Chemical processes during cooking. Physics specialties Technology of foodservice products

About 80 % food products undergo one or another heat treatment, which increases, however, to certain limits, digestibility, softens the products, which makes them available for chewing. Many types of meat, legumes and a number of vegetables would disappear from our diet altogether if they were not cooked. Exposure to heat leads to the destruction of harmful microorganisms and some toxins, which ensures the necessary sanitary and hygienic safety of products, primarily of animal origin (meat, poultry, fish, dairy products) and root crops. Thus, heat treatment increases the microbiological resistance of food products and prolongs their shelf life. When some foods (for example, legumes, eggs) are cooked, inhibitors of enzymes of the human digestive tract are destroyed; when cereals (especially corn) are processed, vitamin PP (niacin) is released from an indigestible inactive form - niacitin. Finally, an important factor is that various types of heat treatment make it possible to diversify the taste of products, which reduces their "palatability".

However, all this does not mean at all that the heat treatment of food is not without its drawbacks. During heat treatment, vitamins and some biologically active substances are destroyed, proteins, fats, minerals are partially extracted and destroyed, unwanted substances can be formed (products of polymerization of fats, melanoidins, etc.). Thus, the goal of rational food preparation is to achieve the desired goal with a minimum loss of the beneficial properties of the product.

Taking into account the peculiarities of the preparation of plant and animal products, we will consider them separately.

Herbal products

A distinctive feature of plant products is their high carbohydrate content: over 70% of dry matter. Therefore, we will consider them in more detail.

The vast majority of plant products used in human nutrition are parts of plants with living parenchymal cells, which contain substances of interest from the point of view of nutritional value: mono- and oligosaccharides and starch. These cells have a primary membrane consisting of low molecular weight cellulose and low molecular weight fractions of hemicelluloses, an important distinctive feature of which is the predominance of B-1,4 bonds between structural units, and it is this bond that is not destroyed by human digestive enzymes. In the median lamina and intercellular spaces there are pectin substances, which are based on the remnants of D-galacturonic acid, interconnected by b-1,4-bonds (this bond is also not destroyed by human digestive enzymes). However, depending on the phase of development of a living cell, the degree of polymerization can vary greatly: from 20 to 200 or more residues. With an increase in the degree of polymerization, the solubility of pectin substances in water decreases and the mechanical strength increases. The so-called protopectin, with which the mechanical strength of fruits, berries and vegetables is associated, is in fact a high molecular weight pectin, which, due to the binding of water, forms a secondary structure, which, due to the special properties of bound water, gives firmness to plant products. At the same time, all plants contain active pectinesterases and less active polygalacturonases. At a certain period of plant life, these enzymes are activated and begin to destroy the secondary structure of pectin with the formation of low molecular weight pectins and water. In this case, the product softens. This enzymatic process can also occur during storage. Since the primary wall is easily permeable, and there is no secondary and even more tertiary walls in living cells, the low molecular weight pectin and water formed under the action of pectolytic enzymes partially pass into the protoplasm of the cells.

Heat treatment of plant products containing a noticeable amount of pectins (vegetables, fruits, potatoes, roots) is also aimed at destroying the secondary structure of pectin and partial release of water. This process begins at temperatures above 60 ° C and then accelerates approximately 2 times for every 10 ° increase in temperature. As a result, the mechanical strength in the finished product is reduced by more than 10 times. For example, the mechanical strength in compression of raw potatoes is 13-10 a Pa, boiled - 0.5-10 th, beets - 29.9-10 s and 2.9-10 5 Pa, respectively.

It should be noted that the mechanical strength of plant products also depends on their water content. The less free water in a product, the greater its strength, other things being equal. (Freeze-dried products do not contain free water and have high mechanical strength, which decreases when hydrated.) The release of water when protopectin breaks down also helps to soften the product.

With this in mind, let us consider the main processes occurring during thermal cooking. During cooking, in addition to the thermal decomposition of the secondary structure of pectin, the cells are saturated with water (the introduction of water into proteins, pectins, starch). In this case, the gelation of starch and low molecular weight pectin, which at a temperature of 60-80 ° C inside the product, become partially soluble in water, is of particular importance. Although starch remains in the cell plasma, and pectin remains in the intercellular space, the extraction of starch and pectin occurs not only from the surface destroyed cells, but also from the inner layers. Simultaneously, during cooking, a number of water-soluble substances (sugars, amino acids, organic acids, minerals and vitamins) are extracted from the layers of the product in contact with water.

In general, during cooking, there is often an absolute loss of water, the amount of which depends on the nature of the product (for example, when cooking potatoes 2-6%, cabbage - 7-9%, which is explained by the destruction of the secondary structure of pectins).

The cooking time depends on the temperature and size of the product. When cooking under pressure, when the temperature rises against the usual by 2-3 °, the cooking duration is reduced by about 1.5 times. Small pieces warm up to 70-80 ° С in the entire volume faster than large ones, but at the same time, the extraction of water-soluble substances increases. Therefore, the fineness should not be strong. In practice, the optimal modes of cooking duration and degree of product grinding have been established.

Cooking unpeeled products (beets, carrots, potatoes in the skin) does not affect the duration, but leads to a noticeable decrease in the loss of nutrients, since the dense surface layer (epidermis, peridermis) prevents extraction.

Steaming also reduces the loss of nutrients compared to boiling in water, since the extraction only occurs from the surface layers themselves.

When frying occurs, mainly thermal decomposition of the secondary structure of pectins with the formation of soluble pectins and water. Starch grains and low molecular weight pectin begin to react with water and partially become gelatinous. However, if the evaporation of water from the product during frying occurs sufficiently intensively, the gel dries up and the product becomes solid again, its mechanical strength increases several times.

Often, frying is carried out in a large amount of fat (in Deep Fat). In fact, this is not frying, but cooking in fat. In this case, the temperature of the medium turns out to be higher than during conventional cooking, softening occurs faster. There are few fat-soluble substances in plant products, therefore, the loss of nutrients during deep-frying is insignificant, with the exception, of course, of the vitamins that break down in this case.

Heat treatment of plant products containing a significant amount of pectin, but a lot of starch (cereals, legumes), is accompanied by gelatinization of starch and usually consists in boiling in water. The absorption of water by gelatinized starch reaches 100-200%.

Shpak Oksana and Mizinova Alyona

The relationship of chemical processes and cooking technologiesin molecular cooking

Shpak Oksana, Mizinova Alyona

GBOU SO NPO "PL No. 8" group 36 "Cook, confectioner", Saratov

Scientific advisers: Dorozhkina Svetlana Vladimirovna, master of industrial training and Bulatova Tatyana Vitalievna, teacher of chemistry

Any science does not stand still, along with technology. Today, innovations have embraced all spheres of human life, and cooking has not been ignored either. Cooking is an activity that you need to know from all sides.

In our work, we put forward a hypothesis: The modern development of cooking is impossible without knowledge of chemistry and biology.

We began our research with a survey of students of the II-III course of the Lyceum with the profession “Chef, Confectioner”. 42 people took part in the survey. Based on the data obtained, the following conclusions can be drawn. Most of the respondents are sure that a modern chef should know the basics of chemistry, since without this it is impossible to be a highly qualified specialist in his field of activity. Also, ¾ of the respondents have an idea of molecular cooking and most of them received this knowledge at the lyceum, participating in extracurricular activities.

When preparing food, many of the operations used in chemistry are used: weighing, grinding, mixing, heating, dissolving, filtering.

Molecular cooking is unlikely to be successful everywhere. Firstly, not every guest is able to accept such innovations and force himself to even try such unusual dishes, and secondly, it is too expensive a pleasure. Equipment for such cooking costs thousands and even millions of dollars, not every restaurant can afford it.

Having studied the theoretical and practical aspects of this topic, we made the following conclusions: we can confidently say that the hypothesis has been fully confirmed, chemistry, biology and cooking are an example of well-coordinated and friendly work.

Gradually, these new ideas, technologies and methods penetrate cookbooks, recipes are adapted and adopted by the food industry - and, finally, new dishes appear on the shelves of grocery stores, as happened with dishes of the "new cooking" or fusion style. And it is possible that in ten years, the applied technologies used in scientific gastronomy, such as quick freezing in liquid nitrogen, will also find application in the home kitchen.

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Hello! I am a student of vocational lyceum No. 8 in the city of Saratov Shpak Oksana! The topic of my research work

RELATIONSHIP OF CHEMICAL

INTRODUCTION OF PROCESSES AND TECHNOLOGIES OF COOKING DISHES IN MOLECULAR COOKING

I chose this topic because it interested me in the course of my participation in a binary lesson and in extracurricular activities held on this topic in the Lyceum.

An object research of this work of the dishes of molecular cooking.

Subject of study- molecular cuisine as a professional chef's field of activity.

Purpose of the study: to establish empirically the relationship of chemical processes with the technology of cooking dishes in molecular cooking.

In our work, we put forward a hypothesis:

The modern development of cooking is impossible without knowledge of chemistry and biology.

Research objectives:

Establish the relationship between molecular cooking and chemistry.
Determine the features of molecular cooking, its advantages and disadvantages.
Carry out research on the relationship between chemistry, biology and cooking.
Determine the prospects for the development of molecular cuisine.

Research methods:

theoretical : analysis of scientific literature and information sources in the field of applied chemistry and public catering technologies; generalization and systematization of scientific facts.

Empirical : questioning, research work.

1 THEORETICAL ASPECTS OF COOKING DEVELOPMENT
IN MODERN CONDITIONS

RELATIONSHIP OF MOLECULAR COOKING WITH CHEMISTRY

I began my research with a survey of students of the II-III course of the Lyceum on the profession "Chef, Confectioner". 42 people took part in the survey. The following results were obtained.

The existence of molecular cooking?

4) In what conditions is it possible to prepare a molecular cuisine dish?

Based on the data obtained, the following conclusions can be drawn.

Most of the respondents are sure that a modern chef should know the basics of chemistry, since without this it is impossible to be a highly qualified specialist in his field of activity.

Also, ¾ of the respondents have an idea of molecular cooking and most of them received this knowledge at the lyceum, participating in extracurricular activities.

In the second subsection of my work, I examined the features, advantages, features and disadvantages of molecular cooking.

Molecular cuisine, or molecular gastronomy, is a line of research related to the study of the physicochemical processes that occur during cooking. She studies the mechanisms responsible for the transformation of ingredients during the culinary processing of food, as well as the social, artistic and technical components of culinary and gastronomic phenomena in general (from a scientific point of view). Thisa thoughtful approach to cooking based on modern knowledge that is given to us by fundamental science, which has generalized various culinary phenomena, origins in the history of cooking, plus modern innovative technologies.

As a result of working with various sources of information, I learned that there is an opinion: molecular cooking was not invented in the West at all, but in the Soviet Union.

Despite the fact that molecular cooking is considered a new direction, but such goodies known to us for a long time as marshmallow, marshmallow, cotton candy, doctor's sausage and artificial caviar, are prepared using the same technology.

In Russia, the restaurateur Anatoly Komm is engaged in molecular cuisine, who experiments with European culinary technologies on primordially Russian dishes like borscht, herring under a fur coat and Borodino bread.

There are many examples of world gastronomic restaurants. The most famous is London's "Fat Duck", where chef Heston Blumenthal treats guests with his signature dishes: liver with jasmine, banana with parsley and strawberries with candied celery.

To begin with, food preparation uses many of the operations used in chemistry: weighing, grinding, mixing, heating, dissolving, filtering. Equipment in chemistry and cooking also has similarities .____________

Basic techniques of molecular cuisine:

processing of products with liquid nitrogen,
emulsification (mixing of insoluble substances),
spherification (creation of liquid spheres),
gelation,
carbonation or enrichment with carbon dioxide (carbonation),
vacuum distillation (alcohol separation).

The following chemicals are used to make meals in molecular cuisine:

Agar-agar and carrageenan - algae extracts for making jelly,
Calcium chloride and sodium alginate convert liquids into caviar-like balls,
Egg powder (evaporated protein) - creates a denser structure than fresh protein,
Glucose - slows down crystallization and prevents fluid loss,
Lecithin - combines emulsions and stabilizes whipped foam,
Sodium citrate - prevents fat particles from bonding.

In the second chapter of my work, I explored the practical aspects of
the relationship of chemistry, biology and cooking

I will demonstrate the results of my practical research to you in the formtables "The relationship of chemical processes and cooking technologies"

1 To demonstrate the experiments, I used one of the most commonly used products in cooking: chicken protein .___________

2 In the course of the second experiment, I established under what conditions protein foam forms faster and denser, which is important when preparing a number of dishes .______

3 In the third experiment, we examined the interaction of carbonic acid salts

with stronger acids, such as acetic acid. The carbon dioxide released as a result of the reaction is also used in the preparation of flour confectionery products.

4 Molecular cooking is used and the chemical and physical properties of substances, for example the experiment "Tower of Density"

CONCLUSION

Having studied the theoretical and practical aspects of this topic, we made the following conclusions: we can confidently say that the hypothesis has been fully confirmed, chemistry and cooking are an example of well-coordinated and friendly work.

Even the best and most proven recipe does not guarantee that the result will be a great dish. Too many secondary factors affect the final product. In order to never be disappointed in your own culinary talents, it is enough to have basic knowledge of chemistry. Likewise, new culinary trends and trends begin in restaurants, gourmets and professional chefs are fond of them, carefully developing every detail of the dish, coming up with new, unusual taste combinations and product combinations, experimenting with cooking technology - and as a result, these dishes are almost impossible to reproduce. ...

It would seem that everything that is possible has already been prepared and tasted, but cooking continues to develop. The fusion style in “haute cooking” is being replaced by molecular cooking, which changes the consistency and shape of products beyond recognition. The analysis of chemical processes in the course of food preparation and the use of new technologies have spawned the direction that can be called molecular cooking.

Is there a connection between cooking and chemistry, or are culinary products obtained without the use of chemicals?

1) Get acquainted with the term "cooking"; 2) Find information on how chemistry "serves" cooking 3) Shed light on the "food of the future" - "the latest technology in our stomach" 4) Draw conclusions and conclusions.

Cooking (from Lat. Culina - kitchen) is the art of cooking, as well as the collective name for dishes. According to legend, Kulina was the servant and assistant of the mythical healer Aesculapius (patron of medicine) and his daughter Hygea (patroness of health). Cooking is the oldest branch of human activity. One of the first methods of thermal culinary processing was frying over an open fire, in ashes and on hot stones. Cooking reflects the collective experience of the people and therefore is physiologically expedient in many respects, since food personifies the most ancient connection that unites all living things, incl. and man, with the nature around him.

The national cuisine of every nation is an integral part of its material culture. Distinguish between folk and professional cooking. The latter arose on the basis of the folk, which was developed and improved by professional chefs. Professional cookery, on the one hand, is an art, and on the other, a science based on the achievements of physics, chemistry, physiology of nutrition and other branches of natural science. Many famous cultural figures were fond of cooking: Leonardo da Vinci, S. Botticelli, A. Dumas, V. Odoevsky, etc. D. Kanshin was the founder of scientific culinary in Russia. After the emergence of mechanized out-of-home catering enterprises, cooking became a technical discipline - food preparation technology.

With this interesting question, we turned to our teacher of chemistry and ecology, Oksana Vladimirovna Korzhevskaya, and received many answers. We have selected the most important, in our opinion.

Saltpeter Saltpeter is used in meat processing and smoking of meat products. Firstly, it is a preservative that contributes to a longer shelf life of the product. Secondly (and this is the main thing!), It helps the meat product after heat treatment to retain a more or less natural color: from deep red in hard-smoked sausages to appetizing pink in hams. Saltpeter should be special - food grade, with a high degree of purification, and not the one that is used in the manufacture of gunpowder or explosive devices. It is important to be careful about the dosage. In large quantities, food nitrate can turn into a terrible poison. One should not think that at industrial enterprises a meat product is literally soaked in a solution of nitrate before smoking. Of course, in reality, everything is more complicated. Before smoking, the washed meat is aged (slightly marinated) in a solution with a more complex composition: containing salt, vinegar, spices and herbs, and with. a slight addition of this very saltpeter.

Sodium glutamate The correct name for the substance mentioned in the question is the monosodium salt of glutamic acid. Glutamic acid is an organic substance. Some representatives of the plant world - mushrooms, rich in proteins, also contain glutamic acid. By the way, it is to this acid that individual mushrooms (after their preparation) owe a weakly expressed meat taste and the ability to improve. the taste of other dishes. Are you already starting to guess about the purpose of supplements? Yes, glutamine supplements improve, enhance the meaty taste of meat-containing dishes and, one might say, give it even to those products where there was no trace of meat. Is sodium glutamate harmful or useful? What is not useful is obvious. After all, it is not a vitamin, not a mineral salt with microelements useful for the body. It is a kind of trick to improve the taste of the product. Sodium glutamate provokes appetite, it is a kind of “drug”: I ate something with glutamine, it’s delicious, I want the same thing, or something like that ... If you have a desire to try using glutamine in your kitchen, one piece of advice: be sure to buy it only in stores, in the spice departments. On the market, you can safely buy greens, and with white glutamine powder, falsifications are possible.

Smoked liquids Tasty food was loved at all times. But the main purpose of using smoking products was not the joy of gourmets, but the desire to preserve the product for a longer time. Over time, with the emergence and improvement of conservation products and the emergence of refrigeration technology, the emphasis has shifted. Of course, today smoking is mainly used to give a product a certain taste. Inventive people have come up with ways to condense aromatic fumes, because they also contain moisture in the vapor fraction. (The closest analogs of the condensation process are tar cooking from birch bark or, forgive me, home brewing.) The liquid condensate obtained from smoke, having undergone appropriate purification, is suitable for use as a very concentrated natural flavoring that imparts a smoked flavor to dishes. Smoked liquids are now widely used in the food industry as one of the additives in minced meat for some sausages and sausages. Perhaps in these cases, synthesized flavors with a smoky flavor are used? Modern chemistry is omnipotent ...

Cooking Jam, jam and compotes Sulphitation of whole fruits and berries, puree from them, juices and other products with sulfur dioxide is a more progressive method of processing. It is not associated with the need to obtain anhydride from sulfur and is safe. In order for sulphitated fruit products (mainly semi-finished products for jam, jam, preserves, jellies) to be stable in storage, technological instructions set permissible rates for the introduction of sulfur dioxide into them (% by weight). Whole fruits and berries are sulfitized in barrels, filling up to 90% of their volume, then sealed, leaving open the tongue-and-groove opening in the upper bottom for filling with a hose of a working solution of 1-2% concentration in an amount of no more than 10-15% (less often - 20%) of the mass of fruits, or sulfurous anhydride is introduced into barrels. A significant part of fruit semi-finished products (especially mashed potatoes) is sulfitized in large stationary basins, tanks with a capacity of 10-25-50 tons and more. Liquid sulfurous anhydride is also used for fumigation of fruits instead of processing with sulfur dioxide.

Cooking, which changes the consistency and shape of products beyond recognition, is no longer news. An egg with a white inside and a yolk outside, frothed meat with a garnish of frothed potatoes, jelly with the taste of pickled cucumbers and radishes, crab syrup, thin slices of fresh milk, ice cream with tobacco flavors exist not in science fiction novels, but in our time. Perhaps food will become “digital”, and dishes will be “downloaded” from the Internet and “printed” on special “printers”.

The food that awaits us in the future on the shelves of supermarkets or on the tables of restaurants will look no different from today's food. However, it will be produced, processed and prepared in a different way. Much more attractive will be "functional food" - foods and drinks with the addition of vitamins, minerals, polyunsaturated fatty acids Omega-3. Molecular cooking will allow you to create fundamentally new types of food, connecting the incompatible. Smells and tastes that the world did not know will appear. In particular, the chemists and biologists of the Swiss perfume giant Givaudan, who have created over 20,000 artificial scents (300 for just one strawberry), organized expeditions to the forests of Madagascar in search of molecules from which new scents can be extracted.

The space industry is also ready to offer new types of products. Space flight factors (weightlessness, crowding, difficulty warming up) impose strict requirements on food products. But the most important requirement is to preserve the freshness and taste of the food for weeks or even months. The American space agency NASA operates Advance food technology, which specializes in preparing food for space missions. To increase the shelf life of space food, experts process it with high pressure, pulsating electric field. In this way, a sandwich was already prepared, edible even after seven years!

So, at the beginning of our research, we put forward a hypothesis. At the end of the study, we can say with confidence that the hypothesis is fully confirmed, chemistry and cooking are an example of a well-coordinated and friendly "team". This "team" forces scientists to strain their brains, and us - to try and taste more complicated and more delicious foods. But do not forget about the "harmfulness" of chemistry - in large quantities, it can become destructive for the "pioneers" - scientists, as well as for such consumers as you and me. But the real surprises lie ahead - recipes created as a result of molecular research, genetic discoveries and space exploration. And it is possible that in ten years, the applied technologies used in scientific gastronomy, such as quick freezing in liquid nitrogen, will also find application in the home kitchen. Good luck in your culinary (and other!) Matters, And bon appetit to everyone!

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The main chemical processes occurring during the thermal culinary processing of products

The nature of the processes occurring during the heat treatment of plant and animal products is significantly different.

A distinctive feature of plant products is their high content of carbohydrates - over 70% of dry matter. The vast majority of plant products used in human nutrition are plant parts containing living parenchymal cells. They contain substances of interest in nutrition - mono- and oligosaccharides and starch. These cells have a primary membrane consisting of low molecular weight cellulose and low molecular weight fractions of hemicelluloses, a distinctive feature of which is the predominance of the p-1,4-bond between the structural units (this is important, since it is this bond that is not destroyed by human digestive enzymes). In the median lamina and intercellular spaces there are pectin substances. They are based on the remains of galacturonic acid, interconnected by a-1,4-bonds (this bond is also not destroyed by human digestive enzymes). However, the degree of their polymerization, depending on the phase of development of a living cell, can vary greatly: from 20 to 200 or more residues. With an increase in the degree of polymerization, the solubility of pectin substances and water decreases and the mechanical strength increases. So the reclaimed "protopectin", with which the mechanical hardness of fruits, berries and vegetables is associated, is actually a high molecular weight pectin, which forms a "secondary" structure due to the binding of water, which, due to the special properties of the "bound" "ode," gives mechanical strength to plant products. At the same time, all plants contain active pectinesterases and somewhat less active polygalacturonases, which are activated at a certain period of plant life and begin to destroy the secondary structure of pectin with the formation of low molecular weight pectins and water. In this case, the product softens (this enzymatic process can also occur during storage). Since the primary wall is easily permeable, and the secondary, and even more so tertiary, walls are absent in living cells, the low molecular weight pectin and water formed under the action of non-political enzymes partially pass into the protoplasm of the cells.

When cooking under pressure, when the temperature rises against the usual by 2-3 C, the cooking duration is reduced by about 1.5 times. Small pieces warm up (up to 70-80 CC in the entire volume) faster than large ones, but the extraction of water-soluble substances increases. Therefore, the grinding cannot be very strong. Practice has established the optimal product size and cooking duration.

Cooking products in the skins (for example, potatoes in the skins, beets and carrots in the skins) does not affect the duration, but leads to a noticeable decrease in the loss of nutrients, since the dense surface layer (epidermis, peridermis) prevents extraction. Steaming also reduces the loss of nutrients compared to boiling in water, since the extraction only affects the outermost layers.

During frying, the thermal decomposition of the "secondary" structure of pectins occurs mainly with the formation of soluble pectins and water. Starch grains and low molecular weight pectin begin to react with water, and they partially become gelatinous. However, if the evaporation of water from the product during frying occurs rather intensively, then the gel dries up and the product becomes solid again - its mechanical strength increases several times. To reduce the evaporation of water, frying is carried out in the presence of fat, which, enveloping the product, reduces the surface temperature and the rate of evaporation of moisture. With frequent stirring, a crust forms, which also retards evaporation, and the product becomes juicier.

You can generally fry in a layer of fat ("deep fat"). In fact, this is not frying, but cooking in fat. At the same time, the temperature of the medium is higher than with conventional cooking and softening occurs faster. There are few fat-soluble substances in plant products, therefore, the loss of nutrients during deep-fried frying is insignificant, with the exception, of course, of the vitamins that decompose during this process.

In conclusion, about the heat treatment of plant products containing a small amount of pectin, but a lot of starch (cereals, legumes). Their processing consists mainly in the kleisterization of starch at elevated temperatures and in the presence of external water. Therefore, only cooking is applied to them. Water absorption of gelatinized starch reaches 100-200%,

In animal products, proteins are the most valuable in nutritional and culinary terms (it is more correct to say not “protein”, but “proteins”, that is, there are many individual proteins that differ in composition and properties).

The mechanical strength of a meat product is due to a certain rigidity of the “tertiary” structure of proteins. The highest rigidity is possessed by proteins of connective tissues (collagen and elastin). One of the main, but not the only factor that determines the rigidity of the "tertiary" structure of most proteins of animal origin (with the exception of eggs, eggs) is the presence of water in them (in the form of "tightly bound", "hydrated", etc., which are not considered here) ... In meat products, the water in the "tertiary structure is associated mainly with muscle weaknesses and not with connective tissue. The content of connective tissue proteins depends on the nature of the raw material, the age of the animals and a number of other conditions.

At the same time, the mechanical strength of meat products decreases markedly.The temperature coagulation of proteins, depending on the nature, starts from 60 ° С, and for most of them 70 ° С When cooking and frying meat, the temperature inside the product, depending on the type of meat and the size of the cusp, usually reaches 75 -95 ° C. However, frying meat with a large amount of connective tissue is not recommended, since the water released when the “tertiary” structure of muscle proteins is destroyed may not be enough for gelatinization (moreover, some of the water evaporates). Such "stringy" meat is best cooked or stewed. Since the acidic reaction of the medium contributes to the gelation of connective tissue proteins, it is advisable to soak the meat in acidic solutions (in vinegar, in dry wine) or stew in the presence of vegetables containing organic acids (for example, tomatoes), or with tomato paste - in these cases, the tissues soften significantly faster. Mechanical destruction of connective tissue has the same effect.

With traditional frying of meat products, despite the fact that fat is added, there is a rather intense evaporation of water; the product simply dries out during prolonged frying and becomes harder again. To reduce this undesirable process, it is recommended to first fry a piece of meat from different sides until a partially waterproof crust is formed (which also gives a pleasant specific taste) or bread it in flour or ground breadcrumbs. As a result, the moisture content does not drop so sharply and the meat is more tender.

Loss of nutrients during cooking occurs due to partial melting of fat and the extraction of a number of extractive components from tissues (nitrogenous and non-nitrogenous substances, minerals and vitamins). When frying, losses occur as a result of melting a large amount of fat, partial release of juice, thermal destruction of vitamins.

Oddly enough, at first glance, water losses occur not only during frying, but also during cooking, in water, and they reach noticeable values (in comparison with vegetable products) - on average, from 30 to 50%, depending on the type of meat. These losses occur due to the destruction of the "tertiary" structure of muscle proteins during their coagulation. At the same time, the "secondary" structure is no longer able to retain a large amount of water, which is released together with water-soluble substances into external water.

Pressure cooking, by increasing the temperature, accelerates gelatinization and thus shortens the time to obtain the finished product.

You will get some idea of the amount of loss of basic nutrients in various methods of thermal cooking by looking at table. 23.

Summarizing what has been said about the heat treatment of foodstuffs, the following conclusions can be drawn.

The most rational heat treatments from the point of view of preserving valuable nutrients are: for vegetable products - cooking without draining the broth and cooking in the peel; for animals - stewing, baking, using meat in the form of cutlets, especially steam.

With any heat treatment, the most intense destruction of vitamins, especially vitamin C.

What practical advice can be given to a housewife for choosing a method of heat treatment, which is better - to boil, fry or stew?

It seems that for the preparation of everyday food it is necessary to use the most rational methods of heat treatment. At the same time, greens, fresh vegetables and cabbage are often served for appetizers and side dishes in order to compensate for the loss of vitamins that occur during heat treatment. Rational methods of heat treatment are also very useful for those who need a dietary diet: there are no mechanical irritants in the gastrointestinal tract (toasted kidney) in the products.However, it would be wrong to completely abandon the taste of their fried foods for practically healthy adults. But it is better to postpone cooking until Sundays and holidays. Such a variety in the diet can be given.

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Home cooking basicsHome cooking technology

Rice. 1.3. Starch grain structure:

1 - the structure of amylose; 2 - the structure of amylopectin; 3 - starch grains of raw potatoes; 4 - starch grains of boiled potatoes; 5 - starch grains in raw dough; 6 - starch grains after baking

When heated from 55 to 80 ° C, starch grains absorb a large amount of water, increase in volume several times, lose their crystalline structure, and, consequently, anisotropy. The starch suspension turns into a paste. The process of its formation is called gelatinization. Thus, gelatinization is the destruction of the native structure of the starch grain, accompanied by swelling.

The temperature at which the anisotropy of most grains is destroyed is called the temperature gelatinization... The gelatinization temperature of different types of starch is not the same. So, the gelatinization of potato starch occurs at 55-65 ° C, wheat - at 60-80, corn - at 60-71 °, rice - at 70-80 ° C.

The process of gelatinization of starch grains is carried out in stages:

* at 55-70 ° C, the grains increase in volume several times, lose optical anisotropy, but still retain their layered structure; a cavity ("bubble") is formed in the center of the starch grain; a suspension of grains in water turns into a paste - a low-concentrated sol of amylose, in which swollen grains are distributed (the first stage of gelatinization);

* when heated above 70 ° C in the presence of a significant amount of water, starch grains increase in volume tens of times, the layered structure disappears, the viscosity of the system increases significantly (the second stage of gelatinization); at this stage, the amount of soluble amylose increases; its solution partly remains in the grain, and partly diffuses into the environment.

With prolonged heating with excess water, starch bubbles burst, and the viscosity of the paste decreases. An example of this in culinary practice is the liquefaction of jelly as a result of excessive heating.

The starch of tuberous plants (potatoes, Jerusalem artichoke) gives transparent pastes of a jelly-like consistency, and cereals (corn, rice, wheat, etc.) - opaque, milky white, pasty consistency.

The consistency of the paste depends on the amount of starch: when its content is from 2 to 5%, the paste turns out to be liquid (liquid jelly, sauces, mashed soups); at 6-8% - thick (thick jelly). An even thicker paste forms inside potato cells, in cereals, pasta dishes.

The viscosity of the paste is influenced not only by the starch concentration, but also by the presence of various nutrients (sugars, mineral elements, acids, proteins, etc.). So, sucrose increases the viscosity of the system, salt reduces, proteins have a stabilizing effect on starch pastes.

When starch-containing products are cooled, the amount of soluble amylose in them decreases as a result of retrogradation (precipitation). At the same time, aging of starch jellies (syneresis) occurs, and the products become stale. The aging rate depends on the type of products, their humidity and storage temperature. The higher the humidity of the dish, culinary product, the more intensively the amount of water-soluble substances in it decreases. Aging occurs most rapidly in millet porridge, slower in semolina and buckwheat. An increase in temperature slows down the retrogradation process, therefore, dishes from cereals and pasta, which are stored on bain-marie with a temperature of 70-80 ° C, have good organoleptic characteristics for 4 hours.

Starch hydrolysis. Starch polysaccharides are capable of breaking down to the molecules of their constituent sugars. This process is called hydrolysis, as it goes with the addition of water. Distinguish between enzymatic and acid hydrolysis.

The enzymes that break down starch are called amylases. There are two types of them:

α-amylase, which causes partial degradation of starch polysaccharide chains with the formation of low molecular weight compounds - dextrins; with prolonged hydrolysis, the formation of maltose and glucose is possible;

β-amylase, which breaks down starch to maltose.

Enzymatic hydrolysis of starch occurs when making yeast dough and baking products from it, boiling potatoes, etc. Wheat flour usually contains β-amylase; maltose, formed under its influence, is a breeding ground for yeast. In flour from sprouted grain, α-amylase predominates, the dextrins formed under its influence give the products stickiness and unpleasant taste.

The degree of hydrolysis of starch under the action)