PREPARATION.
Alimentary matters are used either in their crude or raw state, or after having undergone some kind of preparation.
Fruits and salads, although they admit of various forms of cookery, are most frequently eaten in as fresh and natural a state as possible.
Cookery is either necessary to destroy some dele terious property, or to render food more palatable and nutritious. Of the former effect the most re markable example is furnished by various species of arum, which, in their crude state, are acrid, or even poisonous, but, by being cooked, become mild and wholesome. The acrimony resides in a very vola tile principle, which is easily dissipated by heat. A more familiar example in this country is furnish ed by the onion tribe, the acrimony and flavour of which are entirely destroyed by being long subjected to the action of heat Numerous as the receipts are, the processes of cookery are but few. In some, the chief object is to extract the fluid or soluble parts of the substance cooked ; in others, to alter the nature of the sub stance itself, and often to combine both purposes. Fire is a principal agent in almost all the processes of cookery, and the most economical mode of ap plying it has engaged the attention of many philo sophers and artists. * Convenience and economy are the objects pro posed by all alleged improvements. The nature of the fuel is of no little importance, and is different in different countries. Pit-coal has the advantage of forming a lasting fire, and producing an intense de gree of heat, which renders it almost indispensable for roasting ; but its smoke is very detrimental, both by the unpleasant flavour it imparts, and by the inconvenience arising from the flame, and from the soot deposited upon the vessels and in the chim ney. Wood and turf evolve less smoke, but their flavour is more penetrating, and they give less heat, and are less durable. The cleanest and most gene rally useful fuel is charcoal of wood, or coke ; nei ther giving out any smoke, or imparting any fla vour. Charcoal is more easily kindled, but coke lasts longer, and gives out more heat. Well burnt cinders are an excellent substitute fOr coke, which in every family ought to be carefully preserved for the purposes of cookery.
The heat, from whatever fuel produced, is ap plied in various ways to the substances to be cook ed, either directly or indirectly. Heat is applied directly, as radiant heat in the process of roasting, in which the effects are produced entirely by the rays of heat impinging directly upon substances placed at a short distance before it. For this pur pose a clear glowing fire is necessary, and the bars of a good roasting grate should impede as little as possible the radiation of its heat. Another
very direct mode of applying heat is by placing the substance over the fire by suspending it in the stream of heated air ascending from it, or laying it directly on the burning fuel, or on bars, or a plate of iron, or other substance capable of supporting the heat. Broiling is the result of this mode of apply ing heat. Heat is also often applied through the intervention of fluids, chiefly of water or steam, as in boiling or stewing ; or of some oily substance, as in frying. The peculiarity orbaking consists in the substance being heated in a confined space, which does not permit the escape of the fumes arising from it.
To understand the theory of cookery, we must attend to the action of heat upon the various consti tuents of alimentary substances, as applied directly and indirectly through the medium of some fluid. In the former way, as exemplified in the processes of roasting and broiling, the chief constituents of animal substances undergo the following changes— the fibrin is corrugated, the albumen coagulated, the gelatine and osmazome rendered more soluble in water, the fat liquified, and the water evaporated. If the heat exceed a certain degree, the surface be comes first brown, and then scorched. In come quence of these changes, the muscular fibre becomes opaque, shorter, firmer, and drier ; the tendons less opaque, softer, and gluey; the fat is either melted out, or rendered semitransparent. Animal fluids become more transparent ; the albumen is coagulated and separated, and they dissolve gelatine and osmazome. Lastly, and what is the most important change, and the immediate object of all cookery, 'the meat loses the vapid nauseous smell and taste peculiar to its raw state, and it becomes savoury and grateful. Heat applied through the intervention of boiling oil or melted fat, as in frying, produces nearly the same changes, as the heat is sufficient to evaporate the water, and to induce a degree of scorching. But when water is the medium through which heat is applied, as in boiling, stewing, and baking, •the ef fects are somewhat different, as the heat never ex ceeds 212°, which is not sufficient to commence the process of browning or decomposition, and the so luble constituents are removed by being dissolved in the water, forming soup or broth ; or, if the di rect contact of the water be prevented, they are dis solved in the juices of the meat, and separate in the form of gravy.