MEATS AND MEAT PRODUCTION. The discussion of the subject will be confined to a consideration of the properties, use and production of the flesh of cattle, sheep and swine for human food. All animal tissues are made up of dry substance, or solid material, and water. The per cent of water in meats varies from 10 to 78. The two things which appear to have the greatest influence upon the per centage of water in meat are the age and con dition, or degree of fatness, of the animal. Other things being equal, the younger the ani mal the more water its flesh as well as other tissues contains, while the higher the percentage of fat in meat the lower the percentage of water. The extreme variation in the water content of different cuts and varieties of meats is due largely to an extreme variation in fat content. Thus all lean meat consists approximately of 75 per cent of water and 25 per cent of solid material. While the water in meats aids in their digestion and absorption in the alimentary tract, the nutritive value of meats rests largely on the quantity and character of the dry sub stance or solid material they contain. From 50 to 65 per cent of the fat steer is meat. In ether words, the dressed carcass of a steer rep resents from 50 to 65 per cent of the weight of the live animal. The remainder is made up of by-products, in general, such as hides, fat, offal, less valuable than beef. A physical exam- nation of meats shows them to be made up of muscular tissue or lean meat, fatty tissue or fats, cartilaginous tissue or the gristle, and bone. From the standpoint of the nutritive value of meat, gristle and bone are practically refuse.
Chemically, meat is com posed of protein, fats, water, ash and carbo hydrates, which are the necessary food constitu ents for the production of energy and repair of the animal body. The amount of carbo hydrates is so small as to make it almost a negligible factor. Extractives are also present in meats which are believed to be responsible for meat flavors. While differences in the chemical composition of two cuts of meat are not necessarily an indication of their relative food value, yet the composition of meats in gen eral is important as indicating their place in the diet of man. Lean meat contains from 15 to 21
per cent protein; whole eggs, 12.5 per cent; fresh, whole milk, 3.4, and cheese from 25 to 30 per cent. Fresh vegetables, other than peas and beans, contain 0.5 to 3 per cent protein; fresh peas and beans, 2 to 7 per cent; wheat flour, 10 to 12 per cent; and dry peas and beans, 18 to 25 per cent.
Thus it will be seen that meat contains a relatively high per cent of protein as compared with other staple foods. The mineral matter comprising the ash of meats is made up chiefly of potassium phosphate, with small amounts of magnesium, sodium, calcium,phosphates and chlorides. The percentage of ash in fresh edible meats varies from 0.5 to 1.5 per cent. The organic extractives of meat consist mainly of creatine, certain basic nitrogenous sub stances including the purine bases, and small amounts of lactic acid, glycogen or animal starch and glucose in traces. Glycogen and glucose are the only carbohydrates in meat and occur normally in very small quanti ties. The percentage of organic extractives m meat varies widely with the kind of meat and the location of the cut, from 0.7 to 2 or 3 per cent.
Dietetic Meat is a staple food in the American dietary, chiefly as a source of protein and fat. In the average American dietary, 28 per cent of the protein and 58 per cent of the fat is represented by the consump tion of meat from cattle, sheep and swine. Pro tein is essential for the growth and repair of body tissue, and while the actual bodily re quirement for, protein may be relatively small, it seems probable that a fairly liberal protein intake is essential for optimum conditions of health and vigor. Meat is an especially satis factory, source of protein in the diet, first, be cause it is so readily and completely digestible as compared with the vegetable proteins, and, second, because it is better adapted to the body's requirements and thus possesses a higher physio logical value. Illustrative of the latter point, in a recent experiment on a human subject it was shown that the following minimal amounts of the various proteins indicated were required to the protein requirements of the body and to protect body protein from loss: Meat protein 30 plata pert day.