Meat is cooked to sterilize it and for most persons to make it more palatable. It should be cooked in such a way as to increase its tenderness if it is a tough cut, and to keep it tender if it is a tender cut. It is desirable in cooking meat to have maximum tenderness of both fibers and connective tissue, so that the meat carves well and cuts easily. Meat cooked so long, or at such a high temperature that the connective tissue is dissolved, is not attractive and the fibers are tough and stringy. As a general rule, it should be cooked in such a way as to retain its nutritive value, i.e., to prevent cooking losses to as great an extent as possible, either dripping losses or destruction of some food constituents by heat. When the drippings are used in gravy or other ways this loss is not a serious one.

The flavor and the tenderness of the cooked meat depend to a great degree upon the quality of the meat before cooking, for cooking cannot make a well-flavored piece of meat from one of poor quality and flavor, nor does it always produce a tender piece of meat. However, the method and length of time of cooking may and often do spoil a good piece of meat, yet the method of cooking may improve a poor piece of meat.

Browning and thoroughly cooking meat develop a different flavor, just as cooking cabbage a long time develops a characteristic flavor. Many persons prefer the development of this flavor.

Coagulation of proteins. The heat renders the soluble proteins of meat insoluble, the extent of denaturation depending on the stage of cookery or temperature reached, the time held at this temperature, the pH of the meat, its salt content, its degree of ripeness, and probably other factors. The higher the temperature reached and the longer the meat is held at this temperature, the greater the denaturation. The relation of pH to denaturation has been considered in Chapter I (The Relation Of Cookery To Colloid Chemistry). With increased denatura-tion the meat becomes firmer and denser, with shrinkage in volume.

Formation of gelatin. After the meat is heated in a moist atmosphere to a definite temperature for a sufficient time the connective tissue dissolves. If the concentration of gelatin in the liquid reaches 1.5 or higher percentages, it forms a jelly when cooled. Connective tissue is composed largely of collagen. Collagen is changed to gelatin more rapidly at higher temperatures. Smith states that the phosphate ion accelerates the rate at which collagen is changed to gelatin at a given temperature. The addition of acid to meat may also increase the rate of hydrolysis of collagen.

Juiciness. Juiciness is given as a desirable quality of cooked meat. Meat loses moisture during cooking, even when cooked submerged in water. The higher the interior temperature to which the meat is cooked, if the composition and cooking conditions are standardized, the less moist the meat. Meat that contains a large amount of fat within and around the muscle fibers may seem juicy because of melting of the fat by heat in cooking. The fibers with a high fat content may also have a high water content, particularly if part of the fat is in an emulsion that will not break with high temperatures, thus retaining part of the moisture.

Some pieces of meat are apparently far more juicy than others after cooking. It seems rather certain from the results of Hoagland et al, Grass-man, and others, that the increase of amino nitrogen with aging is one factor in bringing this about. The amino acids may not be able to bind as much water as the protein, so that the free water content and apparent juiciness may be increased with increase of amino nitrogen. Sometimes the juiciness seems to be related to the fat content. How great an influence the method of distribution of the fat within the fiber, the salt content of the fiber, the pH, or the development and maturity of the fiber have upon this point cannot be stated. The tissues of old animals lose their power to bind as much water as tissues from younger animals. Although this may partially explain the better quality of meat from younger animals it does not explain why veal is less juicy than baby beeves. Perhaps, if the water is bound too tightly by the coagulable protein micelles, the dryness is more apparent to the tactile sense.

Child and Fogarty found that approximately 11 per cent more fluid could be pressed from one semitendinosus muscle when heated to an interior temperature of 58°C. than for the other semitendinosus muscle from the same animal heated to 75°C.

Noble, Halliday, and Klaas found: "When subjected to a pressure of 3,800 pounds per square inch, the ribs cooked to 61° C. yielded more juice than those heated to 75°C. and the round more than the corresponding ribs. The larger quantity of juice was found to be richer in solids, total nitrogen, and, in one case, also richer in coagulable nitrogen."

Empey states that for uncooked meat there is a direct relationship between the hydrogen-ion concentration of the muscle fiber and its capacity for holding muscle fluid, but the author knows of no work in which juiciness of cooked meat has been related to pH.

Change in color. During the heating of meat, after a temperature of about 50°C. is reached, the color gradually changes from red or pink to a lighter shade and finally, if a sufficiently high temperature is reached, becomes brown or gray. Veal and pork are more gray, beef and lamb develop a browner shade. This color change has been discussed in connection with meat pigments, the oxyhemoglobin being broken down by heat to the brown hematin. The degree of ripeness of the meat affects the temperature at which the color change occurs, ripened meat becoming gray at a lower temperature.

The extreme browning on the surface of meat is accompanied by breakdown of surface proteins and fat, probably with liberation of sulfur and other compounds.

Tenderness. Methods of estimating. Tenderness is one quality universally desired in cooked meats. Tenderness may be estimated by subjective methods such as the ease of cutting or chewing. At present the most widely used method for comparing the tenderness of meat is the grading chart. The chart developed by the Cooking Committee of the National Project,