pats tesnren PN irae oes rerocan “sph iske alshewasiat aa Pts tothe at aleie S ihdeeash ek tated Class Copyright NO | COPYRIGHT DEPOSIT: iat. wee! ae ie / a vc Male ; } f y | 4 f ‘ ty, A es) rR hE rae - vs DA he yale ‘ aut ih in Py 14 { ” ak: | he " f i‘ ey rh i ; - i (nl 7 A Ls Yad eC. ais eke i THE PUBLOW ACID TEST Questions and Answers on Milk and Milk-Testing By CHAS. A. PUBLOW, A. B.M.D.C.M. Assistant "Professor of Dairy Industry in Cornell University And HUGH C. TROY, B.S. A. Agricultural Chemist for the New York State Department of Agriculture ILLUSTRATED : NEW YORK ORANGE JUDD COMPANY LONDON KEGAN PAUL, TRENCH, TRUBNER & Co., LIMITED 1909 Copyright, 1909 ORANGE JUDD COMPANY NEw YORK {ENTERED AT STATIONERS’ HALL, LONDON, ENGLAND] Printed in U. S. A. ©o.a252939 PREFACE Anyone who has had experience in teaching short-course students in dairying realizes the dif- ficulty most of these students have in taking notes and in preparing for examinations. Many of these men and boys are good cheese and butter makers, but through lack of preliminary education they are unable to successfully place on paper the knowledge they really possess. It is for these men more particularly that the authors have prepared this little book. All up-to-date dairy literature has been freely consulted with the hope of making these question compends of the greatest service. Many new facts that have never appeared in any dairy books have been added and written in simple language. The special work on adulterations should be of consid- erable value to dairy instructors and to those who wish to prepare for civil service examinations for state positions in dairy work. It is the intention of the authors to keep this book strictly up to date, and they will be grateful to all readers who may suggest any corrections or improvements that might be made to further the usefulness of the book. CHAS, A.-PUBLOW HUGE: CS PROY September, 1909 Questions and Answers on Milk and Milk-Testing What is the average composition of cow’s milk? Witter ipa oot aint ties 87.0% L221 eR aires PS 4.0% Se ais amor 5-0% Serr Ueeaeaerienae 2.6% Alpen \a75,. Ge ak. 7% Jacl 1 eee eee era 7% 100.0% How does the composition of cow’s milk compare with the composition of human milk? Human milk contains more sugar, less casein and - albumin and less ash. Konig gives the following composition of human milk: Rupee hizo". ye atareregsiye 87.41% Piatt ceca fees iets 3.78% Sale ess, Mie a weemee a o = 6.21% Casein and albumin 2.29% POR eae nisikecnc ea 31% 100.00 % The specific gravity of human milk is lower than cow’s milk, being about 1.027. 2 QUESTIONS AND ANSWERS How does the natural water in milk differ from other water? Well water, spring water, and water from other sources varies considerably in composition. So does the composition of water in milk. But, ordi- narily speaking, water in milk is not different from other fresh water. In what form does fat exist in milk? In small round globules held in suspension and forming an emulsion with the other constituents. These globules vary in size from—,4,— to —,- of an inch in diameter. What can be seen when milk is examined under a high-power microscope? Small fat-globules floating around in the milk serum. In what form does sugar exist in milk? In solution. What is the composition of milk sugar? Carbon) (occs 5. 42.10% Hydroger 55! o¢ 6.72% Oseyeen 21° 4y 51.18% In what form does ash exist in milk? Part in suspension and part in solution. What forms of mineral ash are found in milk? Calcium, sodium, potassium, phosphorus, mag- nesium. ON MILK AND MILK-TESTING 3 In what form does casein exist in milk? In minute particles held in suspension. In what form does albumin exist in milk? Albumin is in solution. How does the action of casein differ from that of albumin? Casein is in suspension. It is precipitated by rennet and acids. It is not precipitated by heat. Albumin is in solution. It is not precipitated by rennet and acids, but is precipitated by a heat of rao" F. What is the composition of casein? Carvany enc. .s 53.00% Waryrre tiene 22.70% Nitrocemrs 14).2.2 15.70% Elydrosen,. 7.2% 7.00% Phosphorus ... 85% Splat $5. 26 oss 75% 100.00% What are the melting points of the important fats? ORs (Rie sedial ea. ea > 45° BF: Palmariny 325 ; rag? EF: Meayristitr <2 y 2... £20. F: These fats become oily when heated and solidify on cooling, some fats sooner than others. What is the specific gravity of fat? About .93. 4 QUESTIONS AND ANSWERS Of what is milk fat formed? Fatty acids and glycerin. What fats are present in milk? Babyritn ss. 3.85% Volatile 2 Caproin ..... 3.60% Capry linc... 55% (Oledat rs cecr 35.00% \Palmatin .... 25.70% Non- |Myristin 20.20% Volatile | eaunin WP ies ob 7.40% |Caprin SE Rs 1.90% StCArIN sei. 1.80% 100.00% What is a volatile fat? One composed of a soluble volatile fatty acid and glycerin. What is a non-volatile fat? One composed of an insoluble non-volatile fatty acid and glycerin. _ What factors influence the size of fat-globules in Breed of the cow. Individuality of the cow. Character of the food. Period of lactation. Age of the cow. Diseased conditions. | The part of the milk examined. ON MILK AND MILK-TESTING 5 What is the theory of an envelope surrounding fat- globules? Some chemists have been unable to find any such covering, but Storch says he has found it to exist. and that it is composed of 94 per cent water and 64 per cent proteids. How is the acid in milk, cream starters, or butter- milk measured? By an acidimeter. Describe an acidimeter and the method of testing. There are several tests for measuring acid, and sold on the market under different names, such as Publow’s, Mann’s, Farrington’s, and Marshall’s, but the principle is the same in all of them. An alka- line solution of known strength and an indicator called phenol-phthalein are the reagents used. The purpose of the indicator is to indicate the reaction of the milk or cream; that is, it shows whether the milk or cream is acid, alkaline, or neutral. The indicator has no color effect in an acid solution, but it turns an alkaline substance red. When the neutral point is reached, the faintly pink color is barely distinguishable. To make the test: A known quantity of the milk or cream to be tested is placed in a white cup. To this a few drops of indicator are added. An alkaline solution of known strength is then allowed to run in, drop by drop, from a eraduated burette until the milk or cream assumes a faintly pink color, which signifies that all the acid in the milk or cream has been neutralized by the alkali used. The amount of alkali used can be read on the 6 QUESTIONS AND ANSWERS How can bacteria be killed? Most bacteria can be killed by heating to a tem- perature of 212° F. Many forms are killed by lower temperature, but spores are not destroyed by boil- ing. How can spores be killed? By fractional sterilization, i. e., by first heating to. boiling point, 2t2 7 Phen) cooline 1G, Gor 7a. allowing remaining spores to develop at this latter temperature into bacteria and heating again to 212- i. to “kill these: | ‘This procedure may ebeure- peated several times. How can milk or cream be tested on the receiving platform? 1. For acidity by the use of an acidimeter. 2. For odors by sense of smell. 3. For flavors by sense of taste. 4. For insoluble dirt by eyesight and by allow- ing samples to stand a few minutes in small glass jars so that the dirt will settle to the bottom. 5. In cold weather flavors and odors can be de- tected more readily if milk and cream are warmed up by steam. 6. By the use of fermentation or Wisconsin curd test. 7. Milk can be tested for adulteration by the use of a lactometer. 8. Samples can be taken for composite bottles or for daily testing for fat. What is the fermentation test? Commonly called “ Wisconsin curd test.” Sam- ON MILK AND MILK-TESTING 7 5. In cold weather flavors and odors can be de- tected more readily if milk and cream is warmed up by steam. 6. By the use of a fermentation test. 7. For adulteration by the use of a lactometer. 8. Samples can be taken for fat-testing in the Babcock test. Where is milk secreted? In the mammary glands of all mammals which suckle their young. Describe a mammary gland system of a cow. A cow possesses two mammary glands situated on either side of the median line of the body on the under and hind part, and each gland is divided into two parts, called lobes. Each gland is composed of glandular tissue, being constructed largely of blood vessels and epithelial cells. Each of the four lobes has a small duct opening through which milk is carried after secretion to the teat outlets. Describe the udder of a cow. The udder is the milk reservoir of the cow, and is situated between her hind legs on the posterior part of the abdomen. It varies in size and shape and also in structure. The udder is composed of glandular tissue such as fatty tissue, milk ducts and canals, secreting cells, arteries, veins, lymphatics, nerves, and connective tissue which binds all the other tissues together. The glands are sup- ported from the abdomen by a heavy band of fibrous tissue which extends from the abdomen through the udder in the median line. The whole 8 - QUESTIONS AND ANSWERS mass, which is more or less grayish red in color, according to its varied structure, is covered on the outside by a heavy fold of skin which is covered with fine hair and has marked elasticity. Internally the udder is divided into four quar- ters, the two quarters on the same side communi- cating with each other and each quarter being sup- plied with an outlet or teat. At the upper end of each teat is a fairly large cavity called a milk cistern, each of which may hold as much as one-half pint. In these the milk col- lects after being secreted and carried from the glandular cells by a more or less complicated series of milk ducts and canals. At the lower end of each teat a circular muscle exists, which, when con- tracted, has the power of closing the lower opening and preventing the escape of milk. Considerable muscular tissue exists in the udder, especially around the walls of milk ducts and their dividing points. These muscles are well supplied with nerves so that the animal can by her will power control to a considerable extent, for a short time, the evacuation of milk after it has been secreted by the small cells. She cannot, however, control the actual secreting process. The milk- producing power of an udder depends largely upon the amount of blood carried to and from it through the arteries and veins. How and from what is milk secreted? Milk is secreted from the blood while it passes through the smallest blood vessels in the udder called. the capillaries and from the lymph while it passes through the lymphatics. ON MILK AND MILK-TESTING 9 The water, albumin, casein, and ash all come directly from the blood stream being more or less changed as they pass through the very thin walls of the capillaries and by the action of the glandular cells. The sugar is formed from the blood. The fat is derived from the breaking down of the gland cells by a process of fatty degeneration and from the lymph stream. The amount of milk secreted depends upon the amount and composition of the blood and lymph carried to and from the udder in a given time and also upon the activity of cell construction and cell destruction in the mammary glands. What is colostrum? Colostrum, or beastings, is the first milk secreted by a cow after the birth of her calf. What is the average composition of colostrum? (Konig. ) Wel hetues cars oi arts. 74.60% BG Vad ss oe dee els 3.6% Cageiay 22h a. 4.0% Vath Gl cnrbs Miva iar ge 13.6% Siode salina. 2.7% PANSEMRY eh or. ores 1.5% The composition of colostrum varies in individ- ual cows to such an extent that only an average composition can be given. How does colostrum differ in composition from ordinary milk? Colostrum contains less water, less fat, less sugar, more casein, more albumin,and more ash. It is higher Io QUESTIONS AND ANSWERS in color and strong in odor, and has a laxative effect upon the bowels of the calf. Varied amounts of blood and broken-down cells are usually present, and the viscosity is greater. The specific gravity is also higher and colostrum is unfit for human consumption. Examined under the microscope, large colostrum corpuscles can be seen. By what tests can colostrum be detected? 1. By the use of a lactometer, which shows a very high specific gravity. 2. Boiling throws down a large amount of al- bumin. ; 3. Examined under the microscope, colostrum corpuscles can be seen. What is the natural color of milk due to? 1. To lactochrome. 2. To the color of the milk fats, especially pal- matin. What is milk serum? The serum of milk is that part which is left after all fat has been removed. What factors influence the composition of milk? I. Breed of the cow. Individuality of the cow. Period of lactation. Time of milking. Part of milk tested. Health of the cow. Food and water consumed by the cow. NE QUA WN ON MILK AND MILK-TESTING II What ferments are present in milk? I. Organized (Bacteria). 2. Unorganized (Galactase). What is the difference between an organized and an unorganized ferment? An organized ferment is due to the action of bac- teria and has the power of reproducing itself. An unorganized ferment or enzyme is formed by the action of glandular tissue and has not the power of reproducing itself, although its action may not be destroyed after performing its function. As an example of this we have rennet, which does not lose its power after coagulating milk. What are bacteria? They are the lowest forms of microscopical plant life, and are composed of protoplasm. What are spores? A spore is the breeding cell of a bacterium. All bacteria do not form spores, many reproducing by a process known as “ fission,” the cell simply divid- ing into two or more parts or bacteria. What are the three necessities for bacterial growth? I. Suitable food. 2. Moisture. 3. A proper temperature. What bacteria are commonly found in milk? I. Those that sour milk, called lactic acid bac- teria. I2 QUESTIONS AND ANSWERS 2. Those that produce gas and bad flavors in milk, called putrefactive bacteria. 3. Those that produce disease called pathogenic bacteria. | 4. Specific bacteria, such as those producing blue milk, bitter milk, ropy milk, etc. How do bacteria gain entrance to milk? 1. From the air. The purity of the air deter- mines the number and character of the bacteria. The air in unclean stables contains many bacteria. 2. From dirt or dust. All dirt and all dust carry many bacteria, mostly of the putrefactive type. 3. From the hands, clothing, or body of persons that have or recently have had or are caring for persons who have contagious or infectious diseases. 4. From unclean utensils. 5. From infected water supply. 6. From diseased cows. What effects do bacteria produce in milk? Some forms sour milk. 2. Some forms produce gas in milk. 3. Some produce undesirable flavors. 4. Some cause sweet coagulation. 5. Some cause ropy milk. 6 7 = Some cause bitter milk. Some produce abnormal colors in milk. 8. Some carry disease and render milk unfit for consumption. How is the bacterial content of milk controlled? 1. By absolute cleanliness in all things sur- rounding the production and handling of the milk. ON MILK AND MILK-TESTING 13 This tends to prevent the entrance of bacteria into milk, 2. By keeping milk cold. This checks the growth of bacteria. The lower the temperature, the more their growth is prevented and the longer will milk keep sweet. 3. By high temperatures. High temperatures are used to destroy bacterial life in milk. This is the principle of pasteurization. 4. Preservatives are used to kill bacteria or to prevent their growth. The use of preservatives in milk is prevented by most pure food laws. 5. Electricity has been used to destroy bacteria in milk. 6. The use of carbonic acid gas is used to car- bonate milk and prevent the growth of bacteria. What methods are used to keep bacteria out of milk? 1. The health of the cows is considered. The tuberculin test is used to diagnose tuberculosis. Milk from diseased animals is not used. 2. Cows’ udders, flanks, and legs are shorn of hair to make cleaning easy. 3. These parts are washed or wiped with a damp cloth before milking. 4. Stables are properly ventilated, made free from dust, whitewashed, or otherwise made sani- _tary by cleanly methods. 5. The health, clothing, hands, and person of the milkers are regulated in sanitary requirements. 6. Small-top milking pails are used. 7- Milk is strained or filtered in a clean place. 14 QUESTIONS AND ANSWERS 8. Cans, bottles, and all utensils are sterilized before use. 9. Milk is bottled to prevent the entrance of air and bacteria. 10. Milk is cooled to low temperature as soon ' as drawn, and kept cold to prevent bacterial growth. How can bacteria in milk be destroyed? 1. By heating to a high temperature for a time. Some forms are killed in ten minutes at 140° F., while others require a much higher temperature for a longer period. 2. By electricity. 3. By the use of certain poisons which destroy bacterial life. What diseases are carried in milk? 1: Byphoid’ tever. 2, “Scarlet sever, 3. Diphtheria. 4. Tuberculosis. Intestinal infections, such as the cholera of fafaene and dysentery in adults. How do the germs of disease enter milk? t. In dust laden with disease-producing bac- teria. 2. From the body or clothing of milkers who have had or have been exposed to diseases that are contagious or infectious. 3. From infected water used in washing or rins- ing cans or utensils. ON MILK AND MILK-TESTING 15 4. From diseased cows, especially when the udder is diseased. 5. From the excreta of animals, which may enter milk in small particles carrying disease-pro- ducing bacteria. What causes milk to sour? The lactic acid bacteria change the milk sugar into lactic acid, which is sour and as soon as suf- ficient acid is formed the whole volume of milk becomes sour to the taste. What are the causes of bad flavors in milk? 1. Bacteria, which may enter milk in any of the following ways: (a) From dust. (6) On dirt from the body of the cow. (c) From the atmosphere. (d) From hands, body, or clothing of persons handling milk. (e) From dirty utensils. (f) From impure water. (g) From diseased cows. 2. Flavors absorbed when milk is exposed in places where strong-smelling substances, such as turnips and decayed vegetables, are kept. 3. From strong-smelling foods eaten by the cow. 4. Keeping milk at too warm a temperature. When milk is warm, bacteria present grow rapidly, and their action on the different constituents of milk produces bad flavors. How should milk cans and utensils be washed? They should be first rinsed with lukewarm 16 QUESTIONS AND ANSWERS water, then washed with a brush and hot water containing some good washing powder. Then boiling water or steam should be used to sterilize. The utensils should then be placed in a clean place free from dust. It is a good plan to expose milk cans, etc., to the direct rays of the sun, which have the power of destroying bacteria. What is pasteurization? It is the heating’ of milk to at least 240°" KH ior at least ten minutes for the purpose of destroying bacteria. The milk is then usually cooled to a low temperature. The word 1s derived from. Louis Pasteur, an eminent French scientist. What is sterilization? It is the heating of milk to at least 212° F. for the purpose of destroying both bacteria and spores. How is milk usually pasteurized for commercial purposes? 1. By some form of pasteurizing machine in which steam is the heating agent. 2 > By electricity: What are some of the reliable pasteurizing machines on the market? rt. Simplex, 2. Miller-Tyson. 3. Farrington. 4. Wizard. 5. Reid. ON MILK AND MILK-TESTING 17 How can buttermilk be prepared from skimmed milk? Skimmed milk is heated to 165° F. for ten minutes and then cooled to 70° F., when about 5 per cent of a good culture of lactic acid is added. The milk should be softly coagulated in 12 hours. It is then churned for five minutes and the result is a fine quality of buttermilk. How are the fancy acid milk drinks prepared? By pasteurizing skimmed milk, then cooling and adding cultures of some acid-producing bacteria or yeasts. The milk is securely bottled to prevent outside contamination. What is market milk? Milk that is produced and marketed solely for its use as milk. How is milk marketed? Milk in its raw state is marketed in one of two ways. (1) In bulk form. (2) In bottles or sealed vessels. Milk is sold under many descriptive and yet de- ceiving names, such as aerated, clarified, modified, pasteurized, standardized, etc. These words usually indicate some special treatment given to milk by the producer or dealer. What is sanitary milk? Milk that is produced under sanitary conditions. What is aerated milk? Milk that has been exposed to the air for the pur- pose of cooling it or allowing animal odors to pass 18 QUESTIONS AND ANSWERS off. Many forms of aerating devices are used for this purpose, but aeration has many disadvantages and practically no advantages in the production of clean, sweet milk. What is clarified milk? Milk that has been run through a separator or centrifugal machine for the purpose of removing insoluble dirt. This process has few beneficial ef- fects on milk. It is much better to keep dirt out of muk in the first place than try to remedy the evil later. What is modified milk? Milk that is modified for some special purpose, such as infant feeding, by the addition of such agents as lime water and barley water, or by the removal of part of the fat or casein. What is electrified milk? Milk that has been treated by a current of elec- tricity for the purpose of destroying bacteria. What is pasteurized milk? Milk that has been heated to a high temperature (at least 140° F.) for a period of time for the pur- pose of destroying bacteria. The milk is usually cooled immediately to at least 50° F. in order to increase its keeping power. A great deal of the milk consumed in the larger cities is treated in this manner, as it is a necessary way for the present at least, of remedying, in part, defects in milk caused by carelessness. ON MILK AND MILK-TESTING 19 What is carbonated milk? Milk that has been treated with carbonic acid gas for the purpose of preserving it. What is malted milk? Milk that has been heated to a high temperature for the purpose of killing bacteria, partly con- densed and then a small quantity of malt added. What is peptonized milk? Milk to which some pepsin has been added for the purpose of making milk more easily digestible. The pepsin may be added to whole milk, or the milk may first be partly condensed. What is condensed milk? Milk from which a large amount of water has been extracted by some process of evaporation. Sometimes cane sugar is added for making what is known as sweetened condensed milk. What is the composition of unsweetened condensed milk? (Konig.) Nad ge Ne ey tt ariat 58.99% BSE ertecca as tid Aare ase 12.42% Casein and albumin. 11.92% iste seat) ae «ace 14.49% BRS PE Oe Fats, aha ane Ae 2.18% What is the composition of sweetened condensed milk? (Konig.) WVEOEN 33) Hoe tes 3 25.61% Ba fants beri Ment do tre 10.35% Casein and albumin. 11.79% 20 QUESTIONS AND ANSWERS Mill sugar ei i te 13.84% Cane ysusarjes ch). a: 36.22% INS Kee eae sins Sid 5 2.19% What is milk powder? Milk that has been evaporated to dryness and then placed in a machine which reduces the dried milk to a finely powdered condition. What is standardized milk? Most states have a standard of quality to which milk must comply before being sold as whole milk. Some states have a law which requires that milk must contain at least 3.5 per cent fat and at least I2 per cent total solids. Some breeds of cows do not give milk that tests that high, so it is necessary to add some cream or take away some skim milk. This process is known as standardizing. At the same time, in some states, milk must comply with a law which says milk must not be adulterated. How can the amount of milk or cream necessary for standardizing be determined? This problem has been made easy by the use of a formula and square devised by R. A. Pearson, com- missioner of agriculture in New York state. Draw a square and write at the two left-hand corners the percentages of fat in the milk and the cream or skim milk that is to be mixed with it. In the cen- ter write the percentage of fat desired. The dif- ference between the figures in the center and the figures at the left are placed on the right-hand cor- ners with which they stand in line. The figures at the two right-hand corners then represent the ON MILK AND MILK-TESTING 21 proportions in which the milk and the cream or skimmed milk should be mixed. The idea can, perhaps, be more easily understood by working out a problem such as the following: How much 5 per cent milk must be added to 3.5 per cent milk to make 1,000 pounds of 4 per cent milk? 5 Xe 5 & X 1000 lbs.=333 Ibs. 3.5 A NS re +2 X 1000 lbs.=666 lbs. he milloaust, be mixed (5 part of 5 per cert milk and 1. part of 3.5 per cent milk in every 1.5 parts. Therefore, as figured above we must mix 333 pounds of 5 per cent milk and 667 pounds of 3.5 per cent milk in order to make 1,000 pounds of 4 per cent milk. Prof. Oscar Erf has also prepared a table to be used in standardizing milk and cream, but it is not necessary to give it here. What means are commonly used to improve the milk supply of towns and cities? This work usually is conducted under direction of the boards of health. In most places all per- sons delivering milk in towns and cities must com- ply with the requirements of a special law which states that all milk sold must be produced and handled in such a manner that it reaches the con- sumer in a clean, sanitary condition. Inspectors are appointed to inspect the dairies and, if necessary, compel the farmer to improve his 22 QUESTIONS AND ANSWERS dairy methods. Educational means are used as far as practicable, but if any man refuses to com- ply with the sanitary requirements the inspector reports him to the board of health, which usually cancels his license and prevents him selling milk until he fulfils the demands of the board. For the convenience of both the farmer and the inspector, and to insure uniform inspections, a score card is used upon which most conditions can be reported. The score card on pages 24 and 25 is the one lately devised by the official dairy instructors’ as- sociation, and which is now most used in the United States: | What is meant by specific gravity? ' It means the ratio existing between the weights of equal volumes of a substance and water at. 4 degrees centigrade. Why is the temperature of 4 degrees centigrade chosen? Because water reaches its greatest density at that temperature. What is the specific gravity of whole milk? The average is about 1.032, but, in some cases, it may be as low as 1.029, or it may go as high as 1.034; that is, ifa volume of water weighs I,000, the same volume of average whole milk would weigh 1,030. How would you calculate the weight of 40 quarts milk? ON MILK AND MILK-TESTING 23 I quart water weighs 946.4 grams. I quart milk weighs 946.4 1.032 grams. 453-6 grams=I pound. 976.6848 grams=2.153 pounds. I quart milk weighs 2.153 pounds. 40 quarts milk weigh 2.5340 pounds=—86.12 pounds. How does the weight of 40 quarts milk compare with the weight of 4o quarts water? I quart milk weighs 2.153 pounds. I quart water weighs 2.086 pounds. 40 quarts milk weigh 86.12 pounds. 40 quarts water weigh 83.44 pounds. The weight of milk is 1.032 times as great as the same volume water. What substances make up the milk serum? A 2 a cy le ee eR 87.0% Casein and albumin... 3.4% Willkvsimar bo on. 5-0% Minerale niatiet ss.) 7% What is the specific gravity of melted milk fat? Between the temperatures of 120° F. and 160° F. the specific gravity is .9; that is, when a definite volume of water weighs 1,000 the same volume of milk fat weighs 9oo. What common proof have we that the specific gravity of milk fat and milk serum differs? When milk remains quiet for a time, the globules of fat rise to the surface in the form of cream. UNITED STATES DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY, DAIRY DIVISION. SANITARY INSPECTION OF DAIRIES. OAIRY SCORE CARD. Adopted by the Official Dairy Instructors’ Association. (Subject to revision at future meetings.) Owner. or lessee OF fara crs 8 oo peers ee sib tee aee aies Pe sAOGTORS crn one Se oe Btatey. 22 ee Total number Of COWS. -2---2--22 Number milking.............. cee Gallons’ of milk proguced Gaily 426 ea a ee ee ececcccsece Product.16 retatled by Producer ii... so SS eee DOIG At WHGlESAIG WO aes oe ee ls aera ere errs petesele ee oe Se ae ae Ror milk mip y Or. aces ee Se SS een RR RES ne eee el EY Permit NG: -25622 ee |) Date of inspection 22.2 +<.2.-..22 Sie Oe IRREATS ok fend le ee eae eae aie capi eece ue ee Pe ett Fe Pan) See SA CERNE REDS ER CP at RAE at OBL eines 1a bat 2k Pa SAME Pens 008 SES Rae eee epucedameseteuig cS 82) mice GN eases eee eee EE DER Sk CaN ke eR ae Te Me ROE, ly ED De APNE NE MIR Ge Ree ESR Se at eee PAL ES USES 5 A A eepy serene | Reema tener! SUE EIT E Me td pee es (IQUE) . The use of one-half the amount of milk and acid taken in the Babcock fat test. 3. A specially constructed centrifuge, enabling the operator to add hot water without stopping the machine. 68 QUESTIONS AND ANSWERS Give four formulas used in determining the solids not fat in milk. 1 Ltt = solids not fat. 2 y + 2F+ .14 = solids not fat. 3. 2-2. = golds not fat. 4 L+F = solids not fat. In each of these formulas L—lactometer read- ing and = fat. How do the results secured by the different formulas compare? No. I gives the highest results, while No. 3 gives the lowest. Nos. 2 and 4 give about the same re- sults excepting on rich milks, when No. 4 gives results that are nearly as high as those secured with formula No. 1. With what class of milks does each of the formulas give best results? Formula No. 1 gives results that correspond fairly well with chemical analysis for milks having a Quevenne lactometer reading of 33 or more and having more than 4.5 per cent of fat. Formula No. 2 gives its best results in milks having a Quevenne reading between 31 and 33 and a fat content between 3.7 and 4.5 per cent. Formula No. 3 gives best results on all milks having a Quevenne reading of less than 31 and a fat content of 3.7 per cent or less. Formula No. 4 will give good results with milk of average quality or richer milks. ON MILK AND MILK-TESTING 69 How may the per cent of total solids be deter- mined? By adding the fat as determined by the Babcock test to the solids not fat, as determined by the application of the formula. Is there a formula for determining the per cent of protein in milk? The following formula has been developed by C: . Olsen: Do a 3.694 ~~ y In this formula’ T S=total. solids, A==ash, and P—proteim.~ The ash is) to be ‘ealled .75° 1m all cases. Below what percentage do the solids not fat of pure milk rarely go? The solids not fat of pure milk are usually more than 8.5 per cent, and they very rarely go below a-4° per cent; How does the addition of water to milk affect the specific gravity? Since the specific gravity of water is less than the © specific gravity of milk, the addition of water to milk reduces the specific gravity of the mixture. How does the skimming of milk affect its specific gravity? Since the specific gravity of the fat is less than the specific gravity of the other constituents of milk, skimming increases the specific gravity. 79 QUESTIONS AND ANSWERS Why is it that the specific gravity is not a sure indication that milk has been neither skimmed nor watered? Because a sample of milk might be skimmed, or partly skimmed, and then just water enough added to reduce the specific gravity to what it was be- fore the skimming took place; thus there would be no change in the specific gravity, although the milk was adulterated. What is the approximate proportion of fat to solids not fat in normal pure milks? One cannot state the proportion definitely, since the relative quantity of the constituents in milks from different cows, breeds, etc., varies. In gene eral it will be found that the pure milk of a herd contains fat and solids not fat closely approaching some one of the proportions given in the following table: Solids Fat not fat Total solids 3.00 8.40 11.40 3.25 8.47 11.72 3.50 8.55 12.05 3.75 8.62 12:37 4.00 8.70 12.70 4.25 8.77 13.02 4.50 8.85 13.35 4.75 8.92 13:67 5-00 9.00 14.00 5.25 9.07 14.32 5.50 9.15 14.65 5:75 9.22 14.97 6.00 9.30 15.30 ON MILK AND MILK-TESTING 7% What are the different forms of adulteration of milk often found? Watering. Skimming. Watering and skimming. The addition of preservatives. Addition of coloring matter. The addition of acid neutralizers. Cea ei oe Oa How does watering affect the percentage of the © different milk solids? It reduces the percentage of all the milk solids, and reduces them in the same proportion. How does skimming affect the percentage of the milk constituents? It reduces the percentage of the fat and slightly increases the percentage of all other constituents. How may the presence of added water in milk be determined? Since the water of milk has the same chemical composition as pure water from any source, and the water content of milk varies to some extent, the presence of added water in small amounts cannot be determined directly. When the low lactometer reading, low fat content, or physical characteristics of the milk lead one to suspect that it is adulter- ated a control sample of the milk as produced by the cow or herd should be procured if possible. The composition of the two samples should be com- pared. If the suspected milk is to any great extent lower in quality, and especially if the per cent of 72 QUESTIONS AND ANSWERS solids not fat is reduced, it is safe to conclude that the milk was watered. If a sample of milk gives a Quevenne lactometer reading of 29, and is found, upon testing and applying the formula for solids not fat, to have 4 per cent of fat and 8 per cent of solids not fat, was it adulterated? How much, and what was the form of adulteration? One may conclude that any milk having 4 per cent of fat should have at least 8.6 per cent of solids not fat. It would then be plain that the milk was watered, since the solids not fat are reduced approximately 7 per cent, determined as follows: 6-+-8.6—=.0697% 1006.97 per cent of added water. How may one detect when a sample of milk has been skimmed? if the suspected sample has a low percentage of fat, higher lactometer reading, and an equal or larger percentage of solids not fat than the control sample, then it is safe to conclude that the milk was skimmed. If a sample of milk has a Quevenne lactometer read- ing of 33 and contains 3 per cent of fat, was it adulterated? In what way was it adulterated, and how much? Determine the solids not fat by the formula: +.2F=solids not fat. 33--4=8.25. 2X (2=00. 8.25-++.60—=8.85=solids not fat. ON MILK AND MILK-TESTING 723 By referring to the table given in answer to ques- tions on page 70, it appears that milk having 8.85 per cent of solids not fat should contain 4.5 per cent of fat. 4 -3=—1.5 per cent of fat missing. 1.5-4.5—=.3333 X 100==33-33 per cent of the fat re- moved by skimming. How may one detect when milk has been skimmed and watered? Milk has been skimmed and watered if the per- centage of all the solid constituents are reduced and the per cent of fat is reduced to a much greater extent than the other solids. If a sample of milk contains 2.8 per cent of fat and 8.2 per cent of solids not fat, and the control sample contains 4.5 per cent of fat and 8.85 per cent of solids not fat, how was the milk adulterated and what was the per cent of adulteration ? By comparing the solids not fat in the two samples it will be seen that the milk has been watered, because the solids not fat are reduced. Calculate the per cent of added water by determin- ing the quantity of solids displaced by it. 8.85—8.2—.65. 65--8.85=.0734 X 1007.34 per cent of added water. Next determine how much the fat is reduced. 4.5—2.8=1.7. 1.7--4.5=.3777 X 100==37-7 per cent of fat miss- ing. Since we know that the solids not fat have been 74 QUESTIONS AND ANSWERS reduced 7.34 per cent, and that watering reduces all milk solids in the same proportion, it follows that the fat was also reduced 7.34 per cent by watering. The total reduction of the fat minus 7.34 must have been lost by skimming. 37-777 -34=30.-43- Therefore, the milk was watered 7.34 per cent, and 30.43 per cent of the fat was removed by skim- ming. How should a factory man or shipping station agent determine whether milk has been watered or skimmed when it is impossible to secure a control sample? Farst determine the composition of the suspected milk. Then compare the results with some stan- dard. When suspected milk is furnished by an original producer it usually is not difficult to learn at least the breed of cattle producing the milk. If the herd is of a breed that produces milk of a high quality, then one should use a higher standard for comparison than in the case where the milk is from a herd of a breed that naturally produces milk of a low quality. If the herd is composed of mixed breeds or common stock it may be assumed that the pure milk is of average quality.. To judge milk in this manner would be a difficult problem for one having no experience in dairy work, but an experienced factoryman or agent in a shipping station should have little trouble in gaining in- formation sufficient to warrant a fairly reliable con- clusion. ON MILK AND MILK-TESTING 75 If a sample of milk contained 8.5 per cent of solids not fat and 3.3 per cent of fat, should it be con- | sidered as adulterated? If one should learn that the milk was produced by a herd of Jersey cows, it should be considered adulterated. In that case the composition of the original milk would be at least 4.4 per cent of fat and 8.8 per cent of solids not fat. Those figures could be used as a basis for computing the kind and amount of adulteration. If the milk was produced by a Holstein herd, there would be the possibility that it was adulterated only in the sense that a herd of cows was selected which gave a low grade of milk, thus bringing the quantity of total solids below the legal standard of 12 per cent. If such milk was sold and no information could be gained regarding the character of the herd producing it, then it would be considered as having been actually adulterated. What is the Hart casein test? It is a method of testing milk for the percentage of casein it contains. Upon what principles is the Hart casein test based? 1. That-dilute acetic acid coagulates casein in an insoluble form heavier than the milk serum. 2. The ability of chloroform to extract the fat from the precipitated casein and form a solution heavier than the milk serum or coagulated casein. 3. Adopting a graduated tube and a volume of milk so that the volume of collected casein indicates on the scale the percentage of casein in the milk. 76 QUESTIONS AND ANSWERS 4. Applying centrifugal force to separate the serum, the casein, and the chloroform fat solution. What pieces of apparatus are used in the Hart casein test? I. A 5c. c. pipette for measuring the milk. 2: A ‘cylinder holdings. 2\c.'c. to the mark; Tor measuring the chloroform. 3. A strong test tube 5.6 inches long. About 2.6 inches of one end is formed into a graduated neck one-half the diameter of the remainder, which forms the body. The body of the tube should hold 35 c. c. and the graduated part exactly 5c. c. Each etaduation on the scale represents .1 of I c. ¢c., or & per cent of casein. ‘The opening is at the large end of the tube. 4. A strong centrifuge properly constructed for holding the test tubes and geared to give a speed nearly twice as great as would be required in a Babcock fat test machine having a revolving disk of the same size. 5. A thermometer for determining the tempera- ture of the milk and acid solution. What reagents are used in the Hart casein test? Dilute acetic acid and chloroform of the best quality. How much and of what strength is the acetic acid used in the Hart casein test? Use 20 c. c. of a solution containing 0.25 per cent of acetic acid. ON MILK AND MILK-TESTING af How may an acetic acid solution of proper strength be made? Mad to 10. c) of pure glacial acetic acid go. ¢Ac: of water. Take 25 c. c. of this solution and make it up to 1,000 c. c. by the addition of water. The solution then contains 0.25 per cent of acetic acid. How is the Hart casein test carried out? Add 2c. c. of the chloroform, 20 c. c. of the dilute acid, and 5 c. c. of the milk, in the order named, to - the test tube. The temperature of the milk and acid solution must be within 5° of 70° F. A lower temperature tends to give a higher reading, and a higher temperature has the reverse effect. The thumb is placed over the opening and the tube inverted several times and shaken with some vigor for not more than 20 nor less than 15 seconds. The agitation must be just sufficient to thoroughly mix the contents and yet not form an emulsion. The tubes may be whirled in the centrifuge at once or may stand 20 to 25 minutes before whirling, if necessary. ‘The speed of a revolving disk 15 inches in diameter should be approximately 2,000 revolu- tions per minute, and should continue seven and one-half to eight minutes. If the test has been properly made there will be found in the bottom of the tubes on taking them from the centrifuge a layer of the chloroform fat solution and immedi- ately over it the layer of casein. Allow the tubes to stand Io minutes after removing from the ma- chines to allow the casein to come to a constant volume. Then read the test, 78 QUESTIONS AND ANSWERS What points should receive special attention in making the Hart casein test? 1. The temperature of the milk and acid solu- tion must be right. 2. The mixture must be shaken properly and for the right length of time. 3. The speed of the centrifuge must be sufficient, yet not too great. 4. Allow ten minutes to elapse after complet- ing the whirling before reading the test. What coloring matters are sometimes added to milk? 1. Annatto. 2. Coal-tar colors. 3. Caramel, How does artificially colored milk differ in appear- ance from uncolored milk? In uncolored milk the natural yellow is contained largely in the cream. In colored milk the color remains after the cream has risen or been removed. The skim milk does not show the familiar bluish tint when coloring matter has been added. What is the nature of annatto coloring matter? Annatto is a reddish-yellow coloring matter ex- tracted by weak alkaline solutions from the pulp inclosing the seeds of a shrub that grows in South America and the West Indies. The alkaline solu- tion is used for coloring purposes. Give a simple test for annatto coloring in milk. In a tightly corked vial or test tube shake ON MILK AND MILK-TESTING 79 vigorously 10 c. c. of milk and an equal volume of ether. If annatto is present the amount will be in- dicated by the depth of the yellow coloring in the ether layer which forms on the surface when stand- ing quiet. } How may foreign color be detected in milk? The following method was developed by Leach: 1. Warm about 150 c. c. of milk in a porcelain dish and add about 5 c. c. of acetic acid, after which slowly continue the heating to the boiling point while stirring. Gather the curd, when possible, into one mass by the stirring rod and pour off the whey. If the curd breaks up into small flakes, separate from the whey by straining through a sieve. Press the curd free from adhering liquid, transfer to a small flask, and macerate for several hours (preferably overnight) in about 50 c. c. of ether, the flask being tightly corked and shaken at intervals. 2, Detection of annatto in the ether extract. Decant the ether as obtained above into an evapo- rating dish and evaporate the ether over hot water. Make the fatty residue alkaline with sodium hy- droxide, and pour upon a very small wet filter while still warm. After the solution has passed through, wash the fat from the filter with a stream of water and dry the paper. If, after drying, the paper is colored orange, the presence of annatto is indicated. Confirm by applying a drop of stannous chlorid solution, which, in the presence of annatto, produces a characteristic pink on the orange-colored paper. 3. Detection of coal-tar color (“ aniline orange ’’) in the curd. The curd of an uncolored milk is per- 80 QUESTIONS AND ANSWERS fectly white after complete extraction with ether, as is also that of milk colored with annatto. If the extracted fat-free curd is distinctly dyed an orange or yellowish color, aniline orange is indicated. To confirm the presence of this color, treat a lump of the fat-free curd in a test tube with a little strong hydrochloric acid. If the curd immediately turns pink, the presence of aniline orange is assured. 4. Lythgoe’s test for aniline orange is as follows: Treat about Io c. c. of the milk with an equal volume of hydrochloric acid (specific gravity 1.20) in a porcelain casserole and give the dish a slight rotary motion. If an appreciable amount of aniline orange is present, a pink color will at once be im- parted to the curd particles as they separate. 5. Detection of caramel! (an the card): Ti tie fat-free curd, after extraction with ether, is colored a dull brown, caramel is to be suspected. Shake a lump of the curd with strong hydrochloric acid in a test tube and heat gently. In the presence of caramel the acid solution will gradually turn a deep blue, as will also the white fat-free curd of an un- colored milk, while the curd itself does not change color. It is only when this blue coloration of the acid occurs in connection with a brown curd, which itself does not change color, that caramel is to be suspected, as distinguished from the pink colora- tion produced at once under similar conditions by aniline orange. Name several of the preservatives that are some- times used in milk. a, .Peroxides. 2. Borax and boric acid. ON MILK AND MILK-TESTING 81 Formaldehyde. Benzoates and benzoic acid. Carbonate and bicarbonate of soda. Salicylic acid. Oven a te How may the presence of peroxides in milk be de- tected? Add to 15 or 20 c. c. of milk in a milk test bottle or test tube a quantity of paraphenylenediamin hydrochlorid the size of a pea and shake the mix- ture vigorously for five or ten seconds. If per- oxides are present the milk will turn blue within a few minutes. When the blue solution is made alkaline the color changes to a yellowish light red. If the peroxide has been in the milk for a long time, the test may not work well. How may borax or boric acid in milk be detected? To 50 c. c. of the milk add enough sodium hydrate to make alkaline. Evaporate the solution to dry- ness and incinerate. Acidify the ash with a small amount of strong hydrochloric acid. A _ strip of tumeric paper is then soaked in the solution for a few minutes and afterward dried on a clean glass or porcelain surface. If the paper when dry is a reddish color and turns to a dark olive green on the addition of dilute ammonia, the presence of boric acid or borates is assured. How may the presence of formaldehyde in milk be detected? To 15 or 20 c. c. of milk in a Babcock milk test bottle or in a test tube add 4 or 5 drops of a 10 per cent solution of ferric chlorid. Then add a volume of 82 QUESTIONS AND ANSWERS sulphuric acid equal to the volume of milk taken. Shake the bottle in a circle, but not sufficient to mix the milk and acid to any great extent. In the presence of formaldehyde a deep bluish-violet color- ation appears in the circle where the milk and acid join. Hydrochloric acid having a specific gravity of 1.2 may be substituted for sulphuric acid in the LESE- How may the presence of carbonates in milk be de- tected? 1. The ash of milk containing carbonates will effervesce upon the addition of a few drops of diluted hydrochloric acid. This is a strong indica- tion of added carbonates. 2, Add to 20 or 15 ¢.'c. of the: milk an equal volume of alcohol and a few drops of a I per cent solution of rosalic acid. In the presence of car- bonates a rose-red color appears, while pure milk shows a light yellowish-red color. How may the presence of benzoic acid in milk be detected? Add 5 c. c. of dilute hydrochloric acid to 50 c. c. of the milk in a flask and shake to curdle. Extract the curdled milk with successive portions of ether. Transfer the ether to a separatory funnel and shake with dilute ammonia, which separates the benzoic acid from the fat, in the form of ammonium ben- zoate. Draw off the ammoniacal solution and evaporate in a dish over hot water until all free ammonia has disappeared, but before dryness is reached add a few drops of ferric chlorid reagent. A flesh-colored precipitate indicates benzoic acid. ON MILK AND MILK-TESTING 83 All free ammonia should be driven off, otherwise ferric hydrate would be formed. How may the presence of salicylic acid in milk be detected? The acid is seldom used as a preservative in milk. If its presence is suspected, proceed exactly as in testing for benzoic acid. On applying the ferric chlorid to the solution after the evaporation of the ammonia a violet color indicates the presence of salicylic acid. How can the presence of starch in milk be de- tected? To Io or 15 c. c. of milk in a test tube or vial add a few drops of an iodine solution. If starch is present it will be colored blue by the iodine. How may milk that has been heated to 175° F. be detected? tr. *To 15 or 20 c. c. of milk in a small bottle or test tube add I c. c. of a concentrated starch solu- tion and 6 or 8 drops of a Io per cent solution of potassium iodid. Next add 4 or 5 drops of a 2 per cent solution of hydrogen peroxid. Upon shak- ing the mixture it will turn to a dark blue color if the milk has not been heated to 175° F. 2. Inthe same manner as above, add a quantity of paraphenylenediamin hydrochlorid about the size of a pea and 4 or 5 drops of a 2 per cent solution of hydrogen peroxid. The mixture turns blue on shaking if the milk has not been heated to 175° F. 84 QUESTIONS AND ANSWERS What causes the color of the milk to change in the tests for heated milk? The enzymes of the milk set free oxygen from the hydrogen peroxid and the free oxygen sets free iodine from the potassium iodid. Then the free iodine colors the starch blue. When the enzymes are destroyed by heat no action takes place and the milk remains white. In the second test the oxygen, set free by the enzymes, acts upon the other reagent, causing it to change to a blue color. What are the common ways of adulterating cream? I. By diluting the cream with milk. 2. By the addition of thickeners. 3. By the addition of preservatives. 4. By the addition of acid neutralizers. How may the tendency to dilute the cream be over- come? By buying and selling cream upon the basis of the fat content. How may the presence of condensed milk or con- densed skim milk in cream be detected? Separate the fat of the cream from the serum. Determine the per cent of solids not fat in the serum. If the serum contains a greater percentage of milk solids not fat than is found in skim milk, the presence of condensed milk or condensed skim milk is assured. How may the presence of gelatin in cream be de- tected? ON MILK AND MILK-TESTING 85 Prepare an acid solution of mercuric nitrate by dissolving mercury in twice its weight of nitric acid of 1.42 specific gravity, and diluting the solution to 25 times its bulk with water. To toc. c. of the cream to be examined, add an equal volume of acid mercuric nitrate solution, shake the mixture, add 20 c. c. of water, shake again, allow to stand five minutes, and filter. If much gelatin is present the filtrate will be opalescent and cannot be ob- tained very clear. To a portion of the filtrate con- tained in a test tube add an equal volume of a saturated aqueous solution of picric acid. A yellow precipitate will be produced in the presence of any considerable amount of gelatin, while smaller amounts will be indicated by a cloudiness. In the absence of gelatin the filtrate obtained will be per- fectly clear. The test will work equally well for determining the presence of gelatin in milk. How may the presence of starch in cream be de- tected? By adding a small amount of iodine solution as in the test for starch in milk. A slightly larger quantity of the iodine solution should be added, as: the greater amount of fat in cream will absorb more of the iodine. What substances are often used as cream thicken- ers? 1. Sucrate of lime (viscogen). 2. Condensed milk or condensed skim milk. 3... Gelatim. Ae i erba nel 86 QUESTIONS AND ANSWERS How is sucrate of lime made? Slake 3 pounds of freshly burned lime in hot water. Make the quantity up to 5 gallons by add- ing water. Dissolve 10 pounds of sugar in five gallons of water. Mix the two solutions and stir at intervals for about three hours. Let settle and use the clear solution. How may the presence of viscogen in cream be detected? Determine the number of .c: c. of *— acid re- quired to neutralize the ash from I00 grams of the cream. The -‘— acid should be added in excess and titrated back with -* alkali. If more than 14 c. c. are required it is a strong indication that viscogen is present in the cream. How may the presence of preservatives in cream be detected? The methods used for detecting preservatives in milk may be applied to cream as well. In some cases it may be necessary to dilute the cream before applying the tests. How may the presence of acid neutralizers in cream be detected? The substances used to neutralize the acid are alkalies or carbonates and the methods for detecting them are the same as those used on milk. How is butter sometimes adulterated? 1. By substituting a foreign fat for the whole or a part of the butter fat. 2. By selling renovated butter as fresh butter. ON MILK AND MILK-TESTING 87 3. By incorporating an excess of moisture dur- ing the process of manufacture. 4. By the addition of preservatives. How may renovated butter and oleomargarine be distinguished from butter? 1. Melt some of the substance in a spoon by holding it over a small flame. Let the melted fat boil vigorously. Renovated butter and oleomar- garine snap and sputter with noise while boiling and very little, if any, foam is formed. In boiling, butter makes little noise and a large amount of foam forms. 2. On melting butter and allowing the casein and water to settle a transparent oil results. With oleomargarine or renovated butter the oil remains cloudy. How may renovated butter and oleomargarine be distinguished? Heat about half a pint of milk in a tin cup to 140° F. Add to this a tablespoonful of the sub- stance. Stir with a wooden stirring rod until melted. Then set the cup in ice cold water and stir until the fat hardens. It may then be collected | into a lump with the wooden stirring rod ett is oleomargarine, but will remain separated in fine granules if it is butter or renovated butter. What is one of the best methods for distinguishing butter from oleomargarine? By determining the Reichert-Meissl number. 88 QUESTIONS AND ANSWERS What is meant by the Reichert-Meissl number? It means the number of c. c. *~ alkali required to neutralize the volatile acids from 5 grams of the fat. How is the Reichert-Meiss] number determined? Five grams of the fat are placed in a clean, dry flask of 200%C...c.).capacity. 10-c. Cc: or -O5 percent alcohol added, and 2 c. c. of a saturated aqueous solution of sodium hydrate. Place a funnel in the neck of the flask and heat on the water bath with occasional shaking until saponification is com- plete, when the solution will be free from fat-glob- ules and perfectly clear. Then remove the funnel and continue heating over the bath to dryness. Add 135 c. c. of water and warm on the water bath with shaking until the soap is dissolved. Cool and add a few small pieces of pumice stone, to prevent lumping while boiling, and 5 c. c. of dilute sul- phuric acid (200 parts of acid to 1,000 parts water). Connect the flesk with a condenser and distill off L10\c¢. c. in about. 30 minutes.. Titrate the ‘entire distillate with tenth-normal alkali, using phenol- phthalein as indicator. The number of cubic cen- timeters of tenth-normal alkali required express what is called the Reichert-Meiss] number. How does the Reichert-Meiss] number for butter and for oleomargarine differ? The size of the Reichert-Meiss] number for oleo- margarine usually depends to a great extent upon the per cent of butter present in the oleomargarine. This number is not often more than 5 for oleomar- garine and rarely less than 24 for butter. The ON MILK AND MILK-TESTING 89 Reichert-Meiss] number for butter is usually be- tween 24 and 31. What fats are sometimes used to adulterate butter? Lard and beef fat or products manufactured therefrom, as lard stearin and beef stearin. Stearin derived from cottonseed oil is also used. Fats or oils from any source may be used provided they have the proper melting point when mixed and no strong flavors. What fats are used in the manufacture of. oleo- margarine? Neutral lard, beef fat stearin and cottonseed oil stearin are the principal fats used in nearly all the oleomargarine now manufactured. Cottonseed oil stearin is probably not used to so great an extent as the others. Small quantities of a few other oils are sometimes added to change the color to more nearly resemble that of butter. What is neutral lard and lard stearin? Neutral lard is the best quality of lard made from hog fat. The fat is rendered at a low tem- perature and the product washed with water con- taining a little sodium carbonate, salt, or dilute acid. The product then has only a slight acidity and is almost tasteless. Its principal use is in the manufacture of oleomargarine. Lard stearin is made by melting lard and holding it at a tempera- ture between 50° and 60° F., until the stearin sep- arates in crystals. It is then filtered and pressed in cloth sacks. The oil obtained is used for illumi- nating and lubricating purposes. The _ stearin gO QUESTIONS AND ANSWERS which is collected in the sacks is mixed with other fats and manufactured into oleomargarine or com- pounds like lard and cottonseed oil. How is oleomargarine manufactured? The process of manufacture depends somewhat upon the ingredients used and the markets to be supplied. When the product goes to a tropical country oils of higher melting points are used in larger quantity than when the product goes to colder climates. In general the oleo oil from beef tallow, the neutral lard or lard stearin from hog fat, and the cottonseed oil stearin are mixed in pro- portions giving a melting point about that of butter. The mixture is then churned with skim milk or whole milk and the process thereafter is practically the same as that for the making of butter from cream. What preservatives may be used in butter? 1. Boric acid or borates. 2. Formaldehyde. 2.-) Saliey ic acid: 4. Sulphurous acid. How may the presence of boric acid or borates be detected in butter? Melt an ounce or two of the butter at the tem- perature of boiling water and collect the aqueous solution at the bottom. To a small amount of the aqueous solution add a few drops of hydrochloric acid. Then apply tumeric paper to the liquid. If the paper turns red upon drying and turns to a dark ON MILK AND MILK-TESTING QI olive green upon being made alkaline with ammonia the presence of boric acid is assured. How may the presence of formaldehyde in butter be detected? Melt the butter at a low temperature and sep- arate some of the water solution that collects at the bottom. To this add milk free of formaldehyde. Then test the mixture for formaldehyde by adding a few drops of ferric-chlorid solution and con- centrated sulphuric or hydrochloric acids, as in the case with milk. A violet blue color assures the presence of formaldehyde. How may the presence of salicylic acid in butter be detected? Separate some of the water solution that settles to the bottom on melting the butter and follow the directions given for the detection of salicylic acid in milk. How may the presence of sulphurous acid in butter be detected? Separate some of the water solution that settles out on melting the butter. Distill off a part of it and to the distillate add bromine water and barium chlorid. Aprecipitate indicates the presence of sulphurous acid or a sulphite in the butter. How is butter tested for its salt content? 1. Weigh into a glass beaker 10 grams of butter. Add about 20 c. c. water. Warm it to melt the butter and then transfer the butter and water to a separatory funnel. Insert the stopper. Shake for Q2 QUESTIONS AND ANSWERS a few moments. Allow the mixture to stand a few minutes until any remaining fat has collected on the surface. Then draw the water into a flask, being sure that no fat passes through. Again add hot water to the beaker and repeat the washing in the funnel several times, using 15 c. c. of. water each time. Determine the sodium chlorid in a measured part (Io c. c.) of the liquid by titrating with stand- ard silver nitrate solution, using potassium chro- mate as an indicator. Ic.c. + silver nitrate solu- tion=.005837 grams of salt. To determine the total amount of salt divide the total number c. c. of water used by 10 and multiply by .005837. This will give the total number grams of salt in Io grams of butter. Then, knowing the amount present in IO grams, it is an easy matter to determine the amount in 100 grams by multiplying by 10. This gives the percentage of salt in the butter tested. 2. Gray’s salt test. A representative 10-gram sample of butter is placed in a small glass dish. The dish is then half filled with boiling water and the mixture of fat and water poured into a 500 ¢. c. glass flask. The dish is rinsed several times with hot water and each time the rinsings are poured into the flask. The flask is then filled to-the 500 ¢.¢ mark with boiling water and thoroughly shaken. Then allow the contents of the flask to cool and after the fat has collected on top and hardened, measure with a pipette 50 c. c. of the clear solution beneath the fat and place it in a clean glass dish. Fifty c..c. of a potassium chromate indicator is then added and the solution titrated with a standard ON MILK AND MILK-TESTING 93 silver nitrate solution. The strength of this silver nitrate solution is such that 1 c. c. of it represents one-tenth of I per cent of salt. 3. The Fitch salt test. A representative 3.5- gram sample of butter is placed in a 300 c. c. glass flask and 180 c. c. of boiling water added. The flask is then corked and thoroughly shaken, care being taken to remove the cork often to relieve the pressure. The mixture is then allowed to cool and after the fat has collected on the top and solidified 17.6 c. c. of the clear solution beneath the fat is placed in a white cup. Then 17.6 c. c. of potassium chromate indicator is added and the solution titrated with a standard silver nitrate solution meas- ured from a graduated cylinder till the solution be- comes a permanent reddish color. The number c. c. silver nitrate used divided by 1o=per cent salt. How is the moisture content of butter determined? 1. By chemical analysis. 2. By practical moisture tests. What are the names of the more commonly used moisture tests? 1. Cornell test. 2. Mitchell-Walker. aii Stish: 4. Gray’s. 5. Farrington. How should a representative sample of butter be secured and prepared for making a moisture, salt, or fat test? From the mass of butter to be tested take several 04 QUESTIONS AND ANSWERS samples from various parts. The samples when added together should make about 6 ounces. These are placed in a wide-mouth sample bottle or fruit jar and placed in hot water until the butter melts to the consistency of thin cream. While melting, the butter should be thoroughly and _ continuously stirred with a table knife or similar instrument. The bottle should then be well shaken to secure a uniform mixing of the sample. The bottle is then placed in cold water to solidify, but while cooling the butter should be stirred continuously. As soon as the butter has become fairly solid or plastic, the sample for testing can be secured. If in melting the butter becomes oily great care and skill must be used to reincorporate the water evenly during cooling. Describe and give directions for using the Irish moisture test. A representative 10-gram sample of butter is placed in a small metal cup and held over a flame with a pair of special forceps until all the moisture has evaporated from it. While the butter is heat- ing it foams considerably. As soon as the foaming has ceased, and before the fat begins to char, a small mirror is held over the cup to show if any moisture still remains. When the sample is thus freed from moisture it is cooled to room tempera- ture, 60° F.to 70° F.,and reweighed upon a special scale by which the difference between the weight of the butter before and after heating is indicated in the form of percentage by the use of small weights. ON MILK AND MILK-TESTING 95 Describe and give directions for using Gray’s moisture test. This test consists of a scale, glass flask, gradu- ated glass tube, condenser, amyl reagent, and an alcohol lamp. A representative Io-gram sample of butter is placed in the glass flask. To this 6c. c. of amyl re- agent is added and the different parts of the test then connected for use. The condenser is filled with cold water. The butter and amyl mixture is heated over a flame, the moisture is driven off and collects in the graduated glass tube, where it can be read in the form of percentage. The heating is stopped as soon as the mixture in the flask becomes brown and the crackling noise ceases. This usually requires about six minutes. Should heat be applied too severely to the flask the steam may go above the I5 per cent mark. This should be prevented by withdrawing the heat for a short time. Great care must be exercised in collecting all the moisture in the graduated tube if reliable readings are to be secured. Describe and give directions for using Farrington’s moisture test. In Farrington’s test Io grams of a representative sample of butter is placed in a small dish. The dish is then placed in a special oven heated to from 240° F. to 270° F. under steam pressure. Here the butter is left until all moisture has been evaporated, indicated by the browning of the casein in sample. This usually takes about 30 minutes. After the moisture has been evaporated the dish and its con- tents is reweighed and the difference from the 96 QUESTIONS AND ANSWERS original weight determined. ‘The per cent moisture can thus be easily determined. Occasionally a re- verse beam scale is used upon which the per cent moisture evaporated can be read direct. Describe and give directions for using the Cornell moisture test. This is a simple, accurate, and durable test re- cently prepared by Mr. H. E. Ross of the dairy department of the New York state college of agri- culture. The test resembles the Irish test, but has several important improvements. A 10-gram sample of butter is secured in the usual way. ‘This is placed in a special cast alum- inum cup and the cup held over a flame with special forceps or placed on some heated surface. The important features of the test are the use of this cup and the use of a thin sheet of asbestos between flame or heated surface and the cup. The asbestos prevents all the sputtering of the heating butter and eliminates a great deal of the danger of charring. The sample is heated till all moisture is driven off. This usually requires about 25 minutes, and is in- dicated by the casein losing its snow-white color and becoming brown. The sample is then cooled and reweighed with a special scale upon which the per cent moisture can be read directly and accu- rately. Describe and give directions for using the Mitchell- Walker test. The apparatus in this test consists of a metal evaporating cup, condenser, graduated glass re- ceiver, scale for weighing sample, spirit lamp, amyl ON MILK AND MILK-TESTING 97 acetate reagent, and a stand to support the appa- ratus. A representative 10-gram sample of butter is placed in the metal cup. To this is added Io c. c. of the amyl acetate reagent. The apparatus is then connected and the condenser filled with cold water. The alcohol flame is then applied under the evaporating cup. In about a minute the water and reagent will begin to pass over and drop from the condenser tube into the receiver. After all the water has been evaporated from the cup, the reagent will cease dropping for a moment and then begin again as soon as it has reached its own boiling point, which is higher than that of the water. Con- tinue to apply the flame until practically all the re- agent is driven off and it ceases to drop freely from the condenser tube. By this means all the water is washed out of the condenser tube and the major portion of the reagent is recovered. The flame is now extinguished. The mouth of the receiver is corked and taken by the top and shaken a few times to detach any drops of water that may adhere to the sides. The per cent moisture can now be read in the graduated receiver. The water is withdrawn from the receiver, and then the reagent, which is collected in a bottle and preserved for use in later tests. 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