This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
The total loss that occurs during the cooking of meat includes the losses known as drippings and the volatile losses. The greater part of the volatile loss is from evaporation of water. It may include volatile substances from the decomposition of fat and volatile aromatic substances. The drippings include fat, water, salts, and both nitrogenous and non-nitrogenous extractives.
Time, stage of cookery and losses. The stage of cookery is one factor that affects the cooking loss. Meat cooked rare gives less total cooking loss than meat cooked well done. A longer time is required to reach the well-done stage, if all other conditions are the same. Thus length of time of cooking and the stage to which the meat is cooked are related factors.
Composition and cooking losses. Meat containing a high percentage of fat cooked under standardized conditions gives greater cooking losses than lean meat. The amount of drippings is always greater for the fat meat than for similar lean cuts from the same kind of animal. This is also true for poultry. Cooking temperatures that melt the fat cause a heavy fat loss from the meat.
Surface area and cooking losses. The shape and surface area of the meat also influence the loss that occurs during cooking. The greater the surface area of the meat, the greater the area at which losses may occur. Compact pieces of meat with correspondingly small surface areas give smaller losses than irregular-shaped pieces with greater surface areas.
Cooking temperature and cooking losses. The cooking temperature is in many instances the principal factor in determining the percentage of weight that is lost during cooking. Occasionally time may be a more important factor than cooking temperature in its effect on the resulting losses. For example, cooking losses were greater for halves of chicken roasted at 125°C. (about 250°F.) than for the corresponding halves roasted at 175°C. (about 350°F.). In the former instance, twice as long was required for the interior of the thigh to reach 85°C. (185°F.). Alexander and Clark found similar results for very small, poorly finished legs of lamb. However, in general the higher the cooking temperature the greater the cooking losses; the lower the cooking temperature the smaller the cooking losses. Intermediate cooking temperatures give corresponding intermediate cooking losses.
Method of cooking and cooking losses. The method of cooking the meat may also influence the cooking loss. A broiled steak may have a far greater total loss than a pan-broiled one, yet the interior of the meat may be just as juicy. The radiant heat as well as the temperature reached usually causes a high fat loss from the edge of the boiled steaks, whereas a pan-broiled one may have a small fat loss.
Degree of ripeness. Alexander and Clark found cooking losses decreased with longer ripening.