Scientists have been trying for a long time to determine just how much of these tissue-building foods is necessary for individuals, but they have found this a difficult matter. Nevertheless, it is generally conceded that most persons are likely to use too much rather than too little of them. It is essential then, not only from the standpoint of economy, but from the far more important principle of health, that the modern housewife should know the nutritive value of meats.
4. In her efforts to familiarize herself with these matters, the housewife should ever remember that meat is the most expensive of the daily foods of a family. Hence, to get the greatest value for the money expended, meat must be bought judiciously, cared for properly, and prepared carefully. Too many housewives trust the not over-scrupulous butcher to give them the kind of meat they should have, and very often they do not have a clear idea as to whether it is the best piece that can be purchased for the desired purpose and for the price that is asked. Every housewife ought to be so familiar with the various cuts of meat that she need not depend on any one except herself in the purchase of this food. She will find that both the buying and the preparation of meats will be a simple matter for her if she learns these three important things: (1) From what part of the animal the particular piece she desires is cut and how to ask for that piece; (2) how to judge a good piece of meat by its appearance; and (3) what to do with it from the moment it is purchased until the last bit of it is used.
5. Of these three things, the cooking of meat is the one that demands the most attention, because it has a decided effect on the quality and digestibility of this food. Proper cooking is just as essential in the case of meat as for any other food, for a tender, digestible piece of meat may be made tough and indigestible by improper preparation, while a tough piece may be made tender and very appetizing by careful, intelligent preparation. The cheaper cuts of meat, which are often scorned as being too tough for use, may be converted into delicious dishes by the skilful cook who understands how to apply the various methods of cookery and knows what their effect will be on the meat tissues.
6. Unfortunately, thorough cooking affects the digestibility of meat unfavorably; but it is doubtless a wise procedure in some cases because, as is definitely known, some of the parasites that attack man find their way into the system through the meat that is eaten. These are carried to meat from external sources, such as dust, flies, and the soiled hands of persons handling it, and they multiply and thrive. It is known, too, that some of the germs that cause disease in the animal remain in its flesh and are thus transmitted to human beings that eat such meat. If there is any question as to its good condition, meat must be thoroughly cooked, because long cooking completely eliminates the danger from such sources.
STRUCTURE AND COMPOSITION OF MEAT
7. An understanding of the physical structure of meat is essential to its successful cooking. Meat consists of muscular tissue, or lean; varying quantities of visible fat that lie between and within the membranes and tendons; and also particles of fat that are too small to be distinguished except with the aid of a microscope. The general nature of the lean part of meat can be determined by examining a piece of it with merely the unaided eye. On close observation, it will be noted that, especially in the case of meat that has been cooked, innumerable thread-like fibers make up the structure. With a microscope, it can be observed that these visible fibers are made up of still smaller ones, the length of which varies in different parts of the animal. It is to the length of these fibers that the tenderness of meat is due. Short fibers are much easier to chew than long ones; consequently, the pieces containing them are the most tender. These muscle fibers, which are in the form of tiny tubes, are filled with a protein substance. They are held together with a tough, stringy material called connective tissue. As the animal grows older and its muscles are used more, the walls of these tubes or fibers become dense and tough; likewise, the amount of connective tissue increases and becomes tougher. Among the muscle fibers are embedded layers and particles of fat, the quantity of which varies greatly in different animals and depends largely on the age of the animal. For instance, lamb and veal usually have very little fat in the tissues, mutton and beef always contain more, while pork contains a greater amount of fat than the meat of any other domestic animal.
8. The composition of meat depends to a large extent on the breed of the animal, the degree to which it has been fattened, and the particular cut of meat in question. However, the muscle fibers are made up of protein and contain more protein, mineral salts, or ash, and certain substances called extractives, all of which are held in solution by water. The younger the animal, the greater is the proportion of water and the lower the nutritive value of meat. It should be understood, however, that not all of meat is edible material; indeed, a large part of it is made up of gristle, bones, cartilage, nerves, blood vessels, and connective tissue. The amount of these indigestible materials also varies in different animals and different cuts, but the average proportion in a piece of meat is usually considered to be 15 per cent. of the whole. Because of the variation of both the edible and inedible material of meat, a standard composition for this food cannot readily be given. However, an idea of the average composition of the various kinds can be obtained from Fig. 1.
9. PROTEIN IN MEAT.--The value of meat as food is due to the proteins that it contains. Numerous kinds of protein occur 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 fibers, 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.