UC-NRLF DAIRY LABORATORY 1 GUIDE H.E. ROSS GIFT OF Agricultural Educ.Div. LIU W A KY- AGRICULTURE DEFT * fc Sg I! 5 i A DAIRY LABORATORY GUIDE By H. E. ROSS \' Assistant Professor of Dairy Industry New York State College of Agriculture at Cornell University NEW YORK ORANGE JUDD COMPANY 1912 SP253 MAIM C Copyright, 1910, by ORANGE JUDD COMPANY All Rights Reserved , Prtnted in M* C7. PREFACE In the study of any science the student should, so far as possible, work out his own problems. Yet the beginner may be saved much useless time and labor by helpful suggestions at the proper time. This Manual is designed as a guide to students in dairy laboratory work, with just enough explana- tion given to supplement the exercises which are outlined in the Manual. It is not intended for a text book and should not be used in the place of one. The author's thanks are due Prof. W. A. Stock- ing, Jr., for many helpful suggestions in the ar- rangement and preparation of this book. The author recognizes that a book of this kind needs frequent revision, and an effort will be made to keep this Manual up to date. H. E. Ross. Dairy Laboratories, New York State College of Agriculture, at Cornell Uuiversity. August 31, 1910. ill TABLE OF CONTENTS I The Composition of Milk I II Explanation. The Babcock Test 5 III Explanation of Boiled Milk Test and Formalde- hyde Test 18 IV Explanation. Mixing Samples of Butter Be- fore Testing- for Fat and Moisture 19 V Explanation. The C. U. Butter Moisture Test 23 VI Explanation. The Specific Gravity of Milk and the Lactometer 27 VII Explanation. The Board of Health Lactometer 37 VI DAIRY LABORATORY GUIDE VIII Explanation. Use of the Hand Machine in Babcock Test 38 IX Explanation. The Acidity of Milk 43 X Explanation. The Effect of Speed of Machine on the Babcock Test 51 XI Explanation. Commercial Rennet and Its Use. 69 A Dairy Laboratory Guide THE COMPOSITION ' Milk is composed of a great many substances, but, so far as the dairyman is concerned, there are only six constituents which are of prime impor- tance. The following table gives the constituents of milk, together with the per cent of each, ob- tained by a large number of analyses : Water 87 . o per cent Fat 4.0 per cent Casein 2.6 per cent Sugar 5.0 per cent Albumen 0.7 per cent Ash 0.7 per cent Although in the above table the different con- stituents are given definite per cents, yet the com- position of normal milk is very variable. The water needs no discussion, as it is just like the water found anywhere else in nature. Fat is present in milk in the form of minute drop- lets or globules. These globules are distributed throughout the milk and are not in solution, but in fine suspension. This state is called an emulsion. It was disputed for a long time as to whether or not the fat globule had a membrane around it. It is now believed by the best authorities that the fat globule has no membrane, but that the droplet 2 A DAIRY LABORATORY GUIDE keeps its circular form because of its power of con- densing upon its surface the serum of the milk. The size of the fat globules differ in milk from Different breeds qf cows, and it is supposed that the larger ^tfre 'faM> globules the more easily they rise to when 'the milk is left standing in a Butter is composed largely of fat, so we speak of the fat of milk as butter fat. Fat is the most important constituent of the milk, because milk which contains a fair amount of butter fat is more valuable as a food than a milk which is poor in fat. The other food constituents of the milk usually increase or decrease as the fat increases or decreases. This is true, however, only within certain limits. Fat is an important constituent of nearly all of the products of milk, so that in most cases a milk rich in fat is more valuable for manufacturing pur- poses than a milk poor in fat. On account of the importance of the fat, it is made oftentimes a basis of payment for milk. Butter fat is composed mainly of nine different fats. There are a few fats which are present in such minute quantities that they are of no prac- tical importance. All of the fats have the same basis, namely, glycerin, and the fat is made by the chemical union of glycerin and the corresponding fatty acid. For example, the fat butyrin is made of glycerin and butyric acid. The fat stearin is made of stearic acid and glycerin. While the com- position of the different butter fats are known, yet the chemist is unable to make them in the labora- tory. The fats of butter fat are divided into two main groups, the volatile and nonvolatile, and are so A DAIRY LABORATORY GUIDE 3 named because they are made respectively from volatile and nonvolatile fatty acids. The fats under each class are as follows: VOLATILE NONVOLATILE Butyrin Olein Caprin Myristin Caproin Palmatin Caprillin Stearin Laurin There is some dispute as to whether laurin is a volatile or nonvolatile fat, but it is usually consid- ered volatile. The volatile fats compose about 8 per cent and the nonvolatile about 92 per cent of butter fat. The fats of butter fat have different characteristics and properties, and one chief dif- ference of fats is their melting point. For example the melting point of stearin is about 143 F., and the melting point of olein is about 40 F. A varia- tion in the amount of either of these two fats would necessarily cause the melting point of butter fat to vary. The melting point of butter fat is usually between 92 F. and 96 F. Casein is the chief proteid compound of milk, and forms about 20 per cent to 23 per cent of the milk solids. It exists in milk in very fine suspension, and is held in suspension by the salts of calcium. It is, therefore, sometimes called calcium casein. The casein is in such a fine state of suspension that it cannot be filtered out of the milk by any ordinary means. This fine state of suspension is called the collodial state. When milk sours naturally and enough acid is found to unite with the lime salts of the milk, the casein is precipitated. Casein is also precipitated by any acid and rennet or pepsin. Casein is valuable as food both in raw milk and in 4 A DAIRY LABORATORY GUIDE the products of milk, such as the various kinds of cheese. It is also used commercially in many ways, some of them being as a substitute for cel- luloid in the manufacture of buttons and toilet articles. It is also used in cold water paints. By a new process it is said that casein is now being made into a substitute for ivory, making excellent table tops, mantels, etc. Sugar forms about 37 per cent to 39 per cent of the milk solids. The chief value of milk sugar is its food value in milk. It is also used in pharmacy in mixing powders, coating pills, etc. Milk sugar is not used very extensively commercially because of the expensive cost of manufacture. It is not as sweet as cane sugar, because it is not as soluble. It has the same chemical formula (CioH^On) as cane sugar. Acid is produced naturally in milk by the action of bacteria upon the milk sugar. The albumen in milk is in solution. It is valu- able chiefly as a food in milk. It has one commer- cial use in the manufacture of Italian cheese. This cheese is made where large quantities of whey are produced. The whey is heated nearly to the boil- ing point, and this heat precipitates the albumen. The whey is then drawn off and the albumen is dipped into molds. The cheese made from albumen forms a very good, nutritious food. The ash is the part of milk left after burning, and it is the most constant constituent of the milk. It very rarely goes below .68 per cent or above .72 per cent. It consists chiefly of the phosphates of calcium and the chlorides of sodium, potassium, iron and magnesia. Ash is important as a food in furnishing the mineral constituents for the body. A DAIRY LABORATORY GUIDE 5 THE BABCOCK TEST The Babcock test is a test for the per cent of fat in milk and its products. It was invented by Dr. S. M. Babcock, chief chemist for the experiment sta- tion at Wisconsin, and a description of the test was published in a report of 1890 from that station. The instrument used to measure the milk is called a pipette and holds up to its graduated mark 17.6 cc. Since milk is somewhat viscous, the pipette will deliver on an average 17.44 cc., which is for all practical purposes 18 grams. In using the pipette the milk is drawn above the 17.6 cc. mark and the soft part of the index finger placed quickly over the pipette. The column of milk can be easily controlled and allowed to flow out until it is on a level with the 17.6 cc. mark. The pipette should always be held so that the 17.6 cc. mark is on a level with the eye. The sample to be tested is measured into a special bottle with a graduated neck, holding a column of melted fat which is a definite per cent by weight of the 18 grams of milk taken. In adding the milk to the bottle the latter should be held in a slanting position, so that the milk will run down the lower inside of the bottle neck and will not be forced out by the outcoming air. After measuring the milk into the bottle, 17.5 cc. of sulphuric acid (H^SC^) of a specific gravity of 1.82 to 1.83 is added and the milk and acid at once thoroughly mixed. The acid burns up (by moist combustion) everything in the milk except- ing the fat. The same precautions should be ob- served in adding the acid as in adding the milk, namely, to slant the bottle, and the bottle should be revolved as the acid is poured in, so that all of 6 A DAIRY LABORATORY GUIDE the milk adhering to the neck of the bottle will be washed down. The vessel contain- ing the acid should be kept corked in order to prevent the acid taking up moisture from the air and becoming too weak for use. If the acid is too weak more than 17.5 cc. are used, and if too strong less than 17.5 cc. are used. Good acid is colorless, although it may be quite dark and at the same time be useful for the Babcock test. It must, in any case, be free from undissolved foreign particles. After adding the acid to the milk the bottles are placed in a centrifugal machine and whirled. Care should be taken to have the machine balanced, i. e., for every bottle on one side of the machine there should be a corresponding bottle on the opposite side of the machine. The bottles are centrifuged for five minutes and then filled with hot water up to the base of the neck. Centrifuging is then con- tinued for two minutes more and hot water is added to bring the fat into the graduated neck. The cen- trifuge is then run for one minute. The bottles are then ready to read, and in case of whole milk one should read between the extreme points of the fat column. This method of reading, by comparison with the chemical method, has been found to make up for the fat which remains in the bottom of the bottle and cannot be removed by centrifuging. The bottles should be read at a tem- perature of 120 F. It is no trouble to obtain this temperature if centrifuging has been done with a steam machine. Where the machine is filled with steam the bottles should stand for from thirty seconds to one minute in a room at ordinary tem- perature to allow excess of heat to pass off before reading. If a hand machine is used the tester must have hot water placed in it to obtain the required A DAIRY LABORATORY GUIDE 7 temperature. This is especially necessary if the testing is being done in a cold room. The machine should always be kept well oiled and securely fastened to the support on which it is being operated. Skimmed milk contains such a small amount of fat that the fat column could not be read in an ordinary whole milk bottle. A bottle is, therefore, used which has a neck with a small bore. This neck is so small that the milk and acid could not be poured through it, so a funnel tube is pro- vided for this purpose. The skimmed milk bottle should be placed in the machine in such a position that the funnel tube will be on the outside. This will prevent fat lodging in the space between the tube and the wall of the bottle. The sulphuric acid is added to the milk to destroy all of the milk solids except the fat, and the chief solid to be destroyed is the casein. Skimmed milk contains proportionately more casein than does whole milk and, therefore, in making a Bab- cock test of skimmed milk 2 cc. extra of sulphuric acid should be used. The fat globules in skimmed milk are small in size and correspondingly hard to remove. A Babcock sample of skimmed milk should, therefore, be whirled ten minutes, two minutes and one minute. Cream is so viscous that it cannot be measured accurately into a test bottle by means of a pipette It should always be weighed. The New York state dairy laws now consider it a misdemeanor to meas- ure cream for testing where the tests are used as a basis of payment for butter fat. Because the cream is sometimes too rich in butter fat to be tested in an ordinary cream bottle, 9 grams are tested in place of 18 grams and the result multiplied by two. Nine-gram cream bottles are 8 A DAIRY LABORATORY GUIDE also coming into common use. These bottles give the reading direct without any computation. In testing 9 grams one would naturally use one-half "the usual amount of sulphuric acid. On account, however, of the large proportion of fat present, the acid is liable to char the fat ; and for this reason it is better to add approximately 9 grams of water and then add a little less than the usual amount of acid. Butter is tested in the cream bottles, from 3 to 4 grams being used for the test. Enough warm water is added to bring the sample up to approx- imately 18 grams, and from 10 to 12 cc. of the sul- phuric acid are used. Cheese is also tested in the cream bottle, 4 to 5 grams being used. The cheese must first be minced with a knife as fine as possible in order to make it possible for the acid to dissolve all of the casein. After the cheese is weighed into the bottle, about 5 cc. of hot water are added and the mixture shaken vigorously for two or three minutes. This softens the casein. Enough hot water is then added to bring the sample to approximately 18 grams. The sample is again shaken for two or three minutes, and the ordinary amount of H 2 SO4 is then added. If the cheese is old and dry, 2 or 3 cc. of H 2 SO4 in excess of the usual amount are sometimes necessary to dissolve the casein. In mincing the cheese the sample should not be allowed to dry out any more than is absolutely necessary. In the cases of both the butter and the cheese, the results obtained must be reduced to an 1 8-gram basis, because the bottles are graduated for that amount. This can be done by dividing the per cent obtained by the number of grams used and multiply the quotient by 18. A DAIRY LABORATORY GUIDE Q Whey is usually tested in whole milk bottles, although it is best to test it in skimmed milk bot- tles when possible. The right bottle to use can only be determined by actual experiment. Whey requires less acid than whole milk, usually about 12 cc. EXERCISES 12 A DAIRY LABORATORY GUIDE EXERCISE I THE BABCOCK TEST 1. Draw the milk above the mark on the pipette and allow the milk to settle just to the mark. Repeat this until some proficiency in the use of the pipette is obtained. What two special precautions are to be observed in handling the pipette? 2. Test by the Babcock method a sample of whole milk. Perform this test before doing either 3 or 4. 3. Measure out into your white cup 50 cc. of the same sample of milk used in experiment 2. Add to this 15 cc. of water. Mix thoroughly and test in duplicate by the Babcock method. 4. Using milk from the same sample as used in experiment 2, measure out qo cc. of milk and add to it 15 cc. of skimmed milk. Mix thor- oughly and test in duplicate by the Babcock method. Did you obtain the most fat in experiment 3 or experiment 4? Include in your notes a brief description of the Babcock test. A DAIRY LABORATORY GUIDE 13 STUDENT'S NOTES AND REPORT 14 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 1 5 EXERCISE II BABCOCK TEST 1. Test in duplicate a sample of whole milk, skimmed milk and cream. Test the skimmed milk in the same way that the whole milk is tested. Why is cream taken by weight instead of by volume? Why are 9 grams used instead of 18 grams? When 9 grams of cream are tested in an 18- gram bottle, what correction has to be made in the result and why? 2. Retest the cream and skimmed milk. Add acid to the skimmed milk about one-fourth of an inch above the mark and whirl ten minutes the first time, two minutes the second time and one minute the third time. In retesting the cream do not add water, and use one-half the usual amount of acid. In order to save time the cream and skimmed milk may be whirled together. Explain fully the object of using extra acid and whirling an extra length of time in testing skimmed milk. Record carefully any difference in the appear- ance of the fat column of the cream in ex- periments i and 2. What should be the appearance of an ideal fat column in a completed Babcock test? 1 6 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE I? STUDENT'S NOTES AND REPORT l8 A DAIRY LABORATORY GUIDE EXPLANATION OF BOILED MILK TEST AND FORMALDEHYDE TEST There are two principal tests for boiled milk. One test makes use of three chemicals hydrogen peroxide, potassium iodide and starch. In the second test two reagents are employed hydrogen peroxide and paraphenylenediaminehydrochloride. In both cases a blue color results if the milk has not been boiled. If the milk has been boiled no blue color will result. The last named test acts more rapidly than the first one and also gives a more intense color. Any double oxide may be sub- stituted in place of the hydrogen peroxide. Such a double oxide would be calcium peroxide. There is in milk an enzyme galactase which is destroyed by heat. When the milk has not been heated this enzyme sets free the oxygen from the oxidizing agent, and in case of the first test, the free oxygen splits up the potassium iodide and liberates free iodine. The starch in the presence of free iodine turns blue. In case of the second test the oxygen liberated by the galactase acts directly on the paraphenylenediaminehydrochloride and turns the solution blue. Hydrogen peroxide often contains sulphuric acid. When this is the case, the reagent is useless for the test with starch, as the free acid would break up the potassium iodide. If this hap- pened a blue color would result whether the milk had been heated or not. The test for formaldehyde is a delicate one and is easy to perform, inasmuch as it may be done in connection with the Babcock test. The regular amount of milk is measured with the 17.6 cc. pipette into a Babcock test bottle and a few drops of ferric chloride added. The regular amount of sulphuric A DAIRY LABORATORY GUIDE 1 9 acid is next added, and if formaldehyde is present a lavender-colored ring will appear between the layer of acid and the layer of milk. If the contents of the bottle are slowly mixed the dissolving casein will take on a lavender color. The test will not work if the milk is too old or if too much of the formaldehyde has been added to the milk. Sometimes sulphuric acid contains ferric salts as an impurity; and when such is the case, the acid will give the test for formaldehyde without the use of ferric chloride. It is best however, to always add the ferric chloride to make sure there is a ferric salt present. EXPLANATION. MIXING SAMPLES OF BUTTER BEFORE TESTING FOR FAT OR MOISTURE Before testing a sample of butter for either moisture or fat the sample should be thoroughly mixed. Fat and water do not readily mix, and special precautions must be taken to make the sample uniform throughout. The butter should be heated and stirred until it is about the consistency of thick cream. Do not heat the butter too much, as the water and fat will entirely separate and it is difficult to remix them again. The sample should then be cooled and stirred thoroughly while cooling, else the fat will cool rapidly on the outside and force all of the water towards the middle of the sample. The cooling process should be kept up until the sample is quite firm. The heating and cooling may be accomplished by placing the butter in any convenient vessel, such as a glass-stoppered sample jar. The jar may then be held under a water faucet or set in a dish of water. 2O A DAIRY LABORATORY GUIDE EXERCISE III BABCOCK TEST 1. Test by the Babcock method a sample of whole milk, skimmed milk and butter. Mix the butter properly before weighing it out for the test. 2. Measure out about 36 grams of skimmed milk (Babcock pipette twice full to the mark). Divide approximately into four parts. Test two of these parts for boiling by two dif- ferent methods. Boil the remaining 18 grams, divide approximately into two parts and test for boiling by two different methods. Give the chemicals used in each case. Do not add the chemicals to the milk while the milk is hot. 3. Measure out in duplicate a sample of skimmea milk as for the Babcock test. Before adding the sulphuric acid dip your stirring rod into the formaldehyde and rinse it off in one of the samples. Then add to both samples the ferric chloride and sulphuric acid and note the difference in color due to formaldehyde. 4. Test any four of the samples furnished, for formaldehyde. Report by number. Sometimes sulphuric acid will alone give the color test for formaldehyde. Why is this? Why is it best to always add the ferric chloride when making the formaldehyde test? A DAIRY LABORATORY GUIDE 21 STUDENT'S NOTES AND REPORT 22 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 23 THE C. U. BUTTER MOISTURE TEST When butter is heated over a flame, the casein forms a snow-white blanket over the surface of the butter. By a comparison with the chemical method it has been found that when the butter loses its snow-white color and turns a dirty brown color the sample has given up its moisture. When this brown color has appeared it is time to remove the sample from the flame. Heating butter in a direct flame is liable to volatilize some of the butter, even before all of the water has been given off. In order to do away with this danger a sheet of asbestos is placed between the flame and the container of the sample. The asbestos so tempers the flame that while a high heat is produced, the danger of sud- denly volatilizing the butter is largely done away with. The scales used are made especially for use in butter-moisture work. They are so constructed that after the moisture is driven off, each notch the large weight is reversed equals I per cent of moisture driven off, and each notch that the small weight is reversed equals .1 per cent of moisture driven off. Always allow the sample to cool be- fore weighing. While the sample is cooling it is well to cover it with something fa sheet of paper will do), so that the sample will not take water from the air. 24 A DAIRY LABORATORY GUIDE EXERCISE IV BABCOCK TEST AND BUTTER MOISTURE TEST 1. Prepare a sample of butter for the moisture test and test by the C. U. method. 2. Test a sample of milk in the ordinary way. Retest the same sample in duplicate, using only 9 grams of the sample. (It must be weighed out.) Make the sample up to 18 grams by adding water. Add the usual amount of acid. 3. Test a sample of cream in the ordinary way. Retest the cream in the whole milk bottle, divid- ing 18 grams between four bottles (4^2 grams by weight in each bottle). In each case add enough water to bring the sample up to 18 grams and then add the proper amount of acid as indicated by the appearance of the sample. Add the acid slowly, a little at a time, and shake thor- oughly. A DAIRY LABORATORY GUIDE 25 STUDENT'S NOTES AND REPORT 26 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 2? THE SPECIFIC GRAVITY OF MILK AND THE LACTOMETER The specific gravity or density of a substance is a ratio between the weight of a given volume of the substance and the weight of a given volume of some other substance taken as a standard. The standard for liquids is water and its specific gravity is taken as one. Milk is slightly heavier than water, and the specific gravity of normal milk averages 1.032, and the specific varies from 1.029 to 1.035. If we add water to milk the specific gravity is lowered, because water is lighter than milk; and if we skim milk we take away fat which is lighter than milk and the specific gravity is increased. When the water is added to milk the effect is the same as it would be if the solids were actually re- moved from the milk. This is true because the solids which were distributed throughout a given volume on the addition of water, have to distribute themselves throughout the increased volume of the liquid. For this reason we say that the addition of water to milk " decreases " the total solids, and it is a fact that when water is added to milk all of the solids are decreased in the same proportion. It is important to remember this fact when one is figuring out the per cent of adulteration of milk. THE LACTOMETER. The instrument used to measure the specific gravity of a liquid is called a hydrometer, and there are many kinds of specialized hydrometers. The hydrometer used to test the density of milk is called a lactometer, and, for the most part, only two kinds are used. One of these is called the Quevenne (called Q. for abbreviation) and the other is called the New York State Board of 28 A DAIRY LABORATORY GUIDE Health (commonly called the B. of H. lactometer). The Quevenne lactometer has a long, narrow stem which is extended into a hollow glass tube of much larger diameter than the stem itself. At the lower end of the instrument is a bulb of mercury which causes the lactometer to sink in the liquid to its proper level. The upper part of the stem contains a thermometer scale, as it is important to know the temperature of the milk when the lac- tometer reading is taken. This scale does not re- cord high temperature, and, therefore, the instru- ment should never be placed in hot liquids. In order to clean the lactometer wash in cool water and wipe with a dry cloth. Immediately below the thermometer scale is a lactometer scale with num- bers ranging from 15 to 45, the lowest readings being at the upper end of the scale. One may ob- tain the specific gravity reading by prefixing i.o before the lactometer reading. Thus, if the in- strument gives a reading of 33, the specific gravity would be 1.033. The fact that the Quevenne lac- tometer gives specific gravity readings directly is one of its chief advantages. Temperature affects the density of liquids. The colder the milk the more dense it is, and the warmer the milk the less dense it is. For this reason lac- tometers are standardized to give readings at a temperature of 60 F. When milk is warmer or colder than 60 F. a correction must be made, and this correction for the Quevenne is .1 of a lactometer degree for every degree in temperature that the sample is above or below the standard temperature. When we cool the milk down we add ; when we warm the milk we subtract. For example, if a lactometer gave a reading of 32 at a temperature of 66 R, we would add .6 (.1X6) to the lactometer A DAIRY LABORATORY GUIDE 2Q reading, making the corrected or true reading 32.6. In this case the specific gravity would be 1.0326. Familiarity with the action of the lactometer may be obtained by working theoretical problems, of which the following is an illustration : If the lactometer reading of a sample of milk is 31.5 at 62 F., what would be the reading at 57 F.? In this case 57 F. becomes our standard, because it is the temperature to which we are going to lower the sample. Since the sample is 5 degrees too warm, 5 (^XS) of a lactometer degree must be added to the lactometer reading, making the true or cor- rected lactometer reading 32. When used in connection with theBabcock test the lactometer reading is important in obtaining the total solids and solids not fat of milk. There are several of these formulae in use, and while they do not give quite as accurate results as the chemical method, they give results which are accurate enough for all practical purposes. They are as follows : * i. ^=S. N. F. Babcock's formulae. 2. 1^=5. N. F. Troy's formulae. 3. Y 4 L+.2f+.i4=S. N. F. Babcock's modi- fied formula. Generally speaking, the first formula gives the highest results, the second next highest and the third the lowest results. One can find the total solids by adding the fat reading to the solids not fat. In these formulae L stands for the lactometer reading and F for the fat reading. In using these formulae, the following precautions must be especially noted : Board of health readings can never be used in these formulae, consequently B. of H. readings must be changed to Q. ; specific gravity readings cannot be used; the per cent of fat expressed in hundredths cannot be used. 32. In experiment 4, pouring the milk back and forth from one vessel to another tends to mix the CC>2 of the air with the milk. Heat will expel the CO 2 , and so after boiling the milk the acid test would be lower than it would be before boiling. This experiment also shows that milk will take up gases. A DAIRY LABORATORY GUIDE 63 EXERCISE XI BABCOCK TEST AND BUTTER MOISTURE TEST 1. Test a sample of cheese, whole milk and skimmed milk for butter fat. In testing the skimmed milk, run extra time and use extra acid as previously directed. 2. Test cheese for acid, using n/io alkali solu- tion. In order to test cheese for acid, weigh out 3 grams. Place in a white cup and add 17.6 cc. of warm water. Then with a stirring rod grind the cheese up as fine as possible. This will take at least five minutes. Then test the solution as usual, and calculate the per cent of acid. 3. Test a sample of butter for moisture by the C. U. method. NOTE. To what is the high acid content of cheese due? 64 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 65 STUDENT'S NOTES AND REPORT 66 A DAIRY LABORATORY GUIDE EXERCISE XII BABCOCK TEST, LACTOMETER AND ACID TEST 1. Test by the Babcock method a sample of whole milk, cottage cheese and buttermilk. Fill your lightning top sample jar about one-third full of whole milk, add a preservative tablet and shake at intervals until tablet is dis- solved. Set the sample away in your desk and test at the next exercise. Use 9 grams of cottage cheese, and add 9 grams of water. Test in whole milk bottle. Shake well after adding acid. 2. To about 54 grams of skimmed milk add 2 cc. of light machine oil, shake thoroughly and test in duplicate by the Babcock method. Compare the appearance of the fat column with that obtained with ordinary butter. 3. Test with the alkali tablet solution the acid in the whole milk and buttermilk. 4. Take a lactometer reading of the whole milk. Add some water (about 25 cc.) to the sample. Again take a lactometer reading and make a Babcock test. Figure out T. S. and S. N. F. and the per cent of the water added. A DAIRY LABORATORY GUIDE 67 STUDENT'S NOTES AND REPORT 68 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 69 EXPLANATION. COMMERCIAL RENNET AND ITS USE Commercial rennet is a liquid prepared by soak- ing in brine the fourth stomach of the calf. It has under certain conditions the power of precipitating the casein from milk. It is so desirable for this purpose that rennet is used almost exclusively in the manufacture of cheese. One peculiar character- istic of rennet is the fact that it is not destroyed by its use in precipitating casein. If it could be extracted the same rennet could be used over and over again for precipitating the casein in different lots of milk. Temperature has a decided effect upon the action of rennet. The colder milk is, the less rapid the rennet action. This is very noticeable at tempera- tures below 80 F. The rennet acts most rapidly at temperatures from 100 F. to 120 F. At 130 F. the action of the rennet is less active and its action is entirely destroyed somewhere between 140 F. and 150 F. The high temperature destroys the rennin, which is the active principle of the rennet. The action of rennet increases as the acid in the milk increases. The action of rennet seems to depend .to a great degree upon the solubility of the lime salts of the milk. If an insoluble lime salt is added to the milk, the action of the rennet is retarded, and if a soluble lime salt is added to milk the action of rennet is hastened. If milk is heated to a high temperature the lime salts are supposed to be rendered insoluble and the rennet has no effect on the casein. Freezing does not seem to injure rennet. When it is again melted and given the proper temperature it will act as though it had never been frozen. 7O A DAIRY LABORATORY GUIDE EXERCISE XIII BABCOCK TEST, MICROSCOPIC APPEAR- ANCE OF MILK, USE OF RENNET 1. Test the composite sample preserved at the last exercise. 2. Examine under the high-power microscope cream, whole milk and skimmed milk. Make a drawing of each field. Describe fully the difference in the appearance of the fat globules in each of the three fields. 3. Heat 18 grams of skimmed milk to about 100 F. and add four drops of rennet ; shake thor- oughly and let stand. Note the length of time it takes the milk to curdle. 4. To one-half a teacup of water add six drops of sulphuric acid. Add three drops of this solu- tion to 18 grams of milk. Heat to about 100 F. and add four drops of rennet and note the time it takes for milk to coagulate. Compare length of time with that required in No. 3. 5. To about 20 grams of skimmed milk add six drops of sulphuric acid and shake thoroughly. Note time it takes the milk to coagulate and compare the coagulum with that obtained when rennet is used. 6. Measure out two 25 cc. samples of skimmed milk. Warm to 80 F. To one sample add five drops of rennet ; to the other add five drops of sulphuric acid. Note and compare the length of time it takes each to coagulate. A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT 72 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 73 EXERCISE XIV BABCOCK TEST AND USE OF RENNET 1. Test by the Babcock method a sample of butter- milk and a sample of skimmed milk cheese and whole milk cheese. Compare the results of the cheese tests. 2. Boil a sample of milk for about two minutes and then cool. Add some rennet and see if the milk will coagulate. 3. Boil 25 cc. of milk for about two minutes and then cool. Add one-half cc. of sulphuric acid and see if the milk will coagulate. 4. Add to 25 cc. of milk six drops of rennet. Have the temperature of the milk at 100 F. Note the time it takes the milk to coagulate. Test 25 cc. of the same lot of milk for acid. Com- pute the amount of n/io alkali necessary to neutralize the acid in 50 grams of the milk. Divide the milk into two portions of 25 cc. each and bring the temperature of each to 100 F. and add to each six drops of rennet. Note the time it takes the samples to co- agulate. Compare with the length of time required to coagulate the milk before the alkali was added. Y) 74 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT 7 6 A DAIRY LABORATORY GUIDE 2. EXERCISE XV BABCOCK TEST AND LACTOMETER READING Take a lactometer reading and make a Babcock test of a sample of whole milk. Compute the T. S. and the S. N. F. Allow the sample to stand in the lactometer cylinder while you do No. 2. Then remove all of the cream pos- sible and add 25 cc. of water. A^ain make a Babcock test, and take a lactometer read- ing. Compute the per cent of water added, the rate per cent at which water was added, the per cent of fat removed by skimming, the per cent of fat removed bv watering and the rate per cent at which the fat was re- moved. Test in the steam machine a sample of whole milk, and a sample of butter. Retest a sample from the same lot of milk in the hand machine and fill the machine with water at 60 F. Note the result of the low temperature upon the fat column. Run the same bottles Avhich were tested in the hand machine in the steam machine for a period of three minutes and then read the fat column. Note if there is any increase in the fat column. A DAIRY LABORATORY GUIDE 77 STUDENT'S NOTES AND REPORT 78 A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 79 EXERCISE XVI USE OF RENNET. PRECIPITATION OF ALBUMEN 1. Take 18 grams of milk in a white cup and cool to 50 F. Add four drops of rennet and note time it takes the milk to coagulate. Com- pare this with the same amount of milk warmed to 85 F., to which four drops of rennet have been added. 2. Boil some whey and note the albumen which is thrown ^down in a white flocculent pre- cipitate. Fill your lightning top sample jar about one-half full of skimmed milk at about 100 F. Add i cc. of rennet. Set aside to coagulate. Then strain off the whey and precipitate the albumen in the whey by boil- ing. In both cases the boiling should be done in a test tube. It may at first be difficult to see albumen, as it is in very fine particles. The albumen may be distinguished more readily by holding the test tube between the eye and the window. Turn in desk, key and locker. See that all glass- ware is clean before turning in the desk. 8O A DAIRY LABORATORY GUIDE STUDENT'S NOTES AND REPORT A DAIRY LABORATORY GUIDE 8 1 STUDENT'S NOTES AND REPORT INDEX PAGE Acid: Lactic 43 Measure 5 In Milk 43 Sulphuric 5 Acidity : Apparent and real 43 As effected by CO, 62 Alkali Tablet Solution 45 Babcock Test 5 Boiled Milk Test 18 Burette 44 Butter Fat 2 Melting point 3 Moisture in 19 Preparation for fat test 19 Preparation for moisture test 23 Casein 3 Amount in milk 3 Characteristics of 3 Commercial uses of 3 Collodial state 3 Cornell Moisture Test 23 Cream 7 Viscosity of 7 Weighing for testing 7 Fat 1 Composition of 3 Formaldehyde Test 18 Galactase 18 Indicator 44 Lactometer 27 Board of Health 37 Quevenne 27 Uses of 29 Machines 6 Hand 38 Effect of speed on test 51 Melting Point of Butter Fat 3 84 DAIRY LABORATORY GUIDE PAGE Milk 1 Adulteration 31 Albumen in 4 Ash in 4 Composition of 1 Casein in 3 Fat in 2 Sugar in 4 Water in 1 Phenolphthalein 44 Pipette 5 Reading Fat Column 6 Rennet 69 Effect of acid on action 69 Effect of temperature on action 69 Solids Not Fat. 29 Formulae for finding 29 Specific Gravity 27 Of milk 27 Testing : Butter 8 Cheese 8 Cream 7 Skimmed milk 7 Whey 9 Whole milk 5 Temperature : Effect on lactometer reading 28 Effect on fat column 6 Effect on rennet action 69 STANDARD BOOKS PUBLISHED BY ORANGE JUDD COMPANY NEW YORK CHICAGO ASHLAND BUILDING PEOPLE'S GAS BUILDING 315-321 Fourth Avenue 150 Michigan Avenue Any of these books will be sent by mall, postpaid, to any part of the world, on receipt of catalog price. We are always happy to correspond with our patrons, and cordially invite them to address us on any matter pertaining to rural books. Send for our large illustrated catalog, free on appli- cation. First Principles of Soil Fertility By ALFRED VIVIAN. There is no subject of more vitai importance to the farmer than that of the best method of maintaining the fertility of the soil. The very evident decrease in the fertility of those soils which have been under cultivation for a number of years, combined with the increased competition and the advanced price of labor, have convinced the intelligent farmer that the agriculture of the future must be based upon more rational practices than those which have been followed in the past. We have felt for some time that there was a place for a brief, and at the same time comprehensive, treatise on this important subject of Soil Fertility. Professor Vivian's experience as a teacher in the short winter courses has admirably fitted him to present this matter in a popular style. In this little book he has given the gist of the subject in plain language, practically devoid of technical and scientific terms. It is pre-eminently a "First Book," and will be found especially valuable to those who desire an introduction to the subiect, and who intend to do subse- quent reading. Illustrated. 5x7 inches. 265 pages. Cloth. Net, $1.00 The Study of Corn By PROF. V. M. SHOESMITH. A most helpful book to all farmers and students interested jn the selection and im- provement of corn. It is profusely illustrated from photo- graphs, all of which carry their own story am 1 contribute their part in making pictures and text mattet a clear, con- cise and interesting study of corn. Illustrated. 5x7 inches. ioo pages. Cloth Net, $0.50 (l) The Cereals in America By THOMAS F. HUNT, M.S., D.Agri., Professor of Agron- omy, Cornell University. If you raise five acres of any kind of grain you cannot afford to be without this book. It is in every way the best book on the subject that has ever been written. It treats of the cultivation and improvement of every grain crop raised in America in a thoroughly practical and accurate manner. The subject-matter includes a comprehen- sive and succinct treatise of wheat, maize, oats, barley, rye, rice, sorghum (kafir corn) and buckwheat, as related particu- larly to American conditions. First-hand knowledge has been the policy of the author in his work, and every crop treated is presented in the light of individual study of the plant. If you have this book you have the latest and best that has been written upon the subject. Illustrated. 450 pages. 5^*8 inches. Cloth $i-75 The Forage and Fiber Crops in America By THOMAS F. HUNT. This book is exactly what its title indicates. It is indispensable to the farmer, student and teacher who wishes all the latest and most important informa- tion on the subject of forage and fiber crops. Like its famous companion, "The Cereals in America," by the same author, it treats of the cultivation and improvement of every one of the forage and fiber crops. With this book in hand, you have the latest and most up-to-date information available. Illus- trated. 428 pages. 5^x8 inches. Cloth $i-75 The Book of Alfalfa - History, Cultivation and Merits. Its Uses as a Forage and Fertilizer. The appearance of the Hon. F. D. COBURN'S little book on Alfalfa a few years ago has been a profit revela- tion to thousands of farmers throughout the country, and the increasing demand for still more information on the subject has induced the author to prepare the present volume, which is by far the most authoritative, complete and valuable work on this forage crop published anywhere. It is printed on fine paper and illustrated with many full-page photographs that were taken with the especial view of their relation to the text. 336 pages. 6 1 /* x 9 inches. Bound in cloth, with gold stamp- ing. It is unquestionably the handsomest agricultural refer- ence book that has ever been issued. Price, postpaid, . $2.00 Clean Milk By S. D. BELCHER, M.D. In this book the author sets forth practical methods for the exclusion of bacteria from milk, and how to prevent contamination of milk from the stable to the consumer. Illustrated. 5x7 inches. 146 pages. Cloth $i oo (5) Feeding Farm Animals By Professor THOMAS SHAW. This book is intended alike for the student and the farmer. The author has succeeded in giving in regular and orderly sequence, and in language so simple that a child can understand it, the principles that govern the science and practice of feeding farm animals. Professor Shaw is certainly to be congratulated on the successful man- ner in which he has accomplished a most difficult task. His book is unquestionably the most practical work which has ap- peared on the subject of feeding farm animals. Illustrated. 51/2 x 8 inches. Upward of 500 pages. Cloth. . . . $2.00 Profitable Dairying By C. L. PECK. A practical guide to successful dairy man- agement. The treatment of the entire subject is thoroughly practical, being principally a description of the methods prac- ticed by the author. A specially valuable part of this book consists of a minute description of the far-famed model dairy farm of Rev. J. D. Detrich, near Philadelphia, Pa. On the farm of fifteen acres, which twenty years ago could not main- tain one horse and two cows, there are now kept twenty-seven dairy cattle, in addition to two horses. All the roughage, litter, bedding, etc., necessary for these animals are grown on these fifteen acres, more than most farmers could accomplish on one hundred acres. Illustrated. 5x7 inches. 200 pages. Cloth $0.75 Practical Dairy Bacteriology By Dr. H. W. CONN, of Wesleyan University. A complete exposition of important facts concerning the relation of bac- teria to various problems related to milk. A book for the classroom, laboratory, factory and farm. Equally useful to the teacher, student, factory man and practical dairyman. Fully illustrated with 83 original pictures. 340 pages. Cloth. 5 l / 2 x 8 inches $1.25 Modern Methods of Testing Milk and Milk Products By L. L. VANSLYKE. This is a clear and concise discussion of the approved methods of testing milk and milk products. All the questions involved in the various methods of testing milk and cream are handled with rare skill and yet in so plain a manner that they can be fully understood by all. The book should be in the hands of every dairyman, teacher or student. Illustrated. 214 pages. 5x7 inches $0.75 (12) Animal Breeding By THOMAS SHAW. This book is the most complete and comprehensive work ever published on the subject of which it treats. It is the first book which has systematized the sub- ject of animal breeding. The leading laws which govern this most intricate question the author has boldly defined and authoritatively arranged. The chapters which he has written on the more involved features of the subject, as sex and the relative influence of parents, should go far toward setting at rest the wildly speculative views cherished with reference to these questions. The striking originality in the treatment of the subject is no less conspicuous than the superb order and regular sequence of thought from the beginning to the end of the book. The book is intended to meet the needs of all persons interested in the breeding and rearing of live stock. Illustrated. 405 pages. 5x7 inches. Cloth. . . . $1.50 Forage Crops Other Than Grasses By THOMAS SHAW. How to cultivate, harvest and use them. Indian corn, sorghum, clover, leguminous plants, crops of the brassica genus, the cereals, millet, field roots, etc. Intensely practical and reliable. Illustrated. 287 pages. 5x7 inches. Cloth $1.00 Soiling Crops and the Silo By THOMAS SHAW. The growing and feeding of all kinds of soiling crops, conditions to which they are adapted, their plan in the rotation, etc. Not a line is repeated from the Forage Crops book. Best methods of building the silo, filling it and feeding ensilage. Illustrated. 364 pages. 5x7 inches. Cloth $1.50 The Study of Breeds By THOMAS SHAW. Origin, history, distribution, charac- teristics, adaptability, uses, and standards of excellence of all pedigreed breeds of cattle, sheep and swine in America. The accepted text book in colleges, and the authority for farmers and breeders. Illustrated. 371 pages. 5x7 inches. Cloth $1.50 Clovers and How to Grow Them By THOMAS SHAW. This is the first book published which treats on the growth, cultivation and treatment of clovers as applicable to all parts of the United States and Canada, and which takes up the entire subject in a systematic way and consecutive sequence. The importance of clover in the econ- omy of the farm is so great that an exhaustive work on this subject will no doubt be welcomed by students in agriculture, as well as by all who are interested in the tilling of the soil. Illustrated. 5x7 inches. 337 pages. Cloth. Net . . $1.00 (13) 164 674629 UNIVERSITY OF CALIFORNIA LIBRARY