This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
The processes of roasting and grilling or broiling, when performed over a very hot fire, result in cooking the meat in a manner which is in some respects analogous to stewing; in fact, the interior portions of the meat are stewed in their own juices instead of in water (Williams). A coating of coagulated albumin forms upon the outer surface of the meat, while the albuminous material or myosin of the interior is gradually warmed and more slowly coagulated. The outer coating prevents the evaporation of the juices of the meat which, together with the extractive materials, are retained, and add flavour to it. Roasted and broiled meats therefore have a decided advantage in flavour as well as in nutritive value over meat which has been boiled for a long time, although the latter may be tender and easily digested.
Roasting and broiling are the most universal methods of cooking. For them the savage or the hunter requires no utensils, but boiling implies the aid of the potter or worker in metals. The Polynesian cooks his meat by roasting it on a hot stone, and sprinkles it with sea water to obtain the salt. The primitive hunter incases his meat or fowl, skin and all, in damp clay and roasts it in hot coals. The Australian savage, the lowest type of man, does all his cooking by roasting.
In roasting, the high temperature which is applied suddenly to the meat produces a firmer coagulation of its outer layers than occurs with boiling. Owing to this fact, the natural juices of the meat are almost completely retained, and, as in boiling, the heat should be strong when first applied, but it may subsequently be reduced to prevent charring of the surface. This may be accomplished by removing the meat farther away from the fire.
The process of roasting and grilling is conducted mainly by radiant heat, although there is slight convection through the air. The main object of an oven is to prevent burning by uneven cooking.
The principle of a proper roasting oven is formulated by Williams, who says "the meat should be cooked by the action of radiant heat projected towards it from all sides while it is immersed in an atmosphere nearly saturated with its own vapour," and the heat applied after reaching a maximum is kept uniform throughout the process.
In boiling or stewing, the heat is applied to the meat by convection through water, and this is an important discrimination because the air which surrounds the roasting meat is constantly removing the water which tends to evaporate upon its surface, and therefore to dry the external surface of the meat. From 20 to 24 per cent of water is lost in this manner, and the meat therefore weighs less. The evaporation of this water, which continually passes from the interior of the meat towards the outer surface, produces a loss of heat in the meat itself which keeps the interior from becoming overheated. If the roasting or broiling is long continued, the water gradually passes out more and more from the interior of the mass, which finally becomes dry and hardened or burned. If too much air surrounds the meat, it is poorly roasted, dry, and leathery, whereas if the heat is applied more directly by radiation from glowing embers, the sudden hardening of the outer coating of the meat, even though it be slightly burned, forms a barrier against the evaporation of water from the interior.
Broiling or grilling is a means of quick cooking which requires very much less time than roasting or boiling, because intense heat is applied to comparatively small pieces of meat or fish. It is really roasting on a smaller scale.
The object of broiling as well as of quick roasting should be to raise the interior of the mass promptly to the point of coagulation, or about 1800 F., so that the water formed shall not have time to wholly evaporate. It is consequently advisable for the meat to be cooked as near the glowing surface as possible to increase the radiation and diminish the convection of air currents (Williams). It is for this reason that steaks and chops are often better cooked in restaurants, where specially adapted grills are used which bring the meat in closer relation to a radiant surface of glowing coals than it is usually possible in domestic cookery. A properly cooked steak or chop is thickened in the centre, but if badly grilled it is thin and dry. It should be remembered that the evaporation depends upon the extent of the surface of the meat, and for this reason thinly cut steaks or chops become comparatively dry and shrivelled in the centre. This principle is well described by Williams, who says that " the smaller the joint to be roasted, the higher the temperature to which its surface should be exposed," and when very large masses of meat are being cooked, it becomes necessary to secure time for the heat to penetrate into the interior without drying up the outside.
This object is accomplished by constantly basting the surface in order to keep it wet and prevent evaporation, for while the surface is moistened, its temperature will not rise above the boiling point of the liquid which is used to moisten it. Pouring melted fat or melted butter over the meat checks evaporation almost completely, and in the case of large joints it prevents the external portion from becoming too dry and indigestible before the albumin of the interior has been coagulated. Small lean joints of meat require more frequent basting with fat.
The roasting of any meat, however, cannot be accomplished without the effusion of some of the meat juice and the melting of a portion of the more superficial fat and of gelatin. These substances together constitute the meat gravy, which is itself quite nutritious and which is advantageously used for basting the meat to prevent drying, as well as to distribute the heat more uniformly over the surface. In overroasted or "burned" meat the external layers become scorched or charred, and this is due chiefly to the carbonising of the fat. Before the fat has become fully burned, certain volatile fatty acids are liberated which have a very disagreeable odour, and various products are developed which are not only of no value for nutrition, but which may be positively irritating to the alimentary canal. According to Yeo, for beef, mutton, and game, a temperature of 1300 F. is sufficient for proper cooking, and the meat is "rare" or "underdone," retaining a good deal of its reddish colour; but veal and poultry should be cooked at a higher temperature - at from 158° to 1600 F. These temperatures are lower than those often used, and apply rather to the degree of heat which is to be maintained after the meat is first placed in position for roasting, when, as previously stated, the temperature may be much higher.
Game or meat which is "high " or somewhat tainted is extremely repulsive if cooked by boiling or stewing, when it disintegrates more or less and the elements of decomposition pass into and flavour the whole mass. Such meat, however, is sometimes palatable, and is not necessarily unwholesome if cooked by roasting, when the external layers which have first commenced to decompose are thoroughly browned and thereby disinfected. Some persons prefer that a leg of mutton should be hung until it becomes slightly odorous before it is roasted, but it must be fresh for boiling.