With a high proportion of collagen in lean meat, its nutritional value sharply decreases. The presence of 12-25% collagen in food does not ensure tissue protein synthesis even with the addition of the missing amino acids. Collagen, when heated with water, turns into glue - glutin (gelatin).
Consumption of foods containing large amounts of collagen in the form of gelatin has a negative effect on kidney function. Elastin makes up about 1% of the total meat.
The high content of connective tissue in meat negatively affects the organoleptic properties of culinary products obtained from such meat. Currently, to determine the nutritional value of meat, a ratio of two amino acids - tryptophan and hydroxyproline - has been proposed. In this ratio, tryptophan characterizes the content of complete proteins, and hydroxyproline characterizes the content of incomplete ones. The ratio of tryptophan to hydroxyproline is inversely related to the content of connective tissue proteins.
The ratio of tryptophan to hydroxyproline and the content of connective tissue in muscle tissue (longissimus dorsi muscle) of cattle
Indicators Tryptophan/hydroxyproline
Connective tissue proteins (% of total protein)
Fatness highest 5.8 2.1
average 4.8 2.4
below average 2.5 3.5
An important component of meat are extractive substances, which are divided into nitrogenous and nitrogen-free. 1 kg of meat contains an average of 3.5 g of nitrogenous extractives. Pork contains the most nitrogenous extractive substances - their total content reaches 6.5 g per 1 kg of muscle tissue. The smallest amount of extractive substances is observed in lamb - 2.5 g per 1 kg of muscle. In this regard, in cases where it is necessary to limit extractive substances, lean lamb may be recommended.
Nitrogenous extractives- carnosine, creatine, anserine, purine bases (hypoxanthine), etc. The main importance of extractives lies in their taste properties and stimulating effect on the secretion of the digestive glands.
The presence of nitrogenous extractives c. The taste of meat, especially broths and the crust formed when frying meat, is largely determined. The meat of adult animals is richer in extractive substances and has a more pronounced taste than the meat of young animals. This explains that strong broths can only be obtained from the meat of adult animals. The extractive substances of meat are energetic stimulants of the secretion of the gastric glands, and therefore strong broths and fried meat stimulate the secretion of digestive juices to the greatest extent. Boiled meat does not have this property and therefore it is widely used in a dietary, chemically gentle diet, for gastritis, peptic ulcers, liver diseases and other diseases of the digestive system.
Nitrogen-free extractives- glycogen, glucose, lactic acid - contained in meat in an amount of about 1%. In terms of their activity, they are significantly inferior to nitrogenous extractives.
The main extractives of wood are resinous substances, tannins and gums. When these substances are extracted from wood, the structure and composition of the cell walls do not undergo significant changes, as a result of which the extracted wood can be used for subsequent processing, just like natural wood. Resinous substances.
Content of extractive substances of poplar bark
E.N. Lubysheva, S.V. Soboleva State Educational Institution of Higher Professional Education "Siberian State Technological University" Poplar is one of the fastest growing tree species of the temperate zone of Russia. The increased interest in it is explained by its biological characteristics and economic value. When harvested and mainly used, the bark remains at the enterprises of the woodworking and pulp and paper industries in the amount of 15% of the processed wood. There are a large number of works in the literature devoted to the study of extractive substances of poplar biomass using various extractants (acetone, ethyl and isopropyl alcohol), but there is practically no data on the isolation
extractive substances of poplar bark Populus balsamifera.
They are interesting because they are rich in biologically active substances that exhibit antimicrobial and antifungal properties, and therefore have been used in folk medicine since ancient times as anti-inflammatory drugs.
The purpose of this work was to determine the seasonal dynamics of the content of extractive substances in poplar bark. Ethanol of various concentrations (60 and 96%) was used as extractants.
The bark of Populus balsamifera was used as the object of study. Sampling was carried out manually in October, February, April in the Kirovsky district of Krasnoyarsk (SibTyazhMash plant) and on the territory of the Stolby nature reserve. The air-dried bark was crushed to a particle size of 3-5 mm and a water-alcohol extract was obtained. The content of extractive substances was determined by the well-known method in wood chemistry (by the loss of mass of the substance), humidity - by the method of drying in an oven at a temperature of 105 °C.
To obtain extracts, it is advisable to harvest the bark in March-April, because during this period it contains the maximum amount of extractives. For the most complete extraction of extractives, it is better to use 96% ethanol, providing a yield of 43.5%. The duration of extraction should not exceed 5 hours at a temperature of 80 °C. A further increase in the time and temperature of the extraction process does not lead to an increase in the yield of extractives. Further studies of the chemical composition of the extracts obtained are necessary to determine the scope of application.
Extractive substances include substances extracted from wood with neutral solvents (water or organic solvents). They are found mainly in cell cavities and intercellular spaces, and can also permeate cell walls.
The content of extractive substances in wood varies significantly, from 1 to 40% (for example, in quebracho wood) and even more, and depends mainly on the species, age, growing conditions of the tree, etc. In our ordinary tree species, the content of extractive substances small, on average 2-4%. Exception. is oak, the wood of which contains a significant amount of tannins. ,
Despite the small content, the role of extractives in wood is very large. They give it color, smell, taste, and sometimes toxicity. The presence of extractive substances determines the resistance of wood to insect attack, fungal attack, and rotting.
The nature of extractives is very diverse. They include almost all classes of organic compounds. 
Sometimes extractive substances cause production difficulties (for example, resin difficulties in pulp and paper production), but more often they find application and provide valuable products.
The most important are tree resins (resin acids), tannins (tannins) and essential oils (terpenes and their derivatives). In addition, extractive substances include dyes, gums (water-soluble carbohydrate compounds), tropolones, fats and fatty acids, phytosterols, aliphatic hydrocarbons, cyclic alcohols, alkaloids, proteins, salts of organic acids, etc.
In the wood of felled trees, especially in stump resin (in stumps that have stood in the ground for several years after the trees were felled), the composition of resinous substances differs significantly from the composition of oleoresin. In addition to resin acids and terpene hydrocarbons, they contain products of their oxidation (oxidized resin acids and terpene alcohols), as well as fatty acids. The extraction of extractive resinous substances from osmol with organic solvents (usually gasoline) and their processing into rosin and turpentine takes place in extraction production. Resinous substances can also be extracted from osmol using a dilute solution of sodium hydroxide. In this case, resin acids are saponified with alkali and pass into lye in the form of rosin soap, which is then salted out of the solution with table salt. This method is very simple, non-flammable and was previously tested at some factories, but did not justify itself due to the extremely low quality of the product. Saponification of resinous substances with alkali also occurs in cellulose sulfate production.
The basis of chemical sparing is the restriction in the diet of foods and dishes, strongly:
- stimulating the secretion of the stomach, irritating its mucous membrane;
- increasing fermentation and putrefaction in the intestines and negatively affecting other digestive organs;
- increasing the excitability of the autonomic nervous system.
These are products rich in extractives, purines, cholesterol, oxalic acid, essential oils and fat oxidation products that occur during frying. Therefore, in diets that require chemical sparing, the consumption of these products is limited, or culinary techniques are used that reduce the amount of these substances in the finished product.
Types of extractives
Extractives- natural water-soluble low-molecular organic compounds, easily extracted from products of animal origin. They are nitrogenous and nitrogen-free.
- Nitrogenous compounds include free amino acids, dipeptides, carbamide (urea), guanidine derivatives (creatine and creatinine), purine bases, etc.
- Nitrogen-free extractives include glycogen, sugars (glucose, fructose, ribose), acids (lactic, formic, acetic, butyric, mesoinositol).
In the composition of nitrogenous extractive substances of animal meat, free amino acids predominate - up to 1% by weight of muscle tissue, creatine is in second place - up to 0.5%; Carnosine and anserine are contained in muscle tissue in an amount of 0.2-0.3%, urea - about 0.2%. The content of purine bases and other compounds ranges from 0.05 to 0.15%.
Fish meat is distinguished by a higher content of nitrogenous extractive substances compared to the meat of slaughtered animals.
The muscle tissue of oceanic fish contains more of them than the meat of freshwater fish.
The special specific taste of fish is explained not only by the presence of extractive nitrogenous substances in it, but also by the originality of their composition. Thus, among free amino acids there is very little glutamic acid and a lot of cyclic (histidine, phenylalanine, tryptophan) and sulfur-containing amino acids.
Nitrogenous extractives of fish contain small amounts of creatine and creatinine. At the same time, methylguanidine, which is not found in the meat of slaughter animals and freshwater fish, was found in the meat of oceanic fish from substances of this group. In large quantities this substance is toxic.
The meat of most fish contains small amounts of purine bases, derivatives of imidazole and choline. For example, cattle meat contains 300 mg% carnosine, and freshwater fish meat contains up to 3 mg%, choline - up to 110 and 2.5 mg%, respectively.
A characteristic feature of fish meat extractives is a significant content of nitrogenous bases, the main representatives of which are trimethylamine oxide, as well as tri- and dimethylamine.
Harm of extractive nitrogenous substances to the human body
From a physiological point of view, a special role in nutrition is given to extractive nitrogenous substances.
From a dietary point of view, extractive nitrogenous substances have a number of significant disadvantages. Nitrogen-containing extractives have a local and general irritant effect. By stimulating the gastric glands and the digestive function of the pancreas, they promote better absorption of food, primarily proteins and fats.
At the same time, these same substances (directly or indirectly) have a stimulating effect on the nervous system, which, as a rule, adversely affects the course of many diseases of the circulatory system, nervous system, gastrointestinal tract and kidneys.
In addition, purine bases are directly related to metabolic processes, the disruption of which is manifested by the retention of uric acid in the body and the deposition of its salts in tissues. In particular, gout and urolithiasis are almost always the result of a disorder in the metabolism of purine substances.
Therefore, for gentle diets, the amount of extractive nitrogenous substances is reduced using various technological methods.
Culinary methods for reducing the amount of extractive nitrogenous substances
The amount of extractive substances extracted depends on the method and mode of heat treatment. The largest amount of soluble substances is extracted from muscle tissue during the process of boiling it in water. Thus, when cooking meat, from 51 to 63% of total creatinine passes into the broth, so in terms of its content, broth, as a rule, exceeds boiled meat.
The method of heat treatment has a great influence on the content of creatinine and creatine in meat: in poached meat their content is 1.5 times higher than in boiled meat.
When poultry is cooked, 0.68% of extractive substances pass into the broth (in % by weight), of which 0.5-0.6 creatine and creatinine. 10-15% more soluble substances pass from white meat into the broth than from red meat.
Given the large accumulation of extractives in the cooking medium, broths are not used in diets that require chemical sparing. Despite the transfer of a significant amount of these substances into the broth, even after heat treatment, extractive nitrogenous substances remain in the meat, therefore, in cooking technology, methods are used that reduce their amount.
The amount of extractive substances extracted from muscle tissue during cooking depends on:
- cooking temperature,
- ratio of product and water,
- degree of product grinding.
It is necessary to take these factors into account to correctly assess the dietary properties of boiled meat and the resulting broth.
How to cook diet broth
1. In traditional technology, meat is cooked by immersing it in hot water. In this case, the liquid in the meat follows the capillaries in the direction of the heat flow, i.e. to the center of the product. When immersed in cold water and subsequent cooking, when the temperature of the meat and water is almost the same all the time, muscle juice with substances dissolved in it “flows” from the meat into the water from the very first minutes of cooking. Therefore, to reduce the amount of extractive substances, meat should be placed in cold water when cooking. At the same time, more uniform heating of the product is also observed.
2. The degree of extraction of extractive substances largely depends on the temperature at which the product is cooked until cooked.
After bringing the water to a boil, you can maintain two modes: boiling temperature or low temperature (about 90 ° C). In the second case, muscle proteins are compacted to a lesser extent, due to which more moisture and extractive substances remain in the meat or fish.
Products cooked in this way turn out to be more juicy and tasty; about 20% more extractive substances remain in them than when cooked in boiling water. Therefore, in the practice of medicinal cooking, cooking meat and fish in boiling water is used in cases where it is necessary to remove extractive substances from them as much as possible.
3. The degree of removal of extractives is greatly influenced by the amount of water in which the product is boiled. When the ratio of meat and water changes from 1:1 to 1:3, the amount of soluble substances digested from meat increases by 25%. This is explained by the fact that with an increase in the amount of water relative to the mass of the product, better conditions are created for the diffusion of soluble substances from it, since the difference in their concentrations in the product and water increases.
4. The amount of extractive substances extracted from meat depends on its grinding. The smaller the pieces of meat, the larger the surface of contact between the meat and water and the more favorable the conditions for the diffusion of extractive substances from it. Small pieces of meat (0.5 kg) release 10-15% more extractive substances during cooking than large pieces (2.5 kg).
During frying In meat, poultry and fish, extractive substances are released in smaller quantities, since with this method of heat treatment the bulk of the moisture released by compacting muscle proteins evaporates, and the substances dissolved in it remain in the product.
When extinguishing products of animal origin are prepared into sauce dishes, the liquid base of which is broth. Since the concentration of extractive nitrogenous substances in the sauce and the products themselves is high, when chemically sparing the gastrointestinal tract, stewing as a method of heat treatment and stewed dishes from meat, fish, and poultry are excluded.
Therefore, in diets with chemical sparing, preference is given to boiled products, in which the amount of nitrogenous extractive substances remains minimal compared to other methods of heat treatment.
In addition, in gentle diets prohibited use:
- meat, fish and chicken broths, because they contain a high concentration of extractive substances and are strong stimulants of gastric juice secretion.
- mushrooms and mushroom decoctions, since their nitrogenous extractive substances contain a large amount of free amino acids. In mushrooms, 23 amino acids have been identified that are in a free state. Their content ranges from 14 to 37% of the total amount of amino acids. Porcini mushrooms are especially rich in free amino acids (8.6% dry matter).
Thus, in order to limit the content of extractive nitrogenous substances when chemical sparing excluded from diets:
meat and fish broths rich in extractive substances, decoctions of mushrooms and vegetables;
all fried foods;
meat, fish and poultry stewed in their own juices;
meat, fish, mushroom sauces and poultry broth sauces.
“Oh, now I would like some soup and giblets!.. Eh, Sharapov? Would you like some soup with giblets?"
G. Zheglov.
Soup is one of the usual dishes of traditional Russian cuisine. Moreover, the richer the broth in it, the more nutritious it is considered. Have you ever wondered why soups cooked in meat, fish or vegetable broth have a special, unique taste?
This article will discuss the benefits and harms of such a dietary product as broth.
What gives flavor to meat and vegetable broths?
Many people believe that rich broth is the most nutritious. In fact, this is a misconception. The finished broth contains mainly not protein, which determines the value of the dish as a food product, but extractives. What is it?
The cells and between the cells of plants and animals contain many substances belonging to different chemical groups that when cooked they easily turn into broth. These substances are usually called extractive. Among them there are many so-called nitrogenous compounds (purine bases, urea, fragments of protein molecules and others). The more of these substances goes into the broth, the richer its taste becomes. Why is this bad? - you might ask.
The bad thing is that these substances can seriously affect the body’s condition, and many people trying to lose weight fall into the unexpected trap of ignoring this effect. But what is special about these substances, why is it important to take into account their content in food?
The effect of extractive substances in broths on the body
You've probably noticed that soups stimulate your appetite (which is why they are often served as a first course). This happens due to the fact that purine bases, which are part of broth extracts, activate the work of the digestive glands (the so-called juice action), that is stimulate digestion. And if you are a reader of our site, then most likely you do not suffer from lack of appetite. So you should consume your first courses very moderately.
However, appetite is not so bad, notes Dr. S.P. Semenov. Many extractive substances have a pronounced biological effect on the autonomic nervous system. Surely you are familiar with this action. After eating, the face turns red, sweat appears on the forehead, one uncontrollably falls asleep, one no longer wants to work...
These symptoms are the result of a kind of mild “poisoning”. Why is that? Yes, because warm broth requires virtually no time for digestion and absorbed into the blood very quickly. Extractive substances fall like an “avalanche” on the liver, overloading it, and some of them remain unharmed... Additionally, it should be noted that modern meat products, chicken, beef are not environmentally friendly and may contain medications, weight gain hormones and other substances that interfere with the body.
When a similar situation occurs regularly, a deformation of metabolism occurs, a shift towards accumulative processes. Which means increased risk of fat accumulation.
Proper preparation of broths. How to eliminate the influence of extractive substances on the body
Extractives is a heterogeneous group of chemical compounds that are easily extracted by water from the original food products during cooking. Extractive substances provide flavor to foods such as meat, fish, poultry, mushrooms, and vegetables. In addition, they stimulate the appetite well and stimulate the functioning of the digestive glands of the gastrointestinal tract. However, extractive substances are biologically very active and, when they enter the main bloodstream, seriously deform the state of the body. Many people are well aware of this deformation, because in modern culture it is widely accepted to eat dishes prepared on the basis of various extracts. I mean mainly a variety of soups. After taking a soup rich in extractive substances, many people develop characteristic phenomena: “pleasant” drowsiness, lethargy; the face turns red; Sometimes perspiration appears on the forehead and face.
At the same time, normal mental activity is seriously hampered... A similar, although less noticeable effect is exerted not only by soups made from meat, fish, poultry, mushrooms, vegetables, but by any dishes rich in extractive substances. If a person constantly uses them for food, corresponding metabolic and regulatory disorders develop quite quickly. To avoid this, the consumption of such dishes should always be accompanied by the intake of products that can slow down the absorption of extractive substances. In modern culture, one of the best products with these properties is porous bread. Therefore, vegetables, mushrooms, meat and fish dishes should be eaten with a small amount of bread. N.B. Big amount of bread to accompany meat, fish and poultry inappropriate
, because bread is a starchy product and it makes them difficult to digest. I should especially note the advisability of refusing to eat soups prepared on the basis of first broth
from meat, fish, poultry. In such a broth the amount of extractive substances is especially high, so consuming soups based on the first broths is clearly unhealthy...
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