Meat is made up of fibers which are embedded in and held together by connective tissue. The connective tissue is composed of two proteins, collagen and elastin. The collagen, when boiled with water, forms gelatine. The fibers are hollow with walls composed of the protein sub-stance called elastin. This is like collagen in some of its properties, but it will not dissolve on boiling with water. The content of the fibers is called muscle juice. It is composed of water in which are proteins, coloring matter, salts, and extractives. Besides this, there is fat deposited in varying amounts, mainly in the connective tissue. In beef, the fat is usually in sufficiently thick layers to be seen readily; in pork, the fat surrounds the fibers in such small particles as not to be visible, although present in a generous amount. The proteins of the muscle juice are mainly myosin and albumin, and both coagulate with heat. The extractives, so named because they can be extracted from the meat by boiling it in water, are of value because they give the meat its flavor. Although they contain nitrogen, they have practically no food value, since they cannot build tissue nor furnish heat to the body. They are stimulants, however, and cause a flow of digestive juices in the stomach, which aids in the digestion of food. Lean meat shows about the following composition:
Composition of Meat.
Mineral matter................ Fat.......
Muscle. fibre............................................. Connective tissue........... Extractives.....................
75.0% to 77.0% 0.8% to 1.8% 0.5% to 3.0%
13.0% to 18.0% 2.0% to 5.0% 0.5%
Shortly after an animal is slaughtered a condition known as rigor mortis sets in, during which the muscles are very stiff. Meat must be eaten either before this begins, or after the meat has hung for a while. In hanging, acids develop which perhaps aid in softening the meat again, and certainly add to its flavor.
The cuts of meat which are tender usually command the highest price. They come from the parts of the animal which are least toughened by exercise, but there is considerable difference in tenderness in the "better cuts," breed, age, size, and the manner in which the animal has been fattened, all affecting the result. The length of the fibers seems to be another factor in the question of toughness. Loin steaks and rib roasts are good examples of choice cuts. It is interesting to know, however, that many of the cheaper cuts contain more extractives and less water, so that they are both better flavored and more nutritious. Waste, too, must be taken into account. Instructive data on this subject can be obtained in Bulletin 158, of the Illinois Agricultural Experiment Station.
Experience is needful before one can recognize good meats in the market. This can best be acquired by getting a butcher to show different grades of meat, and to explain why one is better than another. Here are some of the chief points to be noted.