It requires two pounds of milk to furnish as much ' nutriment as is found in three-fourths of a pound of beef of good quality. Six ounces of bread supplies an equal amount of nutriment, but the nutritive value of the given amounts of the three are not exactly the same. According to the latest advices on the food value of milk, it would make a better single food than meat, because the nutrients are more nearly in the right proportion, but it is not adapted as a single food for man. The proportion of water to solid material is so great that a very large quantity would have to be consumed to obtain the required amount of solid matter. There is too much protein for the fats and carbohydrates present. Milk is a perfect food only for the young of the animal of its own species. Cow's milk is a perfect food for the calf, but not for the human infant. There are certain diseased conditions in which milk alone is considered the best food for a time, but this should not be continued after the digestive organs are strong enough to make use of other foods with it. There is a law of nature to the effect that an organ which is not used, or which is misused, shall either cease to exist, or lose its power. Milk is ordinarily digested in the upper part of the digestive tract, and should have used with it some of the grain foods, beans, cheese, and other foods which are digested largely in the lower part of the digestive canal. Cattle thrive better on a ration containing some hay, than one consisting of grain alone. The same necessity, to a less degree, exists with man. The digestive tract needs a certain amount of bulk in the food to keep all the digestive organs employed, and to produce healthy action.
References: U. S. Dept. Agr., Farmers' Bulletin No. 74, pp. 9-21;
Milk is very valuable in the culinary art, both because it gives greater food value, and because it increases the palatability of many dishes. When milk instead of cream must be used in coffee, hot milk will give a better flavor than cold milk, and leaves the beverage hot. Stewed onions have a less decided and consequently better flavor when served with milk dressing. Bread has a greater food value when milk is used in making it. The sauces in which milk may be used are very numerous, and in each case it embellishes the dish with which it is used, and gives it additional nutriment. For most persons milk is the best-known beverage. The following are, in sub-stance, the conclusions drawn from an experiment made in the boarding hall of the University of Maine, in which the object was to ascertain the effect of a limited and unlimited supply of milk:
"(1) The dietaries in which milk was more abundantly supplied were somewhat less costly than the others, and at the same time were fully as acceptable. (2) The increased consumption of milk had the effect of materially increasing the proportion of protein in the diet. (3) The milk actually supplied the place of other food materials, and did not, as many suppose, simply furnish an additional amount of food, without diminishing the quantity of other materials. (4) The results indicate that milk should not be regarded as a luxury, but as an economical article of diet, which families with moderate incomes may freely purchase as a probable means of improving the character of the diet, and of cheapening the cost of the supply of animal food."*
*U. S. Dept. Agr., Office Exp. Stations. Bulletin No. 37.
Whole milk is more palatable than skim milk, but there is practically no difference in the amount of muscle-forming material in the two. Milk has three and three-tenths per cent., of protein; lean meat contains about thirteen per cent, of protein. Prof. Atwater says there is about the same amount of actual nutritive materials in the protein of the two. The nutrients differ both in number and kind in the two foods.
Milk contains a large percentage of water. This holds some of the solids in solution, and aids in their assimilation by carrying them to the tissues of the boay. The microscopic fat globules of milk are merely held in suspension, they are lighter than other parts of the liquid. When milk sets in a cool place, they rise to the surface in the form of cream, as little wooden balls would rise to the surface of water.
Cream contains practically all the butter fat of the milk, if it has been carefully separated. It contains also some milk, more when hand-skimmed than when removed by the separator. Cream is valuable largely for its heat-giving properties. Cream and butter are not economical sources of fat, but their delicious flavor makes many other foods so much more palatable that they are highly prized as food materials.
The value of milk is usually gauged by the amount of fat it contains. The reason for this is, there are so many things which cause the amount of fat to vary, such as the change of weather, method of handling, etc. The milk of different breeds of cattle varies greatly in composition. With regard to this subject, Prof. Voorhees says:
"The influence of breed is very marked; so much so that dairy breeds are classified into milk and butter breeds, that is, those which give a large quantity of poorer quality, and those which give a smaller quantity of higher quality. With the improvement of the stock by the introduction of recognized butter producing breeds of cows, the quality of the product materially improves. Milk which is rich in fats is more apt to be rich in other nutriments, and vice versa. The most common adulterations of milk reduce the fat either by skimming or by adding water."
The farmer has another reason to be thankful that he need not depend upon the market for milk. The variation in composition of pure milk is so great as to make it possible to pay very much more for the nutrients in one quart of milk than another at the same price per quart.
"The carbohydrate of milk is in the form of milk sugar. This is a white powder of low sweetening power. It resembles cane sugar in chemical composition, but is much less soluble. When milk sours, some of the sugar is changed to lactic acid, which has the effect of coagulating the casein. When about eight-tenths of one per cent, of acid has developed, fermentation ceases, so that the sour milk may still contain much of the original milk sugar, but sour milk is often injurious to the digestive organs, and the value of the remaining nutrients may be much reduced. In each one hundred pounds of milk there are about seven-tenths of a pound of mineral matter, chiefly phosphates and chlorides of potash, soda, and lime.
"Milk is probably the most susceptible of all foods to contamination from its surroundings. It is also admirably adapted for carrying dirt and disease into the human system. People living in towns and villages must trust to the vigilance of inspectors and the honesty of the dairymen for a supply of pure milk. The farmer who understands the best methods of feeding and handling cows, and knows the necessity of absolute cleanliness in caring for all utensils used about the milk, as well as the place of keeping it, is in little danger of the many evils which have their source in the milk supply of the city.
"The sources of contamination of milk are very numerous. In ill-ventilated barns there will be dust from the hay floating in the air, ready to enter the freshly drawn milk. During the milking, dust and dirt are brushed from the under side of the cow's body. The hairs which find their way into the milk often carry large numbers of germs. When milk stands, a sediment often collects in the bottom of the vessel, which can be credited to nothing but the carelessness of the milker. Unless the milker makes a cleanly toilet before beginning the milking, dirt from his hands and clothing is apt to enter the milk. Thorough cleaning of all milk vessels with pure water is always very essential. Impure water may affect the milk very much, and bacterial contamination is often carried into the milk when it is diluted with water. After the milk enters the house, it must be kept in a cool, well-ventilated room, or it will be further contaminated." +
Conn says: "Practically all fresh milk contains bacteria. It is possible in some cases to obtain milk which is free from them, but it is very difficult. In spite of cleanly methods, sterilized vessels, and the greatest care to prevent dirt and dust entering the milk, in the majority of cases some bacteria are present."
The most rigid cleanliness usually prevents the introduction of any harmful organisms. Vaughn believes "ty-rotoxicon may originate in milk of long standing in closed vessels, owing to putrefactive changes which are due to minute organisms. The introduction of these organisms into milk hastens putrefaction, and consequently the formation of ptomaines. Milk from cows kept in filthy stables is likely to undergo speedy putrefaction, and poisonous germs may also adhere to the sides of any vessels which are not kept absolutely clean."*
When milk stands a few hours, if it is in its normal condition, it undergoes what is known as lactic fermentation. In sour milk, some of the sugar has been changed to lactic acid, the food value of which is probably less than that of the sugar which the milk contained previous to souring. Buttermilk has about the same food value as skim milk, unless much water has been added in the churn. "The acid-forming species of bacteria are of the greatest importance of any of the numerous species found in milk. The bacteria which produces slimy fermentation sometimes causes much trouble in dairies, as slimy milk produces no cream, and is useless for all ordinary purposes. There is a fermentative process which produces what is known as 'blue milk.' When growing in ordinary milk, the effect of this organism is very marked. For a few hours no change is noticed, but just about the time when the milk begins to become acid, some intense blue patches make their appearance. The faster the acid forms, the quicker the coagulation appears, and the smaller are the blue patches; while if the acid is produced more slowly, the blue patches are larger and of better color. There can be little doubt that the cause of blue milk is always some unknown source of filth. Blue milk is always an infection due to outside contamination, and its remedy is always to be found in care and cleanliness.
+ U. S. Dept. Agr., Office Exp. Stations Bulletin No. 25.
* Ptomaines and Loucomaines, Vaughn.
"A consideration of the subject of souring of milk would not be complete without reference to the effect of electricity. The popular belief that thunder storms will sour milk is so widespread that it would seem as if there must be some foundation for it. It has been asserted by many that the ozone produced in the air by electricity causes the milk to sour. In experiments in which electric sparks were discharged over the surface of milk, however, little or no effect has been produced upon it. The conclusion is that electricity is not of itself capable of souring milk, or even of materially hastening the process. Nor can the ozone developed during the thunderstorms be looked upon as of any great importance. It seems probable that the connection between a thunderstorm and the souring of milk is one of a different character. Bacteria grow more rapidly in the warm, sultry conditions which usually precede a thunderstorm, and it frequently happens that the thunderstorm and the souring occur together, not be*U. S. Dept. Agr., Farmers' Bulletin No. 29; also, Farmers' Bulletin No. 9.
cause the thunder has hastened the souring, but rather because the climatic conditions which have brought the storm have at the same time been such as to cause unusually rapid bacterial growth. This fact has been verified by many experiments, which have shown that, without the presence of lactic organisms, there can be no spontaneous souring of milk,
"Milk deprived of bacteria will keep sweet during thunderstorms. Dairymen find no difficulty in keeping milk, if it is cooled immediately after being drawn from the cow, and is kept cool. Milk submerged in cool water is not affected by thunderstorms. Dairymen find that during 'dog-day' weather, even when there is no thunder, it is just as difficult to keep milk as it is during thunder-storms ; and they also find that thorough cleanliness in regard to the milk vessels is the best possible preventative against souring milk during a thunderstorm. It is safe to conclude, therefore, that in all cases it is the bacteria which sour the milk, and if there seems to be a casual connection between the thunder and the souring, it is an indirect one only. Climatic conditions have hastened bacterial growth, and have also brought on the thunder-storms. The same conditions would affect milk in exactly the same way, even though no thunderstorm were produced, and this effect, our dairymen tell us, is frequently observed during the warm, sultry, autumn days."
There are various drinks made from milk, among which are koumiss and matzoon. For many generations the nomadic tribes of Tartary have prepared koumiss from mare's milk. In recent times it has been prepared in America from cow's milk by the use of small quantities of yeast and sugar, keeping the milk at the temperature necessary for the best results. It is considered a valuable liquid for invalids in some cases. Matzoon is another milk preparation made by the addition of a ferment. Condensed milk is prepared by cooling the milk to
60° F., then quickly heating to a temperature of 185° F., at which point the water is evaporated. The temperature is not allowed to fall below 1600 F. until the bulk is reduced to about one-fourth its original volume. If sweetening is used it should be added at this time. There is also an unsweetened condensed milk which is claimed to be thoroughly sterilized. The article known as "evaporated cream" is simply milk evaporated to a creamy consistency.
The fuel value of skim milk is only about one-half that of whole milk on account of the loss of the cream. Experimenters have found that skim milk contains nearly all the muscle and bone-forming elements of the original milk, as well as nearly all the milk sugar. One can buy as much energy-giving food for a certain amount of money in skim milk as in whole milk, because the loss of fat in the skim milk is balanced by the greater number of pounds available for the same money, giving more sugar, and both are energy-producing foods. In buying whole milk, one would pay twice as much for an equal amount of muscle-forming food as in skim milk.
It is wise to use skim milk freely in preparing many foods for the table, in families where there are little children, not only on account of its use rendering the food more palatable, but because the albumen and casein of the milk are excellent materials for the production of muscle in young and growing children, and the mineral matter is very useful in forming a solid framework for the body.
"In one hundred pounds of skim milk there are about three and one-half pounds of casein and albumen. When we take into consideration the large amount of water in both skim milk and buttermilk (eighty-seven per cent in skim milk, and ninety per cent in buttermilk), this is a relatively large amount of muscle-forming material. After removing the water from one hundred pounds of stem milk, there will be left about nine and three-fourths pounds of solid matter, of which three and one-half pounds are casein and albumen, five and one-fourth pounds are milk sugar, a little more than three-fourths of a pound is ash, while the remainder is composed of fat and traces of other constituents."*
* Minn. Farmers' Inst. Ann. 1896, No. 9, pp. 66-68.
* Monrad's New Edition of "Pasteurization and Milk Preservation."