Experimental cookery

inches or 100 times its original surface area, and the distance {s — c) to the center is 5 inches, or 10 times the distance of cube A. In other words, the distance to the center does not increase in the same ratio as the surface area and the weight. In heating these cubes, if the heat travels through the material at a uniform rate it will not take 1000 times as long to bring the center of cube 5 to a definite temperature as cube A, but 10 times as long. The diameter of a sphere or a cylinder does not increase in the same pro- portion as the surface area and weight. A piece of meat is not shaped like a cube, but some are cylindrical, and in roasts of similar shape the weight increases more rapidly than the distance that the heat must penetrate. Rolled roasts are cylindrical in shape. Here the length of the radius (r) determines the time for the heat to penetrate to the center of the roast, unless the length of the cylinder is shorter than its diameter. See Fig. 25, diagram C. In a standing rib roast. Fig. 25, diagram D, it is not the distance to the center of the meat, which may be somewhere near the portion marked x, but the distance through the thick portion of the meat, which affects the time required for cooking. The heat travels in from the top along the line tc, from the side along the line sc, and from the bottom along the line be. Ham, leg of lamb, and leg of veal have the thickest portion of the meat nearer one end than the center of the meat. It is obvious from the diagrams that the shorter the distance to the center of the piece of meat the more rapidly the heat will penetrate; the longer the distance, the more time will be required. Weight and surface area are not satisfactory to determine cooking time, for the size of the piece and its shape determine the distance to the thickest part of the meat. A thin, wide roast will cook in less time and a thick compact one will take a longer time. The following examples illustrate this. A standing rib roast weigh- ing 11.6 pounds required 1 hour and 52 minutes to reach an inner tem- perature of 57°C., when cooked for 20 minutes at 275°C. and for the remainder of the cooking period at 125°C. This gives an average of 9.3 minutes per pound. Another roast weighing 11.5 pounds and with the same cooking conditions required 3 hours and 43 minutes, averaging 19.3 min- utes per pound. The first roast consisted of five ribs and was thin and wide ; the latter consisted of three ribs and was thick and compact. If roasts are always of the same shape and the same cooking temperature is always used the time for cooking can be estimated more accurately than when the shape of the roast varies. A large piece of meat cooks in a shorter time per pound than a small one if all other conditions are standardized. Smaller hams and legs of lamb require more minutes per pound than larger ones. The same is true of poultry, smaller chickens and turkeys requiring more minutes per pound than larger ones. Time per pound. Minutes per pound for some roasts are given in Tables 29 and 30, but if not taken in connection with cooking tempera- 236 MEAT