1. Eggs are of great importance in the diet, and to appreciate this fact
fully the true nature of this food must be understood. For domestic use,
the eggs of guinea hens, turkeys, ducks, and geese occasionally find
favor, but as eggs laid by hens are the kind that is commonly used, it
is to such eggs that this Section is devoted. A hen's egg may really be
considered as an undeveloped chicken, because it contains all the
elements required to build the body of the chick and provide it with the
energy it needs to pick its way into the world. When it emerges from the
shell, it is fully developed, and in a short time it begins an
independent existence, seeking and finding its own food. The fact that
eggs store so much nutritive material explains to some extent why they
are a valuable source of food for man and why they are used so
extensively. However, as in the case of milk, the elements that eggs
contain are not in just the right proportion for the sole nourishment of
a human being, so they must generally be used in combination with
other foods.
2. Most persons are familiar with the appearance of eggs, but in order
that satisfactory results may be obtained in their selection, care, and
cooking, it will be necessary to look into the details of their
composition. As is well known, an egg consists of a porous shell lined
with a fine, but tough, membrane that encloses the white and the yolk
and serves to protect them. The yolk is divided from the white by a
delicate membrane, which permits it to be separated from the white when
an egg is carefully broken. This membrane extends to each end of the
shell in the form of a small cord, and it is so fastened to the shell as
to hold the yolk evenly suspended. The porous nature of an egg shell is
required to give air to the developing chick, but it is this
characteristic that permits eggs to spoil as they grow old and are
exposed to air, for through these minute pores, or openings, the water
in the egg evaporates and air and bacteria enter. Of course, as the
water evaporates and is replaced by air, the egg becomes lighter.
Because of this fact, the freshness of eggs can be determined by placing
them in water. When they are fresh, they will sink in cold water, but as
they decompose they become lighter and will float.
Since it is known that the spoiling of eggs is due to the entrance of
air through the porous shell, it may be inferred that their decay may be
prevented either by protecting the shell so that air cannot enter or by
keeping the eggs at so low a temperature that bacteria cannot grow.
Although stored eggs always deteriorate more or less, both of these
methods of preservation have proved very satisfactory, the former being
used largely in the home and the latter finding its solution in cold
storage. A knowledge of how eggs can be preserved, however, is of great
value, for if there were no means of preservation and eventual
marketing, the price of eggs would at times rise to actual
prohibitive limits.
3. That eggs as an article of food are growing in importance is
indicated by the fact that their production has come to be a large and
widely distributed industry. Owing to the private consumption and sale
of eggs, an accurate statement of the number of eggs produced is
difficult to give. Still, in a report, the United States Bureau of
Agriculture estimated the value of the yearly egg production at
something more than three million dollars, with an allowance of about
210 eggs, or 17-1/2 dozen, per capita each year, or 4 eggs a week for
each person. These figures, however, are only suggestive of the
production, use, and value of eggs, for as the population increases so
does the use of eggs. In fact, they are proving to be almost
indispensable to the cook, the baker, the manufacturers of certain
foods, and many others.
4. With the increase in the demand for eggs has come a corresponding
steady advance in the money value of this product and, consequently, an
increase in its price. The housewife who would practice economy in
cookery can readily see, therefore, that with reference to the number of
eggs required and the ways in which they are used, she must choose
carefully the recipes and methods she employs. If the eggs are always
considered a part of a meal, their use is seldom an extravagance, even
at such high prices as they sometimes attain. On the other hand, if a
dessert that requires the use of many eggs is added to a meal that is
itself sufficient in food value, it is not unreasonable to regard such
use of eggs as an extravagance. A point that should be taken into
consideration in the use of eggs in the diet, especially when their
price seems very high, is that there is no waste matter in them, unless
the shell is regarded as waste. Therefore, they are often more
economical than other foods that can be bought for less money.
It must not be understood, however, that eggs are used only as an
article of diet. They are also a very important food ingredient, being
employed in the preparation of many kinds of dishes. For instance, they
are often used to thicken custards, sauces, etc.; to clarify soups and
jellies; to lighten cakes, puddings, hot breads, and other baked
mixtures; to form the basis for salad dressings; and to combine or hold
together many varieties of food.