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The implications of cooking foods and methods used
Part Four
The Principles of Cooking
In the first instance, the object of cookery seems to be to please the palate, so that eating is not simply a necessity of continued existence, but also a source of pleasure and gratification. But a second and very important object in cooking is to render the food to be eaten more readily digestible. These two main objects of cooking are of great importance. It may be that the flavour of a meal has no great influence on its digestion in the case of a healthy man – hunger is the best sauce. But experiments prove that the absence of flavour may be a serious hindrance to the taking of a proper quantity of food. Thus Forster observed that, in the case of one man, meat from which the flavour had been removed was so tasteless he could only eat a necessary quantity with difficulty, and yet the quantity digested and passed into the circulation was as large as with the same meat roasted in the ordinary way. In other experiments with a mixed diet, from which the flavour was also removed, the diet became, when continued, so repugnant that great effort was required to eat it, even though the digestion was unaffected.
Meat vs vegetables. Cooking has very different effects on animal food from those it produces on vegetable food. As a rule, animal food is considerably more digestible in the raw than in the prepared state, while the chief vegetable foods, such as oatmeal, maize, rice, the pulses, green vegetables, etc, must be cooked. On the other hand the flavour of both is largely the result of the method of preparation. The problem is to cook so that the finest flavour is obtained with smallest reduction in digestibility.
Meat
Take, as an example, a piece of beef or mutton. The nutritive material it contains is chiefly the protein constituent, which forms the chief part of the red flesh. This is largely soluble in cold water, and in that form is easily digested. But by water near to the boiling point, or by heat to the same degree, however applied, it is coagulated and rendered insoluble and less easily digested. The greater the heat and the longer it is applied the more solid becomes the coagulated mass, and the more difficult it becomes to digest. On the other hand, the connective tissues or fibrous portions which bind the red flesh together, and also form the tendinous parts, are converted into gelatine by boiling, and are rendered soft, so that the mass of meat can be more easily broken down into particles, can be more easily chewed, and therefore better prepared for the action of the digestive juices. To this extent, therefore, boiling will aid the digestion of animal food by dissolving the connective tissues and thus separating the small fleshy fibres in spite of its coagulant action on these same fibres.
The flavouring materials, the extracts of the meat, are dissolved by water, and in process of cooking with water may readily be dissolved out to a large extent, rendering the meat more or less tasteless. Moreover the action of the heat develops flavouring substances in the meat which did not exist in it before. The nature and extent of these substances entirely depend upon the manner in which the heat is applied. They are specially developed by a dry heat, as applied in roasting, and it is owing to their production that roast beef is so much more full in flavour than raw or boiled beef.
The aims to be achieved in cooking are:
(1) to apply the heat long enough to heat it equally throughout, and to render it as tender and easily chewable as possible,
(2) to guard against extracting from it any of the flavouring materials it already possesses,
(3) to develop as much as possible new flavouring substances,
(4) to avoid so great a degree of heat, or so long continued an application, as would harden the flesh and render it difficult of digestion.
Soups
But if you are making a soup from a piece of meat, the object is very different. You no longer want to retain as much of the meat’s flavouring materials and juices as possible in the meat, but to extract them, and to get as much of them as you can into the surrounding water; and the method must be correspondingly different. If you clearly realise the difference between these two processes, and the different method they imply, then that is a sure foundation for the practice of cookery.
To extract the juices of meat is easy enough: steep the meat, broken down into small pieces, in cold water, and its flavouring material and a considerable quantity of its nourishing material will become dissolved in the water.
Retaining the juices in the meat is another problem. If a leg of mutton is plunged into boiling water, almost immediately the protein portions of the meat in contact with the boiling water will become insoluble, and will coagulate. If the meat be exposed to this heat for a short time only, it will become completely surrounded by a film of coagulated material, the heat not having had time to penetrate far in, and it will have become sealed up. If the mutton is now placed in cold water, this coagulated film, being insoluble, will oppose the passage outwards of the juices of the meat. Were the meat kept in the boiling water the heat would gradually penetrate inwards, coagulating and hardening it, the outer parts becoming always harder and drier because of the prolonged action of the high temperature. But if, after the meat has been two or three minutes in the boiling water, the heat of the water s allowed to fall considerably, then a film of coagulated protein will have formed outside sufficient to retain the juices of the meat, and the cooking can be proceeded with at a lower temperature and a longer period without risk to juiciness and tenderness. Exactly the same principles are applicable in roasting or baking meat. One desires to cook the meat throughout to a certain degree, but to retain all the juice within it. If it is exposed suddenly, and all round, to the full influence of a bright clear fire, or a very hot oven for fifteen minutes, a film of coagulated protein is formed, sealing up the juices; then the meat is withdrawn from its close proximity to the fire, or if it be in an oven the heat of the oven is allowed to fall, and cooking gradually proceeded with.
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