Heat treatment of food to make it more palatable, digestible, and safe. It breaks down connective tissue in meat, making it tender, and softens the cellulose in plant tissue. Some nutrients may be lost in the process, but this does not affect the overall nutritional value of a balanced diet.
Cookery has been practised since prehistoric times, becoming fairly sophisticated in the aristocratic societies of ancient civilizations. Professional cooks existed in medieval Europe, but cookery as a recognized art originated in 16th-century Italy and developed in 17th-century France. French pre-eminence in cooking remained unchallenged until the 1940s, when rapidly-increasing interest led to the rediscovery and appreciation of traditional cooking styles worldwide.
The methods of cooking can be classified according to the method of heat transfer to the food. Conduction of heat is used when cooking in a liquid medium; boiling, stewing, braising, pot-roasting, and pressure cooking are most suitable for food that requires the penetration of water to soften or tenderize the structure of the food, such as tough meat, or vegetables with a high cellulose content. Convection of heat is used in steaming and baking, and is most suitable for tender foods that will cook by heat transmitted through the food. Radiant heat is used in grilling, barbecuing, and roasting - these methods being best suited to tender foods - and microwave cooking.
Effects of cooking
Sugars do not need cooking to be digested, but are used because of their properties of sweetening, crystallization, and colour. Starches are insoluble in cold water, but on heating above 60°C/140°F, the granules swell rapidly, eliminating the uncooked taste, and increasing the viscosity, clarity, and susceptibility to enzyme action. Cooking cellulose, the main component of plant cell walls, does not make it digestible, but, as the cell structure weakens, it enables the digestive enzymes to attack the nutrients contained within the cells. Pectin is present in plants as insoluble protopectin. Enzyme action and absorption of water hydrolyse the protopectin to soluble pectin, which is capable of forming a gel with the correct concentrations of acid and sugar. This makes it useful in preparing jams and jellies. Proteins act as foaming and emulsifying agents. Overcooking causes a loss of water, as the protein structure shrinks. Coagulation of protein structure by heat is extensively used in all forms of cooking, for example boiling an egg or baking a cake. Overheating (above 60°C/140°F) causes denaturization of the protein, which results in a toughening of the mixture, but does not cause loss of nutritive value. In baking, fats shorten the mixture by surrounding some of the starch grains and preventing the formation of some of the gluten strands when water is added to the mixture. Most of the mineral elements in foods are stable to normal cooking conditions. In moist methods of cooking, minerals are leached into the cooking liquids; it is therefore nutritionally beneficial to use these liquids in sauces and gravies. Water-soluble vitamins are most vulnerable to loss in cooking. Vitamin C is lost in washing and cooking water, especially if the food is cut in any way. Of the B group vitamins, thiamin and pantothenic acid are most susceptible to loss by leaching. Vitamins A and D are not affected by normal cooking processes, although vitamin A is destroyed by cooking in fat at very high temperatures.
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