Vitamin destruction temperature table. At what temperature is vitamin C destroyed in cherry plum? Foods that are healthier when cooked
Heat treatment of products is necessary to improve their taste, soften, destroy harmful microbes and toxins. But at the same time, one should also take into account the fact that after heat treatment, the amount of vitamins contained in food also changes.
Table 16
In culinary practice, browned carrots are widely used, which are rich in provitamin A - carotene. So that carotene is not destroyed, browned carrots should be stored in a sealed container at 0-2 ° C.
B vitamins
The vitamins of this group are soluble in water, so some of them are lost during the process. primary processing products (thawing, washing).
During heat treatment of products of animal origin, about 30-40% of vitamin B1, 15% B2 and up to 40-50% of vitamin B6 are destroyed. In products of plant origin, these vitamins are destroyed by 20-40, 20-40 and 30%, respectively. In addition, part of the vitamins during cooking passes into a decoction, which further impoverishes the main product.
To increase the B-vitamin activity of one of the main food products - bread, the flour-grinding industry enriches wheat and rye flour with vitamins B1, B2 and PP (Table 17).
Table 17
Vitamin C
The main source is vegetables, especially potatoes and cabbage, which are found in significant quantities in many culinary products. In autumn, various varieties of potatoes contain about 20 mg% of vitamin C, mainly in the non-oxidized form. By spring, the amount of vitamin is halved, and in addition, most of it is represented by the oxidized form, which is destroyed faster than the non-oxidized form.
Cabbage after harvesting contains 25-100 mg% of vitamin C, by spring its amount decreases by 10-40%, while part of the vitamin passes into an oxidized form. Sauerkraut contains 17-45 mg% of vitamin C, of which 40% is in brine. In the cabbage squeezed out of the brine, vitamin C is quickly destroyed. Cooking destroys the vitamin C in foods.
However, losses vary widely and depend on many factors. Thus, the duration of thermal exposure has a significant effect on the degree of destruction of vitamin C. In potato soup three hours after its preparation and in boiled potatoes stored for two hours on a hot stove, the content of vitamin C is halved compared to its amount in freshly prepared products.
The heat treatment time is reduced if the water in which vegetables are boiled is quickly brought to 100 ° C. Therefore, in production, vegetables are placed in a boiling liquid (water, broth, etc.). Immersing vegetables in a boiling liquid causes a rapid breakdown of the enzymes that are involved in the oxidation of vitamin C, and therefore contributes to the preservation of the vitamin.
It has been established that when cooking unpeeled and peeled potato tubers with their immersion in cold water vitamin C losses are 25% and 35% respectively. Immersion of the same tubers in hot water reduces the loss of vitamin C: for unpeeled tubers - to traces, for peeled tubers - up to 7%.
Vitamin C is largely destroyed by the combined action of high temperatures and atmospheric oxygen, therefore, excessive mixing of food and vigorous boiling of liquids, as well as cooking vegetables in a dish with an open lid, should not be allowed. Significant losses of vitamin C occur during repeated and even more so repeated heating of vegetables.
The influence of oxygen on vitamin C is enhanced by rubbing and chopping vegetables, when the area of contact of the product with air increases significantly. At enterprises Catering this must be taken into account, and especially in the winter and spring seasons. At this time, it is more advisable to use boiled potatoes.
The loss of vitamin C during the heat treatment of potatoes and cabbage in spring is greater than in autumn. This is explained, on the one hand, by an increase in the oxidized form of vitamin C in spring potatoes, which is more easily destroyed when heated, on the other hand, by a decrease in the total amount of vitamin C in potatoes and cabbage in spring, since it has been established that with a decrease in the total amount of vitamin C in vegetables its specific losses during heat treatment increase.
In table. 18 shows data on the safety of vitamin C during the cooking of various products.
Table 18
If vegetables are not used immediately after cooking, this leads to an additional loss of their C-vitamin activity (20% or more), regardless of the storage temperature. Surveys of catering products for C-vitamin activity showed that in summer and autumn, a lunch consisting of cabbage soup and a second course with a vegetable side dish covers up to 40% of the daily requirement for vitamin C.
In spring, the products of catering establishments are defective in terms of vitamin activity. Therefore, at this time of the year, as well as in winter, catering establishments must be supplied with fresh herbs. At the same time, it should be borne in mind that greens lose up to 15% of the vitamin C contained in them during the day of storage. Fortified products and commercially available vitamin C preparations should also be used.
Heat treatment of food products
Changes in food products during heat treatment
Squirrels
At a temperature of 70 C, coagulation (coagulation) of proteins occurs. They lose their ability to retain water (swell), i.e. from hydrophilic they become hydrophobic, while the mass of meat, fish and poultry decreases. The tertiary and secondary structure of protein molecules is partially destroyed, some of the proteins are converted into polypeptide chains, which contributes to their better cleavage by proteases of the gastrointestinal tract.
Proteins, which are in the form of a solution in products, curl up in flakes during cooking and form foam on the surface of the broth. collagen and elastin connective tissue converted to glutin (gelatin). The total loss of protein during heat treatment ranges from 2 to 7%.
Exceeding the temperature and processing time contributes to the compaction of muscle fibers and the deterioration of the consistency of products, especially those prepared from liver, heart and seafood. With strong heating, starch is destroyed on the surface of the product, and reactions between sugars and amino acids take place with the formation of melanoids, which give the crust dark color, specific aroma and taste.
Meat products during cooking and frying as a result of compaction of proteins, melting of fat and transition to environment moisture and soluble substances lose up to 30-40% of the mass. The smallest losses are characteristic of breaded cutlet mass products, since the moisture pressed out by the proteins is retained by the filler (bread), and the breading layer prevents its evaporation from the fried surface.
Fats
When heated, the fat from the products is rendered. The nutritional value it decreases due to the breakdown of fatty acids. Thus, the loss of linoleic and arachidonic acids is 20-40%. When cooking, up to 40% of the fat goes into the broth, part of it emulsifies and oxidizes. Under the action of the acids and salts contained in the broth, the emulsified fat is easily decomposed into glycerol and fatty acids, which make the broth cloudy, give it an unpleasant taste and smell. In this regard, the broth should be boiled at a moderate boil, and the fat accumulating on the surface must be periodically removed.
Deep changes in fat occur during roasting. If the temperature of the pan exceeds 180 C, then the fat breaks down with the formation of smoke, while the taste of the products deteriorates sharply. Food should be fried at a temperature of 5-10 C below the smoke point.
When frying, the main way fat is lost due to its splashing. This is due to the rapid evaporation of water when fat is heated to more than 100 C. Fat loss during splashing is called waste, and they are significant in fats that contain a lot of water (margarine), as well as when frying moist foods (raw potatoes, meat, etc.). ). Overall fat loss is less in breaded products.
The most significant chemical changes in fats occur during deep-frying. As a result of hydrolysis, oxidation and polymerization, harmful compounds accumulate, giving the fat an unpleasant odor and rancid taste. Toxic products of thermal oxidation of fats (aldehydes and ketones) are adsorbed on the surface of the fried products. In addition, fat is contaminated with particles of the product that enters it.
To prevent undesirable changes in fat, deep fryers are used, in the lower part of which there is a so-called cold zone, where the temperature of the fat is much lower, and the particles of the product that get there do not burn out. To protect deep fat from spoilage, a number of technological methods are used: deep-fryers are periodically filtered, hands and equipment are lubricated with vegetable oil, products intended for deep-frying are not breaded in breadcrumbs.
Carbohydrates
When starch is heated with a small amount of water, its gelatinization occurs, which begins at a temperature of 55-60 C and accelerates with an increase in temperature up to 100 C. During the heat treatment of potatoes, starch gelatinization occurs due to the moisture contained in the potato itself.
When baking dough products, starch gelatinizes due to moisture released by coagulated gluten proteins. A similar process occurs when cooking legumes pre-swollen in water. The starch contained in dry products (cereals, pasta) gelatinizes during cooking due to the absorption of environmental moisture, while the mass of the products increases.
Raw starch is not absorbed in the human body, so all starchy foods are eaten after heat treatment. When starch is heated above 110 C without water, starch is decomposed into dextrins, which are soluble in water. Dextrinization occurs on the surface of baked products during the formation of a crust, during sautéing flour, frying cereals, and baking pasta.
Heat treatment promotes the transition of protopectin, which holds plant cells together, into pectin. At the same time, the products acquire a delicate texture and are better absorbed. The following factors influence the rate of conversion of protopectin to pectin:
- properties of products: in some, protopectin is less stable (potatoes, fruits), in others it is more stable (legumes, beets, cereals);
- cooking temperature: the higher it is, the faster the transformation of protopectin into pectin;
- environmental reaction: an acidic environment slows down this process, therefore, when cooking soups, potatoes should not be laid after sauerkraut or other acidic products, and when soaking legumes, they should not be allowed to soure.
Fiber is the main structural component of the walls plant cells- during heat treatment, it changes slightly: it swells and becomes more porous.
vitamins
Fat-soluble vitamins (A, D, E, K) are well preserved during heat treatment. So, sautéing carrots does not reduce its vitamin value, on the contrary, carotene dissolved in fats is more easily converted into vitamin A. Such stability of carotene allows sautéed vegetables to be stored in fats for a long time, although vitamins are partially destroyed during long-term storage due to exposure to atmospheric oxygen.
Water-soluble vitamins of group B are stable when heated in an acidic environment, and in an alkaline and neutral environment they are destroyed by 20-30%, they partially pass into a decoction. The greatest losses of thiamine and pyridoxine occur during combined heating (quenching, etc.). High preservation with a short heat treatment and a small amount of juice flowing out. Vitamin PP is the most resistant to heating.
Vitamin C is most strongly destroyed during heat treatment due to its oxidation with air oxygen, this is facilitated by the following factors:
- increase in the terms of heat treatment and long-term storage of food in a hot state on a food warmer;
The acidic environment contributes to the preservation of vitamin C. When cooked, it partially turns into a decoction. When frying potatoes in deep fat, vitamin C is destroyed less than when frying the main way.
Minerals. Maximum losses (25-60%) minerals(potassium, sodium, phosphorus, iron, copper, zinc, etc.) occur during cooking in a large amount of water due to their transition into a decoction. That is why decoctions from organic vegetables are used to prepare first courses and sauces.
Coloring substances. Chlorophyll of green vegetables during cooking under the action of acids is destroyed with the formation of brown-colored substances. Plum, cherry, black currant anthocyanins, as well as carrot and tomato carotene are resistant to heat treatment. Beet pigments become brown in color, therefore, in order to preserve its bright color, they create an acidic environment and an increased concentration of broth. The meat changes color from bright pink to gray due to changes in hemoglobin.
The maximum loss of nutrients is observed during cooking in the main way compared to other types heat treatment products. The complication of technology (chopping, rubbing raw and boiled foods, stewing) also contributes to the loss of nutrients.
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CHANGES IN FOOD PRODUCTS DURING HEAT TREATMENT
PROTEINS Proteins coagulate at a temperature of 70 C. They lose their ability to retain water, swell, and the mass of meat, fish and poultry decreases (up to 30-40% of the mass). The tertiary and secondary structure of protein molecules is partially destroyed, which is beneficial for people using gastrointestinal proteases.
Proteins, which are in the form of a solution in products, curl up in flakes during cooking and form foam on the surface of the broth. The total loss of protein during heat treatment ranges from 2 to 7%.
If the temperature and processing time are exceeded, this will lead to compaction of muscle fibers and a deterioration in the consistency of products, especially those made from liver, heart and seafood.
The smallest weight loss is characteristic of breaded products, since moisture is retained by a layer of breading, which prevents its evaporation.
FATS Fat melts when heated. Its nutritional value is reduced. Thus, the loss of some acids is 20-40%. When cooking, up to 40% of the fat goes into the broth. strong changes fat occur when frying. Overall fat loss is also less in breaded products.
Significant chemical changes in fats occur during deep frying. As a result of chemical reactions, harmful compounds accumulate, giving the fat an unpleasant odor and rancid taste. Toxic products of fat oxidation settle on the surface of the fried products.
CARBOHYDRATES When starch is heated with a small amount of water, its gelatinization occurs, starting from a temperature of 55-60 C. Raw starch is not absorbed by the human body, therefore, all products containing starch are eaten after heat treatment.
During heat treatment, fiber (the main structural component of plant cell walls) changes slightly: it swells and becomes more porous.
VITAMINS fat soluble vitamins (A, D, E, K) well preserved during heat treatment.
Foods rich in vitamin A: beef liver, butter, egg yolk, fish liver oil, cabbage, sweet potatoes, broccoli, tomatoes, green vegetables, cantaloupe, apricots, peaches, margarine.
Foods rich in vitamin D: fish oil, fish, egg yolks, dairy products, liver.
Foods rich in vitamin E: vegetable oil, almonds, margarine, walnuts, peanuts, butter, wheat germ, eggs, milk.
Foods rich in vitamin K: spinach, lettuce, kale, White cabbage, cauliflower, broccoli, Brussels sprouts, nettle, wheat bran, cereals, avocados, kiwi, bananas, meat, cow's milk and other dairy products; eggs, soy, olive oil.
water soluble B vitamins they are stable when heated in an acidic environment, and in an alkaline and neutral environment they are destroyed by 20-30%, they partially pass into a decoction. The greatest losses occur during combined heating (extinguishing, etc.). Vitamin PP is the most resistant to heating.
Foods rich in B vitamins: peas, beans, spinach, soybeans, yeast, whole wheat bread, liver, kidneys, brain, beef, pork, walnuts, fish, eggs, cheese, bananas, poultry, buckwheat and millet cereals, seaweed.
Foods rich in vitamin PP: meat, liver, kidneys, eggs, milk, wholemeal bread, cereals (especially buckwheat), legumes, present in mushrooms.
It breaks down the most during heat treatment. vitamin C due to its oxidation with atmospheric oxygen, this is facilitated by the following factors:
Cooking food with the lid open;
laying food in cold water;
increase in terms of heat treatment and long-term storage of food in a hot state;
increasing the contact surface of the product with oxygen (grinding, rubbing).
The acidic environment contributes to the preservation of vitamin C. When cooked, it partially turns into a decoction.
Foods rich in vitamin C: kiwi, rose hips, red peppers, citrus fruits, black currant, onions, tomatoes, leafy vegetables (lettuce, cabbage, broccoli, Brussels sprouts, cauliflower, etc.), liver, kidneys, potatoes.
MINERALS The maximum loss (25-60%) of minerals (potassium, sodium, phosphorus, iron, copper, zinc, etc.) occurs when cooking in a large amount of water, because. they go into the broth.
The maximum loss of useful substances occurs during cooking with the main one. The complication of cooking technology (rubbing, pre-frying) also leads to a loss of nutrients.
Therefore, in order to preserve vitamins, it is necessary to cook food in smaller amounts of water, and, if possible, do not chop before cooking, or grind not too much.
Do you know? The content of vitamins in foods can vary significantly:
When milk is boiled, the amount of vitamins contained in it is significantly reduced.
On average, 9 months a year, Europeans eat vegetables grown in greenhouses or after long-term storage. Such products have more low level vitamin content compared to vegetables from open ground.
After three days of storing food in the refrigerator, 30% of vitamin C is lost (50% at room temperature).
During heat treatment of food, from 25% to 90-100% of vitamins are lost.
In the light, vitamins are destroyed (vitamin B2 is very active), vitamin A is exposed to ultraviolet rays.
Peeled vegetables contain significantly less vitamins.
Drying, freezing, mechanical processing, storage in metal containers, pasteurization reduce the content of vitamins in the original products.
Water is the main component of most foods. It affects many quality indicators, especially those related to texture. Such food preservation methods as heat treatment, irradiation also largely depend on the change in the state of the water component of these products.
Raw materials used in food processing industries and in domestic nutrition can be divided into two groups:
crystalline solids (sugar, lemon acid, table salt, etc.);
colloid-dispersed systems, which in turn are divided into three groups.
Elastic gels- bodies that shrink when dehydrated, but retain elasticity. It includes pressed dough, products based on agar-agar (marshmallow, marshmallow) and gelatin (marmalade).
Fragile gels, bodies that become brittle after drying.
Capillary-porous colloidal bodies: bread, grain, etc.
The elastic walls of the capillaries of these bodies are deformed during drying, so the products can change their volume (shrinkage) and shape (crumbling).
Different bodies interact differently with the moisture contained in them, bind it in different ways.
Academician P.A. Rebinder proposed a classification of moisture bond forms based on the bond energy.
a) mechanical - wetting moisture contained in capillaries and microcapillaries. This form of bond is the least strong, it can be easily removed by mechanical action, such as pressing or centrifugation;
b) physico-chemical form of communication - adsorption, osmotic and structural moisture contained in cells and microcapillaries. It takes a lot more energy to break this form of bond. As a rule, the removal of such moisture occurs in the form of steam, that is, it is necessary to first turn the water into steam, spending a large amount of energy;
c) The chemical form of communication is the most durable. This is an ionic bond (NaOH) and water in crystalline hydrates (Cu SO4x 5H2O). This bond can be destroyed either by chemical action or by heating to high temperatures - by calcination.
Due to the tetrahedral structure of the molecule, water can be associated with some other water molecules through hydrogen bonds and thus form a polymeric structure.
Due to the extremely high charge separation, measured by the dielectric constant, water is a good solvent.
When analyzing the effect of water activity on its state, it is necessary to remember the following general properties:
water dissolves the molecules of a substance;
molecules of a substance can pass into the aqueous phase;
molecules of a substance can concentrate in the water-liquid phase up to precipitation;
dissolved molecules of a substance can react within the phase;
water can itself react;
water exists in solution as a polymer, creating and maintaining its structure.
Since the molecules of a substance pass into pure water solution, then they bind water molecules around themselves, which form a hydration shell.
As more and more of the substance dissolves, the mole fraction of water and its activity decrease. The activity of the water will decrease until the solution becomes saturated and crystallization begins.
When processing products of animal origin, the content of water and soluble substances changes in the following steps:
when thawing raw materials and storing semi-finished products;
in the process of soaking salty foods.
During the thawing process, meat products release more or less salt, which is due to a change in the colloidal structures of muscle tissue, the state of proteins before freezing, the freezing mode, storage and thawing conditions.
Meat contains on average 72-78% water, fish 70-80%. In fatty fish, meat, poultry and offal, moisture is slightly less than 46-68%. The amount of water in muscle tissue is determined to a large extent by the hydration of meat proteins. Their minimal hydration is characteristic of the stage of rigor mortis. As this process is resolved, the degree of protein hydration increases.
In meat products, free water is the main one, mechanically retained inside protein micelles, the amount of adsorption-bound water is small (0.6 g per 1 g of protein).
It is known from previously studied material that during freezing, ice crystals are formed primarily in the tissue fluid, since the concentration of substances dissolved in it is lower than in the muscle fiber. Due to the freezing of water, the concentration of the solution increases, therefore, the osmotic pressure also increases, as a result, water from the muscle fiber moves into the tissue fluid, and, freezing, forms crystals of various sizes. The faster the freezing occurs, the less fluid passes into the tissue space from the muscle fibers, and the less crystals form. With slow freezing, large crystals are formed, which leads to mechanical destruction of muscle fibers.
During storage, even with slight temperature fluctuations, small crystals dissolve and large ones increase, which also leads to rupture of the sarcolemma of muscle fibers.
Due to the increase in the concentration of salts in the muscle fiber, salting out of proteins occurs, and sometimes their denaturation, which leads to a decrease in the hydration of colloids. The depth of denaturation changes depends on the state of the proteins before freezing, the intensity of freezing, and the shelf life.
The water-retaining capacity of proteins in the muscle tissue of meat is most strongly reduced if it is frozen during the period of rigor mortis. With subsequent thawing, such meat loses much more juice than frozen in a paired state or ripened.
During thawing, processes are reverse to freezing. But the original properties are not fully restored. The degree of reversibility of the processes of crystal formation, changes in the colloidal state, restoration of the tissue structure is the greater, the faster the freezing occurs, the lower the temperature and the shorter the storage time.
When thawing, water is gradually absorbed by muscle fibers, while the colloidal structure is restored. With slow thawing, water is more fully absorbed by the fibers, therefore, the properties of muscle tissue are more fully restored. Defrosting times:
Beef - 3-5 days,
Small carcasses of animals - 2-3 days.
Such periods ensure almost complete preservation of juice (losses up to 1%). With rapid thawing, losses are 7-15%.
In products of living origin, with all methods of heat treatment, there is a change in the content of water and solids. The amount of loss depends on chemical composition raw materials and processing methods.
We have studied that during denaturation, muscle proteins lose water, and the welding of collagen and its transition to glutin is accompanied by its absorption. The absorption of water by collagen only partially compensates for its loss by muscle fibers. Therefore, meat products during heat treatment are always more or less dehydrated.
The process of extracting water from meat and fish proceeds differently. The higher the heating temperature of the meat, the greater the loss of water. When the fish is heated, this pattern is not observed, the maximum release of moisture is observed at 65-750 C. This difference indicates that the absorption of water by collagen compensates for its loss by muscle proteins of fish to a greater extent than meat.
The release of water from large pieces occurs gradually as the product warms up. Weight loss during cooking for 1 hour - 26%, 2 hours - 40%. When fully cooked different kinds meat lose about 50%, fish - about 25% of the water contained in it.
But in the nature of the release of water during cooking and frying, there are significant differences. During cooking in water, all the moisture released by the product enters the environment in a liquid state. When frying, only a small part of the moisture is released in a liquid state, forming juice. The bulk of it evaporates first from the surface, and then, as it warms up, from deeper layers. When steaming, poaching and stewing, less moisture is released in the liquid state than when boiling in water, but more than when frying.
Soluble substances are removed from the product mainly with water released in the liquid state. Therefore, as follows from the above, the largest number soluble substances are extracted from muscle tissue during its boiling in water. Additional extraction of soluble substances occurs due to diffusion, which equalizes their concentration in the product or broth.
During the frying process, soluble substances are released in the smallest amount, since with this method the bulk of the moisture evaporates in the form of steam.
Boiling, stewing and steaming, in terms of the amount of substances extracted from the product, occupies an intermediate position between boiling in water and frying.
When cooking meat products, soluble proteins, extractive and mineral substances, and vitamins pass into the water.
Extractives are a mixture of various decay products formed during the metabolism of living tissue. They are divided into nitrogenous and non-nitrogenous.
nitrogenous– free amino acids, dipeptides, urea, guanidine derivatives and purine bases.
Free amino acids occupy a significant part of extractive substances - up to 1%. 17 of them were found. But we should especially highlight glutamic acid, the content of which in muscle tissue is 15-50 mg%. Solutions of glutamic acid have a specific complex "meat taste".
Guanidine derivatives: creatine - 0.5% and creatinine - 0.01%.
Dipeptides - carnosine and anserine - no more than 0.3%, urea (urea) - 0.2%.
Purine bases - 0.05% -0.15%, hypoxanthine predominates.
To nitrogen-free substances include: glycogen, sugars, acids, mesoinositol. In the process of maturation of meat, the amount of glycogen is reduced by 3-4 times, and the content of lactic acid increases. Sugars - glucose, fructose ribose - are found in meat in small quantities. The qualitative composition of the extractive substances of beef, pork, lamb is approximately the same, only the tripeptide glutathione, cysteic acid, and the amino acid ornithine were found in lamb.
Soluble substances change during the cooking process - proteins coagulate, extractive substances interact with each other, form new products that have a specific color, taste, smell.
The dynamics of selection is as follows. Soluble protein will stand out in the first half hour of cooking (about 80% of the total). The remaining soluble substances (organic and mineral) are released gradually, almost at the same rate over 2 hours, then the rate of release decreases.
From small pieces, soluble substances are released more intensively, and in the largest amount - in the first half hour of cooking. The release of glutin occurs at the end of cooking.
The amount of substances extracted during the cooking process depends not only on its properties, but also on technological factors:
1. Temperature regime .
Meat products are cooked by immersion in cold or hot water. When immersed in hot water, the protein is lost 2 times less than in cold water, but the losses are still very small (0.03 and 0.06%), since the protein denaturation temperature is very low.
The extraction of the remaining soluble substances when immersed in hot and cold water is almost the same.
The cooking temperature of 97 - 980 C provides the fastest bringing the meat to readiness. Meat with a small content of tissue (veal) can be brought to readiness in the same time at a temperature of 900 C.
By lowering the cooking temperature, muscle protein gels are less compacted, leaving more moisture and solubles in the meat.
2. The ratio between the amount of meat and water .
The loss of soluble substances is the more significant, the more water is taken, since with an increase in the amount of water, Better conditions for the diffusion of minerals from it, that is, the difference in concentrations increases.
3. Degree of mincing meat .
The meat is cooked in pieces from 0.5 to 2 kg. The smaller the pieces, the more area their contact with water, the more favorable the conditions for diffusion.
Minced meat, but molded into a piece, loses less soluble substances than the same piece of meat, since in this case there is no continuous connective tissue base, the compression of which causes a stronger extrusion of moisture.
When cooking vegetables, water is almost completely preserved during cooking. When stewing, stewing and frying, its content decreases to a greater or lesser extent due to evaporation. During the cooking of starchy foods, all moisture is absorbed by the gelatinizing starch. A small loss of it takes place as a result of evaporation from the surface after cooking. The same is true for root crops. Moisture loss during stewing, stewing, frying depends on the type of vegetables, the degree of their grinding, the method of pre-treatment and mainly determines the weight reduction.
Soluble substances that form the dry residue of the cell juice of vegetables are very diverse - sugars, nitrogenous, mineral, pectins, glycosides.
Due to the destruction of the leathery layer of the protoplasm (membrane), which coagulates during heat treatment, the soluble substances of the cell sap freely diffuse into the environment. The loosening of the parenchymal tissue of the cell walls under the action of heat treatment facilitates diffusion.
A significant amount of free amino acids was found in vegetable broths. Relatively large losses of mineral substances during cooking peeled vegetables, as well as beets and carrots in the skin - mainly due to the extraction of K, Fe, Ca, P. The content of Mn practically does not change.
Steam cooking extracts significantly less solubles. The more instances of vegetables, the less loss. An increase in the amount of moisture also leads to an increase in the loss of soluble substances.
It is necessary to separately consider the interaction of leguminous crops and water during soaking and heat treatment. When soaking, the macromolecular substances contained in them swell - proteins and carbohydrates of the cell walls. Due to this, the time of their heat treatment is reduced. The swelling time is 5 - 10 hours, during which time the weight increases by 90 - 110%. Swelling is accompanied by an increase in solutes.
Mineral substances diffuse in the amount of 0.3 ... 0.4% by weight of the product, carbohydrates - from 1.2 to 2.8%, non-protein nitrogenous substances - 0.3%. When soaking some varieties of legumes (beans), substances of a glycosidic nature, which have an unpleasant taste and smell, pass into the water. In this case, water after soaking is not used.
When cooking completely swollen legumes, the amount of water in them practically does not change. There is only a redistribution of it between proteins and starch. When cooking unsoaked cereals of legumes, the moisture content in them increases significantly.
Loss of solutes occurs if the decoction is not used.
Depending on the conditions of technological processing, the amount of vitamins in food products decreases to one degree or another. Vitamins are the most important nutritional substances that are involved in the normalization of metabolism in the body and the formation of enzymes, support the immunobiological properties of the body and its resistance to adverse external factors, play an essential role in preventive and therapeutic nutrition. Since food is the main source of vitamins in a balanced diet, the issue of preserving its vitamin composition during processing is extremely important.
It is known that the classification of vitamins is based on the principle of their solubility in water and fat, therefore they are divided into water- and fat-soluble vitamins.
Vitamin A is found only in products of animal origin, it is resistant to alkali and heat, but not resistant to acids, ultraviolet rays and O2 - it is inactivated under their influence. Vitamin A also includes plant pigments, carotenoids, which play the role of provitamin A.
The daily requirement of an adult for vitamin A is 1-2.5 mg, carotene - 2-5 mg.
Sources of vitamin A (per 100 g of product): liver - 15 mg, cow's butter - 0.6 mg, cheese - 0.2-0.3 mg, cream, sour cream - 0.3 mg. Herbal products containing b-carotene: red pepper, parsley - 10 mg, carrots - 9 mg, sorrel, sea buckthorn - 8 mg, green onions - 6 mg, dill - 5.5 mg, rose hips, spinach - 5 mg.
Vitamin A and carotene in products are much more stable than in their pure form.
When storing carrots and other plant products, the carotene content does not decrease until they begin to deteriorate.
Storing sliced carrots leads to an increase in their carotene content.
During heat treatment of products A - vitamin activity is preserved completely or almost completely. When browning, 20% of the total carotene content passes into fat. When storing browned carrots, the content of carotene decreases the more, the thinner the layer, especially when the lid is open.
B vitamins:
Daily requirement B1, B2 - 2 - 3 mg, B6 - 2-4 mg, PP - 15 - 25 mg. Contained in products of both plant and animal origin.
AT- in cereals - 0.2 - 0.7 mg, liver - 0.4 mg.
AT- liver - 3.3, kidneys - 1.9, egg - 0.5 mg, cereals - 0.2 mg.
AT- meat - 0.3 - 0.5, liver - 0.7, yeast - 4.6, cabbage - 0.1-0.3, green pepper - 0.8.
RR- liver - 14, offal - 3-4, legumes - 2-3.
During cooking, the content of B vitamins changes to a greater or lesser extent. Part is lost with juice during thawing of frozen meat products, as well as during washing of vegetable products. So, when pork is thawed, the loss of vitamin B group ranges from 4 to 11%, while rinsing rice loses 30% of the vitamin.
During heat treatment, B vitamins are destroyed, during cooking and stewing, some of them are extracted from the product into a decoction, and during frying, 5-10% of these vitamins are released with juice.
B6 is destroyed to the maximum during heat treatment: beef - 38% during cooking, 50% - during frying.
During cooking, 30% of vitamin B1 is destroyed, and 28-35% goes into a decoction.
Riboflavin is the most stable during heat treatment. Its losses do not exceed 15%, regardless of the method of heat treatment.
In products of plant origin, during heat treatment, the amount of vitamin B6 decreases sharply - by 30-40% when cooking, but 28-30% when frying.
When cooking vegetables and cereals, no more than 20% of vitamin B1 and B2 are destroyed. And in rice, thiamine is destroyed almost completely.
The more water is taken for cooking, the less vitamins remain in the boiled product. And the ability to extract them into a decoction confirms the feasibility of its use.
Vitamin C - thermolabile, daily requirement an average of 70 mg. Its content in vegetables ranges from 5 (eggplant) to 250 mg ( Bell pepper) per 100g of product. In cabbage, potatoes 20-60 mg per 100 g of the product. Of the fruits, citrus fruits, black currants and rose hips are rich in them, respectively 38, 200 and 470 mg per 100 g).
Ascorbic acid is found in vegetables and fruits in three forms - reduced, oxidized (dehydroform) and bound (ascorbigen). During maturation and storage, the reduced form can be oxidized with the help of appropriate enzymes and converted into a dehydroform, which has all the properties of vitamin C, but is less resistant to external factors and is quickly destroyed. Ascorbigen can undergo hydrolysis, resulting in the release of free ascorbic acid.
During heat treatment, vitamin C is partially converted into a decoction, partially destroyed. At the beginning of heat treatment, it is oxidized under the action of oxygen and oxidizing enzymes, turns into dehydroascorbic acid, and with a further increase in temperature, thermal degradation of both forms of vitamin C occurs. After hydrolysis of ascorbigen, the released ascorbic acid is also destroyed.
The degree of destruction of vitamin C depends on the properties of the raw materials being processed, the rate of heating of the product, the duration of heat treatment, contact with atmospheric oxygen, the composition and pH of the medium.
During cooking, the degree of destruction of vitamin C depends on the ratio of the reduced and oxidized forms. For example, when cooking unpeeled potatoes in autumn, 10% is destroyed, in spring - 25%, cabbage in autumn - 2-3%, in spring - 30%. That is, the less dehydroascorbic acid in relation to the reducing form, the less it is destroyed.
The faster the heating of the product, the less destruction. In potatoes, when immersed in cold water, 35% is destroyed, in boiling water - 7%. That is, when immersed in boiling water, the enzymes that promote the conversion of vitamin C into the dehydroform are almost immediately inactivated.
How longer terms heat treatment, the more the vitamin is destroyed. That is, it is necessary to strictly observe the cooking time. The presence of oxygen contributes to the oxidation of vitamin C and its further destruction.
Copper, iron, manganese ions accelerate the destruction of vitamin C (water, dish walls). Copper ions cause the most catalytic action. When cooking vegetables in an acidic environment, vitamin C is preserved better. Some substances contained in foods have a protective effect on the vitamin. Amino acids, starch, vitamins A, E, thiamine, pigments to some extent protect vitamin C from destruction. Destruction of vitamin C can also occur during storage of boiled vegetables at any temperature.
The total loss of vitamin C depends on the method of heat treatment. The greatest losses are observed during cooking. Steaming leads to minimal destruction of it. When allowed, the loss of vitamin C is somewhat higher than when cooking in water, since in this case the product is in a vapor-air mixture containing oxygen.
Processing in microwave devices leads to a reduction in losses by 20-25%, as this reduces the time of heat treatment due to the rapid heating of the product.
In the process of frying, the destruction of vitamin C is somewhat less than during cooking, since the product is enveloped in fat and prevents its contact with oxygen.
When chopping vegetables, especially mashed potatoes, the loss of vitamin C reaches 90%.
Ways to preserve C-vitamin activity:
ensuring fast warm-up;
cooking at a moderate boil and do not allow the liquid to boil away;
do not exceed the terms of heat treatment;
use of decoctions;
avoid long-term storage of finished products
It is known that vitamins enter our body with food, and if a person is malnourished, he may experience a lack of useful substances in the body. Good nutrition does not imply the intake of excessive amounts of food (many people think so, it would seem that they eat a lot, but beriberi is still present), here we are talking about including a moderate amount of all food groups in the diet.
Even proper nutritious nutrition sometimes cannot provide a person with all the useful substances, and all because you should know how to properly prepare and cook foods so that vitamins do not lose their properties during heat cooking and frying.
Food should be healthy, this is clear, but often people do not pay attention to this, believing that the main thing is the taste of the product, but each nation has its own preferences, sometimes even completely incomprehensible. So in Alaska, the main delicacy is fish heads rotted in a pit with moss, and then rubbed into sauce. Indonesian gourmets, for example, consider a smoked bat to be the best snack, and Colombians, having come to the cinema, instead of traditional puffed corn (popcorn) prefer huge fried ants. Yes, tastes differ!
Reaction to heat treatment
Vitamins behave differently during heat treatment - some are more resistant to high temperatures, while others are completely destroyed even with minimal heating.
Consider the effect of temperatures on each group of vitamins:
- retinol (A) - during heat treatment, the substance can withstand heating up to 120 degrees, provided that the container is hermetically sealed. Outdoor air and sunlight destroy retinol, so products containing it are stored only in a dark, cold place. In ready-made dishes, up to 70% of the substance is retained;
- thiamine (B1) - in a sealed container withstands heating up to 120 degrees, destroys the substance in an alkaline environment, depending on the method of preparation, from 55 to 70% of thiamine is preserved;
- riboflavin (B2) - heating temperature up to 110 degrees, afraid of ultraviolet radiation, from 60 to 90% of the substance is stored, depends on the method of preparation (during cooking, frying, stewing);
- pyridoxine (B6) - all water-soluble vitamins are destroyed during cooking, but not B6. Not afraid of high temperatures, in the finished dish remains from 70 to 80% of the substance;
- folic acid (B9) – heat intolerant and sunlight, in ready-made dishes, from 10 to 30% of the substance remains;
- ascorbic acid (C) - one of the most unstable vitamins, does not tolerate heat, open air, prolonged exposure to water and contact with metal, is preserved only when frozen;
- calciferol (D) and tocopherol (E) - both vitamins are resistant to high temperatures, almost completely retain their properties even when frying;
- niacin (PP or B3) is the most stable substance among water-soluble substances, it does not lose its properties either during heat treatment or during freezing or drying, withstands heating up to 120 degrees, and is almost completely preserved in the finished dish.
All useful substances are lost to a greater or lesser extent after high temperatures (heating) are applied to them, but this is not the only factor that can lead to their destruction.
In addition to knowing whether vitamins are destroyed during cooking, we also need to know how to properly store certain foods in order to ensure the safety of nutrients in them.
After collecting or purchasing products in the store (meaning fruits, vegetables, berries), they should be immediately sent to a dark, cool place, so they retain their beneficial features for several days. If you decide to stock up on them in excess then the best way to save vitamins is to freeze foods. Leafy vegetables, after spending only a few hours in the open air, lose up to 80% of their ascorbic acid content in sunlight. The sooner the product is used in food after collection, the more likely you are to saturate your body with vitamins.
How to cook
The greatest benefits for the body are steamed or baked dishes, so they contain the largest amount of vitamins. In order not to wonder whether useful substances remain in the soup after cooking, you should know a few “golden rules” for cooking vegetables:
- put vegetables only in boiling water;
- do not boil them, but rather do not cook them a little (they will reach under a closed lid on their own);
- potatoes should be boiled (immersed already in boiling water) or baked in their skins;
- if for cooking you need to pre-peel the potatoes, try not to cut off a thin layer of the peel (it is in it that everything is most valuable), do the same with other vegetables;
- wash vegetables under running water, do not soak them for a long time;
- use a stainless steel knife to peel vegetables;
- if possible, do not apply to vegetables or use minimal heat treatment.
Whether or not vitamins are preserved during cooking - everything will depend on you, if you use these simple rules in the process of preparing and cooking vegetables, then the beneficial properties of the products will be preserved to the maximum. However, remember already ready meal should be eaten immediately, after the secondary heating, more than half of the vitamins are destroyed, and heating it for the third time, there will be no useful substances left in it at all.
If you care about your health, give preference to foods prepared by baking, stewing, and best of all, steam, so the food will retain its natural taste and all the nutrients.
If you can’t refuse fried foods, then before putting it in a pan, for example, roll the fish in breadcrumbs. The crust that is formed in the process will retain the juices and nutrients as much as possible when frying the fish.
Also remember that you need to spread the product in a well-heated pan, do not reuse frying oil (carcinogens accumulate in it). In general, the hottest
imperfect cooking process - in addition to the fact that more nutrients are destroyed, dark-colored compounds are also formed that the body does not absorb, so you should not get carried away with fried foods.
Physical and chemical factors that affect the stability of vitamins include exposure to heat, humidity, air or light, and acidic or alkaline environments. Any of these factors can affect the stability of vitamins during food processing or storage. The sensitivity of vitamins to various physical and chemical factors is presented in Table 1.
Table 1: Sensitivity of vitamins to various factors
Light | Warmly | Humidity | acids | alkalis | |
Vitamin A | +++ | ++ | + | ++ | + |
Vitamin D | +++ | ++ | + | ++ | ++ |
Vitamin E | ++ | ++ | + | + | ++ |
Vitamin K | +++ | + | + | + | +++ |
Vitamin C | + | ++ | ++ | ++ | +++ |
Thiamine | ++ | +++ | ++ | + | +++ |
Riboflavin | +++ | + | + | + | +++ |
Niacin | + | + | + | + | + |
Vitamin B6 | ++ | + | + | ++ | ++ |
Vitamin B12 | ++ | + | ++ | +++ | +++ |
Pantothenic acid | + | ++ | ++ | +++ | +++ |
Folic acid | ++ | + | + | ++ | ++ |
Biotin | + | + | + | ++ | ++ |
+ Insensitive or slightly sensitive
++ Sensitive
+++ Highly sensitive
Vitamin stability during food processing and storage
Industrial processing of foods can affect the stability of vitamins in them. The use of stabilized encapsulated forms of vitamins significantly improves the stability of vitamins during food processing and storage.Wheat and yellow corn flours stored at room temperature retain more 95% vitamin A after 6 months. However, the stability of vitamin A at high storage temperatures is not as good. In wheat flour, stored for 3 months at 45 ° C, only 72% vitamin A.
During the baking of bread, limited loss of vitamin A occurs, while the frying process has an adverse effect on the stability of the vitamin. After heating soybean oil to the temperature of frying, fortified with vitamin A, it remains about 65% initial level of vitamin A. If this oil is used 4 more times, it remains less 40% from baseline vitamin A levels.
Sustainability vitamin E depends on its shape. dl-α-tocopheryl acetate is the most stable. Vitamin E, found in foods in the form of tocopherol, slowly oxidizes when exposed to air. However, vitamin E added in the form of α-tocopheryl acetate is perfectly preserved in wheat flour. Losses of vitamin E occur only during prolonged heating, such as boiling and frying.
Thiamin (vitamin B1) is one of the most unstable B vitamins. Baking, pasteurizing or boiling foods fortified with thiamine can reduce its content by 50% . The stability of thiamine during storage is highly dependent on the moisture content of the product. Flour with a moisture content of 12% retains 88% added thiamine after 5 months. If the moisture level is reduced to 6%, there is no loss. Thiamin, riboflavin and niacin are fairly stable in bread baking; the loss of these vitamins is only from 5% to 25%(table 2).
Table 2: loss of vitamins during bread baking
Riboflavin (vitamin B2) very stable during heat treatment, storage and cooking, but subject to degradation when exposed to light. The use of light-tight packaging material prevents its destruction. Niacin is one of the most stable vitamins. Its main losses occur upon contact with water in which food is cooked. Enriched with thiamine, riboflavin and niacin, spaghetti preserves 96% , 78% and 94% the initial level of these vitamins after 3 months of storage in the dark, followed by boiling for 14 minutes.
Losses pyridoxine (vitamin B6) depend on the type of heat treatment. For example, high losses of B6 occur when liquid infant formula is sterilized. But in fortified wheat and corn flour, B6 is resistant to baking temperatures. B6 is sensitive to light, exposure to water can also cause it to be lost. However, vitamin B6 is stable during storage: wheat flour stored at room temperature or 45°C retains about 90% vitamin A.
Folic acid unstable and loses its activity in acidic and alkaline environments. However, it is relatively resistant to heat and humidity; as a result, premixes, baked goods and cereals retain almost 100% of added folic acid after 6 months of storage. More than 70% of the folic acid added to wheat flour is retained during bread baking (Table 2).
Pantothenic acid resistant to heat in slightly acidic or neutral conditions, but its stability is reduced in alkaline environments. Biotin is sensitive to acids and bases. Enriched cornmeal shows good storage stability of various micronutrients.
Ascorbic acid (vitamin C) easily destroyed during handling and storage by exposure to metals such as copper and iron. Exposure to oxygen or prolonged heating in the presence of oxygen destroys ascorbic acid. The stability of vitamin C in fortified foods depends on the food itself, how it is processed, and the type of packaging used. The vitamin C content of fortified foods and drinks stored for 12 months at room temperature ranges from 60% to 97%(table 3).
Table 3: Vitamin C stability in fortified foods after 12 months storage at 23°C
Mineral stability during food processing and storage
Minerals are more resistant to industrial processing than vitamins. However, they are subject to change when exposed to heat, air or light. Minerals such as copper, iron and zinc are also affected by moisture and can react with other food components such as proteins and carbohydrates. Minerals can also be lost when cooking in water, as is the case with fortified rice.Various forms of iron are used for food fortification. Among the most popular are sulfate and elemental iron powders, as they are relatively highly bioavailable. Other potential sources of iron include iron orthophosphate, sodium iron phosphate, ferrous fumarate, and iron chelate (EDTA). Sustainability different forms iron depends on various factors, including the nature of the product to which it is added, particle size, exposure to heat and air.
It is known that ferrous sulfate, due to its reactive nature, accelerates the development of oxidative reactions, leading to a change in the color or odor of the product. It has been found that when added to baking flour in an amount of more than 40 ppm or when stored for more than 3 months at high temperature and humidity, the product becomes rancid and its taste deteriorates.
Elemental iron, in the form of reduced or electrolyte iron, is used to fortify ready-to-eat breakfast cereals and has excellent processing and storage stability. Reduced iron is generally the preferred form of this mineral for fortifying flours that require a long shelf life. However, when added to bread and flour, fine particles tend to discolor the product.
Packaging influence
Foods that are improperly packaged and subsequently transported over long distances in hot and humid conditions experience loss of vitamins and trace elements.Vitamin A when combined with sugar, it is more stable in cold and dry conditions than in hot and humid environments. Vitamin A must be protected from oxygen and light, vitamin C from oxygen, and riboflavin and pyridoxine from light.
In liquid products such as drinks, milk and oils, exposure to oxygen can quickly destroy vitamins A and C. Glass containers are the best option for these fortified foods because they are impervious to oxygen. However, glass is heavy, fragile, and expensive, so plastic is often used instead. Oxygen easily passes through the plastic and comes into contact with the product. This problem can be solved by applying a special coating to the plastic and/or adding more sensitive micronutrients such as vitamin A.
Light-tight containers such as dark glass or plastic, jars and aseptic packaging minimize exposure to light. Due to the high cost, the packaging acquires great importance and should be the main factor to consider when producing vitamin fortified foods.
Shelf life of products processed at very high temperatures ( e.g. milk), may exceed 1 year, and storage losses during this time must be taken into account when calculating the amount of micronutrients added.
The need to increase the amount of added micronutrients
What happens to food before it is consumed can affect the beneficial micronutrients that are naturally present in or added to the food. Even when all precautions are taken to ensure the stability of trace elements in products, some losses still occur during processing, shipping and storage. Therefore, special attention should be paid to the development of enrichment technology that takes into account the amount of added substances.Micronutrients can be added in higher amounts to compensate for their possible losses, so that the product contains the target level of nutrients at the time of consumption.
Organoleptic properties
For a food fortification program to be effective, there must be no change in colour, taste, odor or appearance enriched products. Cooking at home should also be done in accordance with the instructions.Changes in color are due to the reactive nature and the concentration of micronutrients added. Undesirable color changes in cornmeal occur, for example, when riboflavin levels exceed 2.5 mg/kg or when ferrous sulfate is used as an iron source and the product is stored under high humidity conditions. In some cases, color change can be avoided by changing the form of the added substance, combining it with another substance, or reducing its amount.
The most reactive trace elements, such as iron, shorten the shelf life of certain products. Adding minerals to foods containing fat, such as milk and margarine, as well as wheat and cornmeal, can also cause malodors due to lipid oxidation.
Iron is a pro-oxidant and is responsible for altering the flavor of fortified foods, especially those that require a longer shelf life, including wheat and corn flour. Iron can also catalyze the oxidation of vitamins A and C.
Finally
In general, many physical and chemical factors adversely affect the stability of micronutrients that are naturally present in or added to foods. However, the stability of trace elements in fortified foods can be ensured if the products are properly packaged and stored under proper conditions.We hope that after reading this article, you are once again convinced of the benefits of fresh and natural food with minimal shelf life.
Scientific studies have shown that about 90-95 percent of the total amount of vitamins the human body receives through a balanced diet. The actual question is at what temperature vitamin C is destroyed, most often occurs during the period of colds due to the need to strengthen the immune system and effectively fight viruses.
Ascorbic acid is an important factor in health and wellness
This powerful antioxidant not only regulates redox reactions, but also normalizes blood clotting and capillary permeability, has anti-allergic and anti-inflammatory effects.
Vitamin C plays an important role in the synthesis of collagen, catecholamines and steroid hormones. In addition, it regulates metabolic processes associated with calcium, iron and folic acid improving their digestibility. This vitamin is the most important factor protect the body from the effects of stress and its consequences. Therefore, the question of under what conditions and at what temperature vitamin C is destroyed worries almost everyone, including residents of megacities, remote cities and rural settlements.
The main reasons for the destruction of vitamin C
Heat treatment of most products has a beneficial effect on their quality: improves taste, softens the structure, destroys harmful microbes and toxins. Boiled, stewed, baked, steamed and even fried foods are much safer than raw foods. It can save a person from digestive problems (intestinal disorders and pancreatic disorders). But what temperature destroys vitamin C, which is so necessary for the human body? And what other factors influence the destructive processes in ascorbic acid?
Water-soluble vitamin C is an unstable compound that can decompose even during long-term storage, reacts negatively to any chemical and physical influences. Ascorbic acid is easily oxidized. Its preparations cannot be stored in metal containers, since acid reacts when it comes into contact with the container. Vitamin C should also not be exposed to light, heat, high humidity, contact with oxygen, which contributes to its destruction. The presence of this vitamin in foods decreases at any ambient temperature, but to varying degrees.
What does science say?
The ascorbic acid molecule, according to a number of researchers, is completely destroyed at a temperature of 191-192 ° F (88-89 ° C), but only one isomer (L-ascorbic acid), or vitamin C, is biologically active, a natural substance that found in vegetables and fruits. Its quantity is affected by the duration of transportation and shelf life of products, their protection from air and light, and other parameters.
After buying vegetables or fruits, it matters whether they are stored in the refrigerator or not, whole or sliced, how long they cook and at what temperature. Vitamin C is destroyed from a threshold of 60-70 degrees, but is stable in an acidic environment. Salads (cold and hot) with lemon juice, second courses with the addition of tomatoes or tomato paste retain this vitamin much better than first courses with a high liquid content, but do not have acidic ingredients. Drying, cutting, prolonged heating of food in a saucepan with an open lid, reheating dishes, copper or iron utensils actively destroy the powerful antioxidant.
Experiment with the “correct” water and express rosehip infusion
Using distilled water instead of tap water helps retain vitamin C significantly when boiled for a short time. An experiment was conducted by an American chemistry student: in one cup of distillate, he dissolved 1 teaspoon of ascorbic acid to obtain its concentration of 2-25%. As a result measuring device showed 217%. The researcher tightly covered the container with the solution with thermal film and left a small hole for the release of steam. Briefly heated a cup of ascorbic acid (no more than 2 minutes) in the microwave, then cooled for 5 minutes and put in the refrigerator. After 75 minutes, when the solution had cooled to room temperature, he again measured the concentration of vitamin C. Due to short-term evaporation, this figure increased to 219%! For the same purpose, experts advise preparing express infusions of berries rich in vitamin C.
The maximum amount of this vitamin is guaranteed to be preserved if the rose hips are quickly crushed, poured with boiled water with a temperature not exceeding 40-60 degrees, and then insisted for an hour in a tightly closed thermos. Prolonged boiling of rose hips destroys L-ascorbic acid, significantly reducing the value of the decoction compared to freshly squeezed juices and express infusions.
Hot tea and boiling lemon water
On the forums, you can often find a question from hot tea lovers at what temperature vitamin C is destroyed. Japanese researchers, contrary to the widespread belief that this popular drink should not be brewed with boiling water, proved that the L-isomer of ascorbic acid (vitamin C) is destroyed slightly . Its concentration in the first quarter of an hour drops by only 30 percent in brewed tea at a constantly maintained boiling temperature, but after an hour it disintegrates almost completely. At the same time, in ordinary boiling water, dissolved vitamin C is destroyed by 83 percent after 10 minutes.
Experts explain this difference by the fact that tea phenol reacts with copper and iron ions, binding them, which prevents their effect on accelerating the breakdown of vitamin C. If you need to make hot lemonade from 6 lemons, then they are cut in half and thrown into boiling water . After 3 minutes, the container is removed from the stove, the drink is infused for 10-15 minutes. Then it is filtered from the fruits and pulp. This lemonade protects against colds and boosts immunity when drunk hot or warm with a little honey added. Store the drink in the refrigerator, heat it in the microwave to maximize the preservation of ascorbic acid.
When preparing first and second courses
There is no exact data that indicates at what temperature vitamin C is destroyed in each particular dish. It is known that already at 50 degrees Celsius in potato soup, the concentration of ascorbic acid will begin to decrease if you do not cover the pan with a lid and lay the vegetables ahead of time. According to the rules, they must be added to boiling salted water, and the dishes covered with a lid during cooking. The same should be done with frozen vegetables, because boiling water contains much less dissolved oxygen, which destroys vitamin C. In addition, heat boiling activates, next to ascorbine oxidase, other beneficial plant enzymes that contribute to a better preservation of the vitamin. In potatoes, drenched in boiling water and boiled in their skins, its amount is reduced by about 10 percent. Less water also prevents the natural ascorbic acid from breaking down.
So, for example, sauerkraut soup loses 50% of a powerful antioxidant after cooking for an hour, and stewed cabbage loses only 15%. Tomatoes cooked for 2 minutes in a microwave or oven (at 90 degrees) lose only 10 percent of a vital substance. The same tomatoes, cooked for half an hour, lose about 29-30% of vitamin C. Steamed vegetables get rid of 22-34% of the valuable vitamin, and in the microwave - 10% over the same period of time.
At what temperature is vitamin C destroyed in cherry plum?
The benefits of this well-known plum are especially noticeable during the cold season. Its diaphoretic and antitussive action is valued along with a pleasant taste and many others. healing properties. Tkemali, as they call "cherry plum" in the Caucasus and Transcaucasia, contains few sugars, but it contains citric and malic acids, vitamins of groups B, A, E and PP. Plum is rich in pectins, calcium, magnesium, sodium, iron, phosphorus. In addition, it is a real source of vitamin C. The temperature of its destruction also depends on all the factors described above. For example, cherry plum compote will contain much less of this valuable substance than tkemali sauce, because in a large amount of water the described vitamin is destroyed faster than in seasoning without additional liquid. Cherry plum is a powerful source of ascorbic acid also because other acids in its fruits prevent the breakdown of the water-soluble vitamin.
The reaction of other useful elements to heat
Doctors consider vitamin D to be the second, no less important "anti-cold vitamin", which is recommended to be taken along with rosehip infusion. Fish oil, vegetable oils and cheese in the off-season should be on every table. At what temperature is vitamin D destroyed? During heat treatment, fat-soluble vitamins (A, D, E, K) practically do not reduce their activity and are not destroyed. At the same time, vitamin D stably withstands prolonged boiling in an acidic environment, and in an alkaline environment it is prone to rapid destruction. It is known that at a temperature of +232 degrees in the oven, cheese loses up to 25-30% of the “anti-cold” vitamin within 5 minutes. It is known that rosehip, in addition to vitamin C, contains vitamin P (rutin). This substance enhances the effect of "ascorbic acid", and their combined use is necessary when prescribing aspirin with sulfonamides for a full, restoring effect on capillaries. The answer to the question at what temperature vitamin P is destroyed is similar to the recommendations related to ascorbic acid. These two vitamins are largely identical: both are water-soluble, afraid of sunlight, exposure to oxygen and the same temperature. In addition to rose hips, rutin is found in lemons. Complementing and reinforcing each other, these vitamins are also indicated for long-term antibiotic therapy.
Scientific studies have shown that about 90-95 percent of the total amount of vitamins the human body receives through a balanced diet. The actual question of at what temperature vitamin C is destroyed often arises during the period of colds due to the need to strengthen the immune system and effectively fight viruses.
Ascorbic acid is an important factor in health and wellness
This powerful antioxidant not only regulates redox reactions, but also normalizes blood clotting and capillary permeability, has anti-allergic and anti-inflammatory effects.
It plays an important role in the synthesis of collagen, catecholamines and steroid hormones. In addition, it regulates the metabolic processes associated with calcium, iron and folic acid, improving their absorption. This vitamin is the most important factor in protecting the body from the effects of stress and its consequences. Therefore, the question of under what conditions and at what temperature vitamin C is destroyed worries almost everyone, including residents of megacities, remote cities and rural settlements.
The main reasons for the destruction of vitamin C
Heat treatment of most products has a beneficial effect on their quality: it improves the taste, softens the structure, and destroys harmful microbes and toxins. Boiled, stewed, baked, steamed and even fried foods are much safer than raw foods. It can save a person from digestive problems (intestinal disorders and pancreatic disorders). But what temperature destroys vitamin C, which is so necessary for the human body? And what other factors influence the destructive processes in ascorbic acid?
Water-soluble - the most unstable compound that can decompose even during long-term storage, reacting negatively to any chemical and physical influences. easily oxidized. Its preparations cannot be stored in metal containers, since acid reacts when it comes into contact with the container. Vitamin C should also not be exposed to light, heat, high humidity, contact with oxygen, which contributes to its destruction. The presence of this vitamin in foods decreases at any ambient temperature, but to varying degrees.
What does science say?
The ascorbic acid molecule, according to a number of researchers, is completely destroyed at a temperature of 191-192 ° F (88-89 ° C), but only one of its isomers (L-ascorbic acid), or vitamin C, is biologically active, a natural substance, found in vegetables and fruits. Its quantity is affected by the duration of transportation and shelf life of products, their protection from air and light, and other parameters.
After buying vegetables or fruits, it matters whether they are stored in the refrigerator or not, whole or sliced, how long they cook and at what temperature. Vitamin C is destroyed from a threshold of 60-70 degrees, but is resistant to an acidic environment. Salads (cold and hot) with lemon juice, second courses with the addition of tomatoes or tomato paste retain this vitamin much better than first courses with a high liquid content, but without acidic ingredients. Drying, cutting, prolonged heating of food in a saucepan with an open lid, reheating dishes, copper or iron kitchen utensils actively destroy the powerful antioxidant.
Experiment with the “correct” water and express rosehip infusion
Using distilled water instead of tap water helps retain vitamin C significantly when boiled for a short time. An experiment was conducted by an American chemistry student: in one cup of distillate, he dissolved 1 teaspoon of ascorbic acid to obtain its concentration of 2-2.5%. As a result, the measuring device showed 2.17%. The researcher tightly covered the container with the solution with thermal film and left a small hole for the release of steam. Briefly heated a cup of ascorbic acid (no more than 2 minutes) in the microwave, then cooled for 5 minutes and put in the refrigerator. After 75 minutes, when the solution had cooled to room temperature, he again measured the concentration of vitamin C. Due to short-term evaporation, this figure increased to 2.19%! For the same purpose, experts advise preparing express infusions of berries rich in vitamin C.
The maximum amount of this vitamin is guaranteed to be preserved if the rose hips are quickly crushed, poured with boiled water with a temperature not exceeding 40-60 degrees, and then insisted for an hour in a tightly closed thermos. Prolonged boiling of rose hips destroys L-ascorbic acid, significantly reducing the value of the decoction compared to freshly squeezed juices and express infusions.
Hot tea and boiling lemon water
On the forums, you can often find a question from hot tea lovers at what temperature vitamin C is destroyed. Japanese researchers, contrary to the widespread belief that this popular drink cannot be brewed with boiling water, proved that the L-isomer of ascorbic acid (vitamin C) is destroyed slightly . Its concentration in the first quarter of an hour drops by only 30 percent in brewed tea at a constantly maintained boiling temperature, but after an hour it disintegrates almost completely. At the same time, in ordinary boiling water, dissolved vitamin C is destroyed by 83 percent after 10 minutes.
Experts explain this difference by the fact that tea phenol reacts with copper and iron ions, binding them, which prevents their effect on accelerating the breakdown of vitamin C. If you need to make hot lemonade from 6 lemons, then they are cut in half and thrown into boiling water . After 3 minutes, the container is removed from the stove, the drink is infused for 10-15 minutes. Then it is filtered from the fruits and pulp. This lemonade protects against colds and boosts immunity when drunk hot or warm with a little honey added. Store the drink in the refrigerator, heat it in the microwave to maximize the preservation of ascorbic acid.
When preparing first and second courses
There is no exact data indicating at what temperature vitamin C is destroyed in each particular dish. It is known that already at 50 degrees Celsius in potato soup, the concentration of ascorbic acid will begin to decrease if the pan is not covered with a lid and the vegetables are laid ahead of time. According to the rules, they must be added to boiling salted water, and the dishes covered with a lid during cooking. The same should be done with frozen vegetables, because boiling water contains much less dissolved oxygen, which destroys vitamin C. In addition, the high boiling point activates, along with ascorbine oxidase, other beneficial plant enzymes that contribute to better preservation of the vitamin. In potatoes drenched in boiling water and boiled in their skins, its amount is reduced by about 10 percent. A smaller amount of water also prevents the destruction of the natural "ascorbic acid".
So, for example, sauerkraut soup loses 50% of a powerful antioxidant after cooking for an hour, and stewed cabbage loses only 15%. Tomatoes cooked for 2 minutes in the microwave or oven (at 90 degrees) lose only 10 percent of a vital substance. The same tomatoes cooked for half an hour lose about 29-30% of vitamin C. Steamed vegetables get rid of 22-34% of a valuable vitamin, and 10% in a microwave oven in the same period of time.
At what temperature is vitamin C destroyed in cherry plum?
The benefits of this well-known plum are especially noticeable during the cold season. Its diaphoretic and antitussive action is valued along with a pleasant taste and many other healing properties. Tkemali, as they call "cherry plum" in the Caucasus and Transcaucasia, contains few sugars, but it contains citric acid and vitamins of groups B, A, E and PP. Plum is rich in pectins, calcium, magnesium, sodium, iron, phosphorus. In addition, it is a real storehouse of vitamin C. The temperature of its destruction also depends on all the factors described above. For example, cherry plum compote will contain much less of this valuable substance than tkemali sauce, because in a large amount of water the described vitamin is destroyed faster than in seasoning without additional liquid. Cherry plum is a powerful source of ascorbic acid also because other acids in its fruits prevent the breakdown of the water-soluble vitamin.
The reaction of other useful elements to heat
Doctors consider vitamin D to be the second, no less important "anti-cold vitamin", which is recommended to be taken along with rosehip infusion. Fish oil, vegetable oils and cheese in the off-season should be on every table. At what temperature is vitamin D destroyed? During heat treatment (A, D, E, K), their activity is practically not reduced and not destroyed. At the same time, vitamin D can withstand prolonged boiling in an acidic environment, and in an alkaline environment it is subject to rapid destruction. It is known that at a temperature of +232 degrees in the oven, cheese loses up to 25-30% of the “anti-cold” vitamin within 5 minutes. It is known that rosehip, in addition to vitamin C, contains and (rutin). This substance enhances the effect of "ascorbic acid", and their combined use is necessary when prescribing aspirin with sulfonamides for a beneficial, restorative effect on capillaries. The answer to the question at what temperature vitamin P is destroyed is similar to the recommendations related to ascorbic acid. These two vitamins are identical in many respects: both are water-soluble, afraid of sunlight, exposure to oxygen and the same temperature. In addition to rose hips, rutin is also found in lemons. Complementing and reinforcing each other, these vitamins are also indicated for long-term antibiotic therapy.