An appeal to the people of Great Britain on the subject of confederated Greece

Front matter

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Preface

This work is the outgrowth of a course of lectures given by the author for a number of years to the students of the Agricultural Department of the University of Minnesota. During recent years material progress has been made in dairying, and in writing this book it has been the aim briefly to incorporate the results of the more important investigations on the subject. In the preparation of the work extensive use has been made of the bulletins and reports of the Agricultural Experiment Stations of the United States and of other works on the subject. It is the aim to present in as concise a form as possible the principal changes that take place in the handling of milk and in its manufacture into butter and cheese. While our present knowledge of some phases of the subject is incomplete, there are many facts that are known and have been found very useful as an aid in the production of dairy products of the highest sanitary and market value.

It is believed that a knowledge of the general

769789 vi PREFACE

principles of dairy chemistry will be found useful

alike to the farmer, to the factoryman, and to the

consumer, uid this work has been prepared with

the view of giving information to the layman rather

than to the scientist.

HARRY SNYDER.

CHAPTER I The CoMPOsmoK of Milk TAQM

Complexity of composition ; Milk serum ; Milk solids ; Bfilk fats ; Caseio ; Albumin ; Milk sugar ; Ash ; Variations in composition of milk; Percentage composition, and total yields; First or fore milk and strippings; Milk serum, Constancy of its composition . . • • 1

CHAPTER n

Milk Tbstiko

Importance of milk testing ; Reliability of the Baboock test ; Sampling milk ; Measuring milk with the pipette ; Making the test; Reading the fat ; Calibration of test bottles ; Speeding the machine ; Centrifugal action ; The acid ; Composite sample ; Testing skim milk ; Sampling frozen milk ; Cleaning glassware ; Water used in milk testing ; Care of test bottles and apparatus 18

CHAPTER m

Milk Fats

Composition of fats ; Kinds of butter fats ; Palmitin ; Stearin ; Olein; Butyrin; Caproin and Caprylin; Qlycerine and fatty acid content of fats ; Food yalue of fats ; Saponification of fats ; Iodine absorption of butter fats ; Volatile fatty acids of butter ; Melting point and physical properties of butter 29

vii vm CONTENTS

CHAPTER IV

PAAI

Queyenne^s lactometer ; Specific grayity of milk ; Inflaence of temperature ; Other lactometers ; Influence of skimming and watering ; Calculation of solids in milk ; Joint use of lactometer and Babcock test 85

CHAPTER V

Milk Suoab and Lactic Acid

Physical properties of milk sugar; Fermentation of milk sugar ; Production of lactic acid in the milk ; Determining the acidity of milk ; Calculating the acidity of milk ; Alkaline tablets ; Acidity of cream 43

CHAPTER VI

Cbbam

Composition of cream ; Testing cream ; Methods of creaming ; Adulteration of cream ; Ripening of cream ; The use of pure cultures ; Influence of delay on the creaming of milk; Creaming of mixed milks; Cream raising by dilution 60

CHAPTER Vn

Thb Chemistbt of Buttbb Making

Churning; Dairy salt; Buttermilk; Losses of fat in butter making; Composition of butter; Butter colors; Oyerruns ; Dividends ; Judging butter

CONTENTS IX

CHAPTER Vm

Thb Sanitabt Conditioh of Milk

Unwholesome milk ; Factors influencing the sanitary condition of milk ; Condition of the animals as to health ; Care of the animals ; Care of milk and dairy utensils ; Food and water which the animals receive ; Colostrum milk ; Tyrotoxicon ; Fibrin hi milk ; Oases in milk ; Keeping qualities of milk 76

CHAPTER EC

Cheese making and butter making compared; Proteids hi ' milk; Casein; Albumin; Rennet; The rennet test; Process of cheddar cheese making; Process of stirredcurd cheese making; Distribution of milk solids in cheese making ; Curing of cheese ; The cheese yield of milk ; Tesdng cheese by the Babcock milk test ; Composition of cheese ; Testing whey ; Making out dividends in cheese factories; Comparative butter and cheese returns from milk ; Different kinds of cheese 88

CHAPTER X

Milk Bt-pboduots

Uses of by-products; Skim milk — composition, value, and use; Whey — composition, value, and use; Fertilizer value of milk by-products ; Comparative value of skim milk compared with milk of other domestic animals • 107

CHAPTER XI

Thb Adultbbation of Daibt Pboduots

Oleomargarine ; Simple methods for detecting oleomargarine ; Renovated butter ; Adulteration of cheese ; Adulteration of milk ; Other methods for testing milk ; Dairy laws . 112

CONTENTS CHAPTER Xn

FAQM

Variable character of market milk ; Changes in composition of milk during transportation; Pasteurizing milk and cream ; Condensed milk ; Milk as human food • • 119

CHAPTER XIII

Iktluskcb of Diffbbbnt Foods upok thb Qualitt OF Milk and Daibt Pboducts

Food and milk secretion ; Feeding fat ; Production of hard butters ; Production of soft butters ; Effects of individual foods; Desirable flavors in milk products; Influence of balanced rations ; Milk secretion 126

CHAPTER XIV

Thb Rational Feeding of Daibt Stock

Uses of food ; Nutrients and their functions ; Dry matter ; Ash ; Organic matter ; Proteids ; Carbohydrates ; Crude fiber ; Crude fat ; Digestible nutrients ; Caloric value or heat units of a ration ; Nutritive ratio ; Selection of foods for rations ; How to calculate a ration ; Comparative cost and value of grains 131

Appendix

Tables of composition of fodders and feeding stuffs ; Tables for correction of lactometer readings ; Review questions ; References 147

Index 187

CHAPTER I THE COMPOSITION OF MILK

1. Complexity of Composition. — When milk is separated into its component parts, as water, fat, casein, albumin, sugar, and ash, the process is called analysis. While these are the principal compounds obtained when milk is analyzed, there are a number of other substances present in smaller amounts which affect the quality of milk both for manufacturing and food purposes. Milk is one of the vital fluids of the animal body and is necessarily of complex composition.

2. Milk Serum. — Of the various constituents of milk, the sugar, ash, and albumin are in solution, and in the fresh milk the casein is practically in a soluble form. The fat, however, is not in solution, but is in the form of minute globules suspended in the solution which contains the sugar, ash, albumin, and casein and which is known as the milk serum. The milk serum includes all of the constituents of the milk except the fat. The term "serum solids" is applied to those substances of milk which are dissolved in the water, — the sugar, ash, albumin, and casein taken collectively.

B 1

DAIBT CHEMI8TBT

.; .3w JKQUi; Sqiids.rr- When milk is evaporated to dry- '''nes6,^tli€t.Wa}^r-,ifi.. expelled and the milk solids are obtained. Milk solids are a mechanical mixture of fat, casein, albumin, milk sugar, andxash. Normal milk contains about 13 per cent of solid matter ; some samples contain as low as 12 and a few as high as 14 per cent. The amount of milk solids varies proportionally with the fat content of the milk, the higher the per cent of fat the larger the amount of solids.

In the chemical analysis of milk, the solids are obtained by evaporating a weighed quantity of milk to dryness in a small dish which has previously been carefully weighed on a very delicate balance. The weight of the milk solids is then obtained and the percentage amounts calculated.

Fio. 1. — Determining the solids in milk.

Example

Weight of milk + dish Weight of dish Weight of milk

Weight of milk + solids Weight of dish Weight of milk solids iM|^i22 = 12.80 per cent solids. 10.51

100 - 12.80 = 87.20 per cent water. The per cent of water in

Gramb

23.360 12.850 10.510

14.195

12.850

1.345 milk is obtained by subtracting the per cent of solids from 100, as the loss in weight during evaporation is the water expelled as steam. There are rarely more than 88 pounds of water in 100 pounds of milk ; average milk contains about 87 per cent, while some of the richest milks contain 86 per cent or less. The milk solids, unless obtained in a specially constructed water oven, are brown in color, due to slight charring of the sugar and other compounds. The solids of milk are sometimes termed dry matter and sometimes solid matter. They are composed of fat, casein, sugar, albumin, ash, and other compounds found in smaller amounts.

4. Milk Fats. — Average milk contains about 3.6 per cent of fat ; some normal samples may contain 3 per cent or less, while others may contain 6 per cent or more. Fat is the most variable constituent in milk. Cream contains ordinarily from 18 to 35 per cent of fat, and well-made butter about 86 per cent. For butter-making purposes the value of the milk is directly proportional to its fat content. Milk fat is mainly familiar as the product obtained by churning cream. Milk fat and commercial butter, however, are not synonymous terms. By milk fat is meant the pure dry fat, free from water, salt, or casein, while butter contains all of these materials in variable amounts. The determination of the fat in milk by the Babcock test is discussed in the second chapter of this work, and the composition and properties of the fats are considered in other chapters.

As previously stated, the fat in milk is not present in solution, but in suspension in the form of minute globules. These milk fat globules are about one fivethousandth of an inch in diameter. A cubic millimeter of milk is estimated to contain from 2,000,000 to 4,000,000 fat globules, or a single drop from 100,000,000 to 160,000,000, Under the microscope the fat globules appear grouped together in small colonies. The size of the fat globules varies (1) with the breed and individuality of the animal, and (2) according to the length of time the animal has been in milk. When a cow is fresh, there is a smaller number of globules, but the globules are larger ; when the cow is well along in her milking period, the globules are smaller but more numerous. The milk from the Channel Island breeds is characterized by large fat globules, while the milk from the lowland breeds contains smaller globules. The fat globules must be massed together and collected when butter is made. The more completely they are recovered, the greater will be the amount of butter produced.

The fat globules are simply solid masses of fat. At one time it was believed that they were surrounded by a membrane, and in churning it was supposed that the membrane had to be broken before the globules would mass. Recent chemical investigations have shown that there is no membrane surrounding the fat globules. The fat globules are lighter than any of the constituents of the milk

PLATE I

JERSEY MILK FAT GLOBULES ' ' '

PLATE II

HOLSTEIN MILK FAT GLOBULES serum. They retain their form and individuality on account of surface tension, which is the pressure that is exerted on the surface of the globules and is equal on all sides, hence the spherical form of the globules.

5. Casein. — Average milk contains about 8 per cent of casein, which in fresh milk is practically in a soluble condition, but in sour milk is precipitated as curd. The per cent of casein in milk is quite constant, ranging from 2.8 to 3.5 per cent. As a general rule, normal milk contains less casein than fat. In a pure state casein is a grayish white powder. Casein takes a very important part in cheese making and other dairy operations. Its chemical and physical properties and the changes which it undergoes will be considered in other chapters.

6. Albumin. — Average milk contains about one half of one per cent of albumin, which is nearly identical with egg albumin, or the " white " of the egg. Albumin and casein have about the same general composition, but diflferent properties ; they belong to the class of bodies called proteids, and are very complex in composition, differing from fat and sugar by containing the element nitrogen, which is not found in the fats and sugars. When fresh milk is boiled, the coagulum which forms on the surface is albumin. The amount of albumin in milk is quite constant and ranges from one half to three quarters of a per cent.

7. Milk Sugar. — Lactose, or milk sugar, is present in milk to the extent of about 6 per cent. When

6 DAIBY CHEMISTRY

obtained in the pure state, it resembles in appearance confectionery sugar, but not in taste. Milk sugar takes an important part indirectly in butter and cheese making, as it is the material from which the acid is formed that sours the milk. The amount of milk sugar or lactose in milk is quite constant, ranging from 4.6 to 5.4 per cent. In average milk it is the constituent which is present in the largest amount of any of the milk solids. The part which milk sugar takes in butter and cheese making will be considered in other chapters of this work.

8. Ash. — When the milk solids are burned, there is a small amount of grayish white ash obtained. The ash content of milk is constant and varies but little from three quarters of one per cent. Milk ash is composed of common salt, and phosphates and chlorids of potassium, calcium, and magnesium, together with small amounts of other minerals. A portion of the phosphorus is in combination with the casein.

When milk is analyzed in the laboratory, the ash is obtained by completely burning the milk solids at a low temperature. The small dish containing the milk solids (see section 3) is placed either over a specially regulated flame or in a low-temperature mufiEle furnace to completely burn the sugar, casein, albumin, and fat without volatilizing any of the mineral salts. The dish containing the milk ash is then weighed and the per cent of ash determined.

Milk taken 10.51 gm. section 3.

Dish and milk ash

Dish

Ash

Example See

GmAMS

12.928

12.850

0.078

- = .74 percent ash.

10.51

9. Variations position of Milk.

age milk has about following general composition : —

Fia. 2.^Detenniiiing the ash in milk.

It is seldom that the extreme limits as given for the composition of milk are met with; occasionally an individual animal may give milk of abnormally high or low solids and fat, but it is rarely the case that the milk from an entire herd will contain either the

DAIBY CHEMI8TBT maximum or the minimum percentage of milk solids.

Milk varies in composition with the individuality of the animal, period of lactation, care, exhaustiveness of milking, general condition as to health, and nature of the food consumed. Individuality, as breed characteristics, influences the composition of milk to a greater extent than the other factors enumerated. The extent to which some of these factors influence the composition of milk will be discussed in other chapters of this work.

As an example of the composition of milk from diflferent breeds, the following table taken from the New York Experiment Station, and representing one year's work, is given : —

Total

BOLIDB

P«B owrr

Fat

PbB OXNT

Garcht

PXB OXNT

Milk

SUGAB Pbb OlMT

Ash

PXB OKIT

Holstein-Fresian

Ayrshire

Jersey

Am. Holderness

Guernsey

Devon

While these figures do not necessarily hold true for all herds, or for individual animals of any breed, they show the average composition of the milk for an entire season from a number of representative animals of different breeds. In determining the value of milk for butter or cheese making purposes, the yield in pounds as well as the percentage composition of the milk must be considered, as it frequently liappens that the cows giving the richest milk also give the smallest yield of milk.

10. Percentage Composition and Total Yields. — In order to determine the total yield in pounds of each constituent produced by a cow or by a herd for a given period, the total weight of milk is multiplied by the percentage composition. In case it is desired . to compare the yields of milk solids of two cows, giving respectively a total of 110 and 140 pounds of milk in three days, an analysis would have to be made of each milk. Suppose the milks give the following results upon analysis : —

Composition op Milk

Milk solids

Milk fats

Casein and albumin . .

Ash

Total Yield of Milk Solids

Oow No. 1

Oow No. S

10 DAIBT CHEMI8TRT

While the difference in percentage composition of the milk is .8 of a per cent of fat in favor of cow No. 1, the total yield of fat for three days is .1 of a pound in favor of cow No. 2. Cow No. 2, however, produced a larger amount of milk solids in the form of fat than cow No. 1. In general it is to be noted that whenever a cow produces a pound of butter fat, she also produces about 1.1 of milk sugar, about a pound of casein and albumin, and about .15 of a pound of ash. When milk is paid for on the basis of its fat content for butter making purposes, the total pounds of fat are obtained by multiplying the weight of the milk by its per cent of fat, as 287 pounds of milk testing 3.6 per cent fat contain (287 x .036) 10.33 pounds of fat. In dairy operations all comparisons and calculations are made on the basis of the total fat.

11. First or Fore Milk and Strippings. — As is well known, the first portion of milk given by any cow at a milking is poor in fat, while the last portion, or strippings, is very rich in fat. The per centage amounts of casein, ash, and sugar, and other ingredients, however, remain nearly constant. The difference in fat content between the first or fore milk and the strippings suggests the importance of careful and exhaustive milking, and also thorough mixing of the milk before taking a sample for analysis. The composition of the first pint and the last pint of milk from two cows is given as an illustration.

Cow No. 1

Cow

No. a

First pint

Last pint

First pint

Last pint

Total solids

9.42

19.49

10.10

18.47

Fat

0.71

10.84

1.02

9.49

Solids, not fat ....

8.71

8.65

9.08

8.98

Ash

0.68

0.72

0.70

0.74

Casein, albumin . . .

8.44

3.51

3.35

3.65

12. Milk Serum, Constancy of its Composition. —

The solids of the milk serum are fairly constant in composition. This is well illustrated in the example

U^er fat Cam'm tiilKSnp flllmin

FiQ. 3. — Average composition of milk.

given of the composition of first or fore milk and strippings. The solids of the milk serum, also known as the solids not fat, are never less than 8.25 per cent and rarely more than 9.75 per cent. The average is about 9 per cent. The greatest difiference in the composition of various milks is in the fat content. Any material increase in the total solid matter of milk is due mainly to an increase of the fat. The solids not fat are subject to but slight variations compared with the fluctuations of the fat.

Nearly all of the important fluids of the body, like the blood, are normally quite constant in chemical composition. With milk the constancy of composition is confined mainly to the serum solids, or solids not fat.

Chapter II Milk Testing

13. Importance of Milk Testing. — A knowledge of the fat content of milk is essential in order to determine (1) any unnecessary waste in the manufacture of butter and cheese, (2) the value of individual cows, (3) the cost of producing milk, (4) the value of different fodders and grains for milk-producing purposes, and (6) the commercial value of milk.

A number of simple methods have been proposed for testing milk ; some of them require a more extended knowledge of chemical operations than others. The method which is in most general use on account of its accuracy, simplicity, and cheapness is the Babcock centrifugal method.

14. Reliability of the Babcock Test. — This method has been tested by many chemists, and in all cases it has been found to give reliable results. There is a tendency, however, to read the fat percentages too low. This will be considered more in detail in discussing that part of the operation. In the case of skim milk and buttermilk, when the fat is present to the extent of only two tenths of a per cent or less, the method may not give absolute results. This does not impair the usefulness of the test, because frequently the losses in skim milk and buttermilk are greater than this, and so far as the whole milk is concerned the method is perfectly reliable. When the Babcock test shows only a trace of fat in the skim milk or buttermilk, the losses are very small.

15. Sampling Milk. — Milk should be thoroughly mixed before sampling. The milk as it comes from the cow or when it has been standing is not in a condition to sample until it has been thoroughly mixed, either by pouring from one pail to another or by stirring with a long-handled dipper. Milk brought to the creamery in cans also requires thorough mixing before sampling. This is best accomplished by the use of a long-handled dipper. Before sampling, the milk should be weighed.

The milk should not be measured into the test bottles when it is either hot or cold. At a high temperature the milk is expanded and may contain an abnormal amount of dissolved air ; while at a low temperature the milk may be unduly contracted. A temperature of 70° to 80** is the most suitable for measuring milk. If the milk has been standing for some time in the sample bottle, it is necessary to mix it thoroughly before measuring with the pipette. To do this, turn the milk from the sample bottle into another bottle or dish, pouring it down the side to prevent the formation of foam. In case the sample bottle has been standing until the fat has separated into a layer of cream, the bottle may be placed in a bath of warm water, temperature 100% to liquefy the fat before mixing. Milk which shows the presence of clots of cream or small particles of butter formed during the shaking of the sample bottle is not in condition to be measured with the pipette. If the sampling of the milk has not been carefully done, the work of testing is of little value, as the sample taken fails to represent the milk tested.

16. Measuring Milk with the Pipette. — The apparatus used for measuring the milk is called a pipette (see Fig. 4). In order to fill the pipette put the pointed end into the milk, apply suction with the mouth until the milk rises just above the point a on the stem ; then close the end with the index finger of the right hand, holding the pipette in the way shown

Fia. 4. —Measuring milk with the pipette.

in the cut. The second and third fingers are opposite the thumb, while the little finger rests against the stem. When held in this way, the pipette is prevented by the little finger from swaying sidewise ; while the thumb, with the second and third fingers on the opposite sides, secures a good hold atid leaves the index finger free to properly control the flow of milk from the pipette, and thus rapid measurements can be made. If the pipette is wet, rinse it with a little of the milk before using it. In passing from one milk to another, clean the pipette by rinsing it with the milk that is to be tested. The pipette should be thoroughly cleaned, first with cold water, then with hot water at the close of the work. The pipette holds 17.6 cc. of water, and delivers 18 gm. of milk. Hold the test bottle in the left hand at an angle of about 60**, Let the tip of the pipette if large just touch the inside of the neck of the test bottle, in order to permit air to pass out of the test bottle, otherwise the milk will spatter. Allow plenty of time for the pipette to drain ; remove the last few d^*ops by blowing.

17. Making the Test. — The test bottle (see Fig. 5) is provided with a neck which has a graduated scale from 1 to 10. Each larger division is divided into five smaller divisions, each representing .2 of a per cent of fat. The test bottle is usually provided with a copper collar bearing a number. Fill the acid measure, Fig. 6, up to the 17.6 cc. mark with sulphuric acid. The action of the sulphuric acid

MILK TESTiyO will be considered in another paragraph. Pour the sulphuric acid from the acid measure into the test bottle which contains the milk. The acid and the milk shouldbeof nearly the same temperature, 70^ F.

While the acid is poured in, rotate the test bottle so as to wash all of the milk down from the stem. After the acid is added, take the bottle by the stem and mix the acid and the milk by rotating.

The solution becomes a dark coffee color, due to

^<»-\-Miik test the acid charring Dottle*

the sugar. The

acid first precipitates the casein and then dissolves it. The acid does not act on the fat.

The fat is separated from the milk serum by centrifugal action. There are a number of different kinds and sizes of centrifugal machines, but they all act on the same principle. The test bottles are placed in the pockets of the centrifugal machine.

Fio. 6.->Aoid measTue.

In case there are not enough bottles to fill the machine, arrange the bottles so there will be an even number on each side. If this is not done, the machine is unbalanced, and the bearings will soon become badly worn. The bottles are to be whirled five minutes at the rate of 900 revolutions per minute. Directions for speeding the machine will be found in another paragraph. The starting and stopping of the machine should be done gradually.

After whirling five minutes, the test bottles are to be filled with hot water up to about the eighth mark on the stem. The air bubbles which are sometimes caught in the neck should be allowed to escape. The bottles are then whirled two minutes longer in order to collect all of the fat in the graduated stem. In using the machine always put on the cover so as to prevent any accident.

None of the apparatus used in this test is patented, and a good homemade centrifugal machine will answer every purpose. The bottles and other glassware can be purchased separately.

18. Reading the Fat. — When the test is completed, the fat in the stem of the test bottle presents the appearance shown in Fig. 7. Read from the lowest point h to the highest point a. Each large division, as 1 to 2, represents a whole per cent of fat ; each of the smaller divisions one fifth or two tenths of a per cent. Suppose the top registers seven large divisions, and three small, then a = 7.6. If 6 registers two large and three small divisions, b = 2.6. 7.6 — 2.6 = 5.0, the per cent of fat in the milk.

Do not read from other points than a and 5, otherwise the results will be too low. The bottles are made to read in just this way.

The reading should be done before the fat cools and streaks down the sides.

In case a number of readings are to be made, the test bottles should be set in a pan of hot water, or hot water can be run into the pan of the machine, to prevent the bottles from cooling. Dividers can be used as indicated in the figure, but should be spread from to 5.

19. Calibratioa of Test Bottles. — All test bottles should be rejected when inaccuracy of the divisions can be detected with the eye. In the most careful work they should be calibrated with mercury: 27.18 gm. of clean metallic mercury should just fill the

Fio. 7. —Beading the test.

space between the and the 10 in the scale. Each small division is equal to .04 cc, or, as usually made, about one and one half millimeters. The test bottles can also be calibrated with water in the following way: The bottles are filled with pure distilled water up to the mark, and then from an accurately graduated burette, graduated to ^ cc, water is added. It should require 2 cc. of water to fill the test bottle from the to the 10 mark. For ordinary work the bottles can all be tested with one sample of milk, and all bottles rejected that show a greater difference than one small division. Accurately graduated test bottles can usually be obtained from supply houses that deal in chemical apparatus. Inaccurately graduated test bottles are occasionally the cause of much trouble and dissatisfaction in the creamery.