10. GELATINE IN MEAT.--The gelatine that is found in meat is a substance very similar in composition to protein, but it has less value as food. It is contained in the connective tissue and can be extracted by boiling, being apparent as a jellylike substance after the water in which meat has been cooked has cooled. Use is made of this material in the preparation of pressed meats and fowl and in various salads and other cold-meat dishes. Some kinds of commercial gelatine are also made from it, being first extracted from the meat and then evaporated to form a dry substance.
11. FAT IN MEAT.--All meat, no matter how lean it appears, contains some fat. As already explained, a part of the fat contained in meat occurs in small particles so embedded in the muscle fibers as not to be readily seen, while the other part occurs in sufficient amounts to be visible. 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, as will be observed on referring to the table of meat compositions in Fig. 1. 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.
Fat is a valuable constituent of food, for it is the most concentrated form in which the fuel elements of food are found. In supplying the body with fuel, it serves to maintain the body temperature and to yield energy in the form of muscular and other power. Since this is such a valuable food material, it is important that the best possible use be made of all drippings and left-over fats and that not even the smallest amount of any kind be wasted.
12. CARBOHYDRATE IN MEAT.--In the liver and all muscle fibers 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 are concerned, it is of no importance.
13. 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 flavor, 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, as will be seen in Fig. 1, the greater the amount of water in a given weight of food, the less is its nutritive value.
14. MINERALS IN MEAT.--Eight or more kinds of minerals in sufficient quantities to be of importance in the diet are to be 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.
15. EXTRACTIVES IN MEAT.--The appetizing flavor of meat is due to substances called extractives. The typical flavor that serves to distinguish pork from beef or mutton is due to the difference in the extractives. Although necessary for flavoring, these have no nutritive value; in fact, the body throws them off as waste material when they are taken with the food. In some methods of cookery, such as broiling and roasting, the extractives are retained, while in others, such as those employed for making stews and soups, they are drawn out.
Extractives occur in the greatest quantity in the muscles that the animal exercises a great deal and that in reality have become tough. Likewise, a certain part of an old animal contains more extractives than the same part of a young one. For these reasons a very young chicken is broiled while an old one is used for stew, and ribs of beef are roasted while the shins are used for soup.
Meat that is allowed to hang and ripen develops compounds that are similar to extractives and that impart additional flavor. A ripened steak is usually preferred to one cut from an animal that has been killed only a short time. However, as the ripening is in reality a decomposition process, the meat is said to become "high" if it is allowed to hang too long.