Protein in Meat:
The
value of meat as food is due to the proteins that it contains. Numerous kinds
of protein are present in meat, but the chief varieties are myosin and muscle albumin. The myosin, which is the most important
protein and occurs in the greatest quantity, hardens after the animal has been
killed and the muscles have become cold. The tissues then become tough and
hard, a condition known as rigor
mortis. As meat in this condition is not desirable, it should be used
before rigor mortis sets in, or else it should be put aside until this
condition of toughness disappears. The length of time necessary for this to
occur varies with the size of the animal that is killed. It may be from 24
hours to 3 or 4 days. The disappearance is due to the development of certain acids
that cause the softening of the tissues.
The albumin, which is contained in
solution in the muscle fibres, is similar in composition to the albumen of eggs
and milk, and it is affected by the application of heat in the cooking
processes in much the same way.
Fats in Meat:
In the flesh of some animals,
such as veal and rabbit, there is almost no visible fat, but in very fat hogs
or fowls, one-third or one-half of the weight may be fat. Meats that are very
fat are higher in nutritive value than meats that contain only a small amount
of this substance. However, an excessive amount of fat prevents the protein
materials from digesting normally.
The quality of fat varies
greatly, there being two distinct kinds of this material in animals. That which
covers or lies between the muscles or occurs on the outside of the body just
beneath the skin has a lower melting point, is less firm, and is of a poorer
grade for most purposes than that which is found inside the bony structure and
surrounds the internal organs. The suet of beef is an example of this internal
fat.
Carbohydrates in Meat:
In the liver and all muscle
fibres of animals is stored a small supply of carbohydrate in a form that is
called glycogen, or muscle sugar. However, there is not enough of
this substance to be of any appreciable value, and, so far as the methods of
cookery and the uses of meat as food is concerned, it is of no importance.
Water in Meat:
The proportion of water in meat
varies from one-third to three-fourths of the whole, depending on the amount of
fat the meat contains and the age of the animal. This water carries with it the
flavour, much of the mineral matter, and some food material, so that when the
water is removed from the tissues these things are to a great extent lost. The
methods of cookery applied to meat are based on the principle of either
retaining or extracting the water that it contains. The meat in which water is
retained is more easily chewed and swallowed than that which is dry. However,
the water contained in flesh has no greater value as food than other water.
Therefore, the greater the amount of water in a given weight of food, the less
is its nutritive value.
Minerals in Meat:
Eight or more kinds of minerals
in sufficient quantities to be of importance in the diet are to found in meat.
Lean meat contains the most minerals; they decrease in proportion as the amount
of fat increases. These salts assist in the building of hard tissues and have a
decided effect on the blood. They are lost from the tissues of meat by certain
methods of cookery, but as they are in solution in the water in which the meat
is cooked, they need not be lost to the diet if use is made of this water for
soups, sauces, and gravies.
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