1. As is well understood, milk is the liquid that is secreted by the
mammary glands of female mammals for the nourishment of their young. The
word milk as it is commonly used, however, refers to _cow's milk,_
because such milk is employed to a greater extent as human food than the
milk from any other animal. Cow's milk in its perfectly fresh raw state
is a yellowish-white, opaque fluid, called _whole milk,_ and, as is well
known, possesses a distinctly sweet taste and characteristic odor. When
such milk is allowed to stand for some time without being disturbed, it
separates into two distinct layers, an upper and a lower one. The upper
layer, which is lighter than the lower one and occupies a smaller space,
consists largely of globules of fat and is called _cream;_ the lower
layer, which is white or bluish-white in color and is composed of water,
solids, and protein, is, when separated from the cream, called
_skim milk._
2. As an article of diet, milk is very important, because its sole
function in nature is to serve as food. It is required by the infant; it
is needed in the diet of all growing children; and it is desirable in
the preparation of dishes for both young and old.
Milk is used to such a great extent because it fills many of the
requirements of an ideal food. It is generally liked, requires little or
no time for preparation, agrees with the majority of persons when used
properly, and contains substances that supply energy and build and
repair tissue. Still, it does not contain these substances in such
proportions as to make it an ideal or exclusive article of diet for
adults, and it must often be modified to suit the needs of infants,
because it is ideal for only the young of the species for which it is
intended. Therefore, while milk is often called a perfect food, in
reality it is perfect for only the calf. When it is desired for the
feeding of a very young child, it must be changed to meet the
requirements before it can be used with good results.
3. So important is milk as an article of food that, outside of the
purely rural districts, producing the milk supply is a business of
considerable importance. This is due to the fact that the purity of milk
must be constantly safeguarded in order that clean, safe milk may be
provided for the countless numbers that depend on it. In fact, milk
undoubtedly bears a closer relation to public health than any other
food. To produce an adequate amount of clean, safe, pure milk is one of
the food problems of the city and country alike. In the city much of the
difficulty is overcome by the ordinances that provide standards of
composition and cleanliness, as well as inspection to insure them; but
such ordinances are rarely provided for in villages and country
districts.
When there is no law to prevent it, unclean milk is sometimes used in
the manufacture of butter and cheese, but when this happens, great
injustice, if not positive harm, is done to the consumers of these
articles. Then, too, unless milk is carefully inspected, tubercular milk
is liable to be used in the making of butter, and such a condition will
cause the spreading of tuberculosis as readily as the use of the
contaminated milk itself.
4. With its various products, milk helps to form a very large part of
the dietary in most homes, but while nothing can take the place of this
food and while it is high in food value, there seems to be a general
tendency to think of it as an addition to the bill of fare, rather than
as a possible substitute for more expensive food. For instance, milk is
very often served as a beverage in a meal in which the quantity of meat
or other protein foods is not reduced. From an economical standpoint, as
well as from the point of view of the needs of the body, this is really
extravagant, for milk is itself largely a protein food. The serving of a
glass of milk or of a dish that contains generous quantities of milk
offers the housewife an opportunity to cut down considerably the
allowance of meat and eggs. Because of this fact and because milk and
its products may be used to add nutritive value to a food, to give
variety, and to improve flavor, they deserve considerable study on the
part of the housewife.
5. Since milk may be used in such a variety of ways, it may be easily
included in the dietary for the family. Being liquid in form, it may
always be served without any preparation as a beverage or with other
beverages, cereals, and fruits. It also has numerous other uses, being
employed in the making of sauces for vegetables and meats, in the place
of stock for soups, and as the liquid for bread, cakes, puddings,
custards, and many frozen desserts. Because of its extensive use, every
housewife not only should know how to buy milk and care for it, but
should be familiar with its composition, so that she may determine
whether or not it suits the needs of her family. In addition, she should
know the effect of heat on milk and the various methods of preparation
if she would be able to judge what food combinations can be used
with milk.