The goals of studying the discipline “Methods for studying the properties of raw materials and food products” are to study the composition, quality and safety of food products and food raw materials.

Food products- food raw materials, food products and their ingredients, ethyl alcohol and alcoholic products.

Food products- products used for human consumption in natural or processed form.

Food raw materials- objects of plant, animal, microbiological, and mineral origin used for food production.

The enterprise must bear full responsibility for the quality of the product and its competitiveness in the market.

Food quality- a set of characteristics that determine the consumer properties of food products and ensure their safety for humans.

Product property- this is an objective feature of a product that manifests itself during its production, storage, transportation and consumption.

The main properties of food products include nutritional value, shelf life and culinary and technological properties.

Nutritional value of food products - this is a complex property. Its constituent elements are energetic, biological, physiological and organoleptic value, as well as digestibility and good quality of food products.

Under energy value understand the number of calories that a product can give the body depending on the content of proteins, fats, and carbohydrates in it.

The human body's basic need for energy is met by fats, carbohydrates and proteins contained in food. A person receives a small part of his energy from organic acids, alcohol, etc.

The energy value of 1 g of protein is 4.0 kcal, 1 g of fat is 9.0 kcal, 1 g of carbohydrates is 3.75 kcal.

To calculate the theoretical energy value of food products, it is necessary to know the chemical composition of these products, i.e. the percentage of proteins, fats and carbohydrates in them, and the weight of the product. The calorie content calculated in this way is called theoretical, because it does not take into account the percentage of digestibility of basic substances.

Digestibility- the degree of use of the constituent components of food products by the human body. With a mixed diet, the digestibility of proteins is 84.5%, fats - 94%, carbohydrates - 95.6%.

Practical caloric content is calculated by multiplying the caloric content of proteins, fats, carbohydrates by the percentage of digestibility.

Under biological The value of a product is understood as the balance of amino acids, polyunsaturated fatty acids, vitamins, minerals and ballast substances.

Physiological the value is determined by substances that have an active effect on the human body. There are three groups of physiologically active substances that act on the nervous system, gastrointestinal tract, and human immune system. For example, caffeine in tea and coffee has a stimulating effect on a person’s cardiac and nervous activity. Tartronic acid in cucumbers, zucchini, and cabbage helps remove cholesterol from the body.

Organoleptic value is a complex combination of product properties: appearance (shape, color and color, surface condition), consistency, taste and smell. Moreover, the last three are of paramount importance when consuming the product.

Goodness food products combine organoleptic value (color, taste, aroma, consistency, etc.) and safety.

Safety- This is the absence of unacceptable risk associated with the possibility of causing damage to human health (life). Food safety is affected by the presence of harmful chemicals in food (salts of heavy metals, pesticides, nitrates, carcinogens), pathogenic microbes and toxins. Pesticides include substances such as DDT, chlorophos, dichlorophos and other chemical plant protection products against pests. Product standards provide for control over the residual amount of pesticides and the content of nitrates, as well as toxic microelements.

Storability- one of the properties of product quality, classified in the reliability group. Reliability - the ability of a product to perform required functions under specified conditions for a specified period of time.

Product quality indicator This is a quantitative characteristic of one or more product properties. There are quality indicators! single (size) or complex (appearance), defining (for example, appearance, size, taste, smell for various types of fruits and vegetables) and specific (degree of maturity, stalk length for cabbage vegetables, greening of potatoes).

By determination methods properties of food products are divided into groups:

Organoleptic (color, taste, smell, consistency);

Physico-mechanical (humidity, density, viscosity, porosity, etc.);

Physico-chemical (salt content, sugar, acidity);

Microbiological (coli-titer for dairy products, permissible amount of salmonella);

Technological (increasing the mass of pasta after cooking).
By functional purpose properties of food products are divided into:

Environmental;

Ergonomic, reflecting the interaction of the “man-product” system;

Reliability groups (storability indicators) - the ability of a product to maintain quality under certain conditions and shelf life;

Transportability properties (during transportation);

Aesthetic (consistency of presentation, image of brand names);

Consumption safety properties ensuring harmlessness;

Properties of physiological purposes, characterizing the dietary and medicinal properties of products.

Methods for determining the properties of food products include organoleptic, based on the analysis of sensory perceptions, measuring, carried out on the basis of technical measuring instruments. expert, carried out on the basis of a decision made by experts, and sociological, carried out on the basis of collecting and analyzing the opinions of tactical and possible consumers of the product. Most often used in trade practice and at manufacturing enterprises organoleptic and measuring methods determination of quality indicators.

CLASSIFICATION OF FOOD PRODUCTS

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

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

Food products are divided into types and varieties. Product type due to its origin or receipt, and variety- 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 PRODUCTS

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

The chemical composition of most foods 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.

Based on their chemical composition, all nutrients 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 in terms of quantity of all its cells (2/3 of the human body weight). Water is the medium in which the cells of the body exist and communication between them is maintained; it is the basis of all fluids in the human body (blood, lymph, digestive juices). Metabolism, thermoregulation and other biological processes occur with the participation of water. 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 during metabolism.

Products may contain water in free And bound states. It is found in free form in cell sap, intercellular space, and on the surface of the product. Bound water is in combination with the substances of the products. When they are cooked, water can change from one state to another. So, when cooking potatoes, free water turns into bound water during the gelatinization of starch.

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

Water content in each food product - humidity - must be certain. Decreasing or increasing water content affects the quality of the product. Thus, the presentation, taste and color of carrots, herbs, fruits and bread deteriorate with decreasing humidity, and cereals, sugar and pasta - with increasing humidity. Many products are capable of absorbing water vapor, i.e. they are hygroscopic (sugar, salt, dried fruits, crackers). Since humidity affects the nutritional value, presentation, taste, color of food products, as well as the timing and conditions of storage, it is an important indicator in assessing their quality.

The humidity of the product is determined by drying a certain portion of it to a 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 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 do not cook well in hard water, since the protein substances in the products form insoluble compounds with alkaline calcium and magnesium salts. Hard water degrades the taste and color of tea. When boiling, hard water forms scale on the walls of digesters and cookware, which necessitates frequent cleaning.

According to sanitary standards, no more than three E. 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 essential component of food products in which they are presented as 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 is that they participate 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 their content in food products, minerals are divided into macroelements, which are found in relatively large quantities in products, microelements, contained in small doses, and ultramicroelements, the amount of which is negligible.

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

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

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

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

Magnesium(Md) affects neuromuscular excitability, cardiac activity, and has a vasodilating property. Magnesium is a component of chlorophyll and is found in all plant foods. Among animal products, it is most abundant in milk and meat. The body's daily requirement for magnesium is 0.4 g.

Iron(Fe) plays an important role in normalizing 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 is products of plant and animal origin: liver, kidneys, eggs, oatmeal, rye bread, apples, berries. The body's daily requirement for iron is 0.014 g.

Potassium (K) regulates water metabolism in the human body, increasing fluid excretion, and 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 need for potassium is 3.5 g.

Sodium(Na), like potassium, regulates water metabolism, retaining moisture in the body, maintaining the osmotic pressure in tissues. The sodium content of foods is negligible, so it is introduced 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. Chlorine mainly enters the body through table 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) participate in hematopoiesis. They are found in small quantities in animal and plant 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) participates in the construction and functioning of the thyroid gland. With insufficient iodine intake, the functions of the thyroid gland are disrupted and goiter develops. The largest amount of iodine is found in sea water, seaweed and fish. The body's daily requirement for iodine is 0.15 mg.

Fluorine(F) takes part in the formation of teeth and bone skeleton. Fluoride is mainly 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 entering 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. Thus, in 1 kg of product the copper content is allowed to be no more than 5 mg (except for tomato paste), and tin - no more than 200 mg.

The total daily requirement of the 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 are milk, beets, cabbage, and onions; this ratio is less favorable in cereals, meat, fish, and pasta.

Alkaline minerals include Ca, Mg, K and Na. Milk, vegetables, fruits, and potatoes are rich in these elements. Acid-active 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 selecting side dishes for meat and fish to maintain acid-base balance in the human body. Better absorption of minerals is facilitated by the presence of vitamins.

The amount of minerals in a product is judged by the amount of ash remaining after complete combustion of the product.

When food is burned, organic substances are burned, but mineral substances remain in the form ash (ashy 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. Products of plant origin (cereals, vegetables, fruits) contain more ash substances than products of animal origin (meat, fish, milk). The amount of ash may be increased if the product is contaminated with sand and soil. Ash content is an indicator of the quality of some foods, such as flour. The maximum standards for the content of ash substances in products are given in the standards.

CARBOHYDRATES

Carbohydrates- These are organic substances that include carbon, hydrogen and oxygen. The name of these substances is explained by 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 tissues of plant origin (80... 90% of dry matter) and are found in small quantities in tissues of animal origin (up to 2%).

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

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

Glucose(grape sugar) is the most common monosaccharide. It is found in berries, fruits, and in small quantities (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 during the digestion process, and is used by the body as a source of energy, to nourish muscles, the 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- a component of milk sugar. It has a slight sweetness, imparting a sweetish taste to milk, it is beneficial for the human body, it is not found in free form in nature, it is produced industrially by hydrolysis of milk sugar.

Mannose found in fruits.

Disaccharides. Disaccharides include carbohydrates built from two molecules of monosaccharides: sucrose, maltose, lactose. Their composition is expressed by the formula C 12 H220 n.

Sucrose(beet sugar) consists of glucose and fructose molecules and is found in many fruits and vegetables. There is especially a lot of it in sugar beets and sugar cane, which are raw materials for sugar production. Refined sugar contains 99.9% sucrose. It is colorless crystals with a sweet taste, very soluble in water.

Maltose(malt sugar) consists of two glucose molecules and is found in small quantities 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, found in milk (4.7%), giving it a sweetish taste. Compared to other disaccharides, it is less sweet.

Disaccharides, when heated with weak acids, under the action of enzymes or microorganisms, are hydrolyzed, i.e. are broken down into simple sugars. Thus, sucrose is broken down 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 is highly digestible, sweet taste and highly hygroscopic. 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 the cooking process.

Hydrolysis of sucrose under the influence of acids of fruits and berries occurs during cooking jelly, baking fruits, and 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 cooking foods. The solubility of sugars affects their ability to crystallize (sugarization). Sugar and glucose crystallize more often (candied honey, jam), fructose does not crystallize due to its high solubility. When Sugars are heated to high temperatures, a dark-colored substance with a bitter taste is formed (caramel, caramelan, caramel). This change in sugars is called caramelization. The process of caramelization explains the appearance of a golden brown crust when frying, baking and baking products. The darkening of canned milk or bread crust during baking is explained by the formation of dark-colored melanoids as a result of the reaction of sugars and amino acids of proteins.

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

Polysaccharides. These are high molecular weight carbohydrates with the general formula (C 6 H 10 O 5)„. These include starch, fiber, glycogen, and 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 whose diet it makes up 80% of the total amount of carbohydrates consumed, is a source of energy and causes a feeling of fullness in a person.

Starch is found in many plant products: in 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.

There are potato, wheat, rice and corn starch. 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, and jelly. During gelatinization, starch is capable of absorbing 200...400% of water, which leads to an increase in the mass of the product, i.e., the yield of ready-made dishes. In cooking, this increase in mass is often called welding (cooking of porridges, pasta).

Under the influence of acids and enzymes, starch hydrolyzes(breaks 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 dough fermentation, the formation of a dense crust when baking dough products and when frying potatoes.

Starch is colored blue with iodine, which makes it possible to determine its presence in foods.

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

Glycogen- animal starch, found mainly in the liver and muscles. In the human body, glycogen is involved in the formation of energy, breaking down into glucose. Glycogen in food products is not an energy source, since they contain very little of it (0.5 %). Glycogen is soluble in water, turns brown-red with iodine, and does not form a paste.

Inulin upon hydrolysis it turns into fructose and 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 basic nutrients and food products is given hereinafter according to the reference book “Chemical composition of Russian food products”).

A person’s daily need for digestible carbohydrates is on average 365 g (of which 15...20% should be sugar), dietary fiber - 30 g. If there is a lack of carbohydrates in food, the body uses its own fats as an energy source, and then proteins, at the same time the person loses weight. When there is an excess of carbohydrates in food, the human body easily converts them into fats and the person becomes fat.

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

Pectin substances. These substances are derivatives of carbohydrates and are found in 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. There is a lot of it in unripe fruits and vegetables, when they ripen, protopectin, under the action of enzymes, turns into pectin, which leads to the 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 juice of fruits and vegetables. When boiled with sugar (65%) and acids (1%), it is able to form 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 overripening of fruits, giving them a sour taste.

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

FATS

Fats- these 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 and participate 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 the fatty acids they contain, of which about 70 are known. Fatty acids are divided into saturated (marginal), i.e., saturated to the limit with hydrogen, and unsaturated (unsaturated), which contain double unsaturated bonds, 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 and fish oils. The biological value of linoleic, linolenic and arachidonic fatty acids is equal to vitamin F; they are called polyunsaturated fatty acids. They are not synthesized in the human body and must be supplied with dietary fats.

The chemical composition of fatty acids affects the consistency of the fat they contain. Depending on this, fats at room temperature can be solid, ointment-like, or liquid. The more saturated fatty acids a fat contains, the higher its 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 fat - 33...46 °C, cow oil - 28...34 °C, sunflower oil - 16... 19 "C. The melting temperature of fats determines their digestibility in the body. Refractory fats are less easily absorbed by the body, since their melting point is higher than the temperature of the human body; they are suitable for food only after being cooked hot. Low-melting fats can be used without heat treatment (butter and sunflower oil).

Based on their origin, they distinguish between animal fats, obtained from the fatty tissue of animal products, and vegetable fats, obtained from plant seeds and fruits.

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

Fats with water can form emulsions, that is, distributed in water in the form of tiny balls. This property of fat is used in the food industry in the production of mayonnaise and margarine.

During storage, especially when exposed to light and elevated temperatures, fats oxidize(go rancid) with air oxygen, acquiring an unpleasant taste and smell. Fats containing unsaturated fatty acids go rancid most quickly.

Fats that contain unsaturated fatty acids can, under certain conditions, 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 fats.

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, rendered pork fat, sunflower oil, cooking fats.

Under the influence of water, high temperature, acids, alkalis and enzymes, fats hydrolyze, those. are broken 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 turbidity, a 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 - phospholipids (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 and promote uniform heating of foods during frying. By dissolving the coloring and aromatic substances of vegetables during frying and sautéing, fats add color and aroma to dishes. Distributed throughout the entire 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 found in almost all products, but in different quantities: in meat 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; may also include phosphorus, sulfur, iron and other elements. 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 a person's total energy needs, 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, connected to each other in long chains. Currently, more than 150 natural amino acids are known. About 20 of them are found in food products. 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 are divided into replaceable and irreplaceable according to their biological value.

Replaceable amino acids (arginine, cystine, tyrosine, alanine, series, etc.) can be synthesized in the body from other amino acids found in food. Essential amino acids cannot be synthesized by the body, and they must come from food.

Irreplaceable eight amino acids - methionine, tryptophan, lysine, leucine, phenylalanine, isoleucine, valine, threonine. The most scarce and valuable are methionine, tryptophan and lysine, found in animal foods.

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

Simple proteins consist only of 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.

By origin Proteins can be animal or plant. Animal proteins are mostly complete, especially proteins from milk, eggs, meat, and fish. Plant proteins are incomplete, with the exception of rice and soy proteins. The combination of animal and plant 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 become denser 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 influence 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 - collagen of meat and fish - is insoluble in water, diluted acids and alkalis, and when heated with water it forms glutin, which solidifies when cooled, forming jelly. The preparation of jellied dishes and jellies is based on this property.

Under the influence of enzymes, acids and alkalis, proteins hydrolyze to amino acids with the formation of a number of intermediate products. This process occurs when making sauces using meat broths seasoned with tomato or vinegar.

Proteins are capable to swell, what can be noticed when making the dough, and when whipping - form foam. This property is used in the manufacture of puddings, mousses, and sambucas. Under the influence of putrefactive microbes, proteins are exposed 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 requirement of a person for proteins is 75 g, and proteins of animal origin, as complete proteins, should make up 55% of the daily requirement.

In human nutrition, a balance of essential nutrients is very important. The optimal ratio of proteins, fats and carbohydrates for the main groups of the population is considered to be 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 the relative protein starvation on our planet. This problem is solved by chemical synthesis of individual amino acids and the production of protein for animal husbandry with the help of microbes.

VITAMINS

Vitamins- These are low molecular weight organic compounds of various chemical natures. They play the role of biological regulators of chemical metabolic reactions occurring in the human body, participate in the formation of enzymes and tissues, and support the body’s protective properties in the fight against infections.

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

Currently, several dozen substances have been discovered that, based on their effect on the human body, can be classified as 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 its chemical structure. For example, vitamin C is ascorbic acid, vitamin D is calciferol, vitamin B) is 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 - vitamin deficiencies. Insufficient vitamin intake 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 their 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. Vitamins of this group include B, B2, B6, B9, B12, B15, C, H, P, PP, choline, etc.

Vitamin B, [thiamine) plays an important role in metabolism, especially carbohydrate metabolism, and 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 vitamin in the diet leads to vitamin deficiency - a disease of the nervous system “beriberi”. The daily intake of the vitamin is 1.5 mg. This vitamin is found in plant and animal foods, especially yeast, 2nd grade wheat bread, peas, buckwheat, pork, and liver. The vitamin is resistant to heat treatment, but is destroyed in an alkaline environment.

Vitamin B 2 [riboflavin) takes part in the growth process, in protein, fat and carbohydrate metabolism, and normalizes vision. With a lack of vitamin B2 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, and yeast. It is not destroyed during heat treatment. Vitamin loss occurs when foods are frozen, thawed, dried, and stored in 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 blood vessels are observed. The daily intake of the vitamin is 1.8... 2.2 mg. The content of vitamin B6 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) ensures 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 diets 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). The vitamin is very unstable to heat treatment.

Vitamin B p [cobalamin], like folic acid, it plays an important role in the processes of regulating hematopoiesis, in the metabolism of proteins, fats and carbohydrates. With a lack of vitamin B 12, the body develops malignant anemia. The daily intake of the vitamin is 0.003 mg. This vitamin is found only in products of animal origin: 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, and 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 a large role in the redox processes of the body, affects protein, carbohydrate and cholesterol metabolism. A lack of vitamin C in the diet reduces the human body's resistance to various diseases. Its absence causes scurvy. The daily intake of the vitamin is 70... 100 mg.

Vitamin C is found mainly in fresh vegetables and fruits, especially 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 food storage. Light, air, high temperature, water in which it dissolves, and oxidizing parts of equipment have a detrimental effect on the vitamin. It is well preserved in an acidic environment (sauerkraut). During the cooking process, factors that negatively affect the preservation of the vitamin should be taken into account: for example, peeled vegetables should not be stored in water for a long time. When cooking, vegetables should be poured with hot water, completely immersing them, and cooked with the lid closed at a uniform boil, avoiding overcooking. For cold dishes, vegetables should be cooked unpeeled. Vitamin C is destroyed when mashing 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 observed. The daily intake of the vitamin is 0.15... 0.3 mg. It is partially synthesized by intestinal bacteria. Biotin is found in small quantities in foods (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 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. A 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 the 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. When cooking foods, the loss of vitamin is insignificant.

Kholin affects protein and fat metabolism, neutralizes substances harmful to the body. The lack of choline in food contributes to fatty liver degeneration and kidney damage. The daily intake of the vitamin is 500... 1,000 mg. Choline is found in foods of animal and plant origin (except vegetables and fruits): 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 membrane, the body's resistance to infectious diseases. With a lack of vitamin A, growth stops, hair falls out, the body becomes exhausted, and visual acuity becomes dull, especially at dusk (“night blindness”). The daily intake of the vitamin is 1 mg.

Vitamin A is found in products of animal origin: fish oil, liver, eggs, milk, meat. In products of plant origin that are yellow-orange in color and in green parts of plants (spinach, lettuce) there is provitamin A - carotene, which in the human body in the presence of food fat is converted into vitamin A. The need for vitamin A is 75% satisfied by 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. Sunlight, air oxygen and acids have a detrimental effect on vitamin A.

Vitamin D (calciferol) participates in the formation of bone tissue, promotes the retention of calcium and phosphorus salts in it, and stimulates growth. With a lack of this vitamin, children develop a severe disease called rickets, and in adults, bone tissue changes. The daily intake of the vitamin is 0.0025 mg. Vitamin D is found in animal foods: 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 to ultraviolet rays. Adults under normal conditions do not lack this vitamin. Excessive intake of vitamin D (in the form of pharmaceutical preparations) can lead to poisoning.

Vitamin E (tocopherol) influences the processes of reproduction. With a lack of this vitamin, changes occur in the human reproductive and central nervous systems, and 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 people do not lack it. It is especially abundant in cereal germs and vegetable oils. The vitamin content in foods decreases when heated. Vitamin E has an antioxidant effect and is widely used in the food industry to slow down fat oxidation.

Vitamin K (phylloquinone) participates in the process of blood clotting. With its deficiency, blood clotting 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 leaves of lettuce, cabbage, spinach, and nettles. It is destroyed by exposure to light, high temperature and alkalis.

Vitamin-like substances. The most important of these are vitamins F and U.

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 is in lard, peanut and olive oils.

VitaminU (methylmethionine) normalizes the secretory function of the digestive glands and promotes the healing of stomach and duodenal ulcers. The vitamin is contained in fresh cabbage juice.

ENZYMES

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

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

About 1,000 enzymes are known, and each of them has 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, an 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. Thus, 1.6 g of human digestive juice amylase can break down 175 kg of starch in 1 hour; gastric juice air pepsin can break down 50 kg of egg white.

Enzymes have certain properties. Thus, some enzymatic processes are reversible, that is, 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 exhibit 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 the acceleration of enzymatic processes, and this entails spoilage of products. It also depends on the reaction of the medium (pH). Thus, gastric juice pepsin 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 that has coagulated during heat treatment is broken down by an 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 cheese; enzymes secreted by bacteria and yeast take part in the production of fermented milk products, pickled vegetables and dough fermentation.

Enzymes have a great influence on the quality of products. In some cases, this effect is positive, for example, when ripening meat after the slaughter of animals and when salting herring, in other cases it is negative, for example, the darkening of apples and potatoes during peeling and slicing. To prevent browning, apples should be immediately cooked 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 during cooking in boiling water or broth, in which enzymes are quickly destroyed. Under the action of enzymes, fats are oxidized. Souring of soups, rotting of fruits, fermentation of compotes and jams are caused by enzymes secreted by microbes that have entered the food. The negative effect of enzymes can be stopped by increasing or decreasing the air temperature during food storage.

Currently, scientists are doing a lot of work to study enzymatic processes and their further application in the food industry. Methods have been developed to soften the connective tissue of meat using the enzyme prototerrisin, and enzymatic processes that slow down the staling 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 microbial cultures, as well as from plant and animal raw materials.

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1. Rheological, thermophysical, electrophysical, optical and sorption properties of food raw materials.

The differences in the properties of food products are due to the wide variety of structures and chemical compositions. Food products can be solid, semi-solid and liquid. Solids can have a crystalline structure (table salt, solid fats) or an amorphous structure (caramel products). Bread, cereals, pasta, cookies, tissues of meat, fish, fruits and vegetables are characterized by a capillary-porous-colloidal structure, lump sugar - capillary-porous. Starch, marmalade, gelatin - concentrated jellies. Minced meat and fish, vegetable and fruit purees, dough, condensed milk, mayonnaise - semi-liquid products. Liquid products - honey, milk, vegetable oil, wine, beer, juices, drinks are either colloidal solutions or emulsions, suspensions, polar and non-polar solutions.

Most food products (meat and meat products, fish, grain, fruits, as well as their processed products) are complex heterogeneous systems.

The properties of food products depend on temperature, pressure, production technology and other factors. In characterizing the quality of food products, properties play an important role, determining the conditions for their transportation and storage. Some quality indicators make it possible to judge not only the properties, but also the biological characteristics, chemical composition and organoleptic merits.

Methods of culinary processing depend on the properties of food raw materials. Due to the complexity of studying heterogeneous systems, the properties of food products have not yet been sufficiently studied.

Basic physical properties. These include shape, size, weight (weight of a unit of production, density, volume or bulk weight).

The shape of fruits and vegetables is an indicator of the botanical species and variety. The shape of bakery and confectionery products and rennet cheeses characterizes the quality of raw materials and the correctness of the technological process. For rennet cheeses, sausages, pasta, apples, vegetables, the size is standardized; fish are divided by size into large, medium, small, etc.

The weight of a unit of production is established when assessing the quality of many food products. The weight in kg is established when determining the size of some fish; when preparing and selling fresh cabbage, the weight of a head of cabbage is established; and for chocolate, cookies, waffles and some other confectionery products, the weight is limited. For cereal grains and coffee, the quality indicator is the weight of 1000 grains, for nuts - 100 pieces, for caramel and sweets the number of pieces of products per 1 kg is regulated.

Density is the mass (in kg) of a unit volume (in m3) of a homogeneous product, expressed in kg/m3. In liquid products, the relative density is determined - a dimensionless value, which is found by dividing the mass of the product (at 20 ° C) by the mass of an equal volume of distilled water at the same temperature. Due to the thermal expansion of bodies, as the temperature of the product increases, the density decreases.

Density determines, for example, the mass fraction of sugar in grapes used in winemaking, the content of table salt in brines of sauerkraut and pickled cucumbers, the strength of alcoholic beverages, and the starch content in potato tubers (the higher the density of potato tubers, the more starch they contain).

Density can characterize the chemical composition of fats and milk. Since with increasing oxygen content in a fatty acid molecule its density is higher, the density of saturated high-molecular fatty acids will be less than low-molecular fatty acids, and unsaturated fatty acids will increase with an increase in the number of double bonds. Therefore, the density of fat can be used to judge its fatty acid composition.

The volumetric or bulk mass of a product in kg/m3 is determined as the ratio of its mass to the volume it occupies, together with voids and pores. The volumetric mass of the product must be taken into account when determining the capacity of containers, storage facilities, placement of products for storage, and vehicles during transportation.

Structural and mechanical properties of food products. These properties characterize the resistance of food products to mechanical stress. They depend not only on the chemical composition, but also on the structure, or structure, of the product. These include: strength, hardness, elasticity, plasticity, relaxation, viscosity, stickiness.

The mechanical properties of products are manifested in the process of their deformation, when the shape and size of the body changes under the influence of external forces.

Rheology - the science of deformation and flow of various bodies - makes it possible to understand the phenomena that occur during the production and storage of food products. When determining the rheological properties of food products, they measure the amount of mechanical energy spent over time to create reversible (elastic) or residual (plastic) deformations in products, which characterize the strength of chemical bonds between the molecules and links that make up the structure. These data make it possible to judge the speed of chemical and biochemical processes occurring in products.

Strength - the ability of a product to resist mechanical destruction - is determined when determining the quality of pasta, refined sugar, crackers and other products.

Hardness - the edge strength of a body - the property of a body to prevent the penetration of another (harder) body into it. To determine hardness, the surface of the product is impacted with a hard tip shaped like a ball, cone, pyramid or needle. Determine the hardness of sugar, grains, fruits, vegetables and other products.

Elasticity - the ability to instantly restore the shape of the body after applying external force (pressure) and elasticity - the ability to restore shape after pressure after some time - are important during the storage and transportation of goods (bread, fruits, vegetables) and in determining the quality (bread crumb, gluten-free flour , freshness of meat and fish, etc.).

Plasticity - the ability of a product to undergo irreversible deformations - characterizes the quality of caramel mass, dough, etc.

Relaxation is a property of products of a solid-liquid structure, characterizing the time of transition of elastic deformations to plastic ones under constant load. Cheese, cottage cheese, muscle tissue, and minced meat have a certain amount of relaxation. This property is of great importance when transporting bread and bakery products, fruits and vegetables, confectionery products, etc.

The phenomenon of creep - the property of a gradual increase in plastic deformation, especially of a heated product without increasing the load - is typical for cow butter, margarine, rennet cheeses, ice cream, marmalade, jam and other confectionery products.

Viscosity characterizes the internal friction that occurs during the relative movement of adjacent layers of syrups, molasses, honey, mayonnaise, juices, vegetable oils and other liquids and depends on the adhesion forces between particles and molecules of the substance (largely on the temperature of the product).

Stickiness (adhesion) is the ability of products to exhibit varying degrees of interaction force with another product or with the surface of the container in which the product is located. Butter, cheese, minced meat, boiled sausage, toffee, bread crumb and other products that, when cut, stick to the knife blade, crumble or break, have sticky properties. The stickiness of products is determined to control this property during the production and storage of goods.

To characterize the structural and mechanical properties of food products in commodity science, the term “consistency” is used. Consistency refers to viscosity, stickiness, elasticity and other properties detected by touching and chewing a food product.

Optical properties. These are transparency, color, refraction and optical activity, which are determined by vision.

Transparency is an important indicator of the quality of products; it characterizes their ability to transmit light. Transparency is typical for alcoholic beverages, beer, mineral waters, refined vegetable oils, table grape wines, and champagne. Old wines, dessert wines and liqueur wines may have slight cloudiness; minor cloudiness is acceptable for unrefined oils.

The color of food products is due to natural coloring substances (pigments) or the addition of artificial dyes; it must correspond to the type of product and be uniform throughout the mass. During heat treatment (cooking), the color of products (meat, vegetables) changes.

By the ability of products and their solutions to refract a beam of light, characterized by the refractive index of light, the quality of some (sugar, fat) products and the quantity of individual components (mass fraction of dry substances in tomato products, juices, coffee, etc.) are judged.

By optical activity, i.e. the ability to rotate the plane of a polarized beam of light, the types of sugars and their quantity in the solution are judged. Starch, glycogen, sugar, amines, acids and other substances are optically active.

Thermophysical properties. These properties are revealed by the action of thermal energy on food products and are characterized by heat capacity, thermal conductivity, melting point, solidification, and freezing. Knowledge of thermophysical characteristics is necessary to ensure quality during cooking, baking, pasteurization, sterilization, freezing, thawing, transportation and storage of products.

The quality of many products is determined by the speed at which they are cooled at the beginning of storage. Heat capacity is the amount of heat absorbed by a body when heated by 1 °C. The heat capacity calculated for 1 kg of product is called specific heat capacity and is expressed in J/(kg-deg). It depends on the chemical composition, structure, biological characteristics and many external reasons. Products with a large mass fraction of fat have a low heat capacity, while products with a lot of moisture have a high heat capacity.

The thermal conductivity coefficient is the amount of thermal energy that flows through 1 m2 of product surface to a thickness of 1 m at a temperature difference of 1 ° C per unit time. Water and products with a high moisture content have greater thermal conductivity than fat-containing, porous and bulk products.

Products with high thermal conductivity can heat up quickly and cool down quickly. Cooling of the inner layers of a batch of product with low thermal conductivity (fatty pork) is inhibited, which can cause spoilage.

The melting point of fats is slightly higher than the solidification temperature. These characteristics are used to study the composition and quality of fats.

The freezing point of a product must be taken into account when refrigerating, freezing and storing food fresh. Storage below freezing will adversely affect the quality of dairy products, wines and other beverages.

Sorption properties of products. Sorption is a process in which a product absorbs vapors or gases from the environment. The reverse process of sorption is called desorption. Since the sorption and desorption of vapors and gases changes the quality of food products, it is important to know how much vapor and gas the products can absorb under different storage conditions, as well as how the absorbed substances affect the properties of the products.

Humidification of products occurs when the water vapor pressure in the air exceeds the water vapor pressure on the surface of the product as a result of the evaporation of part of the free water of the product itself. In this case, products absorb moisture both through adsorption (the formation of a thin layer on its surface), absorption (through volumetric absorption by hydrophilic substances), and as a result of capillary condensation (in the presence of macro- and microcapillaries).

The absorption of gases or vapors by a product to form chemical compounds is called chemisorption. When the water vapor pressure on the surface of the product is greater than the water vapor pressure in the air, desorption of moisture from the product occurs. Sorption or desorption of moisture by a product occurs before it reaches equilibrium moisture content, when the water vapor pressure in the air and on the surface of the product becomes equal.

Hygroscopicity is the ability of a product to absorb moisture from the environment. This indicator depends on the porosity of loose bodies and, to a greater extent, on the properties of the substances of a given product. Dry and relatively dry foods (milk powder, dried fruits, tea, coffee) rich in protein, starch, fructose and inert sugar are capable of absorbing moisture; foods that are rich in fat or contain a lot of moisture do not absorb it.

The mass fraction of hygroscopic moisture in a product depends on its chemical composition, as well as on the relative humidity of the air, which is measured with a psychrometer or hygrograph.

Relative air humidity, expressed as a percentage, is the ratio of the absolute amount of moisture in the air to the amount of water at the highest saturation for a given temperature, i.e. degree of air saturation with water vapor.

Description of work

The differences in the properties of food products are due to the wide variety of structures and chemical compositions. Food products can be solid, semi-solid and liquid. Solids can have a crystalline structure (table salt, solid fats) or an amorphous structure (caramel products). Bread, cereals, pasta, cookies, tissues of meat, fish, fruits and vegetables are characterized by a capillary-porous-colloidal structure, lump sugar - capillary-porous. Starch, marmalade, gelatin - concentrated jellies.

Sorption properties characterize the ability of food products to absorb water vapor and volatile substances from the environment. These properties play an important role in the transportation and storage of food products.

There are four types of sorption: adsorption - absorption of substances by the surface of the product; absorption - absorption of substances by the entire mass of the product; chemisorption - chemical interaction between substance and product; capillary condensation - formation of a liquid phase in micro- and macrocapillaries of solid products.

The reverse process of sorption is desorption- determines the transition of substances from the surface layer to the environment.

Sorption and desorption of vapors and gases lead to changes in the quality of the product, which can dry out due to lack of moisture in the surrounding atmosphere, acquire an unpleasant odor or lose aroma if storage conditions are violated.

In practice, sorption and desorption of water vapor are of greatest importance.

Humidification of the food product, i.e. sorption of water vapor is observed when the partial vapor pressure at the surface of the product is less than the partial vapor pressure in the air.

The evaporation process (desorption) occurs at a higher vapor pressure at the surface of the product compared to the vapor pressure in the air. If the vapor pressures in the air and in the environment are equal, then a state of dynamic equilibrium occurs. The moisture content of the product corresponding to the equilibrium state is called equilibrium moisture content. It depends mainly on the chemical composition and condition of the product, as well as on the relative humidity and air temperature.

Hygroscopicity - the property of products to absorb moisture from the environment and retain it by capillaries and the entire surface. The hygroscopicity of food products depends on their structure and composition, as well as on the temperature and humidity of the environment. As a rule, powdered foods (milk powder, coffee), tea, dried fruits and vegetables are highly hygroscopic.

The hygroscopicity of the product is significantly increased by the content of substances in it that can actively absorb water vapor from the surrounding atmosphere. These substances include fructose, which determines the hygroscopicity of honey, and calcium and magnesium salts, which are present as impurities in table salt and determine its hygroscopicity.

Thus, food products are characterized by a complex of simple and complex properties - chemical, physical, technological, physiological, etc. The combination of these properties determines their usefulness for humans, i.e. consumer properties. The usefulness of food products is characterized by their nutritional, biological, physiological, energy value, good quality, and organoleptic properties.

Nutritional value of the product - This is the broadest concept, including the content of basic chemical substances in a product: carbohydrates, fats, proteins in a food product, the degree of their absorption and energy value, their taste. The nutritional value of a product is higher, the more it satisfies the body’s need for nutrients and the more fully it complies with the principles of a balanced diet.

Biological value of the product reflects primarily the quality of the proteins in it, amino acid composition and digestibility. In a broader sense, this concept includes the content of vital biologically active substances in a food product - microelements, essential fatty acids, vitamins, etc.

Physiological value of the product characterized by the presence in it of useful elements necessary for the implementation of basic metabolic processes in the body. It also reflects the influence of consumed products on the nervous, cardiovascular, digestive and other systems of the body, and resistance to infectious diseases. For example, caffeine in tea and coffee, theobromine in chocolate, and alcohol in drinks have a stimulating effect on the nervous and cardiovascular system. Immune bodies in milk and antimicrobial substances in eggs increase the body's resistance to infectious diseases. Food acids (lactic, malic) suppress putrefactive processes in the intestines.

Energy value of the product - This is energy that is released from food substances during the process of biological oxidation and is used to ensure the physiological functions of the body.

Benign food products are considered to be those that do not contain substances harmful to the human body (salts of heavy metals, toxic organic compounds, poisonous alkaloids, glycosides, toxins - poisons secreted by some molds), and also do not have unusual tastes and odors. Pathogenic microorganisms, molds and pests are not allowed in food products. The content of copper, tin, nickel, and metal impurities is strictly regulated; salts of lead, mercury, and arsenic are not allowed.

Organoleptic properties of products characterized by indicators determined by the senses: appearance, consistency, taste and smell. They are closely related to the digestibility of the product. The most important indicator is taste. As a rule, products that have a universal chemical composition and contain valuable food acids and aromatic substances have high taste qualities.

Digestibility of food product– degree of absorption of the food product as a percentage.

The digestibility of digested food is affected by; chemical composition, its culinary processing, appearance, volume, diet, food intake conditions, state of the digestive system, etc.

The digestibility of food of animal origin is on average 90%, vegetable - 65%, mixed - 85%. Carbohydrates are digested best, their digestibility reaches 98-99%. Protein digestion is more difficult. Protein from animal products is absorbed in the intestines by 90% or more, and from plant products by 60-80%. The decrease in the digestibility of proteins of plant origin is due to the fact that the membranes of plant cells contain a significant amount of fiber, which is not amenable to the action of enzymes of digestive juices.

Fat is absorbed at different rates. Fats with a lower melting point are digested faster, while solid fats with a high melting point are digested much worse. Butter is 98% digestible.

For more complete absorption of nutrients in the body, their correct ratio in the diet is of great importance. A deficiency of any nutrient, such as protein, reduces the absorption of other nutrients, and excess fat also has a negative effect on the entire absorption process.

Culinary processing of food promotes digestion, and, consequently, its absorption. Mashed and boiled food is digested better than lumpy and raw food. The appearance, taste, and smell of food enhance the secretion of digestive juices, facilitating its digestibility. The diet and the correct distribution of the daily amount of food during the day, the conditions for eating food (the interior of the dining room, polite, friendly service, the cleanliness of the dishes, the neat appearance of the cooks), and a person’s mood also increase its digestibility.

Storability- the ability of a product to retain consumer properties during storage and transportation within the established periods, as well as after them. Storability indicators are: calendar storage period, losses, standard product yield;

Ready to eat- degree of processing, ease of preparation;

Safety- absence in food products of substances harmful to the human body (salts of heavy metals, toxins, poisons), unusual tastes and odors.