Biochemical methods of food preservation. Food preservation methods

Canning - It is the processing of foodstuffs to increase their shelf life.

Based on the biological principles developed by prof. I.I. Nikitsky, canning methods can be divided into four groups:

the principle of biosis - the maintenance of life processes and the use of the natural immunity of living organisms (pre-slaughter keeping of livestock, poultry, keeping live marketable fish, storage of fruits and vegetables;

principle of anabiosis - suppression of the vital activity of microorganisms and the enzymatic processes of the products themselves as a result of: the creation of modified and controlled gas environments for the storage of fresh fruits and vegetables, fish - drug anabiosis; the use of low temperatures above cryoscopic (cooling) - psychoanabiosis; creating a high osmotic pressure in the product (preservation with salt, sugar) - osmoanabiosis; removal of excess moisture from the product (drying) - xeroanabiosis;

The principle of cenoanabiosis - change in the microflora of the product as a result of various external influences (ripening, fermentation, fermentation);

the principle of abiosis - cessation of vital activity of microorganisms, enzymatic processes as a result of high temperatures (thermobiosis), the use of antiseptics and other chemicals (chimabiosis);

Depending on the technological essence, conservation methods are divided into physical, physico-chemical, chemical, biochemical, combined.

Physical Methods

Preservation by the action of low temperatures - this method includes cooling and freezing.

Cooling is a common method of preservation. It is widely used to preserve fresh fruits, vegetables, meat, fish and dairy products, eggs. With this method of preservation, food products are cooled to temperatures close to 0 ° C. Cooling retains the nutritional value and organoleptic properties of goods, but does not ensure long-term preservation of products (for example, sour cream - up to 72 hours, curd products - up to 36 hours; pasteurized milk - up to 36 hours). This method is used when transporting goods over short distances, subject to rapid implementation in the distribution network.

Freezing - This is a preservation method in which the temperature of food is reduced to -8 ° C and below. Freezing contributes to the long-term preservation of food products. The shelf life of frozen foods is measured in months and even years. The lower the temperature, the faster the freezing speed and the higher the quality of the food. Rapid freezing reduces product weight loss. During slow freezing, large ice crystals form inside the cell, which damage it, and during defrosting, cell sap is lost.

Frozen products are inferior in quality to chilled ones, since their nutritional and taste value changes during long-term storage, and nutrient losses during defrosting are also possible.

Canning at high temperatures carried out to destroy the microflora and inactivate the enzymes of food products. This method includes pasteurization and sterilization.

Pasteurization is carried out at a temperature below 100 ° C. With such heating, microorganisms die, but their spores remain. Therefore, although pasteurization extends the shelf life of goods, it does not guarantee their complete safety. Kvass, milk, beer, fish caviar are pasteurized. During pasteurization, the nutritional value of the product changes little, vitamins and some other biologically active substances are only partially destroyed.

Sterilization - more efficient method of preservation than pasteurization. Sterilization is carried out at a temperature above 100 ° C for a certain time (from several seconds - instant sterilization, up to 1 hour), depending on the type of products.

This method is widely used for the preparation of various types of canned food (meat, fish, dairy, vegetables), milk. During sterilization, not only microorganisms die, but also their spores, which prolongs the shelf life of products (up to several years - canned food). However, during sterilization, the nutritional value of the product decreases, and its taste changes.

Preservation by ionizing radiation called cold sterilization or pasteurization, since the sterilizing effect is achieved without raising the temperature. For the processing of food products, b-, b-radiation, x-rays, and a stream of accelerated electrons are used. Ionizing radiation is based on the ionization of microorganisms, as a result of which they die. Preservation with ionizing radiation includes radiation sterilization (radappertization) of long-term storage products and radurization with pasteurizing doses. Irradiation of products is carried out in inert gases, vacuum, using oxidizing agents, at low temperatures. The disadvantage of this method is the change in the chemical composition and organoleptic properties. In industry, this method is used for processing containers, packaging, premises.

Preservation by ultrasound(more than 20 kHz). This method is used for pasteurization of milk, in the fermentation and non-alcoholic industries, for the sterilization of canned food.

Irradiation with ultraviolet rays(UFL). This is irradiation with rays with a wavelength of 60-400 nm. UV radiation is especially detrimental to pathogenic microorganisms and putrefactive bacteria. Therefore, UFL is used to treat the surface of meat carcasses, large fish, sausages, as well as to disinfect containers, equipment, refrigerators and warehouses.

The use of scaling filters. The essence of this method is in the mechanical separation of goods from spoilage agents using filters with microscopic pores, i.e. ultrafiltration process. This method allows maximum preservation of the nutritional value and organoleptic properties of the goods and is used for processing milk, beer, juices, wine and other liquid products.

Physical and chemical methods

Drying (dehydration). This ancient method of preservation is based on the removal of moisture from food, as a result of which microorganisms are not able to develop. Dried milk, dairy products, fish, fruits, vegetables, mushrooms. During drying, the products lose significantly in mass, which facilitates their transportation and storage, and the energy value of the product increases compared to the feedstock. Dried foods have a long shelf life. But during drying, a number of undesirable changes take place: oxidation of lipids and vitamins, deterioration of flavor and aroma properties. Drying can be natural (in the sun and in the shade) and artificial (thermal, sublimation, microwave). Thermal drying is carried out in dryers using air heated to a temperature of 60-200 ° C.

Conductive (contact drying) is the contact of the product with the hot surface of the drums (drying milk, mashed potatoes).

Freeze drying is a type of conductive method based on removing moisture from frozen foods by sublimation (sublimation) of water, i.e. direct transition of ice into vapor, bypassing the liquid phase, under conditions of high vacuum.

During freeze-drying, the chemical composition, nutritional value, organoleptic properties of the product are maximally preserved, and the shelf life of the product can be extended up to 3 years. Freeze drying is used for dehydration of products of plant and animal origin.

Radiation drying is based on the transfer of heat from an energy source by means of electromagnetic oscillations through a medium transparent to thermal radiation. The advantage of radiation treatment is the suppression of the vital activity of many types of putrefactive microflora and insect pests at relatively low doses of radiation.

Preservation with table salt and sugar. The method is based on increasing the concentration of dry substances in the product, which leads to cell plasmolysis and death of microorganisms. The desired effect is achieved at a sugar concentration of 60-65%. Table salt at a concentration of 10-20% has a similar effect. Commodity science and organization of trade in food products: Textbook / Ed. A.M. Novikova, T.S. Golubkina. M. - ProfOborIzdat. - 2001. - p. 44. Canning with sugar is usually combined with cooking, pasteurization or sterilization, which leads to the destruction of vitamins, flavors and other substances.

When salting, the nutritional value of the product decreases, since under the influence of salt, the cell juice flows out, forming a brine. When salting some types of fish, they ripen, resulting in food products with high taste properties. The peculiarity of the method of preservation with salt and sugar is that it significantly changes the properties of raw materials and as a result a product with new consumer properties is formed.

Chemical Methods

Preservation with ethyl alcohol used in the production of semi-finished fruit juices. At an ethyl alcohol concentration of 12-16%, development is delayed, and at 18%, the vital activity of microflora is suppressed.

Pickling- an increase in the acidity of the medium with the addition of acetic acid, which at a concentration of 1.2-1.8% inhibits the activity of microorganisms, primarily putrefactive. Marinate fruits, vegetables, mushrooms, fish.

Preservation with acids (antiseptics) - using sulfurous acid, benzoic acid, sorbic acid (C 6 H 8 O 2).

Preservation of products with sulfuric acid, its salts is called sulfation. Sulfurous acid inhibits the vital activity of molds and bacteria; more resistant yeast. that acid is used for preserving fruits, berries, vegetables, their semi-finished products.

Benzoic acid (C 6 H 5 COOH) inhibits the action of yeasts and molds, bacteria are more resistant. Used for canning fruits and vegetables, fish products.

Sorbic acid (C 6 H 8 O 2) and its salts are used to preserve juices, purees, marinades. These substances inhibit the vital activity of yeasts and molds, but do not act on bacteria. Sorbic acid at a concentration of 0.1% inhibits the action of microorganisms more strongly than benzoic and sulphurous, without changing the organoleptic properties of the product; in small doses, it is harmless to humans. Timofeeva V.A. Merchandising of food products. - Rostov n / a: Publishing house "Phoenix". - 2002. -

Preservation of antibiotics. Like antiseptics, antibiotics have a bactericidal effect. Currently using: biomycin(used for processing meat and fish; nystatin, acting on yeast and fungi that cause mold in meat; lowlands, inhibiting the growth of staphylococci, streptococci and other pathogenic microorganisms, is used in the production of dairy and fruit and vegetable canned food.

Canning gases. The essence of the method is to change the ratio of oxygen and carbon dioxide, as a result of which the vital activity and development of microorganisms are suppressed. The use of gaseous media in combination with the refrigeration processing of food products is effective, and the shelf life in this case increases by 2-3 times. Used for preserving vegetables, fish, meat, poultry, sausages.

Biochemical methods Fermentation - this is a metabolic anaerobic process in which ATP is regenerated, and the breakdown products of the organic substrate serve both as a donor and an acceptor of hydrogen. Fermentation of fruits and vegetables is based on lactic acid fermentation. The term "fermentation" is usually used in relation to cabbage, "salted" - to cucumbers and tomatoes; "soaked" - to apples, watermelons and berries. Alcoholic fermentation is used in the production of wine.

Combined methods.

Smoking - this is a method of preserving a salted semi-finished product with substances of incomplete combustion of wood contained in smoke or smoke preparations. This method combines the preservative effect of smoke, salt, heat or drying. Separate smoke substances and common salt improve the taste of the product and give it a smoked smell. Smoking is cold (at a temperature of 18-40 o C) and hot (60-120 o C). Smoking with the use of smoking liquid is widely used. Its advantage is that the terms of smoking are reduced and the possibility of exclusion from the smoke preparation of carcinogenic substances harmful to the human body is created.

Drying - it is preservation by the simultaneous action of salt and drying. Drying is used to preserve fish, sometimes meat. The action of salt and a small amount of moisture inhibit the development of microorganisms. At low temperatures, dried foods can be stored for up to several months.

concentration - used in the manufacture of canned condensed milk, concentrated juices, tomato products. This method consists in the concentration of solids due to the partial removal of moisture. In addition, the addition of sugar, pasteurization or sterilization has a preservative effect, due to which concentrated food products are stored at a temperature of 0-15 ° C for up to a year or more.

When storing products such as meat and meat products, fish and seafood, milk and dairy products, fresh fruits and vegetables, special conditions are required. Otherwise, they lose their original qualities: taste, smell, texture and color.

These products are perishable because the water and organic compounds contained in them create favorable conditions for the development and vital activity of various microorganisms and enzymes. Microorganisms and enzymes cause decomposition of proteins, hydrolysis of fats, deep transformations of carbohydrates and other changes.

Irreversible processes in products occur:

When exposed to atmospheric oxygen and sunlight;

Due to excessively low or very high humidity;

Due to biochemical processes (activity of tissue enzymes);

Under the influence of the microbiological factor, etc.

To preserve products (raw materials), various preservation methods are used that exclude or reduce the impact of these factors. They are divided into physical, physico-chemical, chemical, biochemical and combined.

Physical methods conservation based on the use of high and low temperatures, ionizing radiation, ultraviolet rays, ultrasound and filtration.

Physico-chemical methods include drying, salting, and the use of sugar.

Chemical methods canning is based on the use of chemicals that are practically harmless to humans and do not change the taste, color and smell of the product.

Biochemical methods preservation is based on the suppressive effect of lactic acid, which is formed as a result of the fermentation of product sugars by lactic acid bacteria.

Combined methods canning are based on the use of other types of canning in addition to the main type of processing (for example, salting and smoking, both hot and cold; storage of fruits using cold and special gaseous media, etc.). Recently, various preservatives have been increasingly used: ethyl alcohol, acetic, sulphurous, benzoic, sorbic acids and some of their salts, boric acid, urotropine, certain antibiotics, ozone, carbon dioxide and a number of others.

Prof. Nikitinsky Ya.Ya. the conservation methods used in practice are grouped according to the following principles - biosis, suspended animation, cenoanabiosis and abiosis.

Bios- maintenance of natural life processes in products. This principle is used, for example, when storing fruits and vegetables, transporting and selling live fish.

Anabiosis- slowing down, suppression of the vital activity of microorganisms and the activity of enzymes. This is carried out during heat and refrigeration, drying and drying, pickling, canning in sugar syrup, etc.

Cenoanabiosis- suppression of vital activity of harmful microflora by the products of vital activity of beneficial microflora. For example, fermentation, lactic acid and alcoholic fermentation in the production and storage of fermented milk products.

Abiosis- complete cessation of vital activity of microorganisms and microflora in products. For example, high-temperature treatment (sterilization), the use of radiant energy, high and ultra-high frequency currents, antibiotics, antiseptics, etc.

Thus, the main task that food preservation solves is to limit or eliminate the destructive action of microorganisms and enzymes.

When choosing a canning method, in addition to the main goal (inhibition of unwanted processes), they strive to achieve maximum safety of the product, as well as the economy of the process.

Therefore, the best preservation method is the one that allows the product to be stored for a longer time with the least loss of nutritional value and weight. These requirements are met by the use of artificial cold.

Canning with the use of cold leads to a slowdown in reactions both naturally occurring in products (autolysis of meat, respiration and ripening of fruits), and caused by the activity of microorganisms.

Depending on the tasks to be solved, the products are subjected to different depths of refrigeration treatment (cooling, supercooling, freezing, freezing, re-freezing), and heat is supplied to the product to restore natural properties (warming, defrosting).

The most efficient use of refrigeration canning is ensured by maintaining a single continuous refrigeration chain throughout the entire path of the product from production to consumer.

Questions for self-examination

1 What causes food spoilage?

2 What methods of canning do you know?

3 Name the principles of canning.

Effect of low temperatures on microflora

And the quality of the products

Microorganisms in relation to temperature conditions are divided into three groups: thermophiles, mesophiles and psychrophiles.

Thermophiles - microorganisms, develop at temperatures of 20 ... 80 ° C; mesophiles live at 5...57°C, and psychrophiles are able to grow at relatively low temperatures of +10...-10°C.

Psychrophilic bacteria actively multiply on products with low acidity - on meat, fish, non-acidic dairy and vegetable products at a temperature of -5 ... -8 ° C.

Most molds are psychrophilic and develop quite actively on frozen foods. Some types of mold stop reproduction only at a temperature of -8 ... -10 ° C.

Microorganisms are sensitive, moderately resistant and insensitive to negative temperatures. The vegetative cells of molds and yeasts are especially sensitive to low temperatures. Soil bacteria are the most resistant. Mold spores are moderately resistant.

Resistance of microorganisms to negative temperatures depends on three factors: temperature, its rate of decrease and exposure time. The effect of negative temperatures on microorganisms is manifested in a change in the state of water in a microbial cell. The maximum damaging effect is exerted by intracellular ice formation. This leads to an increase in the concentration of intra- and extracellular solutions, which leads to protein denaturation and disruption of permeability barriers.

However, cold damage to microorganisms can occur without ice formation. The death of bacterial cells as a result of cold shock occurs with very rapid cooling due to low osmotic pressure. At the same time, the destructive effect of low temperatures is associated with a violation of nucleic acids and the integrity of lipid membranes.

The resistance of microorganisms to negative temperatures also depends on the duration of exposure to cold. At the beginning of freezing, the number of bacterial cells decreases rapidly, then the death of microorganisms slows down, and, finally, cells resistant to low temperatures remain, the number of which depends on the freezing conditions, the individual resistance of the microbial species.

It is possible to develop microorganisms at temperatures above -10°C and this can lead to a decrease in the quality of the stored product and even to its deterioration. So, during long-term storage of frozen meat at temperatures above -8 ° C, mold fungi can develop. They appear in separate colonies, which subsequently increase and become denser. The mycelium of the fungus penetrates the thickness of the meat, and sporulation begins. White, gray or black spots appear on the surface of the product, waste products of mold accumulate in the thickness of the meat, and a musty smell appears. These processes proceed similarly during the storage of frozen fish and other products.

In frozen berries or fruit and berry juices stored at temperatures above -8 ° C, a yeast waste product, alcohol, is formed.

The effect of low temperatures on tissue cells organisms leads to metabolic disorders. This effect is called "temperature shock". As a result of violation of the dynamic balance of biochemical processes, intermediate, often toxic, metabolic products accumulate in cells.

If the cooling process is carried out quickly, then the death of the biological object may occur. With a gradual decrease in temperature, the body can adapt, i.e. adapt to changing conditions, and in this case survive.

When biological objects are cooled below the temperatures at which water turns into ice, the damaging factors of the crystal formation process begin to play the main role. The mechanics of crystal formation is closely related to the conditions of the freezing process, which has a different effect on the state of the object being frozen, its quality.

Due to the mechanical impact of ice crystals on cells, their membranes are broken. The growth of ice crystals in the intercellular space reduces the size of the cell, causes compression and the formation of folds in the membrane, damage to the protoplasm.

With a gradual decrease in temperature, ice crystals first form in the interstitial fluid. The concentration of dissolved substances in it due to the freezing of water begins to increase. There is a difference between the concentrations of solutions in the intercellular space and inside the cells, which leads to the movement of moisture from the cells to the crystals in the intercellular space. Thus, the crystals on the outside of the cells increase and their contents are dehydrated. In the future, the process of crystallization begins in the cells themselves. During thawing, the considered phenomena develop in reverse order.

In the case of a rapid decrease in the temperature of biological objects, crystallization will occur simultaneously inside the cells and in the intercellular fluid surrounding them.

During storage, especially under conditions of unstable temperature conditions, recrystallization is observed - an increase in the size of crystals.

The damaging factor is the increase in the concentration of mineral salts (electrolytes) in the unfrozen part of the cell. An increase in the concentration of saline solutions leads to an increase in the osmotic pressure in the cells, which causes such a phenomenon as "osmotic shock".

Many biological objects are better preserved with fast and ultrafast freezing, because. there is less time left for the impact of saline solutions on the structure of the proteins of the molecules of living cells.

The degree of damaging effect of low temperatures depends on the place of formation of ice crystals in the cells and tissues of biological objects. So, during intracellular crystallization, the elements of protoplasm are intensively destroyed. When plant organisms are frozen, the formation of ice inside the cells always leads to their death. The vast majority of animal cells also cannot withstand intracellular ice formation.

The preservation of the viability of biological objects during their ultrafast freezing is due to the vitrification (glass formation) of water in the protoplasm of cells Vitrification is a deep supercooling of a liquid, in which there is no crystal lattice in it.

During the processes of vitrification and subsequent devitrification (devitrification) during rapid warming, there is no rearrangement of water molecules, which contributes to the preservation of the fine structure of the cell protoplasm.

Thanks to the use of protective substances (glycerin, sugar syrup, polyethylene oxide, etc.), very high freezing rates can be used during freezing.

Questions for self-examination

1 What groups of microorganisms do you know?

2 Name the temperature conditions of their life.

3 What effect do low temperatures have on cells, tissues and organisms?

The storage of perishable foodstuffs is an urgent issue of merchandising. For this purpose, they are subjected to special processing - canning. As a result, the shelf life is extended, the range of products is expanding, their taste, aroma, nutritional value are improving, and the degree of readiness for consumption is increasing. There are physical, physico-chemical, biochemical and chemical methods of preservation. The physical methods of conservation include conservation at high and low temperatures, the use of decontaminating filters, radiant energy, ultrasound, and radiation treatment. Canning at high temperatures ensures the destruction of microorganisms. As a result, inactivation of enzymes in the existing products occurs. Heat treatment is used for pasteurization and sterilization. Pasteurization - heating the product to a temperature of 65-90 °C. Since only vegetative cells of microbes die during pasteurization, and spores retain their vital activity, pasteurized products are unsuitable for long-term storage. Pasteurize cream, milk, juices, beer and other products.

Sterilization - heating the product to a temperature above 100 °C. During sterilization, microbes and their spores are completely destroyed in the product, so sterilized products are stored for a long time. However, with this method of preservation, the nutritional and taste value of products is reduced as a result of protein denaturation and the destruction of part of biologically active substances. Sterilized products are packed in sealed containers. Sterilize meat, fish, dairy, fruit and other canned food. Aseptic preservation is a progressive method. This method is based on short-term high-temperature heating of the product with its packaging in a sterile container. Low temperatures used for cooling and freezing food. The advantage of these preservation methods is the minimal change in the taste and nutritional qualities of the product.

Cooling is the lowering of the product temperature to 0-4 °C. At the same time, microbiological and biochemical processes almost stop in the products. Chilled dairy products are stored for up to 30 hours, fish and meat - up to 14 days, and fruits and vegetables - up to 6-10 months.

Freezing is the cooling of the product to a temperature of -18 ° C and below. Freezing allows you to almost completely stop the chemical, biochemical and microbiological processes in products. Frozen foods taste better than chilled foods.

Using Unplumping Filters(mechanical sterilization) is that liquid products (juices, water, beer, etc.) are passed through filters that trap microbes. At the same time, valuable flavoring and aromatic substances are preserved in the products.

Currently, other effective preservation methods are also used: ultra-high (UHF) and ultra-high (UHF) frequency currents, preservation with ionizing radiation (cold sterilization), irradiation with ultraviolet rays (UVR), preservation with ultrasound. Such methods are used to preserve meat, fish, pasteurize milk, disinfect water, and combat the sprouting of potatoes and grains.

The physico-chemical methods of preservation include drying, preservation with salt and sugar. The preservative factor of these methods is a decrease in water activity and an increase in osmotic pressure.

Drying prevents or slows down physico-chemical, biological and microbiological processes. Microorganisms do not develop in products with a moisture content of 3-20%. Drying is used to preserve grain, fruits, vegetables, milk, eggs, fish. Moisture is removed from them more often by heat drying.

They use artificial drying at reduced pressure (vacuum), in spray and roller dryers, in a fluidized bed, sublimation, etc.

The most widespread is the drying of products with heated air - convective.

Vacuum drying is carried out at low temperatures (up to 50 °C) under vacuum conditions. With such drying, the loss of valuable nutrients is reduced and the original organoleptic properties of the product are preserved.

The essence of freeze drying lies in the fact that in a vacuum chamber, ice passes from a quick-frozen product into a gaseous state, bypassing the liquid phase. Freeze-dried products retain their taste and nutritional value, as well as color and original volume. Canned meat, fruits, vegetables, juices and other products with this method.

To increase the osmotic pressure for the purpose of preserving food products, sugar or table salt. Sugar or sugar syrup is used to make jam, jam, marmalade, jelly, candied fruits and other products from fruits and berries. The sugar concentration is adjusted to 65%

Table salt is widely used for canning fish, meat, mushrooms. The development of putrefactive bacteria stops at a salt concentration of 10%, and at 20-25% the growth of all microbes is delayed. Highly salted foods have low taste. When salting vegetables, mushrooms, fish, the loss of soluble substances reaches 20-50%. There are dry, wet and mixed salting methods.

To biochemical preservation methods include food preservation with lactic acid (fermentation, salting, urinating) and ethyl alcohol. These substances, formed in products as a result of biochemical processes, inhibit the activity of putrefactive microorganisms that cause food spoilage.

When fermenting vegetables and fruits, the sugars contained in them are fermented by lactic acid bacteria into lactic acid. Lactic acid in the amount of 0.6-1.4% gives the product a specific pleasant taste and aroma. In the fermentation of fruits and vegetables, in addition to lactic acid bacteria, yeast is involved, fermenting sugars into alcohol and carbon dioxide. The content of ethyl alcohol in fermented products should not exceed 0.5-0.7%, in pickled apples - 0.8-1.8%.

The quality of fermented products depends on the sugar content, the amount of added salt, storage conditions and other factors.

Chemical preservation methods based on the addition of a small amount of chemicals to food - preservatives that have a bactericidal or antiseptic effect and must be harmless, not change the taste, smell and color of the product. Such substances include acetic, benzoic, sorbic, boric, propionic acids, sulfur dioxide, potassium metabisulfite, urotropin, and some antibiotics.

Pickled foods contain acetic acid in the amount of 0.6-1.2%. At this concentration, the development of microorganisms in the products is delayed, and they acquire a specific taste. Pickled vegetables, fruits, mushrooms, herring, etc.

Sulfitation is the treatment of a product with sulfuric acid or sulfur dioxide. It is used to preserve the natural color and suppress microorganisms. Sulphated fruits and berries are heated before eating to remove sulfur dioxide.

Smoking refers to the combined method of preservation. Its essence is that the product after salting is treated with smoke or smoking liquid. They contain antiseptic substances - phenol, furfural, aldehydes, resins and others, which protect products from the development of microorganisms in them. When smoked, the products acquire a special taste and aroma, their surface is painted in brown-golden tones. Meat and fish products are subjected to this process.

Of the antibiotics in canning, biomycin, nystatin and nisin are currently used.

According to the preservative effect, the methods of preservation are divided into physical, physico-chemical, chemical and biochemical.

To physical methods canning include canning at low (cooling, freezing) and high temperatures (pasteurization, sterilization), canning with ultraviolet rays, ultrasound, and sterilizing filters.

To physico-chemical methods canning include canning with salt, sugar and drying (natural, heated air, vacuum, infrared, freeze-drying).

To combined methods canning include curing and smoking.

Chemical Methods canning are based on the use of various chemicals that have a detrimental effect on microorganisms, for example, antiseptics.

To biochemical methods canning include fermentation.

Physical methods of preservation.Preservation at low temperatures based on slowing down or stopping the development of microbes and the action of enzymes. At cooling the temperature of the product is reduced to 0 to plus 4 °C, not allowing it to freeze. Cooling is widely used in the storage of vegetables, fruits, meat, fish, cottage cheese milk, sour cream and other products.

For longer storage, food products are frozen. Freezing is the process of turning the water contained in the product into ice. It is carried out quickly at a temperature of minus 18-25 ° C. Inside the product, the temperature reaches minus - 8 °C and unfavorable osmotic conditions are created for the development of microorganisms and biochemical processes. When transporting over long distances, the temperature is set to minus 18 °C. Freezing is used to store meat, fish, fruits, vegetables. Re-freezing is not allowed. The disadvantages of freezing include a hard consistency, partial loss of flavor, color changes (yellowing of fat). Frozen foods are inferior in taste and nutritional properties to chilled foods.

shock freezing vegetables and fruits (at minus 35–40 °C) is a modern method of preservation and allows you to preserve nutritional value, taste and appearance for a long time. When food products are quickly frozen, small ice crystals are formed, which are evenly distributed throughout the mass of the product. Such products are easy to prepare and do not require prior defrosting. The exclusion of such labor-intensive operations as sorting, cleaning, washing, cutting allows you to make the process of cooking vegetables comfortable. Shock freezing products have a much longer shelf life.

For high temperature preservation include pasteurization and sterilization.

Pasteurization consists in heating the product to a temperature below 100°C: above 67°C for 30-40 minutes (long-term pasteurization) and up to 85-90°C for 1-1.5 minutes (short-term pasteurization).

During pasteurization, vegetative forms of microbes die, but the spores of some of them remain, so pasteurized products are not stored for a long time. Pasteurize milk, cream, jam, juices, beer.

Sterilization- heat treatment of a hermetically sealed product at a temperature of 113-120 ° C for a certain time. The sterilization mode depends on the pH of the product, its consistency, type and volume of containers. Acidic products are sterilized at lower temperatures (105°C). In this case, all microbes and their spores die. Sterilized products can be stored for a long time, but their nutritional value decreases, since during sterilization, proteins are partially hydrolyzed and denatured, and vitamins are destroyed.

UHT-treated product (UHT-treated product)- a product, for example, milk, subjected to heat treatment at a temperature above 135 ° C for up to 10 s.

A promising method for maintaining product quality is aseptic sterilization– hot filling into sterilized containers of liquid and puree-like products heated to a temperature of 130–150 °C, followed by their rapid cooling to 30–40 °C.

When preserving with currents ultra high frequency (microwave) the product in a sealed container is placed in an alternating current electromagnetic field. Preservation time is reduced by 20 times.

Ultra-violet rays used for processing the external surfaces of refrigerators, meat carcasses, sausages.

When applied conditioning filters microorganisms of the filtered products (juices, beer) linger on the surface of the filters. Products retain their natural taste, color and aroma.

By using ionizing radiation radioactive isotopes cobalt-60 and caesium-137 destroy fruit flies and weevils in imported grapes and oranges.

A lot of experience has already been gained ozone when storing potatoes, carrots, cabbage, onions and fruits (grapes and apples) abroad. Ozonation of air of storages, refrigerating chambers is applied.

Physical and chemical methods of conservation.Preservation with salt and sugar It is based on the fact that most microorganisms do not develop in products with an increased concentration of salt and sugar, which increase the osmotic pressure. Osmosis is the slow penetration of a solvent (water microbes) into a solution (sugar and salt) through a thin partition separating them.

Salty products are well preserved, when salted, specific taste and aroma appear, the structure of the product changes, however, when salted, soluble proteins, vitamins and other substances are partially removed from the product along with water. Salt is mainly preserved for fish, pickled cheeses and mushrooms. For canning, salt is used at a concentration of 4–14%.

canning sugar used in the production of jam, marmalade, condensed milk, marmalade, candied fruits and other products. The concentration of sugar in this case should be at least 60-65% . For better preservation, products with a sugar concentration of less than 65% are additionally pasteurized in a hermetically sealed container.

Drying- the method is based on the removal of part of the water from the product, as a result of which the concentration of solids increases, a high osmotic pressure arises. Products are dried to a moisture content of 4-25%.

Dried fruits, vegetables, mushrooms, milk, eggs, fish.

There are natural drying (in the shade or under the rays of the sun) and artificial (using hot air with a temperature of over 120 ° C in special dryers). Liquid products are dried in spray dryers.

Modern methods are infrared dehydration and freeze drying. For example, freeze drying - this is the drying of frozen products in a vacuum, in which the transition of ice of the frozen product into steam is observed, bypassing the stage of water.

Combined preservation methods.Drying– slow drying of salted products. Smoking - smoke treatment combined with salting. There are hot smoking, which takes place at a smoke temperature of 70–140 ° C, and cold smoking at 40 ° C. Smoke liquid and electrosmoking are also used for smoking. They smoke meat and fish.

Biochemical methods- are based on the property of acids and alcohol formed in products to delay the development of most microorganisms. At fermentation lactic acid (up to 0.7–0.9%) is formed as a result of lactic acid fermentation of sugars contained in fermented fruits and vegetables. To improve the taste and activate cell plasmolysis and the transition of sugar (juice) into the brine during fermentation, 2–5% of table salt is added. At urinating apples accumulate up to 1.5% alcohol. Ethyl alcohol accumulates in wines as a result of yeast activity.

Chemical Methods canning is based on the addition of various antiseptics to products, for example, acids (acetic, sulfuric, sorbic, benzoic), alcohol, hexamine, nisin, in accordance with established standards. At pickling acetic acid in the amount of 0.6-1.5%, sugar, salt, spices are added to the product. As a rule, products are pre-blanched. The preservation effect is provided by the bactericidal properties of acetic acid.

Alcohol added to alcoholic beverages (10–45%), bread intended for long-term storage is processed. Alcohol slows down the action of microorganisms.

Preservation with sulfuric acid, its salts and sulfur dioxide is called sulfitation. For example, fruits and berries are treated with sulfur dioxide, incl. before drying. The sulphated raw material is a semi-finished product and is used for processing after desulphurisation. When storing fresh grapes, potassium metabisulfate is used.

Benzoic acid sodium(0.05–0.1%) is used to preserve sour juices. Sorbic acid at a concentration of 0.1%, it suppresses the action of microorganisms more strongly than benzoic and sulfurous, without changing the organoleptic properties of the products. It is successfully used in combination with sugar for preserving fruit and berry purees.

Causes of spoilage of food products and raw materials. In canning, bacteria, yeasts, molds and viruses are of particular importance. Their effect can be positive, but in most cases - negative.

Reproduction of the living bacteria limited by low temperature, lack of water, nutrients and other factors. The activity of lactic acid bacteria can be useful in fermenting vegetables, fruits and dairy products. Mold are formed on the surface of the product, giving it an unpleasant odor and taste, since air is needed for their activity. Useful properties of some molds are used in cheese making. Beneficial features yeast used in brewing, winemaking, baking (for loosening dough), pickling. Viruses when canned, they are subject to destruction, because they can be a source of diseases dangerous to humans - foot and mouth disease, rabies, influenza.

Most microorganisms die at a temperature of 60-70 ° C, and the higher the temperature, the faster this process. Vegetable and animal fats increase the resistance of microorganisms and their spores when heated, which is taken into account in the manufacture of canned food, providing a temperature above 100 ° C and a longer exposure time. Microorganisms, as well as their spores, are killed at lower temperatures in canned food containing acids.

A detrimental effect on microorganisms during canning is phytoncides, possessing bactericidal properties and contained in garlic, horseradish, onions, as well as anthocyanins(accelerate the death of molds and yeasts) - organic dyes contained in blackcurrant, chokeberry, etc.

If the production technology and storage conditions are violated, unacceptable defects (bombing, souring, etc.) may occur in canned food and preserves. For example, bombing canned fish (preserves) - this is a defect in the form of a bulge of the bottom and lid of the can, which does not disappear after pressing.

canning- a method of preserving food products (preserving canned food), consists in the technical processing of food products to inhibit the vital activity of microorganisms spoiling food. As well as some other ways to increase the shelf life of food products.

In a broad sense, canning refers to any process that significantly extends the preservation of food in a form suitable for human consumption. The main task of conservation is to reduce the level of water activity to a minimum level, which deprives harmful microorganisms of their habitat for further development and spoilage of the product.

20. Up to half of all restaurant business costs are purchasing costs. food. The restaurant manager must ensure strict control over this process.

The following parameters are important:

• determination of standards for technical characteristics of purchased food products (commodity specifics);
• installation of tools and procedures for controlling the theft and loss of products (for example, a tool is an accounting computer program, and a procedure is a detailed instruction on accounting for the movement of material assets and periodic inventories),
• rationing the quantity of each of the products, which should always be available;
• certainty about who is responsible for procurement, both for the selection of a supplier and for compliance with the procurement procedure.
• appointment of those responsible for the acceptance (receipt), storage in the warehouse and the issuance of food products for work

Restaurant business experts note that different restaurants use different procurement process procedures, but all of them can be reduced to three integrated business procedures.

Personal hygiene of catering workers. A uniform.

Personal hygiene is a set of sanitary rules that must be observed by employees of a public catering establishment. Good personal hygiene is essential in preventing food contamination with microbes that can cause contagious diseases and food poisoning. The personal hygiene of employees enhances the culture of customer service and serves as an important indicator of the overall culture of catering establishments.

Keeping the body clean is an important hygienic requirement, so all catering employees, especially cooks and confectioners, need to keep the body clean. It is recommended to take a shower every day before work using soap and washcloths. And immediately before work, wash your hands up to the elbow. Keeping hands clean is of particular importance for food service workers who are in constant contact with food during the preparation of meals.

The appearance of the hands of catering workers must meet the following requirements: short-cut nails, clean subungual space. It is forbidden to wear watches and jewelry. The content of the oral cavity of catering workers is also of great hygienic importance, since a large number of microbes are usually found in the mouth. You need to brush your teeth daily. In case of colds, you can not start work without the appropriate doctor's opinion.

Sanitary clothing protects food products from contamination that can get into them from the body and personal clothing of workers during the cooking process.

The set of sanitary clothing for a cook and pastry chef includes: a jacket or a dressing gown, a cap or a scarf, an apron, a towel, trousers or a skirt, and special shoes.

Sanitary clothing is made from white cotton, easy-to-wash fabric.

When wearing sanitary clothing, the following rules must be observed: do not put foreign objects in the pockets of clothing; do not use pins and needles to fasten bathrobes; remove clothes before leaving the production area; store it separately from outerwear.

The sanitary regime of a public catering enterprise obliges employees to monitor the cleanliness of the workplace, equipment, inventory and utensils.

Catering workers must undergo a medical examination.

Methods and approaches to the quality of products and restaurant service.

The quality of products (goods or services) is the most important indicator of the enterprise. Improving the quality of products to a large extent determines the survival of the enterprise in market conditions, the pace of scientific and technological progress, the growth of production efficiency, saving all types of resources used in the enterprise. The growth of the quality of manufactured products is a characteristic trend in the work of the world's leading firms. Enterprises in the sphere of social and cultural services and tourism are no exception. It is far from a secret that over the past decade the number of service organizations has increased significantly, employment in this area has increased, the range of services offered has expanded, and competition has intensified.

Modern quality management of restaurant services and services consists of the following parameters:

Service management is a holistic integrated management model that serves as the basis for making effective management decisions in the field of creating and implementing services, both in a separate area and in the complex as a whole;

Service management, which is focused on the client of the restaurant and his needs;

Labor cooperation, which is a collective work aimed at a common result, partnership and functional cooperation;

Restaurant product quality management is an integral part of service management;

Personnel management, whose functions include retraining, advanced training, development of personnel of all departments of the restaurant.

conservation methods.

Canning is the processing of food products for the long-term preservation of their good quality in various ways that ensure the suppression and termination of biochemical processes occurring in products under the action of enzymes. Canning allows you to eliminate seasonality in the consumption of perishable products, expand the range of goods and increase their readiness for consumption. In addition, the use of certain preservation methods makes it possible to obtain products with other properties, i.e. essentially other goods.

There are physical, physico-chemical, biochemical and chemical methods of preservation.

Physical methods include preservation using low and high temperatures, filtration, radiant energy, ultrasound, ionizing treatment.

Physical and chemical methods are the preservation of products with table salt, sugar and drying.

Preservative factors are an increase in osmotic pressure (i.e. pressure caused by solute molecules) and a decrease in water activity. An increase in osmotic pressure is achieved by adding table salt or sugar to the product, or by concentrating the solutes of the product itself by drying it. At high osmotic pressure, water activity decreases, plasmolysis (dehydration) of microbial cells occurs, and enzymes are inactivated. The preservative effect of table salt is also due to the fact that active sodium cations and chlorine anions are attached at the site of peptide bonds of protein molecules, as a result of which the proteins of the product become unavailable for microbial nutrition.

Chemical methods. Chemical methods include the following methods:

1. Preservation with ethyl alcohol (based on the destructive effect of alcohol on microorganisms). At concentrations of 12–16%, ethyl alcohol slows down the development of microflora, and at 18% it completely suppresses it. Ethyl alcohol is used as a preservative in the production of semi-finished fruit juices, it causes long-term storage of wine and other alcoholic beverages.

2. Pickling (based on the suppression of the vital activity of microorganisms by acetic acid, which, like lactic acid, increases the active acidity of the medium). Acetic acid in an amount of 0.6 to 1.2% is added when pickling fruits, vegetables, fish, mushrooms. A small concentration of acid cannot fully guarantee the protection of the product from spoilage during storage. Therefore, fruits and vegetables marinated with a small amount of acetic acid are subjected to pasteurization or sterilization, marinating fish is combined with salting. A higher concentration of acetic acid worsens the taste of the product and is not harmless to the human body.

24. Methods for determining quality.

There are the following methods for determining the quality of goods:

Organoleptic;

Laboratory;

Expert;

Measuring;

Registration, sociological.

Organoleptic method - the quality is established with the help of the senses (sight, hearing, smell, touch, taste) in appearance, color, texture.

The appearance of the goods is determined by inspection, making up the overall visual impression.

Color set in natural light:

according to standards (roasted coffee);

by color scale (tea);

according to special recipes (wine).

Taste and smell are the most important indicators of product quality. There are 4 types of taste: sweet, salty, sour, bitter. Various substances can affect the taste, causing a sharp, burning, tart taste. Foreign taste can change the quality of the product.

The laboratory method of quality assessment requires special equipment, tools, it is more complex and lengthy, but accurate and objective. The laboratories conduct physical, chemical, physicochemical, biochemical, microbiological studies of product quality.

expert method. The decision on the quality of products is made by experts.

The expert group includes highly qualified specialists in this product - scientists, technologists, commodity experts, etc.

measuring method. With this method, the numerical values ​​of product quality indicators are determined on the basis of technical measuring instruments. The results of this method are objective and are expressed in specific units of measurement. But this method requires special equipment, chemical reagents, specially trained workers.

registration method. Quality is determined by counting the number of certain events, objects, and also based on observations.

sociological method. Quality indicators are determined based on the collection and analysis of consumer opinions. At specially organized buying conferences, sales exhibitions, tastings, consumers fill out questionnaires, which are then processed.

Comprehensive studies of the quality of goods are possible with a combination of organoleptic and laboratory methods. The quality of goods by laboratory method is determined by the average sample.

The average sample is a sample by which you can judge the quality of the entire batch of goods.

To get an average sample, they usually take a small amount of goods from different places (bottom, top, middle).

With a large number of items in a consignment, an average sample is taken from at least 10% of all items. With a small batch of goods, a sample is taken from each container. Liquid and bulk goods should be well mixed before sampling. The accuracy of determining the quality of the entire batch of goods largely depends on the correctness of taking the average sample.