13. Although milk is used extensively in its natural liquid form,
considerable use is also made of the numerous products of milk, chief
among which are cream, skim milk, buttermilk, sour milk, whey, butter,
and cheese. In fact, all of these occupy such an important place in the
dietary of the majority of homes that it is well for every housewife to
understand their value. Butter and cheese are discussed in detail later,
so that at this time no attention need be given to them. The other
products, however, are taken up now, with the intention of enabling the
housewife to familiarize herself with their production, nature, and use.
14. CREAM.--As has been pointed out, the particles of fat that rise to
the top of milk when it is allowed to remain undisturbed for some time
form the product known as cream. Cream may be removed from the milk by
skimming it off, or it may be separated from the milk by means of
machinery especially designed for the purpose. The greater the
proportion of fat in milk, the thicker, or "heavier," will be the cream.
Various grades of separated cream are placed on the market, the usual
ones being those which contain 8, 12, 16, 20, and 40 per cent, of fat.
Thin cream, which includes the grades that have only a small percentage
of fat, contains a larger quantity of milk than the others and is not so
desirable for many purposes. Still, it is used to some extent, because
it is cheaper and there are definite uses to which it can be put.
Medium-heavy cream is the kind to select when it is desired for
_whipping_. This is a process that consists in beating the cream rapidly
until a mass of tiny bubbles form and become stiff, very much as the
white of egg does.
15. SKIM MILK.--After a part or all of the cream has been removed from
whole milk, that which remains is called skim milk. While practically
all of the fat is taken out when milk is skimmed, very little protein or
sugar is removed. Therefore, skim milk is still a valuable food, it
being used to a large extent for cheese making, for the manufacture of
certain commercial foods, and for the feeding of animals. The housewife
does not, as a rule, buy skim milk; indeed, in some localities the laws
prevent its sale because it is considered an adulterated food. However,
it is really a wholesome, valuable food that is cheaper than whole milk,
and its use in the home should therefore be encouraged from an
economical standpoint. Here it may be used in the preparation of many
dishes, such as sauces, cakes, biscuits, muffins, griddle cakes, bread,
etc., in which butter or other fats are used, and in custards, puddings,
ices, and numerous other desserts.
16. BUTTERMILK.--The milk that remains in butter making after the butter
fat has been removed from cream by churning is known by the name
buttermilk. Such milk is similar to skim milk in composition, and unless
butter is made of sweet cream, buttermilk is sour. Buttermilk is used
considerably as a beverage, but besides this use there are numerous ways
in which it may be employed in the preparation of foods, as is pointed
out in various recipes. An advantage of buttermilk is that its cost is
less than that of whole milk, so that the housewife will do well to make
use of it in the preparation of those foods in which it produces
satisfactory results.
17. ARTIFICIAL BUTTERMILK.--Several kinds of sour milk that are called
buttermilk are to be had, particularly at soda fountains and
restaurants. While they are similar to buttermilk they are not the same,
because they are produced artificially from whole or skimmed sweet milk.
The usual method employed in the making of these artificial buttermilks,
as they may well be called, consists in adding to sweet milk tablets
containing lactic acid or a certain culture of bacteria that induce
fermentation, very much as yeast does, and then keeping it at about body
temperature for a number of hours in order to allow the milk to thicken
and sour. Such milks exert a beneficial action in the digestive tract,
and their food value, provided they are made from whole milk, is just as
high as that of the original sweet milk. Artificial buttermilks
therefore prove a valuable source of food supply for persons who find
them palatable and who do not care for sweet milk. Their food value may
be increased by adding cream to them.
18. SOUR MILK.--Ordinary milk contains large numbers of bacteria that
produce fermentation. When it is allowed to stand for some time, these
bacteria act upon the sugar, or lactose, contained in the milk and
change it into lactic acid. This acid gives to the milk a sour taste and
at the same time causes the casein of the milk to become a mass known as
_curd_, or _clabber_. This mass continues to grow sour and tough until
all the milk sugar is converted into lactic acid, so that the longer the
milk stands, the more acid it becomes. Sour milk, however, is useful
in the preparation of various dishes, such as hot breads and
griddle cakes.
[Illustration: FIG. 1]
19. WHEY.--When the curd is completely removed from milk, as in making
cheese, a clear, light, yellowish liquid known as whey remains. Whey is
composed of water, minerals, and milk sugar or lactic acid, and is the
least valuable part of the milk. The ingenious housewife will never be
at a loss to make use of this product, for, while its food value is
slight, the minerals it contains are important ones. Whey is sometimes
used to furnish the liquid for bread making and, in addition, it may be
used as a beverage for persons who cannot digest food as heavy as
milk itself.
20. COMPARISON OF FOOD VALUES OF MILK PRODUCTS.--So that the housewife
may become familiar with the food values of milk products, there is here
given, in Fig. 1, a graphic table for the comparison of such products.
Each glass is represented as containing approximately 1 pint or 1 pound
of the milk product, and the figures underneath each indicate the number
of calories found in the quantity represented. The triangle at the side
of each indicates the proportion of ash, protein, fat, carbohydrate, and
water, the percentage composition being given at the side. Housewives as
a rule fully appreciate the food value that is to be found in whole milk
and cream, but such products as skim milk, buttermilk, and whey are
likely to be ignored.