Dairy technology; a treatise on the city milk supply, milk as a food, ice cream making, by-products of the creamery and cheesery, fermented milks, condensed and evaporated milks, milk powder, renovated butter, and oleomargarine

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Preface

The manufacture of butter and cheese has been carried on by man from time inunemorial. But there are uses of milk and its products that are comparatively new. Modem man has invented and discovered many ways of increasing the commercial value of milk and its products by using them for a great variety of purposes.

These uses for milk are here grouped together and treated under the one head — " Dairy Technology." This subject treats of the production and preparation of sanitary, certified, modified, fermented, dried and condensed milks, the manufacture of ice cream, renovated butter, oleomargarine, milk sugar, casein, etc.

At the present time information on these subjects is widely scattered and somewhat indefinite. It is the purpose of this work to give experiences and results of work carried on by the authors; to secure from bulletins, papers, addresses, and other sources, reliable data dealing with these subjects; and to compile and arrange this material in such manner as to be a ready reference for the student of this phase of dairying.

The authors realize that many of the subjects treated are in the midst of a transitional period. Future experiments are likely to add valuable information. The writers have endeavored to obtain the best possible present information along the various hues discussed, and they hope to make changes and additions as rapidly as the authentic information can be secured.

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258372

CHAPTER II. Palatability of Cows' Milk 7

DigestibiUty of Milk 8

Raw vs. Heated Milk 9

Use of Milk with Other Foods 9

Relative Cost of Milk lo

* Skim Milk 14

- Cream 18

» Butter 19

* Cheddar Cheese 20

CHAPTER in.

Abnormal Milk 23

Poisonous Milk 23

Colored Milk 24

Bitter Milk 24

Stringy or Ropy Milk 24

Colostrum 24

General 25

V

VI CONTENTS

Chapter IV. Page

Extent and Importance of this Industry 27

. Condition of City Milk Supply in Past Years 29

, Investigations in Illinois Cities 29

Milk and Infant Mortality 30

• Epidemics Spread by Milk 32

• Sources of Milk Contamination 32

Bovine Tuberculosis 33

Chapter V

. Inspection of Dairy Farms and of Milk 35

Cost of Inspection 36

The Score Card 37

Advantages of Score Card Inspection 41

Results of Score Card Inspection 42

Inspection of City Milk Plants 43

Milk and Cream Contests 45

Number of Inspections made in New York City 47

Limitations of General Inspection 47

• Classes of Milk 48

- I. Certified 49

. 2. Inspected 49

3. Pasteurized 50

/ 4. Modified 51

JResults of the Improvement of Milk Supply 51

Jjifants' Milk Depots in New York 52

^ilk Depots in Other Cities 53

Chapter VI

. Origin of the Term "Certified Milk" 55

^ The First Medical Milk Commission 57

^ Milk Commissions 57

- Requirements of the Milk Commission of New York City 57

Details of the Workings of Various Conmiissions 64

• •

CONTENTS VU

PAGE

Use of Certified Milk 64

Produ<;tion of Certified Milk 65

Inspected Milk 66

CHAPTER ^VII.

, Alleged Disadvantages of Pasteurization 68

1. Promotes Carelessness 68

2. Produces Chemical Changes 69

3. Does not Kill all Undesirable Germs 69

4. Toxic By-products Remain in Milk 72

5. Covers Some Defects of Milk 72

6. Affects Flavor and Creaming Property 72

7. Cost of Pasteurization 73

• Advantages of Pasteurization 75

1. Protection against Abnormal and Pathogenic Bacteria. . . 75

2. Decreases the Total Number of Bacteria 75

3. Pasteurized Milk Keeps Longer 77

Pasteurization of Milk Increasing 77

• Official Supervision of Pasteurization- 77

•■ Laws and Ordinances Pertaining to Pasteurization 78

^Home Pasteurization 79

CHAPTER VIII. Use of Modified Milk 80

Digestibility of Modified Milk 80

1. Composition of Human Milk (Colostrum and Normal) 81

2. Normal Human. Milk Compared with Cows* Milk 81

Food Requirements of Infants 82

Methods for Modifying Milk 83

. Homogenized Milk 84

Chapter IX

r The Village Milk Plant 87

« Objectionable Practices ^^

r Equipment of the Plant 89

, I. Cooling the Milk 89

* 2. Bottling the Milk 89

' 3. Bottle Washing 92 viii CONTENTS

Chapter X. Page

• Transportation 94

.The Intake 96

, Sanitary Piping 97

. Clarifying 97

• Pasteurization and Cooling 98

, Pasteurizers 100

' Pasteurization in the Bottle loi

• Bottling 104

• Delivering 105

' Bottle Washing 105

•The Milk Bottle 109

^The Bottle Cap no

Business Principles in

CHAPTER XIV. Ice Cream Making 132

History and Extent of Ice Cream Making 132

Classification of Ice Cream and Ices 135

CONTENTS IX CHAPTER XV.

PAGE

Cream for Ice Cream Making ^ 139

Acidity 139

Homogenized Cream 140

Pasteurization 141

Aging and Cooling 142

Fat Content 142

Chapter XVI

1. Crushed Fruits 144

2. Extracts 144

3. Sweetening 144

Fillers and Binders .' 146

CHAPTER XVII. Ice and Salt , 150

Speed of Dasher 153

Freezing Period 153

Freezing Point 154

Effect of the Sugar Content on the Freezing Point 155

Swell 155

Stopping Point 157

Hardening 157

Returned Goods 157

Fancy Ice Cream 158

Fat Content of Different Portions 159

Binders and Fillers 186

Fat Standard 186

Testing Ice Cream 188

1. Hydrochloric and Acetic Acid Method 188

2. Modified Babcock Method 189

Bacteria in Ice Cream , 189

Chapter XXIII

. Chemicals Used 193

^ Principles of Producing Cold Artificially 194

Transferring the Cold 196

Use of Brine 197

' Strength of Brine 198

. Size of Compressor 198

• Operation of an Ammonia Plant 198

' Insulation 201

CONTENTS XI

Part IV. By-products Of The Creamery And Cheese Factory

CHAPTER XXIV. page

Milk to Use 203

Use of Starters 204

Soiiring the Milk 204

Heating the Curd 205

Draining the Curd 205

Seasoning the Curd 205

Yield of Cheese 205

Use of Rennet in Cottage Cheese Making 206

Use of Hydrochloric Acid 206

Buttermilk Cheese 207

Heating the Buttermilk 207

Draining the Curd 208

Seasoning the Curd 208

Kind of Buttermilk 209

Buttermilk Cream 210

CHAPTER XXV. Original Methods of Making Whey Butter 212

Poor Methods Employed 213

Modem Whey Butter Making 213

Disposal of Whey Butter 214

Profits from Whey Butter Making 215

CHAPTER XXVI. History and Development of Milk Sugar Manufacturing 216

Milk Sugar Making in the United States 217

The Process of Manufacture 218

By-products of Milk Sugar Making 219

Mysost 219

CHAPTER XXVII. Preparation of Casein 221

Casein from Buttermilk 224

XU CONTENTS

PAGE

Casein Glue 225

Casein Paints 226

Milk-Cement Paint 226

Plastic Masses from Casein 227

Manufacture of Galalith ^ . . 228

Casein in the Textile Industry 229

Casein Foodstuffs 230

Casein in the Paper Industry 230

Other Uses for Casein 231

Buttermilk Poultry Food 231

CHAPTER XXVIII. Food Value : 232

Principles Involved 232

Tablet and Capsule Cultures 233

Composition 234

Artificial Buttermilk 235

Bacillus Bulgaricus for Buttermilk 236

Buttermilk Tablets 237

Kefir 238

Kumiss 241

American Kefir or Kumiss 242

Yoghurt, etc 244

Ropy Milk 245

Moscow Sour Cream 245

Clotted or Devonshire Cream 246

Carbonated Milk 247

Chapter XXIX

. Extent of the Industry 249

#> U. S. Standards 250

Quality of Raw Product 251

The Condensing Process 253

Degree of Concentration .' 255

Sterilization 259

Shaking the Canned Milk 260

Composition of Evaporated Milk 261

Composition of Sweetened Condensed Milk 261

Relatively Large Investment Needed 262

CONTENTS Xlll

Advantages of Milk Powder 264

% History and Development of Milk Desiccation 265

The Modern Method 267

Use of Milk Powder 268

Composition , 269

Whey Powder or Dried Whey 269

Chapter XXXI

f Renovated Butter 270

• Ladles 270

• Origin of Renovated Butter 271

- Extent of the Industry ■. 271

• The Processes of Manufacture 272

Melting 272

Refining the Oil 273

Making the Emulsion 273

Crystallizing the Fat 273

Working and Salting 274

\ Extracts from U. S. Laws Relating to Renovated Butter 274

^ Test for Renovated Butter 276

CHAPTER XXXII. Origin of Oleomargarine 277

The Original Process 278

Developments in the Industry 278

Manufacture of Oleomargarine 279

Formulas Used 281

Quantity Produced 284

Food Value 284

Oleomargarine Law 286

Detection of Oleomargarine 287

CHAPTER I. MILK — rrS PROPERTIES AND COMPOSITION

What is Milk? — According to the government standard, " Milk is the lacteal secretion obtained by the complete milking of one or more healthy cows, properly fed and kept, excluding that obtained within fifteen days before and five days after calving.''

Milk is a fluid secreted by females of the mammalian group for the special purpose of providing their yoimg with a proper food. It is a watery solution of milk sugar, albumen and mineral salts, containing casein and fat in suspension.

. The only milk of great commercial importance to man is that of the cow. Unless otherwise specified, therefore, the word " milk " always refers to the product of the cow.

Properties of Milk. — Milk ranges in color from a bluish white to a golden yellow, depending upon the breed of the animal, the food consumed, and the season of the year. It appears completely opaque when in large quantities, but in thin layers is slightly transparent. When freshly drawn it possesses a characteristic odor. This animal odor is very volatile and soon escapes from the milk, if left exposed to the air. The flavor of milk is slightly sweetish. Fresh milk has an amphoteric reaction, turns red litmus paper blue and blue litmus paper red. This reaction, so far as known, is due to the presence of phosphates in the milk. Fresh milk, however, appears acid to phenolphthalein, and when titrated with tenth-normal alkali shows an apparent acidity of from o.io to 0.14 per cent. This acidity is imdoubtedly due to the presence in the milk of phosphates, citrates, casein and carbon dioxide.

The viscosity of milk is greater than that of water. It is increased by age, low temperature, products of fermentation and a high solid and fat content. The viscosity of milk is decreased by high temperature, a low solid and fat content and certain fermentations.

Milk possesses a certain adhesive property. It sticks to wood, glass and metals to a greater degree than does water. A paper moistened with milk or cream makes a label that will stick to any dry object. A similar paper moistened with skimmed milk has less adhesive power. The adhesive property of milk is in part dependent upon the nitrogenous matter. This fact is made use of in painting and whitewashing. The addition of milk causes the paint to adhere better. When milk is allowed to stand at room temperature, it imdergoes fermentation; lactic add is formed and the milk becomes thick and curdled. The curdling of milk may be produced by the addition of any dilute add. If the milk thus curdled is neutralized with an alkali, such as lime water, ammonia or potash, the curd is redissolved. Milk may also be curdled by rennet or pepsin, and the curd thus produced cannot so easily be redissolved by weak alkali solutions.

Milk is slightly heavier than water; its specific gravity varies from 1.029 to 1.034 at 60° F.

MILK — ITS PROPERTIES AND COMPOSITION 3

The specific heat of milk is less than that of water; that is, it requires less heat to warm a definite amount of milk one degree. It also takes less ice to cool a certain volume of milk one degree than it does to cool the same quantity of water one degree. The specific heat of milk is, according to Fjord, 0.94; the specific heat of cream is about 0.7, depending upon the percentage of fat it contains. Rich cream has a lower specific heat than poor cream.

The maximum density of milk is not, like water, at 4° C. (39.2° F.), but at about 32.9° F. The boiling point is a trifle higher, and the freezing point a trifle lower than that of water.

Composition of Milk. — Probably no other food found in nature, except meat, is subject to such great variation in composition as is milk. The average composition of American milk, according to Babcock,^ is:

Albumen 53

Ash 71

The milk of individual animals varies from day to day, and varies as the period of lactation advances. However, the mixed milk from a large herd is not subject to very great variations, but the milk of one herd may differ greatly from that of another herd, due to the breed of the cattle. The constituents subject to the greatest variation are the fat and casein. The following table ^ shows this:

^ Farrington and WoU — Testing MUk and Its Prodttcts. * Van Slyke — Science and Practice of Cheese Making.

Breed.

Holstein. .

Ayrshire.

Shorthorn Devon. . .

Guernsey.

Jersey fat.

3 26

3.76 4.28 4.89

5.38 5.78

Percent casein.

2.20 2.46 2.79

3 10 2.91

3'OS

Per cent total solids.

11.80

12. 75 14.30

14.50 14.90

15.40

Milk from one dealer may contain 25 per cent to 40 per cent more nutrients than milk from another dealer, but in the same locality the consumer usually pays the same price for both.

Chapter II. Normal Milk And Its Products As Food

Food is any substance taken into and used in the body for the purpose of building new tissues and repairing the old, and for supplying the body with heat and energy. The best foods are those which produce the best physiological results with the least amount of waste. They must be hygienic, digestible, palatable, furnish the nutrients needed by the system in proper amoimts and be reasonably cheap.

Milk, properly produced, is a food having all these requirements.

There are three chief classes of nutrients necessary to maintain the human body:

1. Fats, sugars, starches and cellulose. These are the chief food elements that produce energy, fat and heat in the body. Cellulose and starch are not found in milk. The sugar and fat are the most important ones. They are foimd in milk in sufficient and proper quantities to supply the body.

2. Proteids. These chiefly produce the muscles, tendons and hair. They are also to some extent producers of energy. Good examples of the proteid group are casein and albumen found in milk.

3. Mineral foods. The chief of these are phosphates, chlorides and other salts, calcium, potash and soda, with small quantities of iron and magnesia. They chiefly produce the bones of the body.

Milk contains iron and phosphorus in sufficient quantities to supply the needs of a growing individual. These minerals are specially needed during the period of cell and tissue building, the nucleus of the body cell being rich in iron and phosphorus.

The water in milk is also essential to the body. Milk contains enough water to supply the body, providing the body is at rest and no dry food other than milk is consumed.

The nutritive ratio of milk is about i: 4. While this ratio is a Kttle narrow, the proportion of the different components is nearer perfect than in any other single food.

Pure, sweet and wholesome milk as a food is preferred to any other natural food, that is, food not prepared by man. Originally the milk from cows was utilized solely for their yoimg. Owing to man's skill in selecting and breeding, the qualities of dairy cows and their products have been regulated and developed to such an extent that the cow's milk serves in a large measure as a food for man. The specialized dairy types produce large quantities of milk, and the richness of the milk can be regidated by making the proper selection of cows.

Milk cannot be said to be a perfect food for adults, because, in the first place, milk contains too large a per cent of water. As a consequence, too much bulk (8 to 11 lbs. daily) would have to be consumed to obtain the necessary nutrients. Secondly, there is a trifle too large a percentage of protein in milk in proportion to the fat and carbohydrates (1:4). Thirdly, the milk nutrients, not including water, are too concentrated or condensed. A certain amount of bulky food is generally admitted to be necessary to the best digestion and health of a person or animal. Fourthly, a digestive system, receiving no other food than milk, is eventually likely to lack in development, because of being imaccustomed to handle other foods, digested with greater difficulty; just as the muscles of an idle person, or one who does little work, are likely to become soft and weak. Milk as a food for adults is most effective when used in conjunction with other foods.

The present extensive and increasing use of milk as a food is due chiefly to five things:

1. Fresh milk, properly produced and handled, is

palatable and relished by most people.

2. All the chief classes of nutrients (proteids, carbo-

hydrates and fats, and minerals) necessary for the development of the animal and human body are present in such proportions as to render milk most serviceable as a food.

3. The food constituents are present in milk in such

form as to make them easily digestible.

4. Milk is a cheap food.

5. Milk is a food already prepared by nature.

Palatability of Cows' Milk. — The palatability of milk is due to the fact that the different components of milk are present in such a proportion as to produce a flavor suitable to the majority of people. It is a general principle, that the more volatile and soluble a substance is, the more easily it can be detected by the senses of taste and smell. Some of the natural flavoring substances in milk, though present in very small quantities, are volatile and soluble at a low temperature, so that when warmed in the mouth the flavor is quickly detected. Milk, in order to have its best flavor, should be produced from healthy cows, fed on food that will impart the best flavors, such as well-cured, good, sweet hay, grain, ensilage or roots in winter, and grass in summer. Milk is best for direct consumption as soon as possible after it is drawn and cooled. In case of specially fermented milks this does not apply. On standing, milk undergoes fermentation and decomposition. The extent to which these changes occur depends upon the temperature at which milk is kept and upon the number and kinds of germs in the milk. If milk and other dairy products are kept, they should be held at a low temperature. Unpalatable and other abnormal milk will be mentioned later.

Digestibility of Milk. - Milk, generally speaking, ranks high as a digestible food; but in this connection it should be stated that the digestibility of cows' milk varies. First, it varies according to the condition of the milk (whether fresh or old, whether adulterated or not), and according to the composition of the milk. Secondly, the digestibility of milk varies according to the power of digestion of different persons. Thirdly, its digestibility varies according to the amount consumed, and whether it is taken with other foods or not.

When milk is consumed, it passes first into the stomach, where the acid and pepsin in the gastric juice curdle and dissolve it. When milk is consumed in large quantities at a time, without the addition of any other food, the curd or casein may gather in lumps. In this condition the gastric juice digests it with difficulty. Abnormal fermentation may set in and cause sickness before the digestive juices have a chance to bring the normal digestive changes about. This condition is especially common with infants and with adults having a weak digestive system.

Human milk curdles differently from cows' milk. The former contains less casein than the latter, and the casein is probably combined with the mineral salts in a different manner. The casein of human milk is separated and more flocculent when curdled. In this condition the digestive juices attack it with greater ease.

Pasteurized cows' milk coagulates into a more flocculent or separated curd than does raw milk.

Raw vs. Heated Milk. — The effect of heat upon the digestibility of milk is a matter that the best authorities do not agree upon, though it has been the subject of considerable investigation. Heating milk to a temperature sufficiently high for efficient pasteurization partly renders the calcium salts insoluble and may partly coagulate the lactalbimiin. But since investigators obtain diJBferent results in their work, it seems evident that the ease of digestibility of heated milk cannot differ greatly from that of raw milk. And, as will be shown later, the pasteurization of average city milk is beneficial.

Use of Milk with Other Foods. — In a series of digestion experiments conducted by Professor Harry Snyder at the Minnesota Experiment Station, various foods were used at different times, milk constituting in many cases a considerable part of the diet. One fact of great practical importance brought out by this work was that the various foods showed a higher digestibility when milk was included in the diet than when fed alone.

The food components inay undergo many different changes in the digestive tract, depending upon the person and the conditions and demands of the person's system. The complex cleavage and synthetic changes of digestion and assimilation, especially during the end processes, are imperfectly understood.

When the digestibility of the components of milk is compared with that of other food. substances, milk ranks among the most digestible of all foods.

According to experiments, cows' milk contains 3.6 per cent proteid, of which 3.48 per cent is digestible. It contains 4.9 per cent carbohydrates, of which 4.7 per cent is digestible. It contains 3.7 per cent fat, of which 3.7 per cent is digestible.

Relative Cost of Milk. — The place of milk in the diet, its use as a substitute for other foods and the relative value of the nutrients it contains, as compared with the cost of nutrients in other foods, are not generally realized. Some investigations were made at the University of Maine,^ in which the effect of quantities of milk was tried at the xmiversity boarding house. From this investigation the following conclusions were drawn: i. An abimdant supply of milk in the dietary decreased the cost without decreasing the acceptability of it to the consumer. 2. The increased consumption of milk increased the proportion of protein in the diet. 3. The consumption of large quantities of milk was accompanied by a decreased consxmiption of other foods. 4. Milk is not a luxury but an economical food that might be more widely used as a means of improving the character of the diet and of reducing the cost of animal foods.

One quart of milk (2 lbs.), and three quarters of a pound of moderately fat beef, such as sirloin, contain about the same food value,^ but we pay different prices for them. Milk is the cheaper and comes the nearer to being a perfect food. One might live on beef alone, but it would be a one-sided diet, while milk is more nearly a balanced ration.

1 U. S. Dept. of Agr., Office of Exp. Sta. Bid. 37. * U. S. Dept. of Agr., Farmers* Bid. No. 23.