Depending on the intended purpose or the crude product directly exposed to high temperature, or by slow warming gradually brought to the desired temperature.
Heat treatment is often the final stage of cooking, but sometimes it is preceded by cold treatment (wiping, cutting, cleaning, and so on. D.). This occurs
Heat treatment increases the digestibility of food because it causes chemical changes in products. Animal and vegetable proteins processed product under high temperatures lose their original properties (denatured), become less resistant to gastric juice enzymes and therefore easier to digest. However, an extremely long period of heating reduces the digestibility of proteins,
Carbohydrates under high temperatures also alter their properties: gelatinized starch, by the enzymes completely converted to sugar and is quickly absorbed by the human body. At the same time raw starch digested very slowly and incompletely.
Positive effect on the heat treatment and the digestibility of many fats. The melted fat is better emulsified form, and this contributes to their faster absorption. Most of the fat when heated no higher smoke temperature varies relatively little.
butter digestibility after thermal treatment practically does not increase, because its melting point is only 24- 34,7 ° C. Therefore, the butter put food in its natural form; in natural oil are better preserved vitamins. Fat - beef and mutton fat with a high melting point, are better absorbed in melted form.
The digestibility of food largely depends on the taste qualities, appearance and flavor. Pleasant smell, taste and appearance of food kind of cause the secretion of saliva and gastric juice, which it promotes better absorption.
Due to the heat treatment to soften the products formed a number of new flavoring and aromatic substances, which largely affect the secretion of digestive juices, and therefore increases the digestibility of food.
Heat treatment disinfects food as kills most microorganisms; while also volatilized malodorous and decompose harmful substances.
The most reliable way of cooking - steaming, in which almost always provided by heating the product to 100 ° C, and when roasted it is not always possible.
In the heat treatment kills the pathogens of parasitic diseases. In other raw foods contain toxic substances, which when cooked are destroyed or transferred to broths and removed them (morels toxin, solanine, which is found in raw potatoes, and so on. N.).
However, the heat treatment may have a negative impact on quality, as this partially destroyed vitamins, flavorings, color change products, as well as the lost of the nutrients. Therefore, one object of cooking technology is to reduce the negative impact of heat treatment and increase positive.
One of the most important rules is that the heat treatment should not continue for longer than necessary. As a result, a long-acting high temperature, nutrients undergo changes that adversely affect the absorption of food by the body. With digestion products lose much of vitamins and aromatic substances, so the taste and smell of them vary greatly.
Long-term heat treatment, like prolonged heating of cooked food (especially for children) is a culinary mistake. Long-term heating of cooked food in order to maintain its temperature necessary for food (45-40 ° C), promotes the development of microorganisms in it and the formation of certain decomposition products, which can lead to intestinal diseases and nutritional deficiencies. Therefore, as a rule, cooked food should be served to the table as soon as possible after cooking and in no event be subjected to repeated, frequent and prolonged warming up to high temperatures (100-120 ° C), especially second dishes, and even in the oven. Very strong and frequent heating of food leads to the formation in the meat of substances having a bad taste, and leads to the hardening of the fibers due to the evaporation of water; It also makes dishes tasteless.
Culinary technology has many heat treatment processes. The main ones are boiling and roasting. By the combined methods include stewing and brezirovanie to support - sautéing and blanching (scalding).
Cooking. Cooking products can in large amounts of liquid in a small amount of liquid or brine (pripusianie) and steamed. In some cases, foods cooked at a lower temperature in a water bath (cereal egg, egg oil, sauces, etc. D.) And at an elevated pressure in an autoclave (boiling bones).
Products intended for cooking should be on high heat bring to a boil and cook at a quiet boil. If you want to remove from the product more than the taste, aroma and nutrients, they are best cut into small pieces ca. If you want to produce, on the contrary, retain maximum juiciness, put them in boiling water uncut.
Products, steamed, Read any fully preserve its structure, but the vitamin C is destroyed to a large extent, because the products are exposed to oxygen. Vitamin C is destroyed, and when the vegetables, especially leafy, cooked in bad tinned, copper utensils in a pot with a damaged enamel tsli in iron kettles, and in dishes, the capacity of which is much more needed for a given amount of food and water.