milk passes into the vacuum pan without having been properly heated, there is danger of milk, contaminated with these yeasts, to result in fermented condensed milk. Contamination with Yeast in the Factory. As previously stated, yeast fermentation of condensed milk can almost in- variably be traced back to contamination in the factory. After the milk leaves the forewarmers, or hot wells, it is never again heated to temperatures high enough to destroy these destructive yeast cells. The channels through which yeast contamination may occur in the factory are many. Contaminated Sugar. The sucrose itself may be contam- inated with yeast. This is frequently the case and especially so if the sugar is exposed to dampness, and if flies, bees, ants or cockroaches have access to it. Again, the sugar may reach the milk through a sugar chute. The lower end of the chute is usually located directly over the steaming milk in the hot well. The vapors arising from below may be condensed in the chute, causing its inside walls to become damp, and sugar Avill adhere to the damp surface, forming a crust. If the crust is not removed daily, its contamination with yeast and other dangerous micro-organisms is almost inevitable and whenever this crust peels off and drops into the milk, the contamination may be carried into the finished product, giving rise to gaseous fermentation. Contaminated Machinery and Milk Conveyors. Remnants of milk may lodge in the condenser, in the vacuum pan, in the pipes conveying the milk and condensed milk, in the cooling cans or coils, in the supply tank of the filling machine, or the filling machine itself. These remnants are all subject to con- tamination and may become the source of fermented condensed milk. The strictest attention to scrupulous cleanliness and con- tinuous inspection of all parts of conveyors and apparatus which 208 SWEETENED CONDENSED MILK DEFECTS come in contact with the milk are the only consistent safeguards against trouble from this source. Contamination Through "Cut-opens." It is customary to empty the contents of sample cans which are cut open for any purpose, back into the condensed milk of suceeding batches. If these samples happen to be contaminated with the fermenting Fig. 54. Gaseous fermentation in sweetened condensed milk Fig. 55. Yeast cells causing gaseous fermentation This species is capable of fermenting sugar solutions containing 85% sucrose. germs, the defect is naturally propagated from batch to batch and it is exceedingly difficult to locate the source of the trouble. It is obvious that all suspicious "cut-opens" should be rejected and that all "cut-opens" that are utilized should be emptied into the hot well where their contents are boiled up again. Dangerous Effect of Poor Quality of Sugar. (Sweetened condensed milk is not sterile. There is no part of the process that would render it sterile and, from the time it leaves the vacuum pan to the time when the tin cans are hermetically sealed, it is exposed to contamination with microbes, even though the factory observes the most rigid attention to scrupulous sanita- tion and cleanliness. Most of these microbes are harmless and their growth is inhibited by the preservative action of the cane sugar. If, however, a poor quality of sucrose is used, which may SWEETENED CONDENSED MILK DEFECTS 209 contain traces of invert sugar, or acid, etc., many of these com- mon species of micro-organisms, harmless in normal condensed milk, find an opportunity to develop and cause gaseous fermenta- tion. The presence of invert sugar makes unnecessary the action of invertase in order to start fermentation ; thus, microbes which do not secrete invertase and are otherwise harmless, may become detrimental in the presence of invert sugar, added to the milk in the form of a poor quality of cane sugar. In a similar way the use in condensed milk of commercial glucose, as a substitute of a part of the cane sugar, and in order to reduce the cost of manufacture, is bound to cause disastrous results. Nothing but the best refined, granulated sucrose should be used, the best is the cheapest. Dangerous Effect of High Acid in Milk. Acids have the power of inverting sucrose. The inversion by acid is especially active in the presence of heat. The milk in the vacuum pan is condensing at 130 to 150 degrees F. These temperatures are most favorable to inversion of a portion of the sucrose in the presence of acid. The higher the acid content of the milk, the more active is the inversion. Since invert sugar is the very ingredient necessary to cause bacterial action in the finished product, it is essential that the acidity of the milk to be con- densed, should be held down to the minimum in order to avoid trouble from this source. Contamination with Butyric Acid Bacteria. Frequently the troublesome microbe is not a yeast, but belongs to a species of bacteria highly resistent to heat, and which fail to be destroyed by heating the milk to the boiling point. In this case, the con- tamination usually originates on the farm. Organisms of this kind, which infest the milk on the farm in this connection, largely belong to the butyric acid group. The most prominent among them are Granulobacillus saccharo-butyricus mobilis or Bacillus saccharobutyricus, Bacillus esterificans, Bacillus dimorphobuty- ricus. The putrefactive forms of butyric acid organisms, such as Bacillus putrificus, Plectridium foetidum, Plectridium novum, etc., do not seem to thrive in sweetened condensed milk. The contamination may occur from dust of hay and other fodder, grain, bedding, or the unclean coat of the udder and sur- 210 SWEETENED CONDENSED MILK rounding portions of the animal, or from milking with wet and unclean hands, or from remnants of milk in unclean utensils. It is noticeable that the great majority of cases of blown milk appear during late summer and early fall, when the crops are harvested and the air in the barn is frequently loaded with dust from the incoming crops. Gelatin plates exposed in the stable before and during the filling of silos showed an enormous increase of colonies on the plates exposed during the filling of the silos. Milk drawn under such conditions is naturally subjected to excessive contamination, unless special precautions are ob- served. A very common source of these butyric acid organisms also is remnants of milk in pails, strainers, coolers, cans and any other utensils with which the milk may come in contact, also polluted water used for rinsing the utensils. The cheese-cloth strainer, owing to the fact that it is difficult to thoroughly clean and that it is very seldom really clean, is a very serious menace in this respect. Under average farm conditions, unless a new cloth strainer is used at each milking, it is safe to condemn it entirely and to recommend the use of a fine wire mesh strainer containing about eighty meshes to the inch. On some farms the milk is held in a set of old cans which are kept on the farm and which never reach the can washer at the factory. Just before hauling time these cans are emptied into the clean cans from the factory. These old cans are often not washed properly and sometimes not at all. The remnants of milk in these cans breed these undesir- able germs and contaminate the fresh milk. It is obvious that such a practice is bound to jeopardize the quality and life of the finished product and may constitute a continuous cause of blown milk. Effect of Amount of Sucrose. Since the sucrose contained in sweetened condensed milk is the chief agent preserving it, it is obvious that enough of it must be added to insure adequate preservative action. Experience has shown that about 39 to 40 per cent, of sucrose is required to preserve the condensed milk under average conditions. A higher per cent, of sucrose would naturally intensify the preservative action and inhibit the growth of the bacteria normally present more completely ; but if enough sugar were added to also inhibit the growth of and make harm- SWEETENED CONDENSED MILK DEFECTS 211 less those violent gas-producing butyric acid bacteria and yeast cells, which thrive in sweetened condensed milk containing 40 per cent, sucrose, the product would be objectionable from the consumer's point of view. The logical avoidance of "swell heads" as the result of these undesirable germs, therefore, must ever lie in prevention, rather than cure. The sanitary standard of pro- duction on the farm and of the process in the factory must be raised to and maintained on a level where the milk is protected from contamination with these micro-organisms. The writer 1 has isolated yeast from fermented sweetened condensed milk that produced vigorous gas formation in media containing as high as 85 per cent, sucrose (600 grams sucrose in 100 cc. whey bouillon). Effect of Too Thin Condensed Milk. Condensed milk that is too thin is, also, prone to start fermenting, since it is deficient in the chief preserving agents, i. e., density and per cent, of sucrose. It is not safe to put goods on the market, with a ratio of concentration much less than 2.5:1. Effect of Excessively Low Temperatures. The cans of sweetened condensed milk may also bulge in the case of cans with non-hermetical seals, exposed successively to excessive cold and to room temperature. In this case, the condensed milk is entirely normal and unaffected, and the bulging is the result of mechanical contraction and expansion by cold and heat. This is possible only where the seal of the cans is not entirely her- metical. In the case of the Gebee seal with the burr cap, and the McDonald seal with the friction cap, the seal is not absolutely air-tight. While the pores between cap and can are microscopic in size, and not large enough to permit the contents from leak- ing out, they are sufficient to admit air. The cans are usually filled with the condensed milk at a temperature of about 70 de- grees F. If the filled and sealed cans are exposed to a very low temperature, as may be the case in winter, in store houses or in transit, the milk and the air in the cans contract. This con- traction is intensified by the fact that the sweetened condensed milk does not freeze. Its concentration is so great that its freez- ing point is usually below the most extreme cold storage tem- 1 Hunziker, Results not published. 212 SWEETENED CONDENSED MILK perature. This contraction of milk and air in the cans produces a partial vacuum, causing air to be drawn into the cans through the microscopic openings of the seal. When the cans are sub- sequently moved into places with a more moderate temperature, the milk and the air in the cans expand, but the milk on the in- side of the cans forms a seal preventing the escape of the sur- plus air. The result is that the ends of the cans bulge. This phenomenon has been experimentally determined by the author 1 While the contents of such cans are perfectly normal, the package suggests fermented milk and may be rejected on the market. It is evident, from the above data, that the swelling of the cans, as the result of exposure to excessively low temperatures, can readily be avoided, either by protecting the cans against ex- cessive cold, or by using cans that are sealed with solder. The solder-seals are hermetical so that no air can be drawn into the cans when a partial vacuum is formed in their interior as the result of the contraction of air and milk. Rancid Sweetened Condensed Milk General Description. Sweetened condensed milk may de- velop a distinctly rancid flavor and odor, a defect which renders it unmarketable. According to the best authority, there are many agents which may be active in the production of rancidity. The fact that in rancid butter are usually found to predominate certain species of organisms, such as the fungi of Penicilium Glaucum, Penicilium Roqueforti, Cladosporium butyri, Oidium lactis, Actinomycoces odorifora, yeast and various bacterial species, such as Bacterium fluorescens, pjacterium prodigiosum, Bacillus mesentericus, etc., and that these species are capable of making butter rancid, has led to the conclusion that they may be the cause of rancidity, either by direct action, or by the secretion of fat-splitting en- zymes. It is, therefore, quite possible that some of these species, or similar groups of species, may be instrumental in developing rancidity in sweetened condensed milk. It has been further found that the milk products from certain individual cows, or cows under certain physiological conditions are more prone to develop a rancid flavor, than milk products from other cows or cows under other conditions. 2 Hunziker, Results not published. SWEETENED CONDENSED MILK DEFECTS 213 Relation of Polluted Water to Rancidity. Polluted and filthy water is usually contaminated with fungi and bacteria belonging to the species enumerated above and which have been found to be able to produce rancidity. It is, therefore, not improbable, where such water is used in the factory in the washing of cans, conveyors, kettles, pipes, etc., in the condenser of the vacuum pan and in the cooling tanks, as is frequently the case, that the contamination of milk with it may result in the development of rancidity. Relation of Climate to Rancidity. It is frequently claimed that condensed whole milk shipped to the tropics turns rancid, owing to exposure of this milk, rich in fat to a warm climate. Advantage is sometimes taken of this argument, to justify viola- tions of the law by skimming all, or a part of the milk before condensing. This matter has been thoroughly investigated. All experimental results show that sweetened condensed milk, made properly and in conformance with the law, and containing all the butter fat of the original whole milk, does not turn rancid at any temperature. Putrid Sweetened Condensed Milk. General Description. Sweetened condensed milk is best when fresh. With age it gradually develops a stale flavor which frequently develops into a putrid odor and flavor. Causes and Prevention. The purer the fresh milk and the cane-sugar, and the more careful the processor, the longer will the condensed milk retain its pleasant flavor, provided that it is stored at a reasonably low temperature. Age, however, will cause the best sweetened condensed milk to become stale. The appearance of the stale flavor is usually hastened when heating the fresh milk with direct steam; also, where the fresh milk is not heated to a sufficiently high temperature (below 176 de- grees F.) the condensed milk will break down rapidly with age, usually developing a putrid flavor and odor. This defect rarely appears where the fresh milk is heated to 180 degrees F. or above. This phenomenon is probably due to the presence in milk of active enzymes, such as galactase, gradually decompos- ing the proteids. The action of most of these enzymes is destroyed when the milk is heated to 176 degrees F. or above. 214 SWEETENED CONDENSED MILK Metallic Sweetened Condensed Milk. General Description. Sweetened condensed milk frequently is pregnant with a very distinct metallic flavor suggesting copper. Causes and Prevention. This can usually be traced back to an unsanitary condition of the dome of the vacuum pan. The sugar and acid in the boiling milk in the pan tend to cause the formation of copper oxide and copper salts, on those sections of the interior surface of the pan which are not daily completely cleansed. The dome of the pan is neglected in many condenseries from the standpoint of thorough cleaning. If it is permitted to go uncleansed for a considerable period of time, it becomes coated with copper salts and when the pan is again in operation, the boiling milk and its spray wash these metallic salts down incorporating them in the condensed milk. That the copper in the dome is being acted on can be very readily determined by wiping the inside surface of the dome off with a wet sponge, then analyzing the expressed liquid that the sponge has absorbed. This liquid will be found to contain varying amounts of cppper 7 according to the state of cleanness of the dome. In order to avoid metallic flavor in sweetened condensed milk, the dome should be washed down daily with similar care as is given the cleansing of the jacket, body and coils, and each morning, before the milk is allowed to enter the pan, the entire pan, including dome and gooseneck, should be thoroughly rinsed down with plenty of clean water. Brown Sweetened Condensed Milk General Description. Some of the sweetened condensed milk on the market has a brown color, suggesting chocolate pud- ding. In this condition it is usually rejected by the consumer. Causes and Prevention. All sweetened condensed milk not held at a low temperature grows darker in color with age. If manufactured properly and not exposed to unfavorable condi- tions, this brown color appears very gradually and not until the condensed milk is many months old. If exposed to high temper- ature in storage or transportation, when stowed against the boiler room in the hold of the steamer, or laying on the shelves UNSWEETENED CONDENSED MILK DEFECTS 215 of the warm grocery store or drug store, etc., it turns brown rapidly. Condensed milk in cold storage retains its natural color indefinitely. Where milk is recondensed (the condensed milk is redissolved either in water or in fresh milk and condensed a second time), the product is always darker in color. This brown color is due to the oxidizing action of heat on both, the lactose and the sucrose, a portion of the sugar caramelizing. Experience has shown that the sugar is more sensitive to the oxidizing action of the heat of recondensing, than when condensed the first time. CHAPTER XXIV. DEFECTIVE EVAPORATED MILK AND PLAIN CONDENSED BULK MILK The following are the chief defects of unsweetened condensed milk : curdy, grainy, separated and churned, blown or fermented, brown, gritty, metallic. Curdy, Plain Condensed Milk and Evaporated Milk General Description. Curdy, unsweetened condensed milk is a term used for milk in which a part of the casein is precip- itated in the form of lumps of various sizes. The appearance of lumps of curd in this product is a defect that may render the goods unsalable. Causes and Prevention. Lumps are usually due to a poor quality of fresh milk, the use of excessive heat in the sterilizing process and too high a degree of concentration. Lumps in Plain Condensed Bulk Milk. Lumps are prone to appear in plain condensed bulk milk, as this class of goods is usually made from fresh milk that may be slightly sour, as is the case in creameries and in milk plants where the surplus and the returned milk is often manufactured into plain condensed bulk milk. This defect can be avoided by neutralizing the milk before heating, with an alkali (sodium bicarbonate or. lime water), heat- ing less intensely, by not carrying the condensing process quite so far. If the plain condensed bulk milk comes from the pan in lumpy condition, it can usually be reduced to a smooth body by passing it through an ice cream freezer at ordinary temperatures. 216 UNSWEETENED CONDENSED MILK DEFECTS Lumps of Curd in Evaporated Milk. The danger of lump- iness, or curdiness in evaporated milk is greatly augmented by the fact that, in addition to the causes named under plain con- densed bulk milk, the sterilizing process must be dealt with. The high sterilizing temperature used, tends to precipitate the proteids of milk, and the temperature cannot be reduced below certain limits without impairing the keeping quality of the pro- duct. Most of the evaporated milk, after sterilization, is sub- jected to the shaking process in which the coagulum in the cans is reduced to a homogeneous creamy fluid, provided that the curd is not too hard. A curd will form in the sterilizer in the majority of cases. If it is soft enough, so that it can be completely broken up, no harm is done. If it is so firm that mechanical shaking fails to cause it to disappear, then the evaporated milk will reach the market in lumpy condition and is difficult to sell. Effect of Quality of Fresh Milk. The quality of fresh milk is all important in preventing lumpy evaporated milk. The milk must come from healthy cows in good, normal physical condition. It must not contain colostrum milk nor be stripper milk and it must receive the best of care on the farm and reach the factory perfectly sweet. Milk that is not of high quality in every respect should not be received at the factory. 1 Effect of Concentration. The more concentrated the evap- orated milk, the greater the danger of lumpiness. All the con- ditions causing lumpiness are intensified by the degree of con- centration. The manufacturer must, therefore, study the be- havior of his product at different degrees of concentration, and then decide how much evaporation it will stand without develop- ing subsequently a permanent curd in the sterilizer. 1 Effect of Sterilization. The coagulum is formed in the sterilizer. The higher the temperature, other conditions being the same, the firmer the curd. The lowest temperature that will efficiently sterilize the evaporated milk should, therefore, be used. Since the sterilizing temperature to be maintained cannot be modified below certain limits, it is necessary, when the milk is very sensitive to the heat, to lower the degree of concentration. In some factories fractional sterilization is resorted to with i For detailed discussion of relation of quality of fresh milk to curdiness of evaporated milk see Chapter VIII on "Manufacture of Evaporated Milk," "Quality of Fresh Milk," p. 104. UNSWEETENED CONDENSED MII^K DEFECTS 217 batches of milk that are suspicious. By so doing, lower tem- peratures can be used effectively, but this process calls for much more labor, increases the cost of manufacture and decreases the capacity of the factory. Effect of Fractional Curdling. Experience has shown that, if the proteids in evaporated milk are partly precipitated by heat before the milk reaches the sterilizer, the curd, or lumps formed in the sterilizer are less firm and can be shaken out more readily. It is, therefore, advisable to heat the milk in the forewarmers to as near the boiling point as possible and to hold it at that tem- perature for at least five minutes before it is drawn into the pan. The superheating of the evaporated milk before it leaves the pan is an additional safeguard against the formation of excessive curd in the sterilizer. Effect of Homogenizing Evaporated Milk. Excessive pres- sure in the homogenizer tends to so change the physical prop- erties of the casein as to render it more sensitive to the steriliz- ing process. Evaporated milk, homogenized under excessive pressure almost invariably forms a firm, unshakable curd in the sterilizer. The homogenizing pressure should be kept down to one thousand to fifteen hundred pounds. 2 Acid Flux in the Cans Causes Lumps. Similar as in the case of the sweetened condensed milk, the presence of acid flux in the cans of evaporated milk causes lumpiness. The acid that reaches the interior of the cans causes the milk coming in contact with the seams to curdle. Only acid-free flux should be used in the manufacture and sealing of the cans. Grainy Evaporated Milk General Description. This term is sometimes applied to lumpy milk, in which case it means the same. By grainy milk, however, is generally understood milk which contains a sediment of a white granular appearance, which is insoluble. Causes and Prevention. This granular sediment is largely found in the hermetically sealed cans after the sterilizing process. It is due to excessively high sterilizing temperatures or too long 1 For detailed discussion of relation of concentration to curdiness of evap- orated milk see Chapter VIII on "Striking." 8 For detailed discussion of the effect of homogenizing on curdiness see Chapter IX on "Homogenizing" and Chapter XXIV on "Separated and Churned Evaporated Milk." 218 UNSWEETENED CONDENSED MILK exposure of the milk to the process. It consists largely of the mineral matter of milk, rendered insoluble and precipitated by heat. The use of lower sterilizing temperatures or the shorten- ing of the period of sterilization will help to avoid this defect. Evaporated milk in the condensation of which the "Continu- ous Concentrator" was used, has a tendency to show slight grainy condition, though this is barely perceptible. Separated and Churned Evaporated Milk General Description. This is a very common defect. A portion of the butter fat of the contents of the hermetically sealed cans, has separated and appears in the form of lumps of cream or of churned butter, on top of the evaporated milk. While this separated evaporated milk is normal in quality and whole- someness, its appearance condemns it. Causes and Prevention. As explained in Chapter IX on "Homogenizing," p. 110, the fundamental cause of separated and churned evaporated milk lies in the difference of the specific gravity between the butter fat and the rest of the milk constitu- ents. The fat globules, being lighter than the serum, tend to rise to the surface, forming a layer of thick cream. When this separated evaporated milk is subjected to agitation, as is the case in transportation, this 'cream churns into lumps of butter. This tendency of the fat to separate in storage and churn in transportation, increases with the increase of the size of the fat globules, because the larger the globules, the larger is their cubic content in proportion to their surface. This fact is based on the well known physical law, that the surfaces of two spheres are to each other as the squares of their diameters, and the cubic contents of two spheres are to each other as the cubes of their diameters. The cubic contents determine the gravity force, or .buoyancy, while the surfaces control the resistance force. There- fore, the larger the fat globules the greater is their buoyancy and the weaker is the relative resistance w r hich they must over- come in their upward passage. Effect of Locality and Season. Since the predominating size of fat globules in milk, varies with breed and period of lactation of the cows, the ease with which evaporated milk separates and the difficulty of overcoming this defect, differ UNSWEETENED CONDENSED MII.K DEFECTS 219 greatly with locality and season of year. The fat globules in milk from the Channel Island breeds, average two to three times as large as those in milk from the Holsteins and Ayrshires. Therefore, factories located in Holstein and Ayrshire territories are not troubled nearly as much with fat separation in evapo- rated milk, 'as factories in localities where Jerseys and Guernseys predominate. Again, the fat globules are largest at the beginning of the period of lactation and decrease in size as the period of lactation advances. Relation of Breed and Period of Lactation to Size of Fat Globules 1 Months of period Breeds of 3 airy cows of lactation Jersey 25 cows Guernsey 20 cows Holstein 9 cows Ayrshire 33 cows Holderness 20 cows Devon 16 cows 1st month 1104 928 687 546 2nd " 1098 1063 640 580 661 585 8rd 1228 954 576 624 607 450 4th 1097 659 256 426 501 547 5th _ 1149 839 396 384 397 319 6th 7th 8th . 846 1017 733 737 584 568 595 340 310 399 322 298 324 329 379 355 270 20) 9th 10th 715 571 408 426 384 284 241 248 315 336 250 228 Average for year 955.8 716.6 420.1 420.9 427.6 375 In order to equalize the output of evaporated milk through- out the year, condensing concerns make every effort to induce their patrons to time the breeding of their cows in such a way that the fresh cows are distributed throughout the year. The result of this practice is, that the milk supply of these factories represents at all times a mixture of milk from cows at all stages of their period of lactation. This naturally equalizes the be- havior of the finished product as far as separation of the fat is concerned, facilitating the control of this separation. On the other hand, in localities of factories, newly established, summer milk is largely produced and the majority of cows freshen in the spring. This causes a marked increase of the size of the average fat globules in early summer, rendering the manufacture of evaporated milk, that does not separate its fat, more difficult. 1 Hunziker, Mills and Spitzer, "Moisture Control of Butter." Indiana Agri- cultural Experiment Station, Bulletin No. 159, 1912, pp. 330-334. 220 UNSWEETENED CONDENSED MILK DEFECTS Effect of Degree of Concentration. Other conditions being the same, the more concentrated the product the less the danger of fat separation in the finished product. The reason for this lies in the fact that with the concentration the viscosity and the resistance force of the evaporated milk increase, hindering the fat globules in their upward passage. This is partly offset by the increase in the specific gravity of the product, but the in- crease of the resistance force exerts a stronger influence against separation of the fat, than the increase of the gravity force exerts in favor of fat separation. However, as the concentration increases, the evaporated milk becomes more sensitive to the sterilizing process and beyond certain limits it would be necessary to reduce the tem- perature or the length of exposure to heat, or both, in order to prevent the more highly concentrated milk from becoming per- manently curdy. If, in order to increase the viscosity, the degree of concentration is carried so far that the sterilizing process has to be shortened, nothing is gained but much may be lost. It is obvious, therefore, that the degree of concentration does not furnish a practical basis for controlling fat separation. Effect of the Sterilizing Process. Prolonged exposure of the evaporated milk to the sterilizing heat tends to so change the physical properties of the albuminoids, as to render the product more viscous. Within the limits of the necessary sterilizing heat, long exposure to moderate heat is more effective in this respect than short exposure to a high degree of heat. Since the greater viscosity tends to keep the fat globules from rising, the use of a prolonged sterilizing process, in which the heat is applied slowly, is more effective in preventing fat separation in the evaporated milk than a rapid, short process, in which the tem- perature used is very high. It should be understood from the discussion in previous chapters that, in regulating the process of sterilization, the pro- cessor should be governed by the condition and behavior of the milk and that on the one hand the degree and duration of heat should always be sufficient to insure absolute sterility of the product, while on the other he must guard against the formation of an unshakable curd. 1 1 For detailed discussion see Chapter XI on "Sterilizing," page 120. UNSWEETENED CONDENSED MILK DEFECTS 221 Effect of Superheating. The superheating of the milk before sterilization and the stopping of the reel of the sterilizer as ex- plained under "Sterilization," page 120, also tend to so increase the viscosity of the evaporated milk as to minimize its tendency to separate its fat. But here again good judgment is required, otherwise there is danger of spontaneous thickening of the prod- uct after manufacture. Turning the Cans in Storage. Many manufacturers, in an effort to avoid fat separation, have adopted the practice of turn- ing their goods in storage at regular intervals. This operation naturally interferes with and retards the rising of the fat to the surface, as long as the goods remain in the factory. After they leave the factory this control must of necessity cease and if the evaporated milk, owing to the process of manufacture and the condition of the product, is destined to separate its fat, the turn- ing of the cases, while at the factory, cannot permanently prevent separation. Where the goods are consumed immediately after they leave the factory, this practice may serve the purpose ; but, since the large bulk of evaporated milk manufactured, is exposed to prolonged storage, its advantage is very limited. Effect of Homogenizing. Under average conditions careful attention to the precautions above discussed will greatly mini- mize and often prevent fat separation. At best, however, much of the evaporated milk on the market shows signs of separation after sixty to ninety days and some of it even after two weeks, for the fundamental cause of separation, the difference in gravity between the fat globules and the rest of the milk constituents, is still present; then again, under less favorable conditions, even the above precautions may not prove adequate to keep the fat from separating. The introduction of any agent or process, therefore, capable of permanently removing this fundamental cause, must prove a lasting benefit to the manufacturer of evaporated milk. This agent has been found in the homogenizer. The homogenizer makes it possible to divide the fat globules so finely, that their buoyancy or gravity force is not great enough to overcome the resistance of the surrounding liquid. They are unable to rise to the surface, but remain in homogeneous emulsion. It is quite probable that aside from the reduction of the size 222 UNSWEETENED CONDENSED Miuc DEFECTS of the fat globules, the efficiency of the homogenizer to prevent fat separation is due also to the physical change of the casein as the result of homogenization. The casein becomes more viscous. The chief objection to the use of the homogenizer is its effect on the casein of the milk, when subjected to excessive pres- sure. Beyond certain limits of pressure homogenization so affects the casein, that the latter is more prone to curdle in the sterilizer. However, experience has amply shown that the maxi- mum pressure required to prevent fat separation in the finished product, is not great enough to seriously affect the behavior of the casein during sterilization. Hence, the proper regulation of the pressure and the intelligent use of the homogenizer, furnish a satisfactory and reliable means to prevent fat separation. Under average conditions, the use of sufficient pressure to reduce the fat globules to one-third of their original size, practically destroys the power of the fat globules to rise to the surface. A pressure of approximately one thousand pounds per square inch, makes possible this reduction of the size of the fat globules. 1 Fermented Evaporated Milk. General Description. Fermented evaporated milk is evap- orated milk, which after sterilization, has undergone fermenta- tion. The type of fermentations found in this product varies with locality, season of year and factory conditions. The con- tents of the cans may have soured with curd formation, or a curd may have formed without acid development, or the fer- mentation may be gaseous, in which case the cans bulge, and these gaseous fermentations may be accompanied by acid forma- tion or by putrefactive products. In all cases of fermented milk the product is entirely worthless. These defects are usually, though not always, detected during the period of incubation. Fermented evaporated milk is the result, either of incomplete sterilization, or of leaky cans. The causes of fermented evapo- rated milk differ with the specific type of fermentations produced ; they will be discussed separately and as relating to the respective types of fermentations. Acid Fermentation, Sour, Curdled, Evaporated Milk 1 For details on the use of homogenizer see Chapter IX on "Homogenizing," page 105. UNSWEETENED CONDENSED MILK DEFECTS 223 General Description. Upon opening the cans the contents are found to be sour and curdy. Causes and Prevention. This condition is the result of the presence of acid producing species of micro-organisms, usually of the lactic acid type, which sour the milk, and the acid produced curdles the casein. Since the majority of the lactic acid bacteria are not resistant to heat and are destroyed at relatively low heat, this defect is not usually caused by incomplete sterilization. The temperature of sterilization, though it might be insufficient to kill spore forms, is high enough to make it impossible for lactic acid bacteria to pass the process alive. The only way in which this defect can occur is through sub- sequent contamination of the contents of the cans with these germs, and the only possible channel, through which this sub- sequent contamination may occur, is leaky cans, or leaky seals. A careful examination of the cans of sour, curdled evaporated milk usually shows faulty cans or faulty seals. Bitter Curd General Description. When the cans are opened the con- tents present a solid coagulum, generally noticeably white in color and very bitter to the taste, similar to the bitterness of dandelions. There is a separation of practically clear whey, the curd does not break down readily upon shaking and the acid reaction of the mixture of curd and whey is about .35 to .40 per cent., which is normal for evaporated milk. Causes and Prevention. Microscopic examinations under high magnification of cultures in sterile milk show the presence of very small bacilli. The milk forms a firm coagulum in five to seven days and when over one week old the curd has the same strong, bitter taste as that in the cans. The bitterness increases with age. These bacilli grow best at 90 degrees F. They are facultative anaerobes, developing both, in aerobic and anaerobic media, but prefer anaerobic conditions. In the cases under observation no spores were detected and exposure for fifteen minutes to 212 degrees F. destroyed these germs. The above findings do not exclude the possibility of spore formation under conditions very unfavorable to growth and life. The presence of this species of bitter curd organisms sug- gests incomplete sterilization of the evaporated milk. The strik- 224 UNSWEETENED CONDENSED MILK DEFECTS ing whiteness of the curd in all cases that have come to the writer's attention, is further proof of the correctness of this de- duction. It indicates that these cans received relatively little heat in the sterilizer, otherwise the curd would have a darker color. This defect usually does not show up in all the cans of one and the same batch, but only in a limited portion of each batch. This fact suggests that the distribution of heat in the sterilizer is not uniform, some cans getting less heat than others. This defect occurs generally in summer, a fact which may be due to one or both of the following conditions : While it is well known that there is a variety of species of bacteria, yeast and torula that are capable of producing a bitter curd, either direct, or through the secretion of casein-curdling enzymes, and while these different species of micro-organisms come from a variety of sources, the most common sources are, the soil, pasture, water and the udder itself. It is a noteworthy fact that this defect is most commonly found in milk and milk products when the cows are on pasture. It is, therefore, probable that, in most cases, this troublesome germ is carried into the milk on the farm. Again, in summer, at a time when this defect generally occurs, the effect on the cows of the summer heat and flies, and the tendency toward high acid in milk, render the milk most sensitive to the sterilizing heat. The operator finds it difficult to avoid the formation of a disastrous curd in the sterilizer. In order to guard against this trouble he is tempted to either lower the temperature, or shorten the duration of the sterilizing process. This tends towards incomplete sterilization. A very frequent result of this incomplete sterilization in the early summer months, is the formation of a bitter curd. When the processor returns to the proper sterilizing process, the occurrence of bitter curd in the cans disappears and the product is normal. A further safeguard against the recurrence of this trouble lies in providing for uniform distribution of heat in the sterilizer. If the cans have to be stacked in deep tiers, which is un- desirable and should be avoided, slats should be placed over the top of every second row of cans. This will make possible the free access of steam to at least one end of each can. If the circulation of steam in the sterilizer is poor, the uniform distribu- UNSWEETENED CONDENSED MILK DEFECTS 225 tion of heat can be facilitated by filling 1 the sterilizer about one- third full of water so that, with every revolution of the frame- work, the cans have to pass through this water once. The water reaches every nook in the interior of the sterilizer, distributing the heat much more uniformly than the steam. If these pre- cautions fail to remedy the trouble, then the entire process is inadequate and either more heat, or longer exposure to the same heat is necessary. It is obviously imperative that the fresh milk, as it arrives at the factory, be subjected to the most rigid inspection on the platform, in order to guard against the processing of unduly con- taminated milk. Blown Evaporated Milk (Gaseous Fermentation) General Description. The ends of the cans bulge out very noticeably, frequently so much so that the seams of the cans burst open. This is due to gaseous fermentation causing- high pressure in the cans. The pressure is often so great that upon opening the cans, most of the contents are blown out with tre- mendous force. In some cases of blown evaporated milk, the contents have an acid odor, pleasant and aromatic. In most instances, however, they give off very foul odors and suggesting hydrogen sulfide, not unlike aggravated cases of Limburger cheese. These odors are exceedingly penetrating and difficult to remove from anything they come in contact with. Causes and Prevention. The bacteria causing- gaseous fer- mentations in evaporated milk usually belong to the anaerobic group of butyric acid species and in most cases, though not al- ways, the putrefactive types prevail, such as Bacillus putrificus, Plectridium novum and Plectridium foetidum, especially the lat- ter, because of its extraordinary power of resistance to heat. Plectridium foetidum is an obligatory anaerobe and it absolutely refuses to grow under aerobic conditions. It is an actively motile, medium-sized organism with flagella and spores. At one end it has an Indian club-like enlargement, in w r hich appears the spore. The bacillus resembles a kettle-drum stick similar to B. tetani. Under strictly anaerobic conditions, and incubated at 90 degrees F., it ferments milk in four days. The milk first curdles, then gradually the curd dissolves (digests) completely, leaving a clear 226 UNSWEETENED CONDENSED MILK DEFECTS yellow liquid, similar in appearance to butter oil. The fermenta- tion is accompanied by the evolution of a penetrating foul odor. This organism survives exposure for 15 minutes to 245 degrees F. Its thermal -death point lies between 245 and 250 degrees F. Plectridium foetidum, as well as most of the other species of anaerobic, spore bearing butyric acid bacilli and bacteria, is present abundantly in cultivated soil, in field crops and even on the kernels of the grain. Since this type of evaporated milk defect is characteristic, especially, of the product manufactured during the late summer and early fall months, it is very probable that the dust incident to the harvesting of the field crops, fur- nishes the chief source of contamination of the milk. Fig. 56. The result of gas- eous fermentation Fig. 57. Plectridium foetidum, a highly resistant species of an- aerobic microorganisms, caus- ing "swell heads" of evapo- rated milk In order to avoid the occurrence of blown, fermented, evapo- rated milk, therefore, it is necessary to employ the highest steriliz- ing temperatures, or the longest exposure to the sterilizing heat, or both, consistent with freedom of the milk from curdiness. Ex- perience has shown that the use of the ranges of temperature and time of exposure, given under Chapter XI on "Sterilizing," guard effectively against this defect. Blown Evaporated Milk Due to Freezing. If the evapo- rated milk is exposed to storage temperatures below the freezing point of water, the contents of the cans will freeze. While freez- ing, the contents expand sufficiently to cause the ends of the cans to bulge. When the cans are subsequently transferred to warmer UNSWEETENED CONDENSED MILK DEFECTS 227 temperatures, so that their contents melt again, the milk contracts and the cans resume their normal shape. While the wholesomeness and flavor of the product are not affected by, the freezing process, the remelted evaporated milk is usually less smooth and often slightly grainy. This is due to the fact that, during the process of freezing, there is a partial separation of the watery portion from the caseous material. The casein contracts and the watery portion freezes. When melted, the emulsion is less complete than it was before freezing. The casein remains in its contracted form and robs the product of its original smoothness. Blown Evaporated Milk Due to Chemical Action. While properly processed evaporated milk is perfectly sterile, and from the biological point of view, keeps indefinitely, the cans of very old evaporated milk may bulge, as the result of the action of the acid in the milk on the container. Evaporated milk contains from .35 to .50 per cent, acid (calculated as lactic acid). When the tin cans are filled with the evaporated milk, the tinplate is bright and untarnished, both, inside and out. After the sterilizing process, the inside surface of the cans is dark and dull. This is caused by the combined action of acid and heat, which seems to weaken the tinplate. This phenomenon is further illustrated by the fact that where creameries pasteurize their skimmilk and return it to the patrons in the milk cans hot, the milk cans are short-lived ; they soon corrode and begin to leak. The acid in the evaporated milk continues to act on the tin- plate of the can after manufacture and in the case of very old evaporated milk, the acid may decompose a considerable part of the iron. This action is accompanied by the evolution of hydro- gen gas, which causes the cans to bulge. This action is hastened by continued exposure of the goods to high temperatures (sum- mer heat). This fact was -experimentally demonstrated, 1 also, by scratching the bottom of tin cans on the inside with a file, then filling the cans with a .4 per cent, solution of lactic acid and acetic acid, respectively. After sealing, the cans were sterilized in the autoclave, so as to avoid any possibility of bacterial action. After cooling, these sterilized cans were incubated for some time at 90 degrees F. The cans containing the dilute acid began to 1 Hunziker and Wright, Indiana Agricultural Experiment Station. Results not published. 228 UNSWEETENED CONDENSED MILK DEFECTS swell, while the check cans, containing distilled water only, remained normal. Brown Evaporated Milk General Description. It is the aim of the processor to so govern the sterilizing process as to give the evaporated milk a rich, yellow, creamy color. Frequently, this color limit is over- stepped to the extent of imparting to the evaporated milk a brown color, suggesting coffee with milk in it. In this condition evap- orated milk fails to appeal to the consumer. Causes and Prevention. The dark color in evaporated milk is due to the oxidizing action of excessive heat on the milk sugar, causing the milk sugar to caramelize. This can be avoided by reducing the sterilizing temperature, or shortening the sterilizing process, or both. The storing of evaporated milk at high temper- atures (summer heat) also tends to deepen its color with age. Gritty Plain Condensed Bulk Milk General Description. Grittiness in the unsweetened goods appears usually only in the plain condensed bulk milk. It is a defect which renders the product undesirable for ice cream making. Causes and Prevention. The chief cause of this defect is too great concentration. Plain condensed bulk milk which is not condensed over 3.5 parts of fresh milk to 1 part of condensed milk does not become gritty. When the concentration exceeds 4:1, the milk sugar begins to crystallize out, making the product gritty. Milk sugar requires about six times its weight of water for complete solution in cold w r ater. When condensed at the ratio of 4:1 or over, the plain condensed bulk milk contains con- siderably less than five parts, by weight, of water to one part of milk sugar. This high concentration, together with the prac- tice of storing this product at refrigerating temperatures in order to preserve it, is responsible for the grittiness. This trouble can, therefore, easily be prevented by not condensing to quite as high a degree of concentration. Metallic Evaporated Milk and Plain Condensed Bulk Milk. General Description. Both evaporated and plain condensed bulk milk may show a metallic and puckery flavor, though this defect is rather rare. ADULTERATIONS OF CONDENSED MILK 229 Causes and Prevention. The metallic flavor may be due to the same cause as metallic sweetened condensed milk, i. e. an unsanitary condition of the vacuum pan, in which case its recur- rence can be readily avoided by thoroughly cleaning all parts of the pan including the dome and the goose neck, and rinsing down the whole pan thoroughly with clean water each morning before operations begin. Unsweetened condensed milk made by the use of the "Con- tinuous Concentrator" may have a metallic flavor when the scrapers in this machine are improperly adjusted, causing them to cut into the copper walls and thereby incorporating metallic copper in the product. This source of metallic flavor can be removed by proper adjustment of the revolving spider and its essential parts. Evaporated milk may also show a metallic flavor as the result of chemical action of the acid in the milk on the can. This occurs usually only upon prolonged storage. Very old evaporated milk is very prone to have a metallic flavor from this source. It is obvious that this can best be avoided by endeavoring to move the goods sufficiently rapidly to limit the age of the milk to a reasonable period of time. Cans, in the manufacture and sealing of which an acid flux is used, are prone to give the contents a puckery, metallic flavor, due to the zinc chloride and hydrochloric acid present. This can be avoided by using cans only in the manufacture of which a non-acid flux, such as gasoline-resin flux, is used, and by using a non-acid flux for sealing the filled cans. CHAPTER XXV. ADULTERATIONS OF CONDENSED MILK It is the sense of the Federal Pure Food Act that the addition to condensed milk of any substance except sucrose, and the abstrac- tion of any substance from milk except water, is an adulteration. Skimming. Condensed milk made from partly or wholly skimmed milk must be labeled and sold as condensed skimmed milk in order to comply with the Pure Food regulations. However, it is possible for condenseries receiving fresh milk, rich in butter fat, 230 ADULTERATIONS OF CONDENSED to skim a part of that milk and have their product still conform with the food standards. Skimmed sweetened condensed milk can readily be detected by its whitish color, while condensed whole milk has normally a rich yellow color. When diluted, to the consistency of ordinary milk, skimmed condensed milk, both the sweetened and the unsweetened, foams very profusely when shaken, while diluted condensed whole milk behaves similar to ordinary whole milk. 1 Addition of Artificial Fats. In order to lower the cost of manufacture, attempts have occasionally been made to skim the fresh milk and substitute the abstracted fat by artificial fats of animal or vegetable origin. Recent improvements in the method of manufacture have made it possible to manufacture evaporated milk, made from skim milk to which foreign fats, especially vegetable oils, such as cocoanut oil, have been added. This milk has every appearance of, and will commercially keep as well as genuine evaporated milk. A repre- sentative of this imitation evaporated milk is the "Hebe" product. This product consists of skim milk to which have been added vege- table fats to replace the butter fat. The mixture is homogenized in order to form a complete emulsion, then it is evaporated, filled in cans and sterilized in a similar manner as the genuine evaporated milk. The Federal law requires that the composition and ingredients of these imitation products appear plainly on the label of the package. It should be clearly understood by the manufacturer, the dealer and the consumer that this imitation milk is inferior to the genuine evaporated milk, in the fact that it lacks the important growth-pro- moting and curative properties which are inherent in whole milk. If sold on its own merits, and in accordance with the Federal law, there can be no logical objection to the imitation product, but if offered to the consumer as the genuine article the manufacture and sale of imitation evaporated milk is a heinous crime against humanity. Experiments conducted at Ohio State University, by Mr. J. L. Hutchison, instructor in the Department of Agricultural 1 For chemical tests of butter fat in condensed milk, see Chapters XXXI and XXXII. ADULTERATIONS OF CONDENSED Miuc 231 Chemistry under the direction of Professor O. Erf, Chief of Department of Dairy Husbandry and Dr. J. F. Lipman, Professor of Agricultural Chemistry, demonstrated that "Hebe" milk, when fed to young white rats, resulted in malnutrition accompanied by stunted growth, sore eyes and death of some of the experimental rats, in a similar manner as did other rations in which the fat- soluble vitamines were lacking. Mothers who buy evaporated milk for feeding infants and children should be cautioned to observe carefully whether or not they receive the genuine article. Imitation evaporated milk is not a baby food. Babies and growing children need butterfat for their best development. If canned milk is used for infant feeding, it should be made from whole milk only. (See also pp. 176 to 178). Addition of Commercial Glucose. Commercial glucose be- longs to a group of starch products in which dextrose is the leading constituent. It is manufactured by the action of dilute acids in starch and starchy matter, or occasionally woody fibre. In this country it is almost wholly made from maize starch. Starch glucose occurs in commerce in several forms, varying from the condition of pure anhydrous dextrose, through inferior kinds of solid sugar, to the condition of a thick syrupy liquid, color- less and transparent, resembling molasses in consistency and glyce- rine in appearance; it contains a large proportion of dextrin. In connection with the manufacture of condensed milk the term "glu- cose" refers to this thick, syrupy liquid. It is added to the con- densed milk with a view of substituting a portion of the sucrose and thus reducing the cost of manufacture. It has also been sug- gested that the presence of commercial glucose in condensed milk prevents the precipitation of sugar crystals. Experiments have shown, however, that condensed milk containing varying amounts of glucose, will become sandy just as readily as normal condensed milk. That glucose cannot be used as a substitute for sucrose, is obvious from the fact that its presence defeats the very object for which sucrose is added. Instead of serving as a preservative, as is the case with the best refined, granulated cane sugar, glucose acts as a most effective fermentative. It has been explained that the presence in sucrose of traces of invert sugar, or levulose and glu- cose, causes condensed milk to ferment. Glucose belongs to the 232 ADULTERATIONS OF CONDENSED MII %. *-> 2$fl <5 ft a? 3 ! Sucrose per- cent. A fH-M GO 4> OOOU3 )iC . O 'C US .10 O 00 ;OOOOOOOOOO OOOOO -OOOOO oo (O (O o oc5 06 oo oo oo 06 to 06 06 ^od oo ic oo c> loooooooo OOOO OC iO ss Hi 050505 -050505* .050t5 .OJO" ' '0> -00< co coco cocococ s ifoco*cococo'coco'cocoeococo 3 : oo -osoood -adoooo -oooood ' 'o :S : :Sg : :8 : : : S iss i i^id i is' i i idSn'siSJS 888 8 88888 0606 : 1C ic i OO ' 00 ' ' 8J2 :8S saasid :| : i : J'o : : : :o ; : ; 12 i i : lllSls- iiiUJl: ^QQfaoWS; ilSllJ' ^SSiiS; STANDARDS OF DAIRY PRODUCTS 311 :*> & OOO 00 O O ooo oo 0>0 COO oo oo ooo o ;OO oooo o o ooo 222 'coco co |8 :8 06 '06 :8 :8 ooooooo 0600606060606 eo eo co co co co eo 888,S8S 06060606060606 :888S :8 i2223 :2 a :js g3| : : : : ||| ;jS ^ 2 lfiiiilii : il|ijli pkpMdHpscc^eeP^^^^^P QOfiW a ^ I o- a 5' 11 B -a fsg 1 [51 is* a ^3 S H- : 3. uffl IP iS- 9 >-3-4-> | M ^2 is ! 0g ^^|S^ *-r\ rr\ ^ ^ *> !l '333 a 312 CONDKNSKD MlLK AND MilyK POWDER INDEX Absolute pressure 78 Absolute vacuum 78 Accidents in operating pan, preven- tion of 86 Acid fermentation 222 Acid flux 102, 203, 217 Acid in milk 209, 236 Acid tests 45 Acknowledgments 14 Actinomycoses odorifora 212 Adulterants 229 detection of 295 Age 152,200,214 Agitation 95,195 Albumin 168, 199, 264 Altitude 79-82 Altitude of various cities in U. S 81 Altitude, relation to atmospheric pressure 79-82 Ammonium hydroxide 145, 232 Analyses of evaporated milk 171,276,288 milk 261,287 milk powder 283, 291 sweetened condensed milk 166, 282, 291 Anglo-Swiss Condensed Milk Co 20 Annatto, detection of 301 Anilin orange, detection of 302 Annual output of condensed milk in U. S 25 Artificial coloring 301 Artificial fats 176, 178, 231, 232 Ash 165, 171, 218, 262, 273, 282 Atmospheric pressure 78-82 B Babcock test 269, 274, 283 Bacteria and other fungi Actinomycoses odorifora 212 Bacillus dimorphobutyricus 209 Bacillus esterificans 209 Bacillus mesentericus .209 Bacillus putrificus 209 Bacillus saccharobutyricus 209 Bacterium fluorescens .' 212 Bacterium prodigiosum 212 Cladosporium butyri 212 Oidium lactis ! 212 Penicilium glaucum 212 Penicilium roqueforti 212 Plectridium foetidum ...209,226,308 Plectridium novum 209, 226 Bacteriological analyses 306 Barometric condenser 69 Barometric reading at different al- titudes 80 Barrels, condensed milk 97, 204 Basis of buying milk 41 Beaume hydrometer 90, 107, 108, 109, 272, 277 Beet sugar 58 Benzoic acid, detection of 305 Bicarbonate of soda 232, 304 Bitter curd in evaporated milk. .223,224 Blow-down valve, or vacuum breaker 68, 69 Body, or vapor belt 65 Boiling test 46 Borden's Condensed Milk Co 20 Borden, Gail 18,19, 20 Boric acid and borates, detection of. 304 Box shooks 150 Brands 156 Brown evaporated milk 122, 228 Brown sweetened condensed milk... 214 Buflovak rapid circulation evapora- tor 134 Buflovak vacuum drum drier 239 Building and equipment 31 By-Products Recovery Co 24 Campbell process 132 Cane sugar 57 amount of 60-192,197,200 determination of 275 effect on color 214 effect on digestibility 60,175,176 effect on sugar sediment. .. .192, 197 effect on thickening 61,199 incomplete solution of 192 mixing of 61, 165 preservative properties of.... 57, 61 price of 61,187,189 quality of 59,207 solubility of 165 solution of 192 Caramel, detection of 302 Carbonate of soda, detection of 304 Care of milk utensils 44,210 Casein 164,168,264 CONDENSED MILK AND MILK POWDER 313 Casinate of zinc 102, 204 Catch-all, or milk trap 73, 74 Checking work of sealers 148 Classification of condensed milk de- fects 190 Coal, cost of 187, 189 Coating on jacket and coils 164, 202 Coils in vacuum pan 65, 66 Colostrum, effect of 220 Commercial glucose 57, 231 Composition of concentrated milk 132 condensed buttermilk 144 evaporated milk 167 fat in condensed milk 168 milk powder 245 plain condensed bulk milk... 170 sweetened condensed milk 163 Concentrated milk 132 Concentration, ratio of 87, 107, 131, 197, 220 Concrete floors 33 Condensed buttermilk 141 Condensed milk factories 27 drainage of 34 economic arrangement of ma- chinery 39 equipment, list of 37 essentials of suitable location of.. 28 factory sanitation 41 , 49, 201 , 209 floor plan of factory 32 milk supply 28, 41 sanitary arrangement of machin- ery 41,209 sewage disposal 31 tin shop 39 transportation facilities 30 water supply 29, 213 Condensed milk industry 17 Condensed skim milk 131, 184 Condensed whey, primost, myseost.145 Condensery regulations 43 Condenser discharge 83, 84, 85 Condensers 69 Barometric 69 capacity of 83 care of 73 surface 69 wet-vacuum spray 71 Condensing evaporated milk 106 Condensing plain condensed bulk milk 129 Condensing sweetened condensed milk 62, 85 Contaminated machinery 41,49,207 Contaminated sugar 59, 208, 209 Contamination of milk in factory 207 Contamination of milk on farm 42,43,201 Continuous concentrator 24,136 Control of quality of fresh milk 43 Cooling 44, 52, 94, 1 14, 125, 140 Cooling evaporated milk 114, 253 Cooling in sterilizer 125 Cooling plain condensed milk. . .131, 140 Cooling sweetened condensed milk agitation 94-97, 195 effect on sugar crystallization. 91, 195 equipment for 94-97 method of 94-97 temperature 94-97 Cost of manufacture 186-189 Cream of tartar 232 Curdy evaporated milk, caused by acid flux in cans 217 concentration 108, 181, 216 fractional curdling 126, 217 fractional sterilization 126 homogenizing 110, 221 quality of fresh milk 42, 104, 216 sterilizing heat 121, 122 shaking 126-128 Curdy plain condensed bulk milk: effect of quality of fresh milk... 42,43,129,215 neutralizing the acid 215 Decomposition of lactose 205 sucrose 206 Defective cans 223, 224 Defective evaporated milk 215 Defective milk powder 246 Defective sweetened condensed milk. 191 Dehydrated milk 234 Desiccated milk 234 Detection of beet sugar 59 Difficulties in meeting evaporated milk standards 181,217 Digestibility of condensed milk. . 172-178 Digestion experiments 172-175 Dilution of condensed milk 175 Distribution of factories in U. S 27 Distribution of heat in sterilizer 121 Dome 68 Drainage 34 Drawing off condensed milk 94 Drips from jacket and coils 67 Dried buttermilk 248 Dried whey 249 Duration of sterilizing processs 122,221,226 Dry milk 234 Dry- vacuum pump .75 314 CONDENSED MILK AND MILK POWDER Economic arrangement of machinery 39 Effect of heat on ash of milk 170 Efficiency of shakers 128 Efficiency of vacuum pump 75 Ekenberg process 237 Enzymes in condensed milk 175 Equipment of condensery 37, 38, 39 Evaporated cream 24 Evaporated milk 103, 149, 152, 157, 158, 168,181,215,253,276,289 Evaporated milk standards 181 Evaporation, affected by ratio of steam and water 82-86 steam pressure in jacket and coils 82-86 temperature of condenser dis- charge 82-86 temperature in pan 82-86 vacuum in pan 82-86 water in condenser 82-86 Excessive chilling in pan 193 Excessive stirring of sweetened con- densed milk 94, 97, 195 Exports of condensed milk 161, 162 Factory plan 32, 35 Factory sanitation 41,49,201,207 Fat globules, size of 110,218,219 Fat in condensed milk. .163, 169, 218, 230, 231, 274, 281, 283, 288, 291 Fat in milk powder 245, 247, 283, 291 Fat in malted milk 252, 253, 291 Feed for dairy cows 43, 199 Fermented evaporated milk 149, 222 Fermented sweetened condensed milk 204 Fermentation tests 48 Filling in barrels 97 in cans ....97,116 Filling machines 97, 116 Finishing the batch (see striking) Flux for soldering 102,203 Food value of condensed milk. .172-178 Forewarmers, heat in 55, 57 Formaldehyde, detection of 304 Fractional sterilization 126 Gas generators 103 Gasoline 188,189 Gas supply 102 Gebee seal 98,99 Gelatin, detection of 303 Glucose 58,231 Grainy evaporated milk 217 Gritty plain condensed bulk milk, caused by crystallization of milk sugar 165,191,228 degree of concentration 228 Gunning method 262 H Health of cows 43 Heating the fresh milk. .54, 105, 129, 139 temperature 55, 105, 129,139 Hebe product 178,230,231 Helvetia Milk Condensing Company 21,22,23,24 History and development of condensed milk industry 17 milk powder industry 234 malted milk industry 250 Homogenizers 110, 222 Homogenizing effect on curdiness 110, 221 effect on fat separation 110,221 Horlick's Malted Milk Co 250 Horlick, William 250 How to keep factory in sanitary con- dition 41,49 Hydrogen peroxide, detection of.... 305 I Imports of condensed milk 161 Improper cooling 194 Incomplete solution of cane sugar.. ...... 61,165,192 Incomplete sterilization 224 Incubation 128, 308 Individual standards 183 Insoluble albumin 169 Inspection of cans 118, 148 Interest on investment 189 Invertase 206 Jacket in vacuum pan 64 Labeling 149 Labeling machines 149 Labels- cost of 188, 189 quality of 150 rust spots and wrinkles 150 CONDENSKD MlUC AND MlI,K POWDER 315 Labor, cost of 188, 189 Lactase 206 Lactose (see milk sugar) Latzer, Louis 23 Leach's method, detection of color- ing 301 Leaky cans, disposition of 148 Lime, detection of 303 Loading the sterilizer 121 Low's volumetric method 266 Lumpy sweetened condensed milk.. 201 caused by acid flux in tin cans 102, 203 contaminated barrels 97, 205 milk from fresh cows 42, 203 poor quality of fresh milk. .. .43, 201 unclean factory conditions. 41, 49, 201 unclean tin cans 204 white and yellow buttons 201 M McDonald seal 98,99 Malted milk 250,251,252 Market prices . .' 156 Markets of condensed milk 155 Marking the cases 151 Meyenberg, John B 22 Milk, care of before manufacture. ... 51 Milk, quality of 42, 49, .... 104, 129, 201, 203, 206, 209, 216, 217 Control of quality 43 Milkers and milking 44 Milk of lime 142,216,232 Milk powder 234 analysis of 245,282,291 Buflovak process 239 Campbell process 132 composition 245 Ekenberg process 237 history and development of in- dustry 234 Just-Hatmaker process 236 markets 247 Merrell-Gere process 241 miscibility 246 packing for market 245 quality of fresh milk 236 rancidity 247 solubility 246 water content 246 Wimmer process 236 Milk strainers 44, 210 Milk sugar, lactose caramelizing action 164, 170 color 170,214,229 crystallization 165, 193-199, 228 determination 265, 274, 281 powdered to control crystalliza- tion in sweetened condensed milk 198 solubility 164, 191 Milk supply 28,41 Milk tests for purity acid tests 45 boiling test 46 sediment test 47 sense of smell and taste 44 temperature test 44 Milk trap 73 Mojonnier test for fat and solids. 283-294 N Nestle, Henry 21 Neutralizes 142, 232 Neutralizing 215 New York Condensed Milk Co 20 Nitrogen, total 262 Nutritive ratio in sweetened con- densed milk . ..176 Old cans on the farm 210 Output of condensed milk in U. S. . . 25 Packing 150 Packing for export 151 Page, Charles H 20 Page, David 21 Page, George H 20, 21 Page, William B 21 Peroxide of hydrogen, detection of.. 305 Pipe covering 40 Plain condensed bulk milk. . .19, 129,215 Polluted water 29, 213 Practical methods of systematic ex- amination of condensed milk for marketable properties 258 Preface 7 Preface to Second Edition 8 Premiums, cost of 188 Preservatives, detection of 304 Pressure, atmospheric 77-82 in homogenizer ..113 steam 82-84,200 Primost 145 Proteids 164, 168, 169, 262, 274, 282 Putrid sweetened condensed milk.153, 213 316 MlLK AND MlI^K POWDER Quality of fresh milk 42. 43, 104, 105, 206, 209, 218, 236 sugar 59, 207, 208, 210 Quevenne lactometer 261, 297 Rancid sweetened condensed milk, af- fected by- bacteria yeast, molds 212 polluted water 213 tropical climates 213 Rapidity of cooling in sterilizer 125 Relation of steam pressure to boiling point 77 Roese-Gottlieb method. .270, 277, 282, 283 Rust spots on labels 150, 155 Salicylic acid, detection of 305 Sampling of batch 93 Samplers 93 Sandy sweetened condensed milk, caused by cane sugar content 192 chilling in pan 193 cooling, improper 94, 194 incomplete solution of cane sugar 61, 165, 192 stirring, excessive 94,195 Superheating in pan 87, 193 warming up too cool condensed milk 195 Sanitary can 98, 99 Sanitary purity of condensed milk.. 172 Sealing cans 99,118,203,217 Sealing machines 100, 118 Sediment test 47 Selling expense 188, 189 Separation of fat in evaporated milk, affected by 218 concentration 220 fat globules, size of 168,218,219 homogenizing 1 10, 221 locality 218 period of lactation 218 season 218 sterilizing process 120-125, 220 superheating in pan 106, 221 turning cans in storage 221 Settled sweetened condensed milk... 196 affected by cane sugar content 60, 197 density of condensed milk 197 fat content 197 turning cans in storage 197 Sewage disposal 31 Shakers 128 Shaking 126 Skimming, detection of 295, 301 Solder 99, 101, 118, 187, 189 Solids in evaporated milk 167, 180, 184, 277- milk milk powder sweetened condensed milk... 163,179,273, Solids not fat Specific gravity.. 91, 107, 165, 170 281,290 262, 288 282, 291 290,297 253, 297 ,261, 272, 276 .44,209 ....253 115,253 Stables Standardizing Standardizing vat 52, Standards of condensed skim milk 184, 310 evaporated milk 180, 310 malted milk 252 milk powder 250 sweetened condensed milk. . .179, 310 individual 183 by states 310 Starch in condensed milk 233 Starting the pan 85 Steam necessary for evaporation.... 85 Sterilizers 120 Sterilizing distribution of heat 121 duration 122, 216, 220 temperature 122, 216 Storage advisability of 154, 200 duration 152, 200, 214 purpose 152 temperature 153,211,226 turning cans in 197, 221 Straining 44, 209 Strainers 94, 193 Striking or finishing evaporated milk 107 plain condensed bulk milk 131 sweetened condensed milk 87 Sucrate of lime, detection of 302 Sucrose (see cane sugar) Sugar chute 61, 107 Superheating 106, 130, 140 Swelled cans due to chemical action 227 low temperature 153,211,226 CONDENSED MILK AND MILK POWDER 317 Sweetened condensed milk adulterations 229-233 bacteriological analyses 306-309 chemical composition 162-166 chemical tests and analyses ... 260-283 cost of manufacture 189 dietetic value 172-176 defects 190-215 examination 258 federal standards 179 for baby food 175 inspection of cans 147 invention 18-20 manufacture 54-103 markets 155-160 Mojonnier test 288-290 standards by states 310, 311 standardizing 253 storage 152,155 Tests and analyses of milk, condensed milk, and milk powder 261 Thermometer in vacuum pan. ....... 68 Tin cans, cost of 187, 189 Tin shop 39 Total cost per case 189 Transportation 30, 188, 189 Vacuo, science and practice of evap- oration in 76-85 Vacuum pan 62 Vacuum pump 75 Venthole cans 117 Venthole fillers 117 Ventilation 33 w Warming up too cold sweetened con- densed milk 195 Water- in milk 295 in condenser 82 in evaporated milk 167 in sweetened condensed milk.... 163 supply 29 Westphal balance 261 Wet-vacuum spray condenser 71 Wildi, John 23 Yeast 206,207,308 318 CONDENSED MILK AND MILK POWDER INDEX TO ADVERTISERS Page Alois Aufrichtig Copper and Sheet Iron Works, St. Louis, Mo. 319 A. H. Barber Creamery Supply Co., Chicago. 319 Bausch and Lomb Optical Co., Rochester, N. Y 320 Buffalo Foundry & Machine Co., Buffalo, N. Y 321 By-Products Recovery Co., Toledo, 322 Creamery Package Manufacturing Co., Chicago 323 Davis-Watkins Dairymen's Mfg. Co., Chicago 324, 325, 326 F. G. Dickerson Co., Chicago 327 The Engineering Co., Fort Wayne, Ind 328 J. B. Ford Co., Wyandotte, Mich 329 General Laboratories, Madison, Wis 330 Geuder, Paeschke & Frey Co., Milwaukee, Wis 331 Groen Manufacturing Co., Chicago 332 Hamilton Brass & Copper Works, Hamilton, 320 Arthur Harris & Co., Chicago 334, 335 Jalco Motor Co., Union City, Ind 333 Jensen Creamery Machinery Co., Long Island City, N. Y 336 Mojonnier Bros. Co., Chicago 337 Louis F. Nafis, Inc., Chicago 338 The Pfaudler Co., Rochester, N. Y 339 Rice & Adams, Buffalo, N. Y 342 C. E. Rogers, Detroit, Mich 340, 341 E. H. Sargent & Co., Chicago 342 Schaef er Manufacturing Co., Berlin, Wis 344 The Sharpies Separator Co., West Chester, Pa 343 The Simpson Doeller Co., Baltimore, Md 344 L. Sonneborn Sons, Inc., New York 345 Stevenson Cold Storage Door Co., Chester, Pa 346 Sturges & Burn Mfg. Co., Chicago 348 C. J. Tagliabue Manufacturing o., Brooklyn, N. Y 347 Torsion Balance Co., New York 348 The Vulcan Detinning Co., Sewaren, N. J 349 CONDENSED MILK AND MILK POWDER 319 Efficiency and Economy ARE COMBINED IN THE NATIONALLY KNOWN "AUFRICHTIG" VACUUM PAN Our Standard "6' 6"" Pan will condense 10,000 pounds of milk in one hour with two coil and 12,000 pounds with three coil system. Investigate the economically operated Jacketed Hot Wells. We manufacture complete equipment used in Milk Condensories and Dairies. Highest grades of materials and best of workmanship is put into our equipment. Write for specifications and prices. ALOIS AUFRICHTIG COPPER & SHEET IRON MFG. CO. Third and Lombard Streets Saint Louis, Missouri f| "TITAN-ALEXANDRA" POWER SEPARATOR r ~T'HE capacity of T-A Separators 1 ranges as high as 10,000 Ibs. per hour. T-A Separators invariably skim down to one one-hundredth of one per cent butterfat loss, as shown by the double Bore Babcock Bottle. T-A Separators seldom clog, and our records show the operation of many machines at full capacity for five and six hours without stopping, wnere the skim milk showed only ,-/,,, of 1 % butter fat in a sample taken at the end of the run. T-A Separators are very light running requir- ing a minimum amount of power. For instance, the largest size machine is run with a 2-inch belt. We carry a stock of machines and parts at our Chicago Warehouse and we would be pleased to go into further de- tail regarding this Separator at your convenience. A. H. Barber Creamery Supply Co. CHICAGO, ILL. 320 CONDENSED MILK AND MILK POWDER Model FFS8 Microscopes Standards of Optical and Mechanical Efficiency Model FFS8 is especially suitable for bac- ^"i teriological work. Has coarse and fine focusing adjustments, with adjustment heads on side of arm; two iris diaphragms, three objectives including oil immersion in revolving nosepiece; two eye- pieces and an Abbe condenser in quick-acting screw sub-stage. Number of magnifications obtainable ranges from 50 to 1260. Con- struction is rugged, and black crystal finish on arm and base unusually durable. Write for catalog describing this and other models. Bausch & Ipmb Optical @. NEW YORK WASHINGTON SAN FRANCISCO CHICAGO ROCHESTER, N. Y. LONDON Leading American Makers of High Grade Optical Products. Hamilton Copper Vacuum Pan FOR CONDENSING MILK WE GUARANTEE our Pan to use the smallest amount of condensing water and that there is ab- solutely no loss of milk during operation. Our Pan has greater cubic contents per size than other pans. Insist on knowing the thickness of copper and square feet heating surface when you buy a Pan. We make Vacuum Pans in 3-ft., 4-ft., 5-ft., 6-ft. and 7-ft. diameters and make reasonably prompt shipments. We build the Pans complete with Forewarmers and supply the Pump when desired. WHITE FOR PRICES Hamilton Copper & Brass Works HAMILTON, OHIO ESTABLISHED 1885 CONDENSED MII V K AND MILK POWDER 321 "BUFLOVAK" Vacuum Dryers For producing Milk Powder and drying Milk Products The "Buflovak" Vacuum Drum Dryer is the ideal apparatus for converting milk into powder form. The milk is dried at an extremely low temperature, without the slightest danger of over- heating or contamination, which accounts for its solubility when dried in the "Buflovak" Dryer. The dryer is so constructed that every part of the interior is readily accessible and can be easily cleansed, thus making the apparatus perfectly sanitary a distinctive feature of the "Buflovak" Dryer. Dries skim milk, buttermilk, malted milk, and other liquid material containing solids. The "Buflovak" Vacuum Shelf Dryer is used for drying casein and similar products which must be dried in pans or trays. The "Buflovak" line also includes the Rapid Circulation Evap- orator which is especially adapted for evaporating milk and other delicate and foamy liquids. Catalog showing all types of "Buflovak" Dryers and Evaporators will be mailed on request. Buffalo Foundry & Machine Co. 20 Winchester Avenue BUFFALO, N. Y. NEW YORK OFFICE: 17 BATTERY PLACE 322 CONDKNSED MlLK AND MlI,K POWDER The By-Products Recovery Company 1 09 Chamber of Commerce Building Toledo, Ohio Milk Products Department Automatic Concentrators for " Evaporated " Milk, " Preserved " Milk, Dry Milk, and Sugar of Milk Factories Whole Milk, Skim Milk, Buttermilk and Whey Rapidly and Economically Reduced to High Concentrates without the aid of Vacuum Pumps, Condensers, Water or Expert Labor It is More Economical It is Less Complicated It is More Simple to Operate No Water Requirements Excepting for Cooling More than 100 Machines Now in Use FOR PARTICULARS WRITE The By-Products Recovery Co., Toledo, Ohio CONDENSED MILK AND MILK POWDER 323 An Ideal Cooler forJCondensecHMilk THE Wizard Pasteurizer makes an ex-r cellent cooler for Condensed Milk, because the cooling is done gradually so that the sugar in the milk does not crystallize. Owing to the efficient valve control, cooling can be started with tempered water and cooled down as wanted. The coil is multi- ple-fed, which means that within a few seconds after the cooling medium is turned on it has reached every part of the coil. Thus the cooling is uniform in every part of the vat- The Wizard is an ideal machine in which to cool Con- densed Milk and is exceedingly practical and econ- omical. More information about the Wizard will be furnished gladly if you will write, THE CREAMERY PACKAGE MFG. COMPANY Sales Branch Offices: (Write to. one nearest you.) CHICAGO, ILL. NEW YORK CITY SAN FRANCISCO. CAL. 61-67 W. Xinzie Street 47 W. 34th Street 699 Battery Street KANSAS CITY, MO. OMAHA, NEB. TOLEDO, OHIO 931 W. Eigrhth St. 113 S. Tenth Street 119 St. Clair Street MINNEAPOLIS, MINN. PHILADELPHIA, FA. WATERLOO, IOWA 318 Third Street, N. 1907 Market Street 406 Sycamore 324 CONDENSED MILK AND MILK POWDER OHIO CLEVELAND TIGER MILK CANS The "Super-Tinned" feature of D-W-D Milk Cans is of utmost importance. The tin is properly put on. None of it is skimped or rubbed off. This is the most effective way to prevent rust. You will easily recognize D-W-D Milk Cans by the "wavy" or "cloudy" ap- pearance of the tin which covers the steel from which, they are made. Double seamless neck construction is a distinctive advantage. In- stead of joints or seams at the neck to become jammed and leaky, as is common in many constructions, we make the breast and outside neck section of one piece of steel. The two neck sections are jammed to- gether, and slightly spun out, thereby practically welding them into a double-thick neck. The bottoms and bottom hoops are riveted to the sides. This in- sures against breaking the solder by hard usage and rough handling. Every precaution is taken to furnish you with superior milk cans at a reasonable price. Be sure you give D-W-D Milk Cans their rightful consideration when you place your next order. "Honest value" is our motto. DAVIS-XV&TKINS DAIRYMEN^ MFG.CO. Sales Offices: Jersey City, N. J. North Chicago, 111., Denver, Colo. CONDENSED MILK AND MILK POWDER 325 Progress Can Washer The Progress Can Washer has given fine service in many plants for several years. Practical service has proven it efficient, and a profitable investment. It will do your can washing the way it should be done. Investigate it now. The size picture above washes, sterilizes and dries 500 cans and 500 covers per hour. The large diameter permits a long can track, sufficient jets and sprays and a large drying compartment. The drip from the cans is caught underneath the track so that the can is thoroughly drained before passing into the machine. Can and cover are first rinsed inside and out. Then they are passed over jets and sprays from which hot soda solution is forced at high pressure. They are then rinsed, sterilized and dried. It is a continuous auto- matic operation which does the work right and at low operation expense. Write our nearest office about your can-washing needs. Our line includes many sizes. If you want to see a Progress Can Washer in operation, ask us for the name and address of the nearest plant now so equipped. DAMS-\\^TKINS DAIRYMEN'S MFG.GO. Sales Offices: Jersey City, N. J. North Chicago, 111., Denver, Colo. 326 CONDENSED MILK AND MILK POWDKR Progress Homogenizer Progress Homogenizers are built in four sizes. Number 1 handles 90 gallons per hour; Number 2, 200 gallons; Number 4, 400 gallons; Number 8, 800 gallons. Each machine is builded full rated capacity, and it will do the work it is intended for at small expense and to excellent advantage. This machine quickly pays its cost, and oftimes it results in a saving equal to many times its cost in a very short time. You manu- facturers of evaporated milk must avoid the waste which may be ocas- siorued by "separated" milk. The Progress Homogenizer so breaks up the fat globules that the cream cannot possibly separate. It will not injure the casein. Write to our nearest office for full information and prices on the size you need. Many plants have several of these machines. Tell us about the size of your business so we can judge as to your require- ments. "The Davis-Watkins Line" includes everything needed in the manufacture of Dairy Products. Let us quote you prices and co- operate with you. We have thousands of "Satisfied Customers." Why not join your name to this already long list? We want your business and you need our help. DAMSA^VTKINS DAIRYMEN'S MPG.Ca Sales Offices: Jersey City, N. J. North Chicago, 111., Denver, Colo. CONDENSED MILK AND MILK POWDER 327 The Dickerson Vent Filler OUR ORIGINAL IDEAS ON CANNING MILK HAVE NEVER BEEN IMPROVED UPON. JT S** Baby Size I T you appreciate sanitary values, economy in opera- -* / tion, accuracy in filling and neatness in the appear- ^ ance of your finished product: GET IN TOUCH WITH DICKERSON. The F. G. Dickerson Co. 541-557 W. Washington Blvd. CHICAGO 328 CONDENSED MILK AND MILK POWDER The Engineering Company Fort Wayne, Indiana We build Sterilizers from 40 cases per charge to 240 cases per charge and all intermediate sizes. The latest scientific and mechanical ideas are embodied in this machine. It is sanitary; the distribution of heat is absolute and under full control of the operator; it requires less operating power, water and steam than any other style of sterilizer; it saves time in loading and unloading, cannot be overbalanced, has no exposed gears and runs silently. Our shakers are con- structed with a wide range of capacity and are giving excellent satisfaction. We build these machines with clutch and pulley for driving with belt or with motor directly connected by means of silent gears. I THE ENGINEERING CO. I Fort Wayne, Indiana CONDENSED MILK AND MILK POWDER 329 Factory Sanitation From a beginning many years ago with the discovery of the relationship between cleanliness and health on up to the present date no more logical reason has been dis- covered why it is profitable to use than the one reason "It Cleans Clean." However necessary it is to avoid impairing the health of your patrons, the commercial advantage of turning out a pure, wholesome product is more generally the end sought in maintaining clean, sweet, sanitary conditions where your product is manufactured. Just how to keep your factory and equipment in this sanitary condition with the least expenditure of time, labor and money is a question easily answered by the results ob- tained from the use of Wyandotte Dairyman's Cleaner and Cleanser. Your supply house will fill your order for this cleaner on a guarantee of satis- faction, or money refunded. It Cleans Clean. in every package The J. B. Ford Co., Sole Mnfrs , Wyandotte, Mich. 330 CONDENSED MILK AND MII,K POWDER Do Not Scrape Piping Easy to Keep Clean and Purified when B-K is used. The use of Bacili-Kil (B-K) has become standard practice in most of the important milk product plants thruout the United States and Canada, New Zealand and other dairy countries. B-K is safe to use anywhere gives posi- tive sterilization in places where steam cannot be used. Wherever used, B-K reduces the bacterial count, increases the flavor, value and keeping quality of milk and all dairy products. NOTE THESE REMARKABLE QUALITIES: POWERFUL: By Government method of test, B-K has over ten times greater germ killing strength than undiluted carbolic acid. Much stronger than coal tar disinfectants much safer. SAFE: B-K contains no poison, acids, oils nor pre- servatives. CLEAN: B-K is colorless clear and clean as water leaves no stain on utensils, floors or walls. DEODORANT: B-K destroys foul odors by killing the bacteria and germs of decay which cause them. Unlike other deodorants, it leaves no odor of itself. ALBUMIN" SOLVENT: B-K dissolves albuminous matter such as the milk solids which collect in pip- ing, etc. This enables the B-K disinfecting solution to reach the hidden bacteria, while steam and scald- ing water harden the milk solids, leaving them to contaminate future runs. CHEAP TO USE: B-K is so much stronger than other disinfectants that more water can be used. It goes farther, therefore costs less. B-K gives cheap and effective sanitation in milk and dairy products plants by sterilizing cans, vats, piping, pumps, pasteurizers, separators, churns, by disinfecting and deodorizing floors, drains, cold storage rooms, etc. Bulletins and Complete Information Sent on Request. READ THIS LETTER General Laboratories, Nashville, III., Madison, Wisconsin. June 18, 1916. We have been constant users of BK for several years and I think there is nothing like it for the work for which it is recom- mended. We are operating a condensed milk plant and would say that each and every milk pipe line, tank, or vat, as well as all milk cans have their daily bath in a solution of BK. ST. LOUIS DAIRY COMPANY, (Signed) A. J. Volkman, Mgr. "THE STANDARD OF COMPARISON" Separator bowl showing how slime falls away when B-K is used. NOT A POISON LEAVES NO ODOR Awarded Gold Medal Pan.-Pac. Exposition. CLEAN POWERFUL SAFE GENERAL LABORATORIES: 18 So. Dickinson St., Madison, Wisconsin CONDENSED MILK AND MILK POWDER 331 SANITARY M UK CANS WILL SERVE YOU LONG AND WELL 332 CONDENSED MILK AND MILK POWDER Groen Mfg. Co 4535 - 37 Armitage Avenue CHICAGO, ILL. MANUFACTURERS OF MILK CONDENSING EQUIPMENT VACUUM PANS WITH VERTICAL OR HORIZONTAL CONDENSERS Forewarmers Storage Tanks Can Coolers Pipe Coolers Receiving Tanks Cooling Coils, Etc, Get Our Quotations CONDKNSED MlLK AND MlLK POWDER 333 MOHTOR COMPANY UNION cm: INDIANA MOTOR COMPANY UNION Cm: INDIANA JALCO ELECTRIC TESTERS 4 "8" "12" MOTOR COMPANY UNION Cm: INDIANA Sold by all LEADING SUPPLY HOUSES MOTOR COMPANY UNION OT* INDIANA 334 CONDENSED MILK AND MILK POWDER HARRIS COPPER VACUUM PAN FOR MILK CONDENSING AWARDED GOLD MEDAL PANAMA-PACIFFC INTERNATIONAL EXPOSITION ARTHUR HARRIS & Co. Pioneer Constructors of Milk Condensing Apparatus 21 2-21 S CURTIS ST., CHICAGO, ILLINOIS CONDENSED MILK AND MILK POWDER 335 Harris Copper Vacuum Pans AND Milk Condensing Machinery Have been our Specialty for over 30 years. Over this period we have continuously produced High Grade Apparatus which has given most gratifying results both in production and service. Large capacity Harris Copper Vacuum Pans in service today total in the hundreds. We Solicit Your Inquiries for VACUUM PANS STERILIZERS FOREWARMERS SHAKERS VACUUM PUMPS LABELING MACHINES COOLING MACHINES RUBBER PACKED COCKS PIPE COOLERS SAMPLERS RECEIVING TANKS SUPERHEATER BULBS STORAGE TANKS COOLING COILS FILLING MACHINES WEIGH SCALE TANKS PEEPHOLE GLASSES, ETC. Arthur Harris & Go. Established 1884 212 - 218 Curtis St. Chicago, Illinois 336 CONDENSED MILK AND MILK POWDER Jensen Vertical Coolers SPECIALLY BUILT FOR COOLING CONDENSED AND EVAPORATED MILK ELIMINATE CRYSTALLIZATION. Furnish Correct Amount of Agitation to Produce a Smooth Product. Eliminate Air and Gases Thru Rotation of Double Helical Coil During Cooling Process. PREVENT CONTAMINATION as all Packing and Stuffing Boxes are Outside and Above the Machine. Ask for Catalog No. 20 A. Jensen Creamery Machinery Company Long Island City, N. Y. Oakland, California Southern Distributor: BLANK E MFG. <$ SUPPLY CO., St. Louis, Mo. CONDENSED MILK AND MILK POWDER 337 It PAYS to Standardize Your Dairy Products YOU can standardize your dairy products easily, rapidly and accurately by using the Mojonnier Tester for Butter Fat and Total Solids in Milk or Milk Products. You can standardize the Butter Fat to within .03% and Total Solids to within .10% of any standard, and tests can be made in a half hour. Finding the Butter Fat and Total Solids contained in Dairy Products. The cash value of standardizing dairy products is apparent to any business man. We also manufacture and sell a large line of apparatus for standardizing milk and milk products, including Ice Cream Overrun Tester. Fresh Milk Tester. Culture Controller. Complete Milk Laboratory Equipment. Evaporated Milk ControlUr. Vacuum Pan and "Striker." Storage and Mixing Tanks. Complete Equipment for Condensed and Evaporated Milk Plants. Complete information gladly furnished on any of this apparatus. MILK ENGINEERS 833 W. de^kson Boul. Chicag Eastern Office: 501 Fifth Avenue, New York. 338 CONDENSED MILK AND MILK POWDER Invest Your Money Where It Will Bring You The Best Returns A/TONEY paid for NAFIS SCIENTIFIC GLASS- WARE is invested not merely spent be- cause Nafis Glassware is guaranteed to be Accurate and to give excellent service. It is used by the most efficient Cream- eries, Cheese Factories, Condensing Plants, Dairy Schools and Experiment Sta- tions because of its Accuracy and Quality If your dealer cannot supply j you with NAFIS GLASSWARE, write for our illustrated cata- logue and list of our distributors. Nafis Automatic Acidity and Salt Testing Outfits. LOUIS F. NAFIS, Inc MANUFACTURERS OF CREAMERY GLASSWARE 544 Washington Blvd. CHICAGO CONDENSED MILK AND MILK POWDER 339 'The Most Efficient Arrangement Cold Medal Awarded at Panama- Pacific Inter- national Exposition, San Francisco, 1915. that has ever been suggested to me" commented the head of one of the largest condensing companies upon the PFAUDLER GLASS ENAMELED STEEL Jacketed Milk Storage Tanks which he has used for a number of years. By quickly cooling and safely storing the fluid milk, they balance the load on your vacuum pans, and permit one pan to work a full day and do the work of two pans at a half day each. These Tanks prevent milk spoilage, are exceptionally easy to clean, and save much in labor and general upkeep. Their GLASS linings are fused into substantial plate steel bodies and are very durable. They do not cor- rode nor impart metallic flavors to the milk. We also build Enameled Steel Forewarmers, Receiv- ing Tanks, Weigh Tanks, Plain Storage Tanks, Truck Tanks, etc. Jacketed Cooling and Storage Tank, built either in one piece or in sections; equipped either with Mechanical or Air Agi- tator. THE PFAUDLER CO., ROCHESTER, N. Y. Boston Detroit Pittsburgh Branch Sales Offices : New York Chicago St. Louis Minneapolis San Francisco 340 CONDENSED MILK AND MILK POWDER KB -D* D D Sterilizers IN ALL STANDARD CAPACITIES STERILIZER LOADING END Equal Heat Distribution Rapid Loading and Unloading Entire Load Carried on Roller Bearings Requiring Minimum Power Our Shakers are also good C. E. ROGERS 34-42 Goldsmith Ave. Detroit, Mich. D D CONDENSED MILK AND MILK POWDER 341 High Type Copper Vacuum Pans Save Fuel, Water Milk, Labor Largest Capacities Special Coils for utilizing Exhaust Steam MANUFACTURED COMPLETE BY C.E.Rogers 34-42 Goldsmith Avenue Detroit, Michigan 342 CONDENSED MILK AND MILK POWDER R & A Hydraulic Can Washer, Sterilizer and Drier for Clean, Dry Sterile Cans RICE $ ADAMS, Inc., 166-182 Chandler St., Buffalo Fig. 417 Two-Tank Machine Showing Powerful Blower and Hot Air Drier. SARGENT'S ELECTRIC DRYING OVEN (PATENTED) May be set for any tempera- ture from 70 C. to 150 C. and will maintain that tem- perature indefinitely. Almost a necessity in Milk Product Laboratories where the main- tenance of the lowest usable temperature is imperative. Price complete with six- foot cord, plug and thermo- meter, $27.50. Wound for 110 or 220 volt current. Complete catalogues furnished upon application. E. H. SARGENT & CO. Manufacturers. Importers. "Dealers in Chemicals and Chemical ^/ipparatus of High Grade only. 125-127 West Lake Street CHICAGO CONDENSED MILK AND MILK POWDER 343 if: ill *! m *! Maintenance Guarantee 19 for llje Consiberatwn of Twelve Dollars we agree to furnish' for this machine, Serial No , such repairs and oil as may be required by ordinary use for a period of six years from the date of this guarantee. All requests for parts or oil covered by this guar- antee-must be signed by owner of machine, and the old parts must subsequently be returned, transporta- tion prepaid, to us for credit. This guarantee is made in good faith and does not cover accidents or misuse. It is our policy to be liber- al in its fulfillment. We are dependent upon the fair- ness of the owner and his care of the machine for protection against loss. t)f -feharplcs Separator Co. District Manager. $2 oil and repairs The Sharpies Maintenance Guarantee makes it positive that your oil and repair costs on a Sharpies will not cost over $2 a year and holds good for six years. Com- pare this with the $40 to $75 a year cost for repairs alone on disc type separators. SHARPIES Factory Separators Super Clarifiers Sharpies cuts excessive upkeep costs by eliminating all trouble-giving parts no tread wheels or neck bearings, no discs to throw bowl out of balance, no steel points under spindle, no wear on spindle, etc. Takes only 25 to 30 Ibs. of steam to operate Sharpies Separators 10 to 15 Ibs. for the Super Glarifier A big saving in steam! Write to nearest office for catalog mention the type of machine you need. The Sharpies Separator Co. WEST CHESTER, PA. BRANCHES: Chicago, San Francisco, Toronto 344 CONDENSED MILK AND Miuc POWDER Schaefer Manufacturing Go. BERLIN Jt H 6 WISCONSIN MANUFACTURERS OF CONDENSED and EVAPORATED MILK MACHINERY Sterilizers, Shakers, Test Sterilizers, Fillers, Auto- matic Machinery, Can Conveyors, Testers, Can Coolers and Special Machinery for Special Purposes. CONDENSED MILK AND MILK POWDER 345 White sanitary washable interior coating Cemcoat is a snow-white coating applied like paint. It is washable. The Boston Bio-chemical Laboratory after an exhaustive test finds that Cemcoat affords no ground for accumulation of bacteria and fungi. Heat and cold does not affect Cemcoat it is water-proof. TRADE MARK Dust-proofs and wear-proofs concrete floors by chemical action Lactic acid in milk causes deterioration of concrete floors. Extreme wear develops holes. You can prevent these conditions by treatment with Lapidolith, which is a permanent positive cure. A chemical combination is effected thru the action of Lapidolith on the cement making the floor granite-like and non-absorbing so that it will withstand the heavy wear quite common in milk and creamery plants. Many dairies and creameries, after thoroughly testing these materials for a number of years have expressed complete satisfaction. We will gladly refer you to these satisfied users, send you samples and complete informa- tion upon request. Write to-day to Dept. No. 50, L. Sonneborn Sons, Inc. 264 Pearl Street NEW YORK 346 CONDENSED MILK AND MILK POWDER Doors Doors are just a big valve and are a weak point in all Cold Storage. Their insulation is important, so is their tightness, but their quickness is vastly more so, because it affords the workman less excuse for leaving them open. Stevenson's latest, the "Door that cannot stand open." Cuts off all rush of air, ends all losses from operating and neglect of any cold storage door. Made with port for overhead track or without. The ideal freezer door. Rids itself of ice.. Doors lift a little as they open, hence confectioners and others moving liquids in wheeled tanks, can have a perfectly level floor. No frail spring hinge nuisance to renew every little while, put off each time till the entire price of this door is wasted. All Stevenson Doors have been de- veloped with these features constantly in mind. The Doorframe is adjustable to conform always to the Door thus insuring perfect fit and freedom, with- out expense or refitting. The thick portion of the Door fits loosely in the frame and thus avoids binding. The overlapping margin of the Door is held tightly to its seat against the face of the Doorframe by powerful elastic hinges having the largest bear- ings made for Doors of such weight. Its Self-Acting Roller Fastener has enormous strength, is arranged for padlock no slackening as it latches the soft hemp gasket in the joint is always in sight. A mere touch frees and opens it from either side. Stevenson Doors swing entirely out of the passageway, when opened, hence the Doorway may be 6 inches nar- rower, an important economy in re- frigeration. The jambs of the Door- frames are straight, clean, sanitary. No frail rebate strips in the Doorway. The opening in wall as constructed in this year 1918, should be 3 % inches wider and 4% inches higher than the clear size of our Doorway. Follow construction numbered 1 and 2. Fig. B shows wooden bevelled threshold 1% inches thick. Connects lower ends of Doorframe, forms a part of it and is let down into the floor, warehouses. Accommodates trucks. Fig C. Concrete Floors. Shows lower ends of Doorframe extending down into the floor 3 inches, and connected by angle irons extending across the Doorway from one side to the other below the surface. Fig. S shows Doorframe with full standard sill and head, used on all sizes of Door- frames. Suited only to walking through. Revolving Ice Cream Doors (Iron). Do not swell and bind. Combined Self-Closing Ice Door and Chute of two styles. Ice Counters. Stevenson Cold Storage Door Co. CHESTER, PENNSYLVANIA Installation Diagrams. STOCK SIZES. Stevenson's Standard Cold Storage Doors. Size of Doorway in Clear 2-3 x 2-0 2-0x4-0 2-0 x 5-0 2-0 x 5-6 2-0 x 6-0 2-6 x 6-0 3-0 x 6-0 3-6 x 6-0 4-0 x 6-0 3-0 x 6-6 3-6x6-6 4-0 x6-6 Size of Wall Opening to receive our Door Frames 2-6i/ 2 2-3 1/2 2-3 i/ 2 2-3i/ 2 2-31/2 2-9i/ 2 3-3i/ 2 3-91/2 4-31/2 3-3 1/ 2 3-9i/ 2 4-3V 2 x2- 41/2 x4- 41/2 x5- 4V 2 x 5-10 1/2 x6- 4V 2 x6- 4V 2 x6- 41/2 x6- 4% x6- 41/2 x 6-10 1/2 x 6-101/2 x 6-10 1/2 Estimated Weight, crated 100 140 170 185 200 250 300 350 400 325 380 440 No feather edge, no jolt, no splinters. For CONDENSED MILK AND MILK POWDER -Perfect Sterilization- 347 being of such vital importance in the manufacture of evaporated milk, why be at the mercy of skilled attendants when greater perfection is possible with a "TAG" Controller and at a considerably less expense? With this "Automatic" Control, an untrained workman can handle a number of sterilizers, as the actual results are not dependent upon him. This means fewer and less costly men and no embarrassment to the quality or quantity of production when a skilled sterilizer-man suddenly quits to serve a com- petitor. THE "TAG" COMBINATION Time and Temperature Controller performs more perfectly than even the most skilled sterilizer-man because no human hand can throttle a steam valve as quickly and accurately. It controls both the temperature and time of sterilization, and can be adjusted to meet any variation required in time of rise to the sterilizing temperature in time of hold and the degree of the steriliza- tion temperature, so all the attendant need do is to open the hand steam valve wide and the controller will do the rest, and when the sterilizing period is over, the controller will automatically shut off the steam supply blow out the steam admit cooling water and ring a bell. Write for further particulars and also bear us in mind when you are in the market for Indicating, Recording or Controlling Instruments, of which we manufacture a style or type to exactly meet local con- ditions. C.xT.TAGLIABUE MFG. CO. Brooklyn, N. Y. Chicago Boston New Orleans San Francisco 348 CONDENSED MILK AND MILK POWDER Why the Leading Condensed Milk Makers Choose Sturges Cans because they are accurate absolutely true to measure. Sanitary easy to clean and keep clean. Built extra strong to withstand long service. tur&es means are built of the highest grade of steel plate, carefully tinned. Seams sol- dered smooth as a china bowl, no places for milk to lodge and sour. Write for catalog No. 111. STURGES & BURN MFG. CO. "Leaders Since 1865" Chicago, Illinois Torsion Balance Creamery Scales T A* 1530 Style No. 1530 Factory: 147-151 Eighth St. Jersey City, N. J. No Knife-EdgesNo Friction No Wear SENSITIVE and ACCURATE Tares and balances in one operation. No loose parts to shift. Working parts practically in one piece. Torsion Balance four-bottle Cream Test Scale, Style 1530, used by col- lection stations, creameries and milk condenseries on account of its extreme accuracy. Your profits depend on your tests as much as anything else, probably more so. Write for Catalogue. The Torsion Balance Co. Pacific Coast Branch : 49 California St. San Francisco, Cal. Head Office : 92 Reade St. New York, N. Y. CONDENSED MILK AND MILK POWDER 349 The Vulcan Detinning Co. ^ Sewaren, N. J. Streator, 111. ^t^? fl^lL Buyers of --H^V ^^X Sellers of VULCAN PIG TIN -r-r ' T.TDT? AT?.Y. 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