Properties of food raw materials and food products. food products

Food products are different in chemical composition, digestibility, the nature of the impact on the human body, which must be taken into account when building therapeutic diets and choosing the best methods for culinary processing of products. Food products are characterized by their nutritional, biological and energy value. Nutritional value is a general concept that includes the energy value of a product, the content of nutrients in it and the degree of their assimilation by the body, organolentic qualities, good quality (harmlessness). The nutritional value of products is higher, the chemical composition of which is more consistent with the principles of a balanced diet, as well as products that are sources of essential nutrients. The energy value is determined by the amount of energy that the food substances of the product give: proteins, fats, digestible carbohydrates, organic acids. The biological value primarily reflects the quality of the proteins in the product, their amino acid composition, digestibility and assimilation by the body. In a broader sense, this concept includes the content of other vital substances in the product (vitamins, trace elements, essential fatty acids).

Different foods differ in their nutritional value, but none of them are harmful or extremely beneficial. Products are useful if the principles of a balanced diet are observed, but can be harmful if these principles are violated. This provision remains valid in clinical nutrition, although, depending on the disease, some foods in diets are limited, excluded, or allowed after special cooking, depending on the disease, while others are considered more preferable.

Among food products there are no those that satisfy the human need for all nutrients. For example, dairy products are poor in vitamin C and hematopoietic trace elements; fruits and berries are poor in proteins and some B vitamins. Only a wide food set provides the body with all the nutrients. Nutritional disorders of the body are often associated with a lack or excess of some foods to the detriment of others. Accounting for this is especially important when compiling a menu of therapeutic nutrition. You can compare different products in terms of biological value, culinary qualities and other indicators, but not oppose them. When comparing, one should take into account the amount of food used in the diet, national nutritional characteristics and other factors. For example, red sweet pepper has 5 times more vitamin C than white cabbage, but the latter is a real source of vitamin C in everyday nutrition. Lamb is not recommended for many diseases, as it contains refractory fats. However, in those republics where lamb is the main type of meat consumed since childhood, low-fat young lamb can also be used in medical nutrition.

The number of consumed natural products is limited: mainly fresh vegetables, fruits, berries, nuts, honey. Most products are consumed after processing: sausages, confectionery, bakery products, sour-milk products, various dishes, etc. It is advisable to use in clinical nutrition products combined for a better balance of nutrients: new types of cereals, egg and dairy pasta, butter and processed cheese with Ocean pasta, etc. The use of artificial products is promising. These products are obtained on the basis of proteins and other nutrients of natural origin, but their composition, structure, appearance and other properties are artificially formed (artificial cereals and pasta and meat products, granular protein caviar, etc.). In artificial products, it is possible to regulate the chemical composition, which is important for the creation of special health food products.

Many food products, in particular after appropriate cooking, have certain medicinal (dietary) properties in relation to certain diseases. However, this does not give reason to call them dietary products. Diet foods are specially formulated foods intended primarily for sick people. These products are conditionally divided into two groups. 1st group dietary products is used for diseases of the gastrointestinal tract, violation of the act of chewing and swallowing, in the postoperative period. These products must provide mechanically and chemically gentle nutrition, so they have a high degree of grinding, they have little fiber, extractives, sodium chloride (salt), and no spices. Such products include fine flour from cereals; homogenized (especially wiped) canned food from vegetables, fruits, meat, fish freed from the inedible part; enpits - dry water-soluble concentrates of high nutritional value, etc. 2nd group dietary products is intended for diseases associated with metabolic disorders (atherosclerosis, diabetes mellitus, obesity, kidney failure, etc.). In these products, some nutrients are limited (fats with saturated fatty acids, sugar, sodium chloride, purines, etc.) and the content of vitamins, essential fatty acids, lecithin, mineral salts and other nutrients that normalize metabolic processes is increased. Such dietary products include various bakery products (buns with lecithin and seaweed, protein-wheat and salt-free bread, etc.); confectionery, fruit purees, compotes, juices, jams with xylitol or sorbitol instead of sugar; protein-free pasta; fermented milk products and butter enriched with vegetable oils; sausage products with protein-mineral fortifier, etc. Dietary products intended for patients with hereditary metabolic disorders should be specially mentioned. In such products, food intolerable substances, such as certain amino acids or lactose, are excluded or severely limited.

The conditionality of the grouping of dietary products is explained by the fact that some products are used for diseases included in both groups: grain and doctor's bread, fermented milk products with the inclusion of vegetable oils, etc. Some dietary products are also baby food products, for example, homogenized canned food.

Product quality- this is a set of properties that determine the suitability of a given product to meet certain needs in accordance with the purpose of GOST.

Organoleptic properties of products- appearance, texture, color, smell, taste - important indicators of their quality. A change in the organoleptic qualities of a product usually indicates a deterioration in their biological value (a decrease in the content of vitamins, essential fatty acids, etc.) and a possible accumulation of products of protein breakdown, decomposition of carbohydrates, and fat oxidation that are harmful to the body, especially for sick people. Moldy products may produce toxic substances. Organoleptic changes in perishable products may be accompanied by the reproduction of pathogenic microbes.

When receiving products in catering units and diet canteens, as well as before cooking stored products, their quality is checked by organoleptic indicators.

Classification. Taking into account the general characteristic features and features of use, the following groups of food products can be distinguished: 1) milk and dairy products; 2) meat and meat products; 3) fish, fish products and seafood; 4) eggs and egg products; 5) dietary fats; 6) cereals and pasta; 7) flour, bread and bakery products, bran; 8) fresh and processed vegetables, fruits (fruits, berries, nuts) and mushrooms; 9) sugar and its substitutes, honey, confectionery; 10) canned food and concentrates; 11) flavor products (tea, coffee, spices, seasonings, food acids); 12) mineral waters. Products of all groups are divided into types according to origin or receipt. Some products are divided into varieties and categories based on quality in accordance with the requirements of the standard. For example: type of cow butter - creamy unsalted, grades of the highest and 1st; beef of I and II categories - according to fatness; fresh eggs of category I and II - by weight and quality.

The chemical composition and energy value of the main food products are presented in the table "Chemical composition and energy value of 100 g of the edible part of the main food products", and data on the content of amino acids in the products (lysine, methionine, tryptophan), linoleic acid, cholesterol and fiber - respectively in the Tables. , and the section "Fundamentals of Nutrition for a Healthy and Sick Person".

Physical properties

Form for fruits and vegetables - an indicator of the variety and botanical species; for confectionery, bakery products, rennet cheeses, the shape characterizes both the correctness of technological processes and the quality of raw materials.
The mass of a unit of production (absolute mass) is determined in assessing the quality of many food products. For bakery and confectionery products, the mass is limited by the requirements of standards; for seeds of cereals and raw coffee, the mass of 1000 grains is determined, for nuts, the mass of 100 pieces.
Density - the mass of a unit volume, expressed in kg / m 53 0 or g / cm 53 0. For liquid products, the relative density is determined, which is found by dividing the mass of the product at a temperature of 20 degrees by the mass of water at the same temperature. Density characterizes the chemical composition of the product and the degree of its dilution.
The nature (volumetric or bulk weight) of a product is defined as the ratio of its mass to the volume it occupies, together with pores and voids, expressed in kg / m 53 0. Bulk mass must be taken into account when determining the capacity of containers, storage facilities, vehicles.

Structural and mechanical properties
They characterize the resistance of food products to mechanical stress, depend on the chemical composition and structure of the products.
Strength - the ability of a product to resist mechanical destruction; is determined to establish the quality of refined sugar, crackers, pasta.
Hardness - the property of a body to prevent another (harder) body from penetrating into it; determined for grain, sugar, vegetables, fruits.
Elasticity - the ability of a body to instantly restore its shape after the application of an external force (pressure).
Elasticity - the ability of the body to restore its shape after some time after pressure.
Plasticity - the ability of the product to irreversible deformations (characterizes the quality of the caramel mass, dough).
Relaxation is a property of products of a solid-liquid structure, which characterizes the time of transition of elastic deformations into plastic ones at a constant load. This property is of great importance when transporting bread and bakery products, fruits, vegetables, confectionery.
Creep is a property of a gradual increase in plastic deformation without increasing the load, especially of a heated body; typical for jam, marmalade, ice cream, butter, margarine.
Viscosity - characterizes the internal friction formed during the relative movement of adjacent layers of syrups, molasses, honey, mayonnaise. It depends on the adhesion forces between the particles and molecules of the substance, the temperature of the product.
Stickiness (adhesion) - the ability of products to show to varying degrees the forces of interaction with another product or the surface of containers, equipment. Dough, toffee, cheese, boiled sausage, butter, bread crumb have stickiness properties, which, when cut, stick to the surface of the knife, crumble or break.
To characterize the structural and mechanical properties of food products, the term "consistency" is used - the properties of the product, detected by touch or chewing.

Optical properties
The optical properties of products are determined visually or with the help of instruments.
Transparency - the ability of products to transmit light (sugar solutions, refined vegetable oils, beer).
Color - due to natural dyes (pigments) or the addition of artificial dyes. Must correspond to the type and grade of the product, may change during storage and processing.
The refractive index - the ability of products and their solutions to refract light, characterizes the quality and concentration of the product (sugar solutions, vegetable oils).
Optical activity - the ability to rotate the plane of polarization of a polarized beam of light.

Thermophysical properties

These properties are manifested by the action of thermal energy on food products. Knowledge of thermophysical characteristics is necessary to ensure the correct flow of the processes of cooking, baking, sterilization, pasteurization, freezing, thawing and storage of products.
Heat capacity - the amount of heat absorbed by the body when heated by 1 degree. The heat capacity calculated for 1 kg of the product is called specific and is expressed in J / (kg 5 o 0C). Products with a high mass fraction of fat are characterized by low heat capacity, and products with high moisture content are high.
Thermal conductivity coefficient - the amount of thermal energy that flows per unit of time through 1 m 52 0 of the product surface to a thickness of 1 m at a temperature difference of 1 degree. Water and products with a high moisture content are characterized by high thermal conductivity, they are able to quickly heat up and cool down; fat-containing, porous and free-flowing products have low thermal conductivity, which can cause them to spoil.
The melting point of fats is slightly higher than the pour point. These characteristics depend on the composition and quality of fats.
The pour point must be taken into account when refrigerating, freezing and storing products. Storage at temperatures below the freezing point of products adversely affects their quality (for milk, drinks).

Sorption properties
Sorption is the process of absorption of vapors or gases from the environment. Humidification of products occurs if the pressure of water vapor in the air exceeds the pressure of water vapor on the surface of the products as a result of the evaporation of part of the free moisture from them. Products absorb moisture in this case both due to adsorption (formation of a thin layer on their surface) and absorption (through volumetric absorption by hydrophilic substances), and as a result of capillary condensation (in the presence of micro- and macrocapillaries. Absorption by the product of vapors or gases with the formation of chemical compounds is called chemisorption.
Hygroscopicity - the ability of products to absorb moisture from the environment. Dry and relatively dry foods (flour, cereals, grains, sugars, milk powder and others), as well as those rich in protein, starch, fructose, invert sugar, can absorb moisture. Foods rich in fat, or containing a lot of moisture, do not absorb it. When the water vapor pressure on the surface of the product is greater than the water vapor pressure in the air, desorption occurs. Sorption and desorption of moisture by the product are carried out until it acquires equilibrium moisture, when the pressure of water vapor in the air and on the surface of the product become equal. The absorption of moisture by a product depends on its chemical composition, structure, as well as the temperature, pressure and relative humidity of the air. Relative humidity is the ratio of the absolute amount of moisture in the air to the amount of water at the highest saturation at a given temperature, expressed as a percentage, measured with a hygrometer or psychrometer.

The composition of the daily diet includes certain foods consumed in their natural form or after various mechanical and thermal culinary treatments. Each food product has a special, inherent property of impact on the body. Depending on the therapeutic purpose of the diet, some foods in the diet are quantitatively limited or completely excluded, others are allowed only after special culinary processing.

When compiling a diet, it must be remembered that different products differ in their nutritional value, but none of them are exclusively harmful or exclusively beneficial. Products are useful if the principles of balanced, adequate nutrition are observed, but can be harmful if these principles are violated. Among food products there are no those that satisfy the human need for all nutrients. It is promising to use combined products, which, in terms of composition and properties, correspond to the needs of people as much as possible.

The main functional properties of some food products are given below.

Milk and dairy products

According to their chemical composition, dairy products occupy an exceptional place among animal products used in human nutrition. This is due to the favorable ratio of the amino acids that make up the milk protein, the good digestibility of fat in the state of a thin emulsion, the special properties of milk sugar, the vitamin and mineral composition of milk.

Whole fresh milk is used in clinical nutrition for gastritis and gastric ulcer, cardiovascular diseases, especially in circulatory failure, tuberculosis, inflammatory processes of various etiologies. Milk is contraindicated in enterocolitis, some forms of gastritis, nutritional allergies.

Lactic acid products (kefir, curdled milk, yogurt, acidophilic drinks) are characterized by high acidity due to the development of beneficial microflora; contain a significant amount of B vitamins (especially B2), have pronounced antimicrobial properties due to the presence of antibiotic substances.

Some types of fermented milk contain alcohol, which was formed as a result of alcoholic fermentation caused by certain yeasts (kefir fungi): in fat kefir - up to 0.6%, in koumiss - up to 2.5%.

Due to its properties of mares, koumiss is widely used in the diet for tuberculosis. Some types of milk (chal from camel milk, koumiss) have an exciting effect on the nervous system and stimulate appetite.

Buttermilk is a secondary dairy product formed during the production of butter after churning cream. Due to the high content of lecithin, buttermilk is used for liver diseases, diseases of the hematopoietic organs, nervous disorders, atherosclerosis, constipation and other diseases.

Cream and sour cream are products with a high content of emulsified fat. They are obtained by separating whole milk (sour cream is additionally fermented, which increases its acidity to 90 0 T). In clinical nutrition, cream and sour cream are used for gastritis, peptic ulcer disease, as a fat component in cooking technology, which shows the exclusion of fats.

Cottage cheese is obtained by acid or acid-rennet coagulation of milk. In cottage cheese, milk proteins, due to conformational changes and a certain spatial arrangement of molecules, have more accessible and easily attacked properties for digestive enzymes. Cottage cheese contains a large amount of water- and fat-soluble vitamins (100 g of the product contains about one daily requirement of vitamins A, E and B12; about half of the daily requirement for thiamine and riboflavin).

The balanced chemical composition of cottage cheese makes it an indispensable product in the diet, however, due to its high acidity (up to 270 0 T for low-fat cottage cheese of the first grade), its use is limited. In case of stomach diseases, the acidity of cottage cheese should not exceed 170 0 T. In this regard, for people suffering from such diseases, cottage cheese is made by curdling fresh milk with calcium salts or table vinegar. The acidity of such cottage cheese does not exceed 50 0. To give a sour taste to such cottage cheese, sour cream is sometimes added.

Cheeses are obtained by lactic acid or enzymatic precipitation of milk proteins, followed by the removal of whey. According to their chemical composition, cheeses are protein-fat concentrates, and proteins and fats retain the properties of natural milk in cheeses.

As a complete food, cheeses are used in medical nutrition after infectious diseases and operations as a source of complete protein and calcium, and also due to their acidotic properties.

Cheeses have a stimulating effect on the central nervous system, especially at night. This is probably due to the fact that as a result of the maturation of cheeses, amine compounds are formed - phenylethylamine and tyramine.

Ice cream is a highly valuable food product because it contains milk, cream, eggs, sugar, fruits and berries and other ingredients. In medical nutrition, ice cream is used for internal bleeding (due to the low temperature, ice cream reflexively narrows the blood vessels of the internal organs and expands the peripheral vessels). Ice cream should be avoided in diets where thermal sparing is indicated.

Dry protein mixture is made from skimmed milk powder and clarified blood of slaughtered animals. The product is rich in B vitamins, easily digestible iron, calcium and other mineral elements. The mixture is indicated for peptic ulcer, gastritis, colitis, anemia.

egg products

Eggs are considered a complete food. They are used in the diet quite often. All nutrients are contained in the egg in a balanced ratio. The protein of a freshly laid egg is used as an alkalizing factor in inflammatory diseases. However, raw egg whites cannot be used because they contain the avedin mucoprotein, which binds vitamin H (biotin). The crude protein contains a trypsin inhibitor, and therefore up to 50% of the egg white is not hydrolyzed and is quickly evacuated from the stomach. It is used in the treatment of peptic ulcer.

A significant (5-10 times) predominance of lecithin over cholesterol contained in the egg yolk ensures its proper use by the body. Therefore, it is impossible to completely exclude eggs from the diet.

Raw egg yolk causes contraction of the gallbladder and the secretion of bile, which limits the number of eggs in diets for patients with cholecystitis and gallstone disease.

Egg products contain sulfur-containing amino acids that are involved in the synthesis of thiol compounds, which determines their use in diseases of the nervous system and inclusion in diets of therapeutic and preventive nutrition for people whose work is associated with exposure to neurogenic industrial substances (arsenic, mercury, lead, tin). The presence of lecithin and iron in egg products enhances hematopoiesis.

Meat and meat products

The diet uses various types of lean meat of young rabbits, poultry, large and small cattle, pigs, as well as some offal (liver, heart, tongue).

Some types of meat products contain a high amount of iron, which is taken into account when preparing diets for people with diseases of the hematopoietic organs. As shown by the results of experiments, a beneficial effect in case of circulatory failure has a raw heart puree with the addition of apples, sugar and spices.

The digestibility of meat depends on its type and method of cooking. It has been established that 250 g of boiled veal leaves the stomach in 2-3 hours, boiled beef in 3-4 hours, fried beef in 4-5 hours.

In general, the digestion of meat proteins by pepsin and trypsin is slower than that of fish proteins. The proteolysis of pork proteins is especially slow. Chicken meat and young lamb are best digested. Lean meats are less digestible. Digestibility can be increased by pre-beating the meat before heat cooking (chopped foods digest even faster), as well as frying the meat with low heat. The digestibility of meat dishes increases with an increase in the thoroughness of chewing. Meat semi-finished products, rich in connective tissue, are best boiled, as this type of thermal cooking provides effective breakdown of connective tissue proteins.

In the diet, the quantitative and qualitative composition of extractive substances is of great importance. Nitrogenous extractive substances of muscle tissue, in addition to soluble proteins, include creatine, creatinine, carnosine, methylguanidine, inositic acid, carnitine, amino acids and purine bases, which include hypoxanthine, guanidine, xanthine (which are part of nucleic acids).

Concentrated broth with a water ratio of 1:1 contains up to 8 g of extractives and purines, 2 g of proteins, 9 g of glutin, 2.5 g of fat and 4.7 g of minerals.

Table 1

During heat treatment, depending on the type of product, extractives are removed: when cooking from 100 g of meat in a piece until cooked, 65% of extractives are removed, when cooked in the form of cutlets from minced meat with bread - 38%, from minced meat with rice - 27%, and cutlets without bread - 52%

All extractive substances of meat are stimulants of gastric secretion, have a stimulating effect on the central nervous system and increase appetite. The end product of purine metabolism in humans is uric acid. This determines their differentiated use in clinical nutrition.

The liver is most widely used in clinical nutrition (for urolithiasis associated with violation of the epithelium) due to the presence of a significant amount of B vitamins, fat-soluble, hormones, minerals and other substances.

Gelatin is a defective protein of the hydrothermal breakdown of collagen. The ability to form jellies, which are easily digestible, and do not have a stimulating effect on the secretory organs, allows it to be used in the diet and in cardiovascular diseases. It was found that jelly from some by-products containing an increased amount of connective tissue proteins, it is advisable to use for internal bleeding. The mechanism of this phenomenon (the positive effect of gelatinized collagen) has not been established, however, gelatin in jelly is more effective, since in its pure and dialyzed form it loses its ability to enhance blood clotting.

Some types of sausages have also found application in diet therapy. Meat sausages differ in the method of preparation (boiled, semi-smoked, smoked, raw smoked). Due to the content of spices and smoking in the recipe, they excite the appetite well. It is advisable to use black pudding and brawn in the diet for diseases of the hematopoietic organs, as they are high in iron.

However, it must be remembered that semi-smoked, smoked and fatty varieties of sausages burden the digestive organs and are practically not used in clinical nutrition. In the diet, boiled sausages are used, especially doctor's, dietary, dairy, children's, diabetic.

Fish and non-fish aquatic raw materials

Fish and non-fish aquatic raw materials (seaweed, mussels, crabs, shrimps, crayfish, lobsters, lobsters, etc.) are a significant reserve for the production of special-purpose products at public catering enterprises. The products of this group serve as a source of complete protein, as they contain all the essential amino acids. This is especially true for caviar of partial fish (on average, fish of various species contain 15-20% protein).

100 g of partial caviar contains 0.95 g of tryptophan; 3.39 g lysine and 1.27 g methionine.

In the diet, mainly low-fat fish and medium-fat fish (up to 8%) are used. Fatty fish (herring, eel, sturgeon, stellate sturgeon, beluga) are used less often. However, it should be borne in mind that some types of fish contain a significant (more than 15%) amount of fat (cod liver contains up to 68% fat). Fish oil has a high content of vitamins A and D (up to 10,000 IU).

The nutritional value of fish and non-fish aquatic raw materials varies depending on age, diet, season, species and other factors. The most significant changes occur in the chemical composition during reproduction.

Chum salmon during spawning loses more than 7% of proteins; the amount of fat is reduced by 120 times.

Due to the low content of connective tissue in fish meat and the relatively low content of hydroxyproline, the rate of digestion of fish meat and non-fish aquatic raw materials is comparable to the time of digestion of milk proteins. This is facilitated by an increased (compared to the meat of slaughtered animals) secretion of gastric juice. Dried and dry fish are digested much worse.

Connective tissue is made up of non-essential amino acids, of which three predominate: proline, glycine, and hydroxyproline. Amino acids connected to each other by an amide (peptide) bond are twisted in the form of spirals. The strength of this scaffold depends on the presence of hydroxyproline, which is the main forming element of the connective tissue structure.

The fish contains a significant amount of purine bases (50-100 mg%) and uric acid (10-30 mg%). In a significant amount, these substances are found in canned food (especially sprats and sardines).

The rationale for the use of fish meat and seafood in diets for diseases of the kidneys, stomach and metabolic diseases are the results of experiments showing the content of extractives in the feedstock and their transition to the cooking environment. It has been established that the amount of residual nitrogen in the urine when consuming fish is 2 or more times higher than when consuming meat products (this serves as a basis for reducing the consumption of fish products in case of relevant diseases).

When using salted fish and caviar, it is necessary to take into account the content of table salt in it: in granular - 5-10%, in pressed - 5%, in caviar of partial fish - up to 10%. Fresh caviar of partial fish has lipotropic properties, which has been used in diseases of the liver and cardiovascular system.

Some fish dishes (mainly gastronomy) are distinguished by high taste qualities. They are included in the diet in limited quantities to increase appetite.

In anti-sclerotic diets, the use of seafood of all kinds increases the coagulating ability of the blood, stimulates the excretion of cholesterol, and normalizes lipid metabolism. Seaweed stimulates intestinal motility and is indicated for constipation, as well as in cases of hypothyroidism (decrease in thyroid function).

Flour, bran, bread

Flour obtained by fine grinding consists of small particles of the center of the grain, the outer layers of which have been removed. The finer the grinding and the higher the grade of flour, the less protein and especially minerals and vitamins it contains. dietary fiber, but more starch and better digestibility and absorption of starch and proteins.

Rich in proteins, B vitamins, dietary fiber, lecithin and other phospholipids, soy flour is used for flour products for liver diseases and atherosclerosis.

Wheat bran is rich in dietary fiber, B vitamins, magnesium, potassium, used in medicinal cooking to add to flour products, cereals, soups, minced meat, fish, vegetable dishes, and to prepare vitamin drinks. They are used in diets for hypertension, diabetes, atherosclerosis, obesity, constipation, cholelithiasis. Bran washed from starch is used for kidney diseases, diabetes, obesity.

The diet uses various varieties of white and rye bread, as well as their specialized (dietary) varieties, which are designed for people with certain diseases (for example, salt-free bread or bread with an increased amount of ballast substances for patients with obesity and diabetes).

Bread lingers in the stomach for a long time due to the slow attack by pepsin and trypsin (the exception is white bread made from premium flour). Bread requires three times more gastric juice than milk proteins.

Vegetables and fruits

Vegetable products are widely used in dietary nutrition. Black currant, raspberry, wild rose, pumpkin, prunes, dill, onion, etc. have healing properties. Most vegetables and fruits are sources of water-soluble vitamins, mineral salts, enzymes, organic acids and tannins. Fruits and vegetables promote bile secretion, stimulate intestinal motility and promote the excretion of cholesterol. The cell walls of plants contain pectin substances (polymers consisting of galacturonic acids), which, when swollen in the body, form sparingly soluble complexes with organic and inorganic toxins (radionuclides, heavy metals, etc.). The ability of pectin substances to adsorb toxins depends on the content of free (non-esterified) carboxyl groups.

With a low calorie content, fruits and vegetables are large in volume, which contributes to a feeling of satiety. Plant foods contain tartronic acid, which inhibits the conversion of carbohydrates into fats; the ash residue of most fruits and vegetables has an alkaline reaction, which serves as a regulator of pH balance in the body (prevents acidosis).

Leafy greens (parsley, spinach, sorrel, green onions, etc.) are distinguished by a large amount of vitamins C, E, K and some B vitamins (pyridoxine, folic acid, inositol). In moderation, the use of leafy vegetables is indicated for atherosclerosis. Due to the high content of oxalic acid (up to 400 mg%), leafy vegetables (especially sorrel, rhubarb and spinach) are excluded with iron and calcium deficiency (it blocks the absorption of these elements by forming insoluble salts). The presence of an increased amount of fiber makes fruits and vegetables indigestible food, which is used for constipation.

There is an opinion that raw cabbage juice, due to the presence of vitamin U, contributes to an effective effect on the body with gastritis, peptic ulcer, hepatitis and colitis. However, when compiling diets, it must be remembered that cabbage juice has a juice effect and promotes gas formation.

Sauerkraut also has medicinal properties. As a result of mixed fermentation (alcohol and lactic acid), it becomes more accessible to the action of digestive enzymes. Sauerkraut juice stimulates secret glands. Due to the large amount of lactic acid, the juice is indicated for diabetes.

Cauliflower is widely used in medical nutrition. It contains up to 70 mg% of ascorbic acid; 1.4 mg% iron and 0.1 mg% vitamin B1. Cauliflower contains a reduced amount of sulfur and fiber, which makes it easier to digest without irritating the walls of the stomach. Cauliflower is not recommended for gout and kidney disease, as it contains much more purines than white cabbage.

The main tuber crop used in human nutrition is the potato. It is widely used in the diet given that it contains a low amount of fiber. However, potatoes, among other vegetables, are high in starch, which makes them high in calories and are excluded from diets recommended for obesity.

Potato proteins are complete (contain all essential amino acids), but the amount of protein is 8-12 times lower than in animal products. According to some researchers, raw potatoes contain a pepsin inhibitor, and therefore raw potato juice is included in the diet for gastric ulcers and gastritis.

Potatoes are easily digested - 150 g of potatoes are evacuated from the stomach in 2-3 hours. This is obviously due to the presence of solanine sugar, which stimulates the activity of the gastrointestinal tract. In some people, potatoes, due to their high starch content, cause increased gas formation; when combined with carrots, this phenomenon is noted much less frequently. The high content of potassium (compared to sodium) has a diuretic effect of this tuber and determines its use in the diet of people with diseases of the kidneys and heart.

Mechanical and thermal cooking should contribute to the preservation of nutrients in the product (mainly vitamins and mineral salts). To do this, you need to use steaming, peeling, baking; recommended potato dishes in diets with mechanical sparing - mashed potatoes and soufflés.

Other types of root crops (beets, carrots, rutabaga, etc.) are used for food mainly in boiled form. Many of them contain sugars (up to 7% or more), mineral elements (potassium and iron are very important, as well as other elements that are part of the ash residue and have alkaline properties), betaine, which is necessary for the synthesis of choline. Betaine and choline prevent fatty degeneration of the liver. The activity of betaine is three times lower than that of choline.

The proteins of most root crops are incomplete (the rate of some amino acids is 50% or less). When vegetables are included in the diet, the digestibility of protein received from food increases by an average of 10-20%.

Of particular practical interest is protopectin, which is contained in root crops in therapeutic and prophylactic amounts. During heat treatment, water-insoluble protopectin turns into soluble pectin. The property of pectins to adsorb cholesterol, heavy metal ions, radionuclides, organic poisons and other substances toxic to the body is due to their structure. During hydrolysis, pectins give a significant amount (up to 70%) of galacturonic acid, which has free carboxyl groups and has adsorption capacity.

Radish, swede, radish, onion, garlic and other vegetables have a choleretic effect due to the presence of essential oils and phytoncides (defenzonate, sinigrin, allicin, sativine). This property is enhanced when vegetable oils (especially olive oil) are used as a dressing. Most substances have antibiotic and other medicinal properties (they are used to reduce putrefactive processes in the intestines, to normalize pressure, and in atherosclerosis). However, these vegetables are contraindicated in peptic ulcer, gastritis and kidney disease.

Pumpkin, due to the high content of iron and potassium, is used for diseases of the hematopoietic organs and as a diuretic. Pumpkin seeds have curative and preventive properties against helminthic invasion.

Cucumbers, melons and watermelons, due to their high water content (up to 97%) and potassium and low sodium content, have a diuretic effect. Cucumbers are shown in the preparation of diets for fasting days (low-calorie diets). There is evidence of the activity of tartronic acid contained in cucumbers and inhibiting lipogenesis. Watermelons and melons contain up to 0.15 mg% folic acid.

Legumes are a source of protein, carbohydrates (and in soy - and fat). Legume protein - legumin is less complete than animal tissue protein due to a small amount of deficient amino acids - tryptophan, methionine and lysine. The exception is soy. It contains 0.714%; 0.927% and 1.826% tryptophan, methionine and lysine, respectively, which is 3; 1.9 and 1.1 times more than in beef meat.

Legume lipids are represented by highly unsaturated triglycerides and lecithin. The presence of a significant amount of fiber (up to 5%) contributes to irritation of the gastric mucosa, meteorism and prevents the rapid breakdown of starch.

By digestibility, legume proteins are classified as slowly attacked by pepsin and trypsin. Heat cooking promotes the breakdown of proteins. Some legumes (soybeans, beans) contain proteinase inhibitors. Anti-enzymatic substances can retain their activity after two hours of boiling.

The heat treatment of legumes should include the removal (or softening) of the fiber-rich skin: cooking in an alkaline environment (in soft water) ensures better digestion and absorption of legumes. Note that, with the exception of green peas and soybeans, legumes contribute to a shift in the pH of the body's environment to the acid side (contribute to acidosis).

In clinical nutrition, fruits, berries and nuts are widely used in fresh, boiled, dried and canned form. When using fruits and berries, it is necessary to take into account the qualitative and quantitative composition of sugars, pectin and tannins, organic acids, essential oils, mineral salts and vitamins contained in them. It must be remembered that in the same fruit, depending on the selection, the content of nutrients can vary significantly.

Of the three organic acids found in fruits, tartaric acid gives the sharpest sense of sour taste. The sensation of sour depends not only on the amount, but also on the type of organic acid. The most pleasant sensation is given by citric acid.

Astringent and tart taste is given to fruits by tannins, the presence of which justifies their use in the diet.

Carbohydrates in fruits are represented mainly by monosaccharides: glucose and fructose (less often, sucrose, which forms glucose and fructose during hydrolysis). Due to the fact that fructose is absorbed without insulin, fruits containing it (for example, pome fruits) are recommended for diabetes. In stone fruits (except for cherries and sweet cherries), glucose and fructose predominate. In berries, the amount of glucose and fructose is approximately the same, but they have the least amount of sucrose.

Fiber in berries is contained in an amount of 0.3% (cherries) to 5.5% (raspberries). Other indigestible carbohydrates include pectin. Its technological property to form jellies (jelly) determines the widespread use of fruits and berries in the diet. Berries are easily evacuated from the stomach and are easily digested. Most fruits and berries prevent acidosis. Fruits and berries are shown for cardiovascular insufficiency, obesity, liver and kidney diseases.

An increased amount of potassium causes the diuretic properties of fruits and berries. Potassium-sodium ratio ranges from 130:1 to 400:1, which is favorable for the human body. The high content of iron and copper in stone fruits made it possible to recommend them for anemia and anemia.

Canned and dry fruits and berries, juices based on them (especially with pulp), due to the seasonality of obtaining the main raw materials, are widely used in clinical nutrition, since they often retain the medicinal properties of fresh products.

Due to their high calorie content, nut fruits have not been widely used in diet therapy. They are recommended in pure form for hypertension, constipation, anemia and atherosclerosis. Due to their high fat content, nuts stimulate bile secretion.

Mushrooms are also rarely used in medical nutrition, since they have a low nutritional value and contain a lot of nitrogenous extractives and purine bases. Due to the high fiber content, mushroom proteins are poorly digested.

Cereals and pasta

Cereals made from various types of cereals, as well as pasta, are widely used in the diet.

Proteins of cereals and pasta are limited in some amino acids. The amount of fiber is usually low and depends on the way the cereal is processed, and in pasta - on the type of flour. The ash residue of cereals has an acidic reaction. From some types of cereals, very finely ground flour is prepared (this is especially important with mechanical sparing).

Oatmeal (oatmeal, oatmeal, oatmeal), with proper heat cooking, form mucous decoctions, which are used for gastric diseases. Proteins of oatmeal have lipotropic properties (have found application in diseases of the heart and liver).

In chronic lead poisoning, oatmeal is included in the diet, which helps to mobilize lead from the depot and remove it from the body. In baby food, oatmeal is prepared with milk, which makes up for calcium deficiency.

Semolina, due to its good digestibility, is used for kidney diseases. Corn groats contain poorly digestible protein, but well inhibits the processes of fermentation and putrefaction in the intestines.

Although millet contains a lot of nicotinic acid and mineral elements (copper, nickel, manganese, zinc), it is used to a limited extent due to the rapid oxidation of the lipids it contains. Fresh millet is indicated for diseases of the cardiovascular system and liver due to lipotropic properties.

Buckwheat (especially buckwheat) contains a lot of fiber, as part of the shell remains on the grains. In combination with milk, buckwheat porridge gives the body an ideal aminogram. Buckwheat is rich in lecithin, which leads to its use in diseases of the liver, nervous and cardiovascular systems.

Barley cereals (barley and barley) contain a lot of fiber, which is used in the treatment of constipation. The increased amount of folic acid and iron allows us to recommend them for anemia.

Thanks to grinding, rice contains only 0.4% fiber. It is widely used in clinical nutrition for diseases of the gastrointestinal tract. When boiled, rice forms a slimy decoction. Protein-starch mucus weakly excites gastric secretion and quickly leaves the stomach.

Sago grits are obtained by processing the starch of sago palms and are used in diets that require the elimination of cereal gluten.

Combined cereals have an improved amino acid composition, an increased amount of protein, minerals and B vitamins. For their manufacture, enrichers (milk, soy flour, yeast) are introduced into cereal flour of one or several types, the mixture is steamed and cereals are formed. These cereals do not contain impurities, boil quickly, and are convenient for preparing various dishes. When rice flour is enriched with skimmed milk, “Health” cereals are obtained, buckwheat - “Pioneer”, oatmeal - “Sports”.

For cereal decoctions and pureed cereals in mechanically and chemically sparing diets, dietary flour is used - buckwheat, rice, cereal.

Pasta contains little dietary fiber and is highly digestible. The nutritional value is increased by adding egg products to the dough. Exclude pasta for obesity and diabetes, as well as celiac disease (a disease in which cereal proteins are excluded from the diet).

Sugar and flavor foods

The first group is foods high in sugar. A distinctive feature of the products of this group (drinks, sweet dishes, confectionery) is a high energy value. Due to the high calorie content, the use of sugar should be moderate, and sometimes completely excluded (for example, with obesity or diabetes). Sugar helps bind water in the body. However, the presence of sugar in the diet is a necessary condition for the neutralizing function of the liver.

Excess sugar disrupts the normal course of the Krebs cycle, leading to the accumulation of acetylcoenzyme A, which is involved in the synthesis of fatty acids and cholesterol.

Increased consumption of sugars leads to disruption of the processes of excitation and inhibition in the cerebral cortex, and also worsens the activity of the cardiovascular system.

Gelled confectionery products have good organoleptic characteristics, but have low nutritional value. The expediency of their use is explained by the presence of various pectins (beet, apple, citrus) as a structural element, which have adsorption properties for toxic substances of various nature.

Bee honey contains up to 75% sugars. Possessing some medicinal properties (for cardiovascular diseases, peptic ulcer, tuberculosis), honey is included in the diet, taking into account the general effect of an increased amount of sugar on the body. In addition, honey contributes to the manifestations of allergies. The daily requirement for honey should be no more than 120-150 g.

Starch hydrolysis products (molasses, maltose syrup) are rarely used in diet therapy. Sometimes they are used instead of sugar for liver diseases and heart failure.

Limited use of cocoa and chocolate in medical nutrition. In the diet, they play the role of mainly flavoring fillers and increase the calorie content of the diet. Although these products are high in iron, this is not used in the diet, since the high content of iron-binding oxalic acid in cocoa and chocolate makes this element difficult to digest.

In the diet, a special place is given to sweeteners - six-atomic alcohol sorbitol and five-atom - xylitol. In terms of sweetness, xylitol is equivalent to sucrose, and sorbitol is half as sweet. Both alcohols are recommended for obesity and diabetes instead of saccharin, as they are non-toxic. The energy value of xylitol is 4 kcal/g, sorbitol is 3.4 kcal/g. Xylitol, to a greater extent than sorbitol, has a choleretic and laxative effect when taken on an empty stomach in an amount of 30-35 g. A dose of xylitol up to 50 g per day with meals in several doses does not cause relief.

Due to the significant content of caffeine (up to 3.3%), tea has a stimulating effect on the nervous system, increases vascular tone, and slightly increases blood pressure. Tea is recommended for various colitis due to the high content of tannins.

Coffee contains tannins and a large amount of nicotinic acid, which makes it advisable to use it for appropriate indications. Coffee has a pronounced tonic effect and excites the central nervous system.

In clinical nutrition, the content of table salt is very often limited, since sodium cations support inflammatory processes, increase the water-retaining capacity of tissues, increase blood pressure, and have an exciting effect on the central nervous system. Table salt is indicated for severe sweating, diarrhea, burns and vomiting.

Spices are herbal products that improve the taste and aroma of food due to the presence of essential oils, glycosides and other substances in them. Dried parts of plants are used: fruits (anise, cumin, coriander, cardamom, pepper, vanilla), seeds (dill, nutmeg), flowers (saffron, cloves), leaves (bay leaf), bark (cinnamon), roots (ginger) . The use of permitted spices and food acids is especially important for “masking” salt-free dishes; in other cases, the use of spices is limited (except for diets No. 2, 9, 15 and others, depending on the severity of the disease).

Sanasol is a table salt imitator. Consists of potassium salts (70%), calcium and magnesium, ammonium chloride and glutamic acid. Sanasol is added to the second (rarely - to the first) dishes immediately before their use.

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Food properties

Culinary products are made from a variety of components (ingredients). Ingredient - a substance of animal, vegetable, microbiological or mineral origin, as well as natural or synthesized food additives used in the preparation or production of a food product and present in the finished product in its original or modified form. Among them there are liquid and powdery bulk products, as well as those having a pasty and solid consistency. Individual instances of food products having a solid consistency can be characterized by linear, sometimes quite significant sizes. The physical properties of food products include structural-mechanical properties, flowability, self-sorting ability, porosity, sorption and thermophysical properties.

Structural-mechanical properties -- features of the product, manifested under impact, compressive, tensile and other influences. These properties characterize the ability of products to resist applied external forces or change under their influence. These include strength, hardness, elasticity, elasticity, plasticity, viscosity.

Strength, i.e., the ability of a solid body to resist destruction when an external force is applied to it in tension or compression, is one of the most important structural and mechanical properties. The strength of a material depends on its structure and porosity. Materials with a linear arrangement of particles and less porosity are stronger. The stronger a single copy of the product, the less it collapses or deforms. Strength is important for the qualitative characteristics of such food products as pasta, refined sugar, cookies, fruits, vegetables, etc. If food products are not strong enough, the amount of scrap and crumbs increases. Hardness is the local edge strength of a body, which is characterized by resistance to the penetration of another body into it. The hardness of products depends on their nature, shape, structure, size and arrangement of atoms, as well as intermolecular cohesion forces. The hardness of crystalline bodies is affected by water of crystallization, which weakens internal bonds and reduces hardness. Hardness is determined when assessing the degree of maturity of fresh fruits and vegetables, since their tissues soften when ripe. Deformation - the ability of an object to change size, shape and structure under the influence of external influences that cause the displacement of individual particles in relation to each other. The deformation depends on the magnitude and type of load, structure and physico-chemical properties of the object. Deformations can be reversible and irreversible. With reversible deformation, the original dimensions, shape and structure of the body are completely restored after the load is removed, while with irreversible deformation, they are not restored. The ability to reversible deformations is characterized by elasticity and elasticity, the difference between which lies in the time during which the original parameters are restored. Irreversible deformations are due to density. Elasticity is the ability of an object to instantly reversible deformations. This property is possessed by bakery products, for which the elastic properties of the crumb are one of the most important indicators characterizing the degree of freshness. Flowability - the ability to move along inclined planes. All powdered products (flour, cereals, granulated sugar, etc.), as well as those consisting of single specimens of more or less rounded shape (grain, root crops, vegetables, many fruits) have good flowability. With an increase in the moisture content of the product, its flowability decreases significantly. The flowability of products is taken into account in the design and operation of storage facilities, mills and other enterprises. Self sorting. Any movement of bulk products is accompanied by self-sorting, i.e., uneven distribution of their constituent components over individual sections of the embankment. Self-sorting is due to the unequal flowability of the mass components, it violates the homogeneity of the mass of the product and creates conditions conducive to the development of undesirable phenomena. With a free fall of the mass of the product (for example, in the process of filling the silo of the elevator), self-sorting is facilitated by windage, i.e., the unequal resistance exerted by air to each individual particle. As a result of self-sorting, areas appear in the product embankment that differ sharply in composition. When storing grain and a number of other products, this is extremely undesirable, since in those areas where small, feeble grains or light impurities accumulate, active physiological processes begin, which can lead to grain spoilage.

Openness. Many products do not absolutely densely fill volumes. There are gaps between solid particles that are filled with air. The presence of such gaps is called porosity. The formation of wells in the mass of the product affects many physical and physiological processes occurring in it. The porosity allows you to blow the product with air or introduce vapors of various substances into it for disinfection. The volumetric or bulk mass of products depends on the porosity. The higher the porosity, the less product will fit in a container of a certain size, so the porosity of the product must be taken into account when designing storages and vehicles. Humidity, or mass fraction of moisture, is one of the most important indicators for assessing the quality of raw materials, semi-finished products and finished products. The amount of moisture in an object must be known first of all to determine its energy value. The more water in the product, the less useful solids it contains per unit mass. Not only does the dry matter content depend on humidity, but also the suitability of the product for storage and further processing. Excess moisture promotes the development of microorganisms, including those that cause rotting and decomposition of the product, accelerates enzymatic, chemical and other processes. In this regard, the moisture content in the object determines the conditions and terms of its storage. In addition, the moisture content of raw materials affects the technical and economic performance of enterprises. Thus, an increase in the moisture content of flour by 1% reduces the yield of bread by 1.5-2%, and an increase in the moisture content of the crumb of bread by 1% leads to an increase in its yield by 2-3%.

thermophysicalproperties of foodstuffs

The most important thermophysical properties of food products include specific heat, thermal conductivity, thermal diffusivity, specific enthalpy, cryoscopic temperature, density, equilibrium vapor pressure.

The specific heat capacity is a value that is numerically equal to the amount of heat required to heat or cool 1 kg of a substance by 1 ° C. The change in the specific heat capacity of products in the freezing temperature range is determined mainly by the initial moisture content of the product and the amount of frozen water. The heat capacity decreases with decreasing temperature, tending to zero at absolute zero temperature (the third law of thermodynamics). The specific heat capacity of water is 1 J / K, carbohydrates - 0.34, fats - 0.42, proteins - 0.37 J / K, so the heat capacity of products depends on their chemical composition. Thermal conductivity is one of the types of heat transfer, at which the heat transfer has an atomic-molecular character. The phenomena of thermal conductivity occur when the temperature difference between the individual parts of the body (product). The thermal conductivity coefficient is numerically equal to the amount of heat transferred through a unit surface area per unit time at a temperature gradient equal to one.

At positive temperatures, the thermal diffusivity of the product is practically unchanged, but with the onset of ice formation, it sharply decreases. This is due to the release of heat of crystallization. With a further decrease in temperature, due to an increase in thermal conductivity and a decrease in heat capacity, the thermal diffusivity increases and reaches a constant value, when water completely turns into ice. Enthalpy is an unambiguous function of the state of a thermodynamic system, often called the heat function or heat content, and is measured in J/kg. Data on the change in the enthalpy of food products in refrigeration technology is usually used to determine the heat removed or supplied during the refrigeration of products. Enthalpy is measured at some initial temperature (usually? 20 ° C), at which its value is taken as 0.

Cryoscopic temperature is the temperature at which the liquid phase of products begins to freeze. The tissue juice of food products is a dissociated colloidal solution of complex composition, which corresponds to a cryoscopic temperature of ?0.5 + ?5°C.

Density is the ratio of the mass of a product to its volume. When frozen, the density of the product decreases (by 5-8%), since the water in the tissues, having turned into ice, increases in volume with a constant mass. The density of most perishable products is about 1000 kg/m3.

The equilibrium vapor pressure over the surface of the product Pp due to the content of dissolved substances in the moisture of the products (sugar, salt, etc.) is somewhat lower than the saturated vapor pressure Pn at the same temperature, even at full saturation.

The ratio of the vapor pressure of the water contained in the product to the vapor pressure of pure water (or ice) at the same temperature is called the relative reduction in water vapor pressure.

Refrigeration Processes

The best canning method is the one that allows you to store the product for a long time with the least loss of nutritional value and weight. In addition, temperature is one of the most powerful factors influencing chemical reactions: as a result of its decrease, reactions in biological objects and food products slow down. The temperature regime of refrigeration is set depending on the properties of the product, the seasonality of their receipt, the required duration of storage and the purpose of the product.

The duration of the freezing process depends on the type of product, its packaging and thickness. Freezing starts from the surface. After some time, the product is covered with a hard frozen crust, while its inner layers remain soft. Then the inner layers begin to freeze. The duration of freezing depends on the same factors as the duration of cooling: on the fat content, on the thickness, on the packaging and container, on the temperature and speed of the cooling medium.

All refrigeration processes are divided into two groups:

BASIC - mandatory conditions, without which it is impossible to provide the population with a diet:

1. Processes in which heat is removed from products and their temperature decreases:

Cooling is the process of lowering the temperature of the product from the initial to the final value, which is higher than the temperature. Freezing solution in the product, which is close to -1 for most products, the change in natural properties is small.

Supercooling (freezing) - temperature drop .... Which is not lower than -4 at a depth of 1 cm from the surface and 0 - 3 in the thickness, and the thickness of the frozen layer should not exceed 25 cm. This technical process slightly reduces the quality of the chilled product, for example salmon, meat, goth. meat dishes. 2. Processes in which they strive to maintain a constant temperature: Storage, transportation

3. Processes in which heat is supplied to products in order to increase their temperature and restore their original state:

Defrosting - increasing the temp. Frozen product for melting the ice they contain.

Warming - the supply of heat to chilled products with an increase in their temperature to the ambient temperature or slightly lower.

DERIVATIVES - processes in which cold is used as the basis for processing, changing the shape, type and properties of food products:

Freeze drying is a method of preserving a product by drying it in a frozen state. With this method, food products retain almost all their properties, only moisture is removed. Original quality long shelf life for a number of years and the product is able to quickly recover (dry starter cultures, biological products, granulated coffee, space food).

Cold drying is a process that takes place at low positive temperatures.

Cryoconcentration is a method of preserving a product (drinks, various fruit and vegetable juices, milk, tea, coffee ..) by partial dehydration by freezing. It consists of 2 processes of ice formation and ice separation.

Cryogrinding is a process in which the product becomes brittle and can be ground to any given size (in the temperature range from -50 to -190oC).

Cryogrinding is a process carried out at temperatures below cryoscopic, in which fractionation is performed - the separation of particles of various sizes that stick together at positive temperatures. Cryoscopic temperature is the temperature at which ice crystals begin to form in the liquid phase of food products. The temperature corresponding to the end of ice formation, which is in the product in a free or bound state of water, is called the eutectic (cryohydrate) temperature.

Process duration.

Freezing depends on the type of product, its packaging and thickness. Freezing starts from the surface. After some time, the product is covered with a hard frozen crust, while its inner layers remain soft. Then the inner layers begin to freeze. The freezing time depends on the same factors as the cooling time: fat content, thickness, packaging The thickness of the layer to be frozen affects the duration of the freezing process. At high values ​​of the heat transfer coefficient, the duration of freezing is proportional to the square of the thickness of the product layer, in connection with which it is sought to reduce this thickness, for example, when packaging the product and containers, on the temperature and speed of the cooling medium. In freezers, it is possible to obtain a frozen product of the correct geometric shape and standard sizes, which, in turn, makes it possible to increase the load on storage chambers and vehicles, to mechanize and automate technological operations. From a thermophysical point of view, freezing involves lowering the product temperature below the cryoscopic temperature, accompanied by ice formation. Due to the transformation of water into ice, a kind of dehydration of the product occurs, which, combined with the action of low temperatures, increases the stability of the products during storage. The size, shape and distribution of ice crystals formed during freezing depends on the properties of the product and the freezing conditions. The rapid decrease in product temperature promotes the formation of small, evenly distributed ice crystals. The degree of damage to the cells of the product depends on the size of the ice crystals. During slow freezing, large ice crystals are formed and the greatest structural damage is observed. Significant mechanical damage, the appearance of microcracks are possible with ultra-fast freezing of the product. Thus, with a decrease in temperature and an increase in the rate of its change, on the one hand, the productivity of the freezer increases, and on the other hand, energy costs increase and the quality of frozen products may deteriorate, i.e. we are talking about choosing the optimal freezing speed. The choice of speed is not possible without calculating the duration of freezing. The possibilities of lowering the temperature of the heat-removing media to reduce the duration of freezing are small. As the air temperature drops from -18 to -25°С by 1°, the duration of freezing is reduced by an average of 4.5%. However, this increases the cost of producing cold. At very low temperatures, there is a danger of freezing the surface layers of the product. Internal stresses and, as a result, the appearance of cracks may occur. Most often, the acceleration of the freezing process is achieved by increasing the heat transfer coefficient. It should be borne in mind that an increase in this coefficient has a greater effect on reducing the duration of the process when freezing thin layers than thick ones. Depending on the design of freezers, an increase in the heat transfer coefficient is realized in various ways. In air vehicles - with intensive (at a speed of 4--5 m / s) air blowing of the product. At the same time, the power of the electric motors of the fans increases, and thermal compensation of the operation of the fans is also necessary.

Temperature calculation in the thermal center of the cooled product

ingredient food product fluidization

To perform calculations according to the cipher, the initial data from Appendix 2 are selected. Calculations should be performed in the following sequence.

Determine the thermal diffusivity of the product:

a \u003d lox / (Cox s), m? / s,

where lox is the thermal conductivity of the product, W / (m k); cox - heat capacity of the product, kJ / (kg K);

c is the density of the product, kg/m?.

The Biot criterion is calculated: Bi = (b R) / lox, where b is the heat transfer coefficient between the product and the cooling medium, W / (m? K), is selected depending on the heat transfer conditions;

R - half the value of the characteristic size (thickness, diameter) of the product, m.

The Fourier criterion is calculated: F0 = (аох f) / RI.

According to the nomogram (Appendix 4, 5, 6), the value of the dimensionless temperature U is found, taking into account a specific physical model.

Substituting into the expression: U=(tk - ts) / (tM - ts), the known values ​​of ts, tM, U determine tk.

Name, product		cryoscopic temperature,	Density,	Heat capacity Сoh, kJ / (kg K)	Coefficient thermal conductivity, l, W/(m K)
Beef
Potato
Strawberry

fluidization

The company "AGROPROMHOLOD" presents equipment for freezing and food units: shock freezing chamber, injector. Our experts will calculate the parameters of installations for various branches of food production (for example, industrial freezing). When the speed of the conveyors needs to be increased, and the quality of the product must be maintained for a long time, quick freezing is used.

fluidization (deep freezing) of berries, fruits, vegetables, mushrooms and other products. The principle of operation of these devices is based on freezing the product in a high-pressure air stream, which is fed under the conveyor belt from high-pressure fans, after passing through the air cooler. Products are frozen relatively quickly and without deformation, which is important for products that are moist, with a delicate texture, which can stick together. In the fluidization layer (in a suspended state), only small piece products or products cut into small pieces that are similar in shape, size (20 - 25 mm.) and weight can be frozen, for example, green peas, carrot cubes, apple slices, strawberries, raspberries , currant.

The main advantages of these systems are: preservation of the presentation and shape of the product; reduction of moisture loss of the product (preservation of taste and cost reduction); obtaining a product of the so-called "dry freezing", separated from each other; easily integrated into the production line; low operating costs.

The disadvantages of these devices include the following: loss of mass of the product due to evaporation; rapid growth of frost on the surface of air coolers; significant energy consumption for the drive of centrifugal fans; the need for a relatively low boiling point and high operating costs of the refrigeration unit.

Freeze processliving

Freezing is the removal of heat from products with a decrease in temperature below cryoscopic during the crystallization of most of the water contained in the product.

The freezing process is also used to achieve the following goals:

1. separation of moisture when concentrating liquid food products;

2. changes in the physical properties of products (hardness, brittleness, etc.) when preparing them for further technological operations;

3. freeze drying;

4. production of original food products and giving them specific taste and commercial qualities (ice cream, dumplings and other quick-frozen products).

The effect of freezing is achieved at a temperature in the center of the product of minus 6 °C and below. The water in the products contains dissolved salts, so it does not freeze at 0 ° C, but at a lower temperature, called cryoscopic, the value of which is several degrees below the freezing point of water.

At - 5 ° C, about 75% of the water in meat usually freezes, at - 10 ° C - more than 80%, and at - 20 ° C - about 90%. A further decrease in temperature has practically no effect on this value.

Below are the values ​​of cryoscopic temperature for a number of products: meat from - 0.6 to - 1.2 ° C; fish from - 0.6 to - 2.0? C; eggs - 0.5? C; cow's milk - 0.55? C; apples from - 1.5 to - 2.1? C; potatoes from - 1.1 to - 1.6? C.

Freezing food can be fast or slow. Fast freezing produces smaller ice crystals in the tissues, which cause less damage to the tissues, so the quality of the products is better preserved. The duration of the freezing process depends on the type of product, its packaging and thickness. Freezing starts from the surface. After some time, the product is covered with a hard frozen crust, while its inner layers remain soft. Then the inner layers begin to freeze. The duration of freezing depends on the same factors as the duration of cooling: on the fat content, on the thickness, on the packaging and container, on the temperature and speed of the cooling medium.

A frozen product differs from a chilled one in a number of features and properties:

1. hardness - the result of the transformation of water into ice;

2. color brightness - the result of optical effects caused by ice crystallization;

3. decrease in specific gravity - a consequence of the expansion of water during freezing;

4. change in thermodynamic characteristics (heat capacity, thermal conductivity, thermal diffusivity).

During freezing, in contrast to cooling, there is a partial redistribution of moisture, injury to the tissues of the product with ice crystals, and sometimes partial denaturation of the protein. In total, all this can reduce the taste and nutritional value of the product if the freezing is carried out incorrectly.

During the freezing of products, their shrinkage occurs. The moisture carried away by the air is deposited on the surface of the air coolers in the form of a "snow coat". Shrinkage almost does not occur if the product is in a sealed container or package.

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CLASSIFICATION OF FOOD PRODUCTS

Depending on the raw materials and peculiarities of use, food products are divided into the following groups: vegetables and fruits; sugar, starch, honey, confectionery; grain processing products; flavor products; fish products; meat products; dairy products; dietary fats.

In public catering, food products are classified according to storage conditions: meat and fish; milk fat; gastronomic; dry; vegetables and fruits.

Food products are divided into types and varieties. Product type due to its origin or receipt, and grade- quality level in accordance with the requirements of the standard. Types and varieties of products make up the assortment.

Topic: Nutritional value of food.

CHEMICAL COMPOSITION OF FOOD

To maintain a normal life, a person needs food. Food contains substances that serve to build the cells of the human body, provide it with energy and contribute to the flow of all life processes in the body.

The chemical composition of most foodstuffs is complex and varied.

The composition of food products includes: water, minerals, carbohydrates, fats, proteins, vitamins, enzymes, organic acids, tannins, glycosides, aromatic, coloring compounds, phytoncides, alkaloids.

All these substances are called food. The chemical composition, nutritional value, color, taste, smell and properties of food products depend on their content and quantitative ratio.

According to the chemical composition, all food substances are divided into inorganic- water, minerals and organic - carbohydrates, fats, proteins, vitamins, enzymes, etc.

Water(H 2 0) is an integral part of all food products. It plays an important role in the life of the human body, being the most significant component of all its cells (2/3 of the human body weight). Water is the medium in which the cells of the body exist and the connection between them is maintained, it is the basis of all fluids in the human body (blood, lymph, digestive juices). With the participation of water, metabolism, thermoregulation and other biological processes take place. Together with sweat, exhaled air and urine, water removes harmful metabolic products from the human body.

Depending on age, physical activity and climatic conditions, a person's daily need for water is 2 ... 2.5 liters. With drinking, 1 liter of water enters the body, with food - 1.2 liters, about 0.3 liters is formed in the body in the process of metabolism.

In products, water can be in free And bound states. In a free form, it is contained in the cell juice, intercellular space, on the surface of the product. Bound water is in combination with the substances of the products. When they are cooked, water from one state can pass into another. So, when cooking potatoes, free water turns into bound water in the process of starch gelatinization.

The more water in the product, the lower its nutritional value and the shorter the shelf life, since water is a good environment for the development of microorganisms and enzymatic processes that result in food spoilage. All perishable products (milk, meat, fish, vegetables, fruits) contain a lot of moisture, while non-perishable ones (cereals, flour, sugar) contain little.

The water content of each food product - humidity - must be defined. Reducing or increasing the water content affects the quality of the product. So, the presentation, taste and color of carrots, herbs, fruits and bread deteriorate with a decrease in humidity, and cereals, sugar and pasta - with its increase. Many products are able to absorb water vapor, i.e., they are hygroscopic (sugar, salt, dried fruits, crackers). Since moisture affects the nutritional value, presentation, taste, color of food products, as well as the terms and conditions of storage, it is an important indicator in assessing their quality.

The moisture content of the product is determined by drying its specific sample to constant weight.

Water used for drinking and cooking must meet certain standard requirements. It should have a temperature of 8 ... 12 ° C, be transparent, colorless, without foreign odors and tastes. The total amount of mineral salts should not exceed the norms established by the standard.

The presence of magnesium and calcium salts makes the water hard. Hardness depends on the content of calcium and magnesium ions in 1 liter of water. According to the standard, it should not exceed 7 mg / l (7 mg in 1 liter of water). Vegetables and meat are poorly boiled in hard water, since the protein substances in the products form insoluble compounds with alkaline salts of calcium and magnesium. In hard water, the taste and color of tea deteriorates. When boiled, hard water forms scale on the walls of cooking pots and kitchen utensils, which necessitates frequent cleaning.

According to sanitary standards, no more than three Escherichia coli are allowed in 1 liter of drinking water, and no more than 100 microbes in 1 ml. Drinking water should be free of pathogenic bacteria.

MINERALS

Mineral (inorganic) substances are an obligatory component of food products, in which they are present in the composition of mineral salts, organic acids and other organic compounds.

In the human body, minerals are among the irreplaceable, although they are not a source of energy. The significance of these substances lies in the fact that they are involved in the construction of tissues, in maintaining the acid-base balance in the body, in the normalization of water-salt metabolism, in the activity of the central nervous system, and are part of the blood.

Depending on the content in food products, minerals are divided into macroelements, which are found in relatively large quantities in foods, microelements, contained in small doses, and ultramicroelements, the amount of which is negligible.

Macronutrients. These include calcium, phosphorus, magnesium, iron, potassium, sodium, chlorine, sulfur.

Calcium(Ca) is necessary for the body to build bones, teeth, the normal functioning of the nervous system and the heart. It affects human growth and increases the body's resistance to infectious diseases. Calcium salts are rich in dairy products, eggs, bread, vegetables, legumes. The daily requirement of the body for calcium is on average 1 g.

The average daily physiological need of a person for basic nutrients is hereinafter given in accordance with SanPiN 2.3.2.1078 - 01 for a conditional (average) person with the energy value of the diet of 2,500 kcal per day.

Phosphorus(P) is part of the bones, affects the functions of the central nervous system, is involved in the metabolism of proteins and fats. The largest amount of phosphorus is found in dairy products, especially cheeses; in addition, phosphorus is found in eggs, meat, fish, caviar, bread, legumes. The body's daily need for phosphorus is on average 1 g.

Magnesium(MD) affects neuromuscular excitability, cardiac activity, has a vasodilating property. Magnesium is an integral part of chlorophyll and is found in all plant foods. Of animal products, it is most found in milk and meat. The daily requirement of the body for magnesium is 0.4 g.

Iron(Fe) plays an important role in the normalization of blood composition. It is necessary for the life of animal organisms, is part of hemoglobin and is an active participant in oxidative processes in the body. The source of iron are products of plant and animal origin: liver, kidneys, eggs, oatmeal, rye bread, apples, berries. The daily requirement of the body for iron is 0.014 g.

Potassium (K) regulates water metabolism in the human body, increasing fluid excretion, improves heart function. There is a lot of potassium in dry fruits (dried apricots, apricots, raisins, prunes), peas, beans, potatoes, meat, milk, fish. The body's daily requirement for potassium is 3.5 g.

Sodium(Na), like potassium, regulates water metabolism, retaining moisture in the body, maintains the osmotic pressure in tissues. The sodium content in foods is negligible, so it is administered with table salt (NaCl). The body's daily need for sodium is 2.4 g (10 ... 15 g of table salt).

Chlorine(Cl) is involved in the regulation of osmotic pressure in tissues and in the formation of hydrochloric acid (HC1) in the stomach. Basically, chlorine enters the body due to salt added to food. The body's daily need for chlorine is 5-7 g.

Sulfur(S) is part of some amino acids, vitamin B 1g of the hormone insulin. Sources of sulfur are peas, oatmeal, cheese, eggs, meat, fish. The body's daily requirement for sulfur is 1 g.

Microelements and ultramicroelements. These include copper, cobalt, iodine, fluorine, zinc, selenium, etc.

Copper(Si) and cobalt(Co) are involved in hematopoiesis. They are found in small quantities in animal and vegetable foods: beef liver, fish, beets, etc. The body's daily requirement for copper is 1.25 mg, for cobalt - 0.1 ... 0.2 mg.

Iodine(I) is involved in the construction and operation of the thyroid gland. With insufficient intake of iodine, the functions of the thyroid gland are disturbed and goiter develops. The largest amount of iodine is found in sea water, seaweed and fish. The daily requirement of the body for iodine is 0.15 mg.

Fluorine(F) takes part in the formation of teeth and bone skeleton. Most fluoride is found in drinking water. The body's daily need for fluorine is 0.7 ... 1.5 mg, for zinc - 15 mg, for selenium - 0.07 mg.

Some trace elements that enter the body in doses exceeding the norm can cause poisoning. The standards do not allow the content of lead, zinc, arsenic in products, and the amount of tin and copper is strictly limited. So, in 1 kg of the product, the copper content is allowed no more than 5 mg (except for tomato paste), and tin - no more than 200 mg.

The total daily requirement of an adult human body for minerals is 20 ... 25 g.

A favorable ratio of minerals in food is also important. So, the ratio of calcium, phosphorus and magnesium in food should be 1:1:0.5. The most consistent with this ratio of these minerals is milk, beets, cabbage, onions, this ratio is less favorable in cereals, meat, fish, pasta.

Alkaline minerals include Ca, Mg, K and Na. These elements are rich in milk, vegetables, fruits, potatoes. Acid-acting minerals include P, S and O, which are found in significant quantities in meat, fish, eggs, bread, and cereals. This must be taken into account when preparing dishes and choosing side dishes for meat and fish in order to maintain the acid-base balance in the human body. The presence of vitamins contributes to better absorption of minerals.

The amount of mineral substances in the product is judged by the amount of ash remaining after the complete combustion of the product.

When products are burned, organic substances are burned, and mineral substances remain in the form ash (ash substances). The composition of ash and its amount in different products are not the same. The ash content in each product is definite and ranges from 0.05 to 2%: in sugar - 0.03 ... 0.05, milk - 0.6 ... 0.9, eggs - 1.1, wheat flour - 0.5 ... 1.5. In products of plant origin (cereals, vegetables, fruits) there are more ash substances than in products of animal origin (meat, fish, milk). The amount of ash can be increased if the product is contaminated with sand and earth. Ash content is an indicator of the quality of some food products, such as flour. The maximum standards for the content of ash substances in products are given in the standards.

CARBOHYDRATES

Carbohydrates are organic compounds that are composed of carbon, hydrogen and oxygen. The name of these substances is due to the fact that many of them are composed of carbon and water. Carbohydrates are synthesized by green plants from carbon dioxide and water under the influence of solar energy. Therefore, they make up a significant part of plant tissues (80 ... 90% of dry matter) and are found in small quantities in animal tissues (up to 2%).

Carbohydrates predominate in human food. They are the main source of vital energy, covering 58 % the body's entire energy requirement. Carbohydrates are part of human cells and tissues, are contained in the blood, participate in the body's defense reactions (immunity), and affect fat metabolism.

Depending on the structure, carbohydrates are divided into monosaccharides (simple sugars), disaccharides, consisting of two molecules of monosaccharides, and polysaccharides - high-molecular substances, consisting of many monosaccharides.

Monosaccharides. They are simple sugars made up of one carbohydrate molecule. These include glucose, fructose, galactose, mannose. Their composition is expressed by the formula C 6 H 12 0 6 . In its pure form, monosaccharides are a white crystalline substance, sweet in taste, highly soluble in water.

Glucose(grape sugar) is the most common monosaccharide. It is contained in berries, fruits, in a small amount (0.1%) in the blood of humans and animals. Glucose has a sweet taste, is well absorbed by the human body, without undergoing any changes in the process of digestion, is used by the body as an energy source, to nourish the muscles, brain and maintain the required level of sugar in the blood. In industry, glucose is obtained from potato and corn starch by hydrolysis.

Fructose(fruit sugar) is found in fruits, berries, vegetables, honey. It is very hygroscopic. Its sweetness is 2.2 times higher than the sweetness of glucose. It is well absorbed in the human body without increasing blood sugar.

Galactose- component of milk sugar. It has a slight sweetness, imparting a sweetish taste to milk, is favorable for the human body, does not occur in nature in a free form, and is obtained in industry by hydrolysis of milk sugar.

Mannose found in fruits.

Disaccharides. Disaccharides are carbohydrates made up of two monosaccharide molecules: sucrose, maltose, and lactose. Their composition is expressed by the formula C 12 H220 n .

sucrose(beet sugar) consists of a molecule of glucose and fructose, is part of many fruits and vegetables. Especially a lot of it in sugar beet and sugar cane, which are raw materials for the production of sugar. Refined sugar contains 99.9% sucrose. It is a colorless crystals of sweet taste, very soluble in water.

Maltose(malt sugar) consists of two molecules of glucose, found in small amounts in natural foods. Its content is increased artificially by sprouting grain, in which maltose is formed from starch by its hydrolysis under the action of grain enzymes.

Lactose(milk sugar) consists of a glucose molecule and a galactose molecule, is found in milk (4.7%), giving it a sweetish taste. Compared to other disaccharides, it is less sweet.

When heated with weak acids, under the action of enzymes or microorganisms, disaccharides are hydrolyzed, i.e. broken down into simple sugars. So, sucrose is split into equal amounts of glucose and fructose:

C12H22O11+H20->C6H1206+C6H12O6

This process is called inversion, and the resulting mixture of monosaccharides is called invert sugar. Invert sugar has high digestibility, sweet taste and high hygroscopicity. It is found in honey, and in the confectionery industry it is used in the production of caramel, halva and fudge to prevent their sugaring during cooking.

The hydrolysis of sucrose under the action of acids of fruits and berries occurs when cooking jelly, baking fruits, and the hydrolysis of maltose occurs during digestion under the action of enzymes of digestive juices.

Mono- and disaccharides are called sugars. All sugars are soluble in water. This should be taken into account when storing and culinary processing of products. The solubility of sugars affects their ability to crystallize (candied). More often sugar, glucose crystallizes (candied honey, jam), fructose does not crystallize due to its high solubility. When sugars are heated to high temperatures, a substance of dark color and bitter taste is formed (caramel, caramel, caramel). This change in sugars is called caramelization. The process of caramelization explains the appearance of a golden crust during frying, baking and roasting products. Darkening of canned milk or bread crust during baking is due to the formation of dark-colored melanoids as a result of the reaction of sugars and amino acids of proteins.

Microorganisms ferment sugars. Under the action of lactic acid bacteria, lactose is fermented to lactic acid, which occurs during the production of fermented milk products (curdled milk, cottage cheese). Under the action of yeast, alcoholic fermentation of sugars proceeds with the formation of ethyl alcohol and carbon dioxide, which is observed during the fermentation of dough.

Polysaccharides. These are high-molecular carbohydrates having the general formula (C 6 H 10 O 5) ". These include starch, fiber, glycogen, inulin. Polysaccharides do not have a sweet taste and are called non-sugar-like carbohydrates. These substances, in addition to fiber, are a reserve source of energy for the body.

Starch- is a chain consisting of many glucose molecules. This is the most important carbohydrate for a person, in the diet of which it makes up 80% of the total amount of carbohydrates consumed, is a source of energy and causes a feeling of satiety in a person.

Starch is found in many plant products: wheat grain - 54.5%, rice - 72.9%, peas - 44.7%, potatoes - 15%. In them, it is deposited as a reserve substance in the form of peculiar grains with a layered structure, different in shape and size.

Distinguish starch potato, wheat, rice and corn. Potato starch has the largest grains, rice starch has the smallest.

Starch does not dissolve in water. In hot water, starch grains swell, binding a large amount of water and forming a colloidal solution in the form of a viscous thick mass - a paste. This process is called starch gelatinization and it occurs when cooking cereals, pasta, sauces, jelly. During gelatinization, starch is able to absorb 200 ... 400% of water, which leads to an increase in the mass of the product, i.e., the yield of finished dishes. In cooking, this increase in mass is often called a weld (weld of cereals, pasta).

Under the action of acids and enzymes, starch hydrolyzed(break down) to glucose. This process occurs during the digestion of starch in the human body, while glucose is formed and absorbed gradually, which provides the body with energy for a long period. Starch is the body's main source of glucose.

The process of hydrolysis of starch under the action of acids is called saccharification, it is used in the food industry in the production of molasses. The process of partial saccharification of starch (to obtain intermediate products - dextrins) occurs during the fermentation of the dough, the formation of a dense crust when baking dough products and when frying potatoes.

Starch turns blue with iodine, which makes it possible to determine its presence in products.

Cellulose- a polysaccharide called cellulose and which is part of the cell membranes of plant tissues. Fiber does not dissolve in water, the human body is almost not absorbed. It belongs to the group of dietary fibers (ballast substances), it is necessary to regulate the motor function of the intestines, remove cholesterol from the body, create conditions for the development of beneficial bacteria necessary for digestion. A lot of fiber (up to 2%) is found in vegetables, fruits, cereals, flour products of lower grades. Recently, cellulose has been hydrolyzed under laboratory conditions with the help of acids to obtain simple sugars, which will find industrial application in the future.

Glycogen- animal starch, found mainly in the liver and muscles. In the human body, glycogen is involved in the formation of energy, breaking down to glucose. Food glycogen is not an energy source, since it is contained in them very little (0.5 %). Glycogen is soluble in water, stained with iodine in a brown-red color, does not form a paste.

Inulin during hydrolysis, it turns into fructose, dissolves in hot water, forming a colloidal solution. Contained in Jerusalem artichoke and chicory root, which are recommended in the diet of patients with diabetes.

The energy value of 1 g of carbohydrates is 4 kcal (the energy value of the main nutrients and food products is given hereinafter according to the data of the reference book "The chemical composition of Russian food products").

The daily human need for digestible carbohydrates averages 365 g (of which 15 ... 20% should be sugar), dietary fiber - 30 g. With a lack of carbohydrates in food, the body consumes its own fats as an energy substance, and then proteins, while the person is losing weight. With an excess of carbohydrates in food, the human body easily turns them into fats and the person becomes stout.

The amount of carbohydrates in food products is different: in potatoes - an average of 16.3, fresh vegetables - 8, cereals - 70, rye bread - 45, milk - 4.7%.

pectin substances. These substances are derivatives of carbohydrates and are part of vegetables and fruits. These include protopectin, pectin, pectic and pectic acids. These substances, like dietary fiber, stimulate the digestion process and help eliminate harmful substances from the body.

Protopectin is part of the intercellular plates that connect cells to each other. It is abundant in unripe fruits and vegetables, during the ripening of which protopectin passes into pectin under the action of enzymes, which leads to softening of fruits and vegetables. When heated with water or dilute acids, protopectin also turns into pectin. This explains the softening of vegetables and fruits during heat treatment.

Pectin soluble in water, found in the cell sap of fruits and vegetables. When boiled with sugar (65%) and acids (1%), it is able to form a jelly. This property of pectin is used in the production of marmalade, jelly, jam, preserves, marshmallows, etc.

pectin And pectic acid are formed from pectin under the action of enzymes during the ripening of fruits, giving them a sour taste.

Apples, apricots, plums, cherry plums, black currants are rich in pectins. On average, they contain 0.01 ... 2% pectin.

FATS

Fats are esters of the trihydric alcohol glycerol and fatty acids. They are of great importance for human nutrition. Fats perform a number of important functions in the human body. Fats are involved in almost all vital metabolic processes in the body and affect the intensity of many physiological reactions - the synthesis of protein, carbohydrates, vitamin D, hormones, as well as the growth and resistance of the body to diseases. Fats protect the body from cooling, are involved in the construction of tissues. Like carbohydrates, fats serve as a source of energy (reimbursing 30% of a person's energy expenditure per day) and fat-soluble vitamins.

The nutritional value of fats and their properties depend on their constituent fatty acids, of which about 70 are known. fatty acids subdivided into saturated (limiting), i.e., saturated to the limit with hydrogen, and unsaturated (unsaturated), having double unsaturated bonds in their composition, so they can attach other atoms.

The most common saturated fatty acids are palmitic (C 15 H 31 - COOH) and stearic (C 17 H 35 -COOH). These acids are found mainly in animal fats (lamb, beef).

The most common unsaturated fatty acids include oleic (C 17 H 33 -COOH), linoleic (C 17 H 31 -COOH), linolenic (Ci 7 H 29 - COOH) and arachidonic (C 19 H 31 - - COOH). They are found mainly in vegetable fats, as well as in pork, fish oil. The biological value of linoleic, linolenic and arachidonic fatty acids is equal to vitamin F, they are called polyunsaturated fatty acids. In the human body, they are not synthesized and must be supplied with dietary fats.

The chemical composition of fatty acids affects the consistency of the fat in which they are included. Depending on this, fats at room temperature are solid, ointment-like, liquid. The more saturated fatty acids in the composition of fats, the higher their melting point, such fats are called refractory. Fats, which are dominated by unsaturated fatty acids, are characterized by a low melting point, they are called fusible. The melting point of lamb fat is 44...51 °C, pork - 33...46 "C, cow oil - 28...34 °C, sunflower oil - 16...19 "C. The digestibility of fats in the body depends on the melting point of fats. Refractory fats are absorbed by the body worse, since their melting point is higher than the temperature of the human body, they are suitable for food only after hot heat treatment. Low-melting fats can be used without heat treatment (butter and sunflower oils).

By origin, animal fats are distinguished, obtained from the adipose tissue of animal products, and vegetable fats - from seeds of plants and fruits.

Fats do not dissolve in water, but soluble in organic solvents(kerosene, gasoline, ether), which is used in the extraction of vegetable oil from sunflower seeds.

fats with water can form emulsions i.e., distributed in water in the form of tiny balls. This property of fat is used in the food industry in the production of mayonnaise, margarine.

During storage, especially under the influence of light and elevated temperature, fats are oxidized(rancid) with atmospheric oxygen, acquiring an unpleasant taste and smell. Fats containing unsaturated fatty acids go rancid most quickly.

Fats, which include unsaturated fatty acids, under certain conditions, can add hydrogen. The process of adding hydrogen to fats is called hydrogenation. As a result, liquid fats turn into solid ones. They are called salomas and are used as a base in the production of margarine and cooking oils.

At high temperatures during frying, fats smoke with the formation of the toxic substance acrolein. For frying, fats with a high smoke point (160 ... 190 ° C) should be used, for example, lard, sunflower oil, cooking oils.

Under the action of water, high temperature, acids, alkalis and enzymes, fats hydrolyzed those. break down to form fatty acids and glycerol. This process occurs during intense boiling of meat broths. The fatty acids obtained as a result of hydrolysis give the broth a cloudy, greasy taste and an unpleasant odor. In the human body, during digestion, fats are hydrolyzed by the enzyme lipase.

Natural fats contain fat-like substances - phos-fatides (in the form of lecithin, cephalin) and sterols (in the form of cholesterol, ergosterol), as well as fat-soluble vitamins (A, D and E) and aromatic compounds, which increases their nutritional value.

The energy value of 1 g of fat is 9 kcal.

Fats significantly improve the taste of dishes, contribute to uniform heating of food during frying. By dissolving the coloring and aromatic substances of vegetables during frying and sautéing, fats give the dishes color and aroma. Distributed throughout the mass of the product, fats contribute to the formation of a particularly delicate structure, which improves the organoleptic properties and increases the overall nutritional value of the food.

The average daily physiological norm of fat consumption is 83 g, of which 30% should be vegetable oils - sources of unsaturated fatty acids and 20% - butter - easily digestible, rich in vitamins.

Fats are present in almost all products, but in different quantities: in meat they are 1 ... 49%, fish - 0.5 ... 30%, milk - 3.2%, butter - 82.5%, sunflower oil - 99.9%.

PROTEINS

Squirrels- these are complex organic compounds, which include carbon, hydrogen, oxygen, nitrogen; phosphorus, sulfur, iron and other elements may also be included. These are the most important biological substances of living organisms. They are the main material from which human cells, tissues and organs are built. Proteins can serve as a source of energy, covering 12% of the total human energy requirement, and form the basis of hormones and enzymes that contribute to the basic manifestations of life (digestion, growth, reproduction, etc.).

Proteins are made up of amino acids, linked together in long chains. Currently, more than 150 natural amino acids are known. About 20 of them are found in foods. In the human body, food protein is broken down into amino acids, from which proteins characteristic of humans are then synthesized. Amino acids contained in proteins, according to their biological value, are divided into interchangeable and irreplaceable.

Interchangeable amino acids (arginine, cystine, tyrosine, alanine, serine, etc.) can be synthesized in the body from other amino acids found in food. Essential amino acids cannot be synthesized by the body and must be obtained from food.

indispensable eight amino acids - methionine, tryptophan, lysine, leucine, phenylalanine, isoleucine, valine, threonine. The most scarce and valuable are methionine, tryptophan and lysine contained in animal food.

Depending on composition Proteins are conventionally divided into two groups - simple (proteins) and complex (proteins).

Simple proteins are made up of only amino acids. These include albumins (found in milk, eggs), globulins (in meat, eggs), glutenins (in wheat).

Complex proteins consist of simple proteins and a non-protein part (carbohydrates, phosphatides, dyes, etc.). The most common complex proteins are milk casein, egg vitellin, etc.

Origin Proteins are both animal and vegetable. Animal proteins are mostly complete, especially proteins of milk, eggs, meat, fish. Vegetable proteins are incomplete, with the exception of rice and soy proteins. The combination of animal and vegetable proteins increases the value of protein nutrition.

Proteins have certain properties. Heat, ultrasound, high pressure, ultraviolet radiation and chemicals can cause denaturation(coagulation) of proteins, in which they condense and lose their ability to bind water. This explains the loss of moisture in meat and fish during heat treatment, which leads to a decrease in the mass of the finished product.

Milk protein - casein - denatures under the action of lactic acid during lactic acid fermentation, which is the basis for the preparation of fermented milk products. The formation of foam on the surface of broths, fried meat and fish products is also explained by the coagulation of soluble proteins (albumin, globulin).

Denatured proteins do not dissolve in water, lose their ability to swell, and are better digested in the human body.

Incomplete protein - meat and fish collagen - is insoluble in water, diluted acids and alkalis, and when heated with water forms glutin, which solidifies when cooled, forming a jelly. The preparation of aspic dishes and jellies is based on this property.

Under the action of enzymes, acids and alkalis, proteins hydrolyzed to amino acids with the formation of a number of intermediate products. This process occurs in the manufacture of sauces on meat broths seasoned with tomato or vinegar.

Proteins are capable to swell, what can be seen when making dough, and when whipping - form foam. This property is used in the manufacture of puddings, mousses, sambuca. Under the action of putrefactive microbes, proteins undergo rotting with the formation of ammonia (NH 3) and hydrogen sulfide (H 2 S).

The energy value of 1 g of protein is 4 kcal.

The average daily physiological need of a person for proteins is 75 g, and proteins of animal origin, as complete ones, should be 55% of the daily norm.

In human nutrition, the balance of essential nutrients is very important. The ratio of proteins, fats and carbohydrates for the main population groups is considered to be optimal in nutrition as 1:1.1:4.

Currently, scientists around the world are working on the problems of creating synthetic food. Of the three main nutrients (proteins, fats, carbohydrates), protein synthesis is of particular interest, since the need to find additional resources for its production is caused by relative protein starvation on our planet. This problem is solved by the chemical synthesis of individual amino acids and the production of protein for animal husbandry with the help of microbes.

VITAMINS

vitamins are low molecular weight organic compounds of various chemical nature. They play the role of biological regulators of the chemical reactions of metabolism occurring in the human body, participate in the formation of enzymes and tissues, and support the protective properties of the body in the fight against infections.

The assumption about the existence of special substances in products was expressed in 1880 by the Russian doctor N.I. Lunin. The Polish scientist K. Funk in 1911 isolated in pure form from rice bran a substance containing the amine group NH 2, which he gave the name "vitamin" (vital amine). A great contribution to the study of vitamins was made by teams of domestic scientists led by B. A. Lavrov, A. V. Palladin.

Currently, several dozens of substances have been discovered that, according to their effect on the human body, can be attributed to vitamins, but 30 of them are of direct importance for nutrition. Many vitamins are designated by letters of the Latin alphabet: A, B, C, D, etc. In addition, each of them has a name corresponding to the chemical structure. For example, vitamin C - ascorbic acid, vitamin D - calciferol, vitamin B) - thiamine, etc.

Vitamins, as a rule, are not synthesized by the human body, so the main source of most of them is food, and more recently synthesized vitamin preparations. Some vitamins can be synthesized in the body (B 2 , B 6 , B 9 , K and PP). The daily requirement of the human body for vitamins is calculated in milligrams.

Lack of vitamins in food causes diseases - beriberi. Insufficient intake of vitamins causes hypovitaminosis, and excessive consumption of fat-soluble vitamins in the form of pharmaceutical preparations - hypervitaminosis.

Vitamins are found in almost all foods. Some products are fortified during the production process: milk, butter, flour, baby food, confectionery, etc.

Depending on the solubility, vitamins are divided into water-soluble - group B, C, H, P, PP, choline and fat-soluble - A, D, E and K. Vitamin-like substances include vitamins F and U.

Water soluble vitamins. The vitamins of this group include B, B 2, B 6, B 9, B 12, B 15, C, H, P, PP, choline, etc.

Vitamin B [thiamine) plays an important role in metabolism, especially in carbohydrate metabolism, in regulating the activity of the nervous system. With a lack of this vitamin in food, disorders of the nervous system and intestines are observed. The lack of a vitamin in the diet leads to beriberi - a disease of the nervous system "take-take". The daily intake of the vitamin is 1.5 mg. This vitamin is found in plant and animal foods, especially yeast, wheat bread of the 2nd grade, peas, buckwheat, pork, and liver. The vitamin is resistant to heat treatment, but is destroyed in an alkaline environment.

Vitamin B2 [riboflavin] takes part in the growth process, in protein, fat and carbohydrate metabolism, normalizes vision. With a lack of vitamin B 2 in food, the condition of the skin, mucous membrane, vision worsens and the function of gastric secretion decreases. The daily intake of the vitamin is 1.8 mg. This vitamin is found in eggs, cheese, milk, meat, fish, bread, buckwheat, vegetables and fruits, yeast. During heat treatment, it is not destroyed. Vitamin loss occurs when foods are frozen, thawed, dried and stored in the light.

Vitamin B 6 [pyridoxine] takes part in metabolism. With its lack of nutrition, a disorder of the nervous system, dermatitis (skin diseases), and sclerotic changes in the vessels are observed. The daily intake of vitamin is 1.8 ... 2.2 mg. The content of vitamin B 6 in many foods is low, but human needs can be met with a properly balanced diet. The vitamin is resistant to cooking.

Vitamin B 9 [folic acid] provides normal hematopoiesis in the human body and is involved in metabolism. With a lack of folic acid in the diet, people develop various forms of anemia. The daily intake of the vitamin is 0.2 mg. Properly balanced daily rations contain 50...60% of the daily requirement of vitamin B 9 . The missing amount is supplemented by the synthesis of the vitamin by intestinal bacteria. A lot of this vitamin is found in green leaves (lettuce, spinach, parsley, green onions). Vitamin is very unstable to heat treatment.

Vitamin B p [cobalamin), like folic acid, it plays an important role in the regulation of hematopoiesis, in the metabolism of proteins, fats and carbohydrates. With a lack of vitamin B 12, malignant anemia develops in the body. The daily intake of the vitamin is 0.003 mg. This vitamin is found only in products of animal origin: in meat, liver, milk, cheese, eggs. The vitamin is resistant to cooking.

Vitamin B 15 (pangamic acid) participates in the oxidative processes of the body, having a beneficial effect on the heart, blood vessels, blood circulation, especially in old age. The daily intake of the vitamin is 2 mg. It is found in rice bran, yeast, liver and blood of animals.

Vitamin C (ascorbic acid) plays an important role in the redox processes of the body, affects protein, carbohydrate and cholesterol metabolism. The lack of vitamin C in the diet reduces the resistance of the human body to various diseases. Its absence causes scurvy. The daily intake of vitamin is 70 ... 100 mg.

Vitamin C is contained mainly in fresh vegetables and fruits, especially a lot of it in rose hips, black currants and red peppers, it is also found in parsley and dill, green onions, white cabbage, red tomatoes, apples, potatoes, etc. Potatoes, fresh and sauerkraut, although they contain little of this vitamin, are an important source of it, since these products are consumed almost daily.

Vitamin C is unstable during cooking and storage of foods. The vitamin is detrimental to light, air, high temperature, water in which it dissolves, oxidizing parts of the equipment. It is well preserved in an acidic environment (sauerkraut). In the process of cooking, factors that negatively affect the preservation of the vitamin should be taken into account: for example, it is impossible to store peeled vegetables in water for a long time. When cooking, vegetables should be poured with hot water, completely immersing them, cook with the lid closed with a uniform boil, avoiding overcooking. For cold dishes, vegetables should be cooked unpeeled. Vitamin C is destroyed when rubbing boiled vegetables, reheating vegetable dishes and storing them for a long time.

Vitamin H (biotype) regulates the activity of the nervous system. With a lack of this vitamin in the diet, nervous disorders with skin lesions are noted. The daily intake of vitamin is 0.15 ... 0.3 mg. It is partially synthesized by intestinal bacteria. In products, biotin is present in small quantities (in the liver, meat, milk, potatoes, etc.). The vitamin is resistant to cooking.

Vitamin P (bioflavonoid) has a capillary-strengthening effect and reduces the permeability of the walls of blood vessels. It promotes better absorption of vitamin C. The daily intake of the vitamin is 35 ... 50 mg. This vitamin is found in sufficient quantities in the same plant foods that contain vitamin C.

Vitamin PP (nicotinic acid) is an integral part of some enzymes involved in metabolism. Lack of vitamin PP in food causes fatigue, weakness, irritability and the disease "pellagra" (rough skin), which is characterized by a disorder of the nervous system and skin disease. The daily intake of the vitamin is 20 mg. Vitamin PP can be synthesized in the human body from an amino acid (tryptophan). This vitamin is found in foods of plant and animal origin: bread, potatoes, carrots, buckwheat and oatmeal, beef liver and cheese. With a varied diet, a person receives a sufficient amount of this vitamin. During cooking, vitamin loss is negligible.

Choline affects protein and fat metabolism, neutralizes substances harmful to the body. The absence of choline in food contributes to fatty degeneration of the liver, kidney damage. The daily intake of vitamin is 500 ... 1,000 mg. Choline is found in animal and vegetable products (except vegetables and fruits): in the liver, meat, egg yolk, milk, grains and rice.

fat soluble vitamins. Vitamin A (retinol) affects the growth and development of the skeleton, vision, the condition of the skin and mucous membranes, the body's resistance to infectious diseases. With a lack of vitamin A, growth stops, hair falls out, the body is depleted, visual acuity is dulled, especially at dusk (“night blindness”). The daily intake of the vitamin is 1 mg.

Vitamin A is found in animal products: fish oil, liver, eggs, milk, meat. Vegetable products of yellow-orange color and green parts of plants (spinach, lettuce) contain provitamin A - carotene, which in the human body in the presence of food fat turns into vitamin A. The need for vitamin A is met by 75% due to carotene. The daily intake of carotene is 3 ... 5 mg.

Vitamin A and carotene are resistant to cooking. Carotene dissolves well in fats when sautéing vegetables. Vitamin A is detrimental to sunlight, atmospheric oxygen and acids.

Vitamin D (calciferol) participates in the formation of bone tissue, promotes the retention of calcium and phosphorus salts in it, stimulates growth. With a lack of this vitamin in the body of children, a serious disease "rickets" develops, and in adults, bone tissues change. The daily intake of the vitamin is 0.0025 mg. Vitamin D is found in animal foods: in cod liver, halibut, herring, cod, beef liver, butter, eggs, milk, etc. But it is mainly synthesized in the body, formed from provitamin (a substance found in the skin) as a result of exposure ultraviolet rays. Adults under normal conditions do not lack this vitamin. Excess intake of vitamin D (in the form of pharmaceutical preparations) can lead to poisoning.

Vitamin E (tocopherol) affects the reproduction process. With a lack of this vitamin, changes occur in the sexual and central nervous systems of a person, the activity of the endocrine glands is disrupted. The daily intake of the vitamin is 10 mg. Vitamin E is found in both plant and animal products, so a person does not experience a lack of it. It is especially abundant in cereal germs and vegetable oils. The content of vitamin in foods decreases when heated. Vitamin E has an antioxidant effect and is widely used in the food industry to slow down the oxidation of fats.

Vitamin K (phylloquinone) participates in the process of blood clotting. With a lack of it, blood coagulation slows down and subcutaneous intramuscular hemorrhages appear. The daily intake of the vitamin is 2 mg. The vitamin is synthesized by bacteria in the human intestine. Vitamin K is mainly found in green lettuce, cabbage, spinach, nettle. It is destroyed by light, heat and alkalis.

Vitamin-like substances. Of these, vitamins F and U are the most important.

Vitamin F (unsaturated fatty acids: linoleic, linolenic, arachidonic) participates in fat and cholesterol metabolism. The daily intake of the vitamin is 5 ... 8 g. The best ratio of unsaturated fatty acids in lard, peanut and olive oils.

VitaminU (methylmethionine) normalizes the secretory function of the digestive glands and promotes the healing of gastric and duodenal ulcers. Contains vitamin in the juice of fresh cabbage.

ENZYMES

Enzymes(enzymes) are biological catalysts of a protein nature that have the ability to activate various chemical reactions that occur in a living organism.

Enzymes are formed in any living cell and can be active outside of it.

About 1,000 enzymes are known, and each of them has an exceptional specificity of action, that is, it catalyzes only one specific reaction. Therefore, the name of enzymes consists of the name of the substance on which they act, and the ending "aza". For example, the enzyme that breaks down sucrose is called sucrose, enzyme that breaks down lactose lactase.

Enzymes are very active. An insignificant dose of them is enough to transform a huge amount of matter from one state to another. So, 1.6 g of human digestive juice amylase in 1 hour can break down 175 kg of starch, gastric juice air pepsin - 50 kg of egg white.

Enzymes have certain properties. So, some enzymatic processes are reversible, i.e., depending on the conditions, the same enzymes can accelerate both the process of decomposition and the process of synthesis of a substance.

Enzymes are very sensitive to temperature changes. They show the highest activity at 40 ... 50 "C. Therefore, to prevent spoilage of products from the action of enzymes, they are stored in the cold or subjected to heat treatment.

The activity of enzymes depends on the humidity of the environment, an increase in which leads to an acceleration of enzymatic processes, and this leads to spoilage of products. It also depends on the reaction of the medium (pH). So, pepsin of gastric juice acts only in an acidic environment. The rate of enzymatic processes also depends on the state of the substance on which the enzyme acts, and on the presence of other substances in the environment. Thus, meat protein curtailed during heat treatment is broken down by the enzyme faster than raw protein, and the presence of sautéed flour in soups slows down the destruction of vitamin C under the action of enzymes.

Enzymes play an important role in food production, storage and cooking. Rennet enzymes are used in the production of cheeses, enzymes secreted by bacteria and yeast are involved in the production of fermented milk products, fermented vegetables and the fermentation of dough.

Enzymes have a great influence on the quality of products. In some cases, this effect is positive, for example, during the ripening of meat after slaughter of animals and during salting of herring, in other cases it is negative, for example, darkening of apples, potatoes during cleaning, slicing. To prevent browning, apples should be immediately sent to heat treatment, and potatoes should be immersed in cold water. Enzymes destroy vitamin C, oxidizing it during storage and improper cooking of vegetables and fruits, which should be immersed in boiling water or broth during cooking, in which the enzymes are quickly destroyed. Fats are oxidized under the action of enzymes. Souring of soups, rotting of fruits, fermentation of compotes and jams are caused by enzymes secreted by microbes that have got into food. The negative effect of enzymes can be stopped by raising or lowering the air temperature during storage of products.

Currently, scientists are doing a lot of work on the study of enzymatic processes and their further application in the food industry. Methods have been developed for softening the connective tissue of meat with the help of the enzyme prototerrizin, and enzymatic processes that slow down the staleness of bread are being studied.

Enzyme preparations are used in medicine, animal husbandry, and in the processing of agricultural raw materials. Enzymes are obtained from cultures of microorganisms, as well as from plant and animal raw materials.