of products for a long time will give the chance to diversify a food allowance. At the same time the main objective comes down to maintaining high quality of products, decrease in losses of nutritious and biologically active agents including vitamins.
Short-term storage of products is made generally before cooking. At the same time periods of storage should not exceed 2-3 days. And during this time in perishable products the content of vitamins, especially in green vegetables considerably decreases. So, for example, at storage of fennel, parsley, a green salad and onions during one day of loss of vitamin C makes up to 60%.
Vitamins intensively collapse irrespective of periods of storage in greens and fresh vegetables. For greens 4-5 hours of storage in adverse conditions there are enough, at the same time about 50% of vitamin C collapse.
At long storage of fresh vegetables nearly 1/3 initial content of vitamin C decrease. Also contents and other vitamins decreases.
Decrease in content of vitamins at storage of foodstuff happens as as a result of their expenditure as a part of enzymes, and destruction under the influence of various internal and external factors.
Vitamin A maintains long periods of storage if food are stored in the cool and protected from light and air room. At storage of its loss do not exceed 5-20%. The most destroying factor for vitamin A are oxygen of air and light.
At short-term storage of fresh vegetables, fruit, except greens, losses of carotene in them are not observed. At long storage of loss of carotene happen small and in 6 months do not exceed 6-9%.
Carotene collapses enzymes and also under the influence of oxygen of air and sunshine. Therefore at storage the karotinsoderzhashchy products should be preserved against sunshine, air oxygen influence.
B1 and B2 vitamins in the course of storage of foodstuff do not collapse. However at storage in the crude place in the dried products containing B1 and B2 vitamin the microorganisms splitting these vitamins can develop.
B6 vitamin is unstable to sunlight action, ultraviolet rays destroy it. Therefore, at storage of loss of B6 vitamin can be considerable.
Long storage of the prepared vegetables and fruits is carried out generally in cellars and cellars. At the same time often products get sick (decay), lose consistence, nutrition and vitamin value and also tastes. As a result of it a considerable part of products is thrown out.
The fresh vegetables and fruits prepared for the future are recommended to be stored in cellars and cellars in plastic bags. Fresh vegetables, fruits and fruit are packed into bags capacity in 2 kg and hermetically closed, further being stored on shelves. It is noted that the apples and pears prepared thus can be kept from a harvest till a harvest, apricots, peaches and other gentle fruit – within 1.5-2 months.
At storage of vegetables and fruits in plastic bags as a result of their breath the amount of oxygen decreases and the content of carbon dioxide increases. Thus, the gas structure in a bag differs from composition of air.
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Low content of oxygen and increase in amount of carbon dioxide slow down breath speed and by that promote the best preservation in products of nutrients and vitamins. At storage of vegetables and fruits in plastic bags the taste and aroma also best of all remain. It should be noted that plastic bags, being a protective film, protect fruits and vegetables from hit of the microorganisms causing them I spoil.
Sharp decrease in content of vitamins B products happens during preparation, the subsequent storage of dishes and also at conservation. Only separate vitamins B process of cooking and conservation remain well.
Content of vitamins B finished products depends on many reasons: from a type of products, a way and duration of cold and thermal treatment, storage period of semi-finished products and ready food. At the wrong processing of products and cooking in house conditions there can also be conditions promoting vitamin shortage as a result of violation of technology of preparation.
At preparation of the majority of dishes of the ethnic cuisine the products are exposed to long cooking, suppression, frying and pastries at high temperatures. Naturally, it leads to big losses of vitamins.
In the course of preparation and consumption of food an adverse factor for vitamins is air oxygen. When cooking products in open ware of loss of vitamin C is 1.5-2 times more, than when cooking with the closed cover. It belongs also to other vitamins. Under the influence of air oxygen the vitamins which are contained in products undergo profound changes. As a result they or pass into an unstable form, or completely lose the activity. Therefore, in the course of technological processing it is inexpedient to allow contacts of products with air oxygen, especially at high temperatures of the environment.
Oxidation of vitamins air oxygen at high temperature amplifies under the influence of sunshine.
Especially it is necessary to care for water-soluble vitamins. During cooking of products they pass into liquid and, as a rule, the vitamins which passed into liquid collapse more intensively. And the more liquids per piece, the more passes into it vitamins.
Some vitamins are affected destructively by ions of heavy metals, especially copper and iron. At their presence the extent of destruction of vitamins raises several times. Ions of heavy metals can get to food in various ways: when using not tinned ware from the material containing copper and iron and together with table salt. Even the copper microdoses which are contained in tap water destructively affect vitamins.
Use of stock and tools from stainless steel promotes decrease in losses of vitamins B products, especially in vegetables and fruit.
Gradual heating of vegetables in cold water is followed by more considerable loss of vitamins, than when cooking with immersion in the boiling liquid as as a part of cold water and the vegetables oxygen contains. Besides, at gradual heating the activity of oxidizing enzymes remains during the long time. Therefore, the vegetables and fruit intended for cooking need to be immersed in the boiling water. At the same time and enzymes quickly lose the activity, and transition of nutrients to broth decreases.
Vitamins remain at observance of terms of thermal treatment of products and dishes better.
Many vitamins are sensitive to change of reaction of the environment. The majority of vitamins collapse in alkaline, and some, on the contrary, in acidic environment. Addition during preparation of dishes of food salt or acids leads to destruction of vitamins.
Among vegetables the most active enzyme of an askorbinaz contains in a white cabbage therefore at its cooking a considerable part of vitamin C collapses.
B6 vitamin well transfers influence of oxygen of air and high temperature. However it quickly collapses under the influence of light, is well dissolved in water therefore when cooking its products it is lost more.
In finished culinary products a considerable part of vitamins remains though there are losses. This results from the fact that:
- In vegetables, fruit and berries, except oxidizing enzymes, there are also other enzymes which translate already oxidized vitamins B steadier form. Thus, on the one hand, there is an oxidation of vitamins – transition to an unstable form, to another – the return process, that is restoration
- When cooking, liquid protects products from air oxygen influence
- At immersion of products in fat and hashing on their surface the thin fat film is formed. It serves kind of as an insulating layer. In frying process the film protects products from oxygen access
- As a part of some products such substances as starch, glutathione, carotene contain. They slow down influence of oxidizing agents on vitamins.
Thus, vitamins have friends and enemies. At various ways of technological processing of products the big loss of vitamins is observed, than at their storage and also the mass of finished products decreases.