The analysis of average milk is about as follows:
Since the fat is the most valuable portion commercially, dairymen study to feed their cows in such a way as to increase it, and in some instances milk has been produced containing 6 per cent of fat.
Though mainly water, milk is a valuable nutritious food and should be used freely by itself and in combination with other food materials, in soups, sauces, and puddings. When we remember what the department of agriculture has proved for us, that a quart of milk is quite as nourishing as a quart of oysters for which we pay six or eight times as much, we can see that it is desirable to use it more freely than is generally done. Especially during the summer months we do well to substitute milk and cheese for meats. There are average families which do not use over a pint of milk a day; there are others who find it necessary to take a gallon, and the meat bill in the latter cases becomes proportionately small. A pint of milk a day is not an excessive allowance for each member of a family, though many households consume much less.
To study the composition of milk put a quart of fresh milk in a glass jar and leave it twenty-four hours or longer until it is thick and sour. What percentage of the whole is the cream? Remove the layer of cream on top to another jar, screw on the top, and shake until the fat separates from the watery portion of the milk. Collect the butter on a spoon, wash out the milk by pressing and folding with a knife. Weigh or estimate carefully the value of the butter obtained. What proportion of the original bulk of milk does it represent? Persons fond of unsalted butter may thus prepare it for themselves.
Why is salt added to butter?
The remainder of the milk, now a thick mass of curd, may be pressed out with a spoon or cut with a knife to show the greenish water known as whey. What nutritive substances are there in this?
Turn the thick milk into a two-quart pan and fill with hot water, in twenty minutes drain the water off through a strainer, that no curd need be lost, and pour on more hot water. Do this several times until the curd loses its sour taste and has contracted, but do not allow it to become too hard. If boiling water is used the curd will become unpalatable and indigestible.
Compositi of Milk
Buttons have been made of sour milk treated by heat and pressure.
Press as much water as possible from the curd and compare the quantity with the original amount of milk. Remember that this still contains much water. Now combine the curd with butter or thick cream, salt it and shape in small balls or pack in cups. Thus we learn something of the value of milk and have made a sour milk cheese more palatable than when the whole mass of curdled milk is heated on the stove or strained in a cloth.
With prepared rennet in liquid or tablet form the curd and whey of sweet milk may be separated. The milk should be warmed slightly before the dissolved rennet is added, then chilled in the dishes from which it is to be served. This is known as junket or rennet custard.
Absolute cleanliness is essential for every utensil to come in contact with milk. The souring of the milk is due to the action of bacteria which come to it from contact with utensils and the air. Its fluid form and nutritive material afford a medium peculiarly favorable to the development of germs of disease, as well as to the growth of useful bacteria which aid in butter and cheese making.
The growth of such micro-organisms is hastened by moderate heat, but most of them are killed by raising the milk to the boiling point.
Sterilization requires a temperature of two hundred and twelve degrees F, continued for about twenty minutes; this process usually changes the flavor of the milk so that it is disagreeable to many palates. The high temperature also causes the fat globules to separate instead of being retained in the form of cream.
Pasteurization takes its name from the noted French scientist, and consists in raising the milk to a temperature of about one hundred and fifty-five degrees F. By this means the flavor of the milk is unchanged.
The cook finds it safe to scald the milk for soups, bread, or puddings, to prevent its souring during the process, before cooking it with the other ingredients. There is a gain in the time of cooking when the milk-is heated while the other materials are being prepared.
A bit of bicarbonate of soda dissolved in milk before it is heated often will neutralize any incipient acidity and make it usable for puddings or soups. The "cream" of tomato soup is liable to curdle unless the acid of the tomato is neutralized by soda or the milk thickened with flour before the two parts are combined. It is safer with all "cream" soups to keep the stock and thickened milk apart until just before using.
Lemon or other acid fruit juices are sometimes mixed with milk for sherbet without curdling if, before the juice is added, the milk is thoroughly chilled in the freezer can.
To Prevent Souring
Mixing with Acid
Salt sometimes curdles milk, especially when it is added to hot milk.
Since the solid portions of milk readily adhere to the bottom of the saucepan placed in direct contact with heat, and the resulting burned flavor rapidly penetrates the whole of the milk, a double boiler or its equivalent, one dish set in another of boiling water, is the best way to heat milk.
Milk is an important ingredient in preparing cocoa and chocolate, and such beverages rank with soup in nutritive value. Hot milk sipped slowly is a simple remedy for exhaustion and sleeplessness. Hot milk should be served with coffee when cream is not available. The milk soups are valuable foods and have as their foundation the white sauce described further on.
Most of our puddings require milk, especially the cereal and custard varieties.
Because there are solids in the milk more time must be allowed for the grains of rice or corn meal to absorb the moisture than when cooked in water. The protein portions of the milk have somewhat the same effect as the egg used to coat the croquette or oyster before frying. If the particles of grain are thus varnished over they cannot absorb moisture as rapidly as from clear water. Hence, it is often advisable to cook the grains in water first and finish the process in the milk.
In making blanc mange from Irish moss, if the moss is first cooked in a small quantity of water and the thick paste strained before it is added to the milk, there is no loss of milk. When the moss is cooked directly in the milk there is some loss of milk when the moss is strained out.
The baked Indian meal pudding and the creamy rice pudding require long, gentle baking. There is a continual evaporation of moisture from the surface of the pudding pan, and really a condensing of the milk. In proportion as the pudding dish is refilled with milk, the pudding increases in nutritive value.
Milk is commonly used for mixing dough of many types and this adds to the nutritive value of bread and cakes.
Bread made of milk or part milk will have a browner, tenderer crust than bread made wholly with water. There seems to be good ground, however, for the prevalent idea that bread or cake made with milk does not keep so well as that made with water. A certain cheesy flavor develops where milk is a principal ingredient.
Sour milk is often used for mixing griddle cakes and quick doughs, because the acid it contains will be neutralized by the soda added, and thus produce the effervescence which makes the dough light. The souring process seems to have so affected the protein substances in the milk that such a dough is tenderer than one made with sweet milk and baking powder. The use of sour milk will be further treated in the section on doughs.
For doughs, soups, and puddings, in which additional fat is introduced, skimmed milk may be used as well as full milk.
The use of cream in well-to-do families is increasing. Whipped cream is demanded as a garnish or sauce for many desserts quite complete in themselves.
The process of beating or "whipping" cream gives it an attractive appearance, and by expanding its particles probably makes it more digestible.