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Exercise IX

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MILK.

Cows have been found to give more milk of a good quality for a given amount of feed and care than any other milk-giving animal. For this reason, wherever the climate is suitable, cow's milk is used almost exclusively. In some parts of the world other kinds of milk are used-goat's milk in the hilly districts of Europe, llama's milk in South America, the milk of the buffalo in India, mare's milk in Russia and camel's milk on the deserts, while in the Arctic regions they usually use the milk of the reindeer. Two-thirds of all the milk produced in the United States is used for butter and cheese. In the year 1903 there was enough milk and cream sold in the United States to have furnished every man, woman and child with thirty gallons. It has been estimated that milk and cream together furnish sixteen per cent of the total food of the average American family. Every child should take in some form a quart of milk a day throughout the period of growth.

MILK Composition.

As milk is the sole food of the young of mammals for a length of time varying from a few weeks to several months, milk, like the egg, must contain all the food elements necessary to sustain life. All milk is made up of protein, fat, sugar, water and mineral matter but there is quite a difference in the proportion of each ingredient found in the milk from different animals. Even the milk of the same animal will differ greatly at different times.

Average composition of cow's milk:

Water 87.0% Protein (casein and albumin) 3.3% Fat 4.0% Carbohydrates (milk sugar) 5.0% Mineral matter .7% While milk is a perfect food for the young animal for which it was intended, the various ingredients are not in the right proportion to form the only food of an adult. There is not enough carbohydrate to furnish the required amount of energy and there is so much water that it would be far too bulky a food for a grown person. Taken with carbohydrate foods, however, it forms a valuable addition to the diet. The fat of milk is in the form of little globules floating in the milk. These fat globules being lighter than the rest of the milk, rise to the top, forming the yellowish layer known as cream. There is always some milk mixed with the cream and by the process of churning the fat globules are made to separate from the milk and stick together in the form of lumps of butter. Skim milk (milk from which the cream has been removed) deserves a more important place in the daily dietary than is usually given it. It contains all the constituents of the milk except the fat and a small per cent of the protein and can usually be substituted for whole milk in cooking. In the cities we generally pay almost as much for cream as we should have to pay for the whole milk from which the cream was taken. It would therefore be economy to buy the whole milk, remove the cream and have the skim milk left to use about the cooking. Casein and albumin are the two kinds of protein found in milk. Casein is the more abundant and forms the greater part of the curd of milk used in making cheeses of all kinds. The albumin is more soluble and will be found in the watery portion of the milk after the curd has been separated from it. The casein can be made to separate from the milk by adding an acid as in the case of the natural souring of the milk or by the use of rennet, a digestive fluid taken from the lining of the calf's stomach.

The whey, after it has been separated from the curd contains the water, sugar, albumin, most of the mineral matter and a little of the fat. While the per cent of food material contained in the whey is small, it is sometimes used for invalids and persons of weak digestion. If the white of an egg be dissolved in it and fruit juice added for flavoring it makes a nutritious and palatable food that can sometimes be taken when whole milk could not be digested.

Milk sugar is not so sweet as cane sugar and is more easily digested. It occurs in quite a large quantity and is an important commercial product of milk. It should always be used in preparing modified milk for babies. Cane sugar is not a substitute for it. In the natural souring of milk, certain bacteria, called lactic acid bacteria, get into the milk from the air and change some MILK of the milk sugar to an acid. This acid gives the sour taste to milk and also causes the casein to separate from the whey. Bacteria work faster when kept slightly warm (from 80° to 100° F.). For this reason we warm the milk in making cottage cheese, so that the curd will separate from the whey more quickly.

The mineral matter is more abundant in milk than in most of the common foods. Lime salts, so necessary in building bone, is one of the most important minerals found in the milk. Care of Milk.

Milk and butter absorb odors and impurities readily. They should be kept in covered dishes in a cool, clean place. Milk dishes should be used for milk only. They should be scalded and then turned upside down to drain and cool before the milk is put into them.

Milk almost always contains bacteria of many kinds. "The amount of bacteria in milk of a given age varies with the conditions; that from clean, healthy cows, with freshly washed udders, milked into well-scalded pails, in a clean place, free from air currents, by persons with clean hands and clothes, if quickly cooled and carefully handled may contain very few, while milk from ill-kept animals, untidily handled in a dirty place may contain enormous quantities." Farmers' Bulletin No. 363.

These bacteria may be killed by sterilization. This process however, changes the taste of the milk and makes it less digestible. Pasteurization does not injure the milk as much but it only partially destroys the bacterial life in the milk. The wisest plan is to use milk that you know comes from a perfectly sanitary dairy. In case this cannot be procured, pasteurize the milk at home until you can obtain clean raw milk. ** Pasteurized Milk. 1. Put milk into scalded bottles. 2. Cork the bottles with cotton that has been baked in the oven until a light yellow. 3. Put an inverted, perforated pie tin in the bottom of a pail or kettle and set the bottles of milk on the tin. 4. Fill kettle with cold water until it reaches the top of the milk.

MILK 5. Heat the water to 160° F. or until small bubbles appear on top of the milk next to the glass. 6. Remove from the stove, cover kettle and let stand for twenty minutes. 7. Take bottles out of hot water and cool in water. Have water slightly warm at first so as not to break the bottles. Keep adding cold water until the milk is cold, then place in ice box until ready to use. Do not remove the cotton stoppers until you are ready to use the milk.

Sterilized Milk. 1. Put milk in clean granite kettle and bring to full boil. 2. Cover tightly and let stand a few hours. 3. Repeat this process three times, then put milk into sterilized bottles and cork with sterilized cotton.