Canning are ways of processing food products leading to the destruction of microorganisms that cause spoilage of products, suppression of unwanted enzymes. At the same time, canning helps to increase the nutritional value of products by adding sugar, fat, protein hydrolysates. According to the nature of the impact on raw materials, conservation methods are divided into physical, physicochemical, chemical, biochemical and combined.

Physical methods canning - cooling, pasteurization and sterilization, the use of anti-suppressing filters, ultraviolet rays, ultrasound.

Cooling - storage of food at a temperature of 0-4 ° C. The storage temperature is selected taking into account the freezing point of the product. So, the freezing point of fish is -2 ° C; milk -0.5 ° C; eggs -2.8 ° C. The duration of storage depends on the type of product and is 6-10 months for potatoes, up to 6 months for eggs, 14-20 days for meat, 36 hours for milk.

To maintain product quality, the cooling process must be fast. To do this, use such cooling methods as two-stage, ultrafast. At the same time, the vital activity of microorganisms slows down, biochemical processes are inhibited, the nutritional value of the product is preserved, although the density and viscosity of the cell juice somewhat increase.

Freezing is the process of turning the water contained in food into ice, as a result of which unfavorable conditions are created for the development of microorganisms, the rate of biochemical processes sharply decreases and frozen food is stored for a long period without changing the quality. Freeze fruits, vegetables, meat, fish, egg melange, culinary products, ice cream. When frozen, their microflora is not completely destroyed. Disadvantages of freezing - the food has a solid consistency, partially loses its flavor, their color may change, the fatty tissue turns yellow.

Pasteurization - heating the product to a temperature not exceeding 100 ° C in order to suppress some types of microflora with low thermal stability (yeast, mold), and their spores remain.

There are pasteurization: long-term - at 60 ° C for 30-40 minutes, short-term - at 85-90 ° C for several minutes. Sometimes fractional pasteurization is carried out, while in the interval between periods a vegetative form of microbes develops, which is destroyed by the next pasteurization. Pasteurize milk, puree (for baby food), juices, jams, marinades.

Sterilization - heat treatment product at temperatures above 100 ° C. This suppresses thermophilic microorganisms that cause foodborne toxicoinfections. The sterilization mode depends on the pH (acidity) of the product medium, its consistency, volume, type of container. Acidic products are sterilized at lower temperatures (105 ° C) than less acidic (120 ° C). During sterilization, denaturation of proteins and activation of enzymes occur, vitamins are partially destroyed. In the manufacture of juices, milk, the method of aseptic preservation is used, when the sterilized product is packaged under sterile conditions in a sterile (sealed) container.

A more short-term and effective conservation is with microwave currents, when the product in a hermetically sealed container is placed in an alternating current electromagnetic field. Processing time is reduced by more than 20 times.

Physicochemical methods of conservation. These include drying (solar, heated air, vacuum, infrared, sublimation), canning with table salt and sugar.

When dried in dehydrated products, the vital activity of microorganisms is suspended.

Artificial drying of products is carried out using hot air (over 120 ° C). The disadvantages of this method are the relatively long drying time (3-10 hours), weak heating of the product (up to 60 ° C). At the same time, a change in color, taste, and an almost complete loss of aroma are observed.

More advanced drying methods are sublimation, microwave currents.

The method of drying by microwave currents is distinguished by the mechanism of heat and moisture exchange between the product and the environment, as well as the mechanism of moisture transfer in the product.

Freeze drying consists in the transition of the ice of the frozen product into steam, bypassing the stage of water, moreover, the moisture content is reduced to 4%. The product is restored in 30 minutes (depending on the type).

Liquid products are dried in spray dryers. Varieties of the convective drying method are fluidized drying, osmotic dehydration. A special case of drying is drying (slow dehydration of salted products).

Preservation with table salt and sugar is based on the fact that at their high concentration the osmotic pressure increases and microorganisms cannot develop. At a high concentration of sugar and salt, the protoplasm of microbes is dehydrated due to the difference in partial pressure and plasmolysis.

Biochemical methods are based on the preserving effect of lactic acid or alcohol, which are formed in products during lactic acid and alcoholic fermentation. When fermenting and salting, add 2-5% salt, which also acts as a flavoring additive, to enhance the plasmolysis of cells, which contributes to the transition of juice (sugar) into brine. Fermentation is carried out at a temperature of 20-25 ° C until the accumulation of 0.7-0.9% of lactic acid. Putrefactive bacteria do not develop in an acidic environment. When apples are wetted, up to 1.5% ethyl alcohol can accumulate. Ethyl alcohol accumulates in grape and fruit wines as a result of yeast activity. It is noticed that the accumulation of more than 20% alcohol in wine leads to the death of microorganisms (yeast, mold).

Chemical preservation methods are based on the addition of acid (acetic, sulfurous, sorbic, benzoic), alcohol, urotropin, and nisin to food products. They are introduced into products in small quantities in accordance with the requirements of sanitary supervision. Preservation with acetic acid (pickling) is based on its bactericidal action. When preparing marinades, products are prepared in advance, blanched, poured with marinade filling containing acetic acid(0.6-1.5%), sugar, salt, spices. Higher concentrations of vinegar have a negative effect on taste. Marinades are pasteurized, except for marinated fish, the marinade of which includes sodium benzoate.

Alcohol slows down the activity of microorganisms. Alcohol is added to alcoholic beverages (10-45%), it is moistened with bread intended for long-term storage.

Preservation with sulfurous acid, its salts and sulfur dioxide is called sulphitation. The preservative effect of sulfitation is increased by lowering the temperature and increasing the acidity of the product. Fruits and berries are treated with sulfur dioxide obtained by burning it before drying. Sulfite puree in order to extend the shelf life. Potassium metabisulfite is used to store fresh grapes. Nitrites and nitrates are added to meat products to preserve their natural color.

Combined canning methods include smoking (smoke treatment in combination with salting), drying (salting with drying), canned fish salting (salting and sealing the product). When canning, the product acquires new properties (sausage, salted fish).

PRESERVATION OF FOOD PRODUCTS(lat. conservare to store, preserve) - the processing of food products, which protects them from spoilage and ensures long-term preservation.

With K., methods are used that ensure the death of microorganisms, or transfer them into a state of suspended animation. Under the influence of K., the activity of enzymes of microorganisms is also suppressed. K. allows you to create stocks of perishable food products (see), move them over long distances, regardless of climatic conditions and provide the necessary range of food products throughout the year.

Technological progress in K.'s technology has made it possible to introduce into practice methods that ensure high stability of food products during long-term storage while preserving their food, taste, biol, and properties.

The classification of methods K. is presented in the table.

Table. Classification of food preservation methods

The thermal method is the most widely used. This method K. is based on the dying off of various types of microorganisms under the influence of temperature exposure. Vegetative forms of microorganisms are mainly inactivated at t ° 60-70 ° for 1-10 minutes, with the exception of thermophilic bacteria that can survive at t 80 °. Spores are resistant to high temperatures, for which inactivation requires heating above 100 ° with an exposure of 30 minutes or more. up to 2-3 hours.

Bibliography: Food Hygiene, ed. K. S. Petrovsky, t. 1, M., 1971; Lob and-n about in D.I. Technology of production of products Catering, M., 1967; Petrovsky KS Food hygiene, M., 1975; Commodity Science of Food Products, ed. F.V. Tserevitinova, t. 2, 4, M., 1949.

K. S. Petrovsky.

Chemicals used for preserving food must be harmless and not alter the taste, color or odor of the food.

Currently, the following chemicals are allowed for canning in the Republic of Belarus: ethyl alcohol, acetic, sulfurous, benzoic, sorbic acids and some of their salts, boric acid, urotropin, some antibiotics, etc.

Preserving with ethyl alcohol. This method of canning is based on the destructive effect of alcohol on microorganisms. Ethyl alcohol is used as a preservative in the production of semi-finished fruit juices. At concentrations of 12-16%, ethyl alcohol retards development, and at 18%, it completely suppresses the vital activity of microflora. Juices with an alcohol concentration of 25-30% are used in the production of alcoholic beverages, and with a concentration of 16% in the production of soft drinks.

Pickling. This is a preservation method based on increasing the acidity of the medium by adding acetic acid. At concentrations of 1.2-1.8%, acetic acid inhibits the activity of many microorganisms, and primarily putrefactive. Microorganisms are sensitive to changes in the pH of the medium, because this leads to a change in the surface amphoteric structures of the cell and, as a result, to a violation of the cellular balance and subsequent cell death.

To enhance the preserving effect, pickling is sometimes combined with other types of canning: pasteurization, salting, storage at low temperatures. In pasteurized pickled products, the acetic acid content is reduced to 0.8-1.2%, which has a beneficial effect on their taste.

In the production of pickled products, table vinegar is usually used, containing 3-6% acetic acid, or food vinegar essence with 70-80% acetic acid. For the production of marinades, biochemical vinegar (alcohol, wine, fruit and berry, etc.) is more desirable, since vinegar from the essence has a sharp taste. In addition to vinegar, salt, spices, sugar are added to the marinade filling.

Fruits, vegetables, mushrooms, fish, etc. are marinated. Prepared fresh, blanched or fried foods are poured with marinade filling, the jars are rolled up and pasteurized at a temperature of 90-100 o C. When marinades are stored, they ripen, which lasts from 20 days to 2 months. During the ripening process, acetic acid, sugar and salt diffuse into the products, under the action of acids, about 75% of sucrose is converted into invert sugar, and the taste of the product improves. Store marinades at low temperatures (0 to 4 ° C), since many molds absorb acetic acid and can cause spoilage of food.

Preserving with acids. The preservation of food with sulfurous acid, its salts and sulfurous anhydride is called sulphitation. Sulfurous acid is a strong antiseptic, inhibits the activity of molds and bacteria; yeast, especially wine races, are more resistant to its action. This acid is used for the day of canning fruits, berries, fruit and vegetable semi-finished products. The effectiveness of the action of sulfurous acid depends on the temperature and pH of the environment. With an increase in acidity, the degree of dissociation of sulfurous acid decreases, and thus more undissociated molecules with a preservative effect are retained.

Sulfitation is carried out different ways... On the day of disinfection of premises, barrels, tanks, gaseous sulfur dioxide, which is formed during the combustion of sulfur, is used. Sulfur dioxide can be supplied from steel cylinders in which the liquefied gas is under pressure. Sulphitation is also carried out with a 5-6% aqueous solution or with the help of solutions of salts that emit sulfur dioxide.

In addition, sulfur dioxide can be used by placing sodium bisulfite in boxes of grapes (or other berries). Slowly decomposing or storage time and reacting with the water released by the grapes, sodium bisulfite forms a small amount of sulfurous anhydride, which is quite sufficient to prevent berry spoilage.

Sulfurous acid inactivates enzymes, suppresses the respiration processes of fruits and vegetables, thereby lengthening their shelf life and protecting them from darkening.

When sulfided products are heated, sulfurous acid is rapidly decomposed with the release of gaseous sulfur dioxide. The process of its removal from the product - desulphitation is based on this property of sulfurous acid. Sulphitated products are used only for further processing after removal of sulfurous acid. Sulfur dioxide acts on the respiratory organs and irritates the mucous membrane, therefore, in high concentrations, it is dangerous to humans.

The most commonly used salts of sulfurous acid include sodium bisulfite (NaHSO3), potassium bisulfite (KHSO3), sodium pyrosulfate (Na2S2O3), sodium sulphide (Na2SO3) and potassium sulphide (K2SO3).

Residual content of sulfur dioxide in dried vegetables and fruits should not exceed 0.01-0.06%, in fruit and berry purees - 0.2, in juices - 0.12-0.15%.

Benzoic acid (С6Н5СООН) and benzoic acid sodium are used for canning С6Н5СООН) fruit and berry semi-finished products, juices, kilka.

Benzoic acid is poorly soluble in water; therefore, its salt, benzoic acid sodium (С6Н5СООNa), is usually used for canning. This acid suppresses the vital activity of yeast, acts less intensively on butyric acid bacteria, little on acetic acid and almost does not affect development lactic acid bacteria and mold. The strongest antiseptic effect of benzoic acid and benzoic acid sodium is manifested in an acidic medium at pH 2.5-3.5. The disadvantage of benzoic acid as a preservative is its negative effect on the taste of the preserved product; it also causes turbidity of plant materials containing protein. Therefore, the amount of benzoic acid added to food is strictly regulated and does not exceed 70-100 mg per 100 g of product.

Sorbic acid (C6H8O2) and its salts are strong antiseptics and are harmless. They are used for preserving fruit juices, purees, marinades and other low pH products.

Sorbic acid belongs to unsaturated and represents odorless white or slightly yellowish crystals with a slightly acidic taste. It inhibits the activity of fungi and yeast and has little or no effect on bacteria. This acid is hardly soluble in cold water, therefore, it is more often used in the form of water-soluble salts - sodium or potassium sorbate. The advantage of sorbic acid over other preservatives is that it does not change the taste and smell of canned food.

The amount of sorbic acid allowed for preserving various products is not the same and ranges from 0.05-0.1% ( soft drinks, juices) up to 0.5% (semi-smoked sausages).

Fruit and berry juices with 0.05% sorbic acid are stored for 8 months without the use of cold. Sorbic acid is impregnated with paper and introduced into the composition of films used for packaging food products. With a solution of sorbic acid, loaves of semi-smoked sausages are treated to lengthen their shelf life. Small additions of sorbic acid inhibit alcoholic fermentation in the production of semi-sweet wines.

Preservation with boric acid, brown and urotropin. Boric acid (H3BO3), borax (Na2B4O7 * 10H2O) 0.3% concentration and urotropin are used to preserve granular sturgeon caviar... Boric acid is also used as a preservative in the production of melange.

Ethylene-releasing drugs - 2-chloroethylphosphonic acid - etrel and its derivatives: hydrel, dehydrel, etc. - are inhibitors of growth processes and are used to prevent the germination of potatoes, root crops and onions during storage, they increase their resistance to phytopathogenic microorganisms. Vegetables are treated with a 0.5% aqueous solution of the drug before placing them for long-term storage. The drugs are harmless: in a neutral environment, they decompose to ethylene, phosphoric acid residues, nitrogen and chlorine ions.

To prevent the germination of vegetables, it is allowed to use an aqueous solution of sodium salt of maleic acid hydroside, which is used to process vegetables 2-4 weeks before harvesting, as well as methyl ester of naphthylacetic acid in the form of dust, with which potatoes are dusted in spring.

Preservation with antibiotics. Antibiotics that can be used in Food Industry, along with a pronounced antimicrobial effect, should have a low resistance to the external environment, and also be easily inactivated during heat treatment of products. Chlortetracycline (biomycin), nystatin and nisin are currently used in the food industry.

Chlortetracycline (biomycin), when heated, forms the isochlortetracycline isomer, which is harmless to the human body and has bacteriostatic properties. This antibiotic acts on mucus-forming microorganisms. In the food industry, it is used for processing meat (irrigate the surfaces of carcasses or inject intravenously 1 hour before the slaughter of the animal) and fish transported over long distances. For the processing of cod fish, biomycin ice is used, i.e. ice containing chlortetracycline in an amount of not more than 5 g per 1 ton of product.

Nystatin is an antibiotic that works against yeast and fungi that cause mold in meat. In the food industry, it is usually used in combination with chlortetracycline for more efficient processing of meat carcasses. The concentration of chlortetracycline in solutions should not exceed 100 mg, and the concentration of nystatin - 200 mg per 1 liter of water.

Nizin is used in the production of dairy and fruit and vegetable canned food. It is a polypeptide formed during the metabolism of lactic acid streptococci. The composition of nisin includes various amino acids: methionine, leucine, valine, lysine, histidine, proline, glycine, serine, etc. Nisin inhibits the growth of various staphylococci, streptococci, clostridium, etc. In the human body, nisin is rapidly destroyed without negative effects. An important feature of nisin is its ability to reduce the resistance of packs of heat-resistant bacteria to heating, which makes it possible to reduce the sterilization regime.

Herbal antibiotics are phytoncides. Of these, allyl mustard oil, extracted from mustard seeds, is most applicable for canning. The introduction of this antibiotic into marinades in an amount of 0.002% allows them to be preserved for a year without pasteurization, but provided that the can is sealed tightly.

Gas preservation. To maintain quality in lengthening the shelf life of food products, ozone is used, which has disinfecting and deodorizing properties. As a strong oxidizing agent, ozone inhibits or stops the development of bacteria and molds and their spores, both on the surface of the product and in the air. The effectiveness of ozone depends on the concentration, the relative humidity of the air, as well as on the initial microbial burden of the product.

It is recommended to use ozone for disinfection and deodorization of air in refrigerating chambers, for disinfection of vehicles, equipment and containers. Ozonation must be carried out with high concentrations of ozone (25-40 mg / m3) for 12-48 hours, which reduces the contamination of the chambers by more than 90%.

For the processing of food products (meat, sausages, cheeses), the concentration of ozone should not exceed 10 mg / m3, since its higher content causes a deterioration in their presentation, taste and nutritional value.

Carbon dioxide in high concentrations inhibits or completely stops the vital activity of many microorganisms.

The effectiveness of the effect of CO2 on microorganisms depends on its concentration in the atmosphere, air temperature and the type of microorganisms. A delay in the development of molds occurs at a CO2 concentration of about 20%, and at 40-50% their growth almost completely stops. Bacteria are more resistant to CO2. Some anaerobic hydro-forming bacteria can thrive at 60 - 80% CO2.

However, for the storage of food products, the concentration of CO2 should not exceed 20-22%, since a higher content of carbon dioxide causes a deterioration in their quality. Therefore, it is advisable to use CO2 in combination with refrigeration. In this case, the shelf life of meat, fish, poultry and sausages at a temperature of 0 ° C and 10-20% CO2 increases by 2-3 times in comparison with conventional refrigerated storage.

In the canning industry, refrigerated storage of grape juice in tanks with a capacity of 20-50 tons in an atmosphere of CO2 has become widespread.

Canning methods

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

The choice and application of food preservation methods is determined by their influence on the raw materials and the quality of the resulting canned product. All preservation methods are reduced to the destruction of microbes and the destruction of enzymes, or to the creation of unfavorable conditions for their activity.

Physical methods of food preservation

Physical methods are based on the use of high and low temperatures, ultrasound, ultraviolet and infrared rays, ionizing radiation, etc.

Low temperature preservation consists in suppressing the vital activity of microorganisms, reducing the activity of enzymes, and slowing down biochemical processes.

Food products are a favorable environment for the development of microorganisms. Depending on the relationship to temperature, microorganisms are divided into:

• - thermophilic, developing at 50-70 ° С;
• - mesophilic - at 20-40 ° С;
• - psychrophilic - from +10 to -8 ° С.

Thermophiles include spore forms of microorganisms, the spores of which are particularly resistant, as a result of which they can tolerate sterilization. Mesophiles include many putrefactive bacteria that cause spoilage. food products at positive temperatures, as well as all pathogenic and toxigenic forms of bacteria. Low temperature preservation includes refrigeration and freezing.

Cooling - refrigeration processing of products and raw materials at a temperature close to cryoscopic, that is, to the freezing point of the cell fluid, which is due to the composition and concentration of dry substances. Different food items have different cryoscopic temperatures. For example:

• - for meat it is in the range from 0 to 4 ° С, for fish - from -1 to 5 ° С;
• - for milk and dairy products - from 0 to 8 ° С;
• - for potatoes - from 2 to 4 ° С;
• - for apples - from 1 to -1 ° С.

Cooling of foodstuffs has one common goal - to lower their temperature to a given final temperature, at which biochemical processes and the development of microorganisms are delayed. Storage at low positive temperatures ensures the preservation of food products in a sound condition for a sufficiently long time. So, meat, fish, poultry can be stored for one to two weeks, eggs - for several months, and some fruits and vegetables - until the next harvest.

The most common industrial cooling methods are those that are carried out by the transfer of heat by convection, radiation, and heat exchange during phase transformation. The cooling medium is air moving at different speeds. As a rule, cooling is carried out in refrigerating chambers equipped with a device for distributing cooled air.

Cooling methods based on convective and radiative heat transfer are characterized by low product moisture losses during cooling. This is the cooling of products in liquid media, as well as packed in impermeable casings. In a liquid medium, fish, poultry, some vegetables are cooled, in casings and packages - sausages, semi-finished products, culinary, confectionery and etc.

Cooling - the best way preservation of nutritional value and organoleptic properties of the product, but it does not provide a long shelf life. So, chilled milk and dairy products are stored for 36-72 hours, meat - 15-20 days, fish - from 2 to 15 days. At the same time, some fruits and vegetables last up to 5-10 months.

Freezing is the process of lowering the temperature of food products below the cryoscopic temperature by 10-30 ° C, accompanied by the transition of the water contained in them into ice. Freezing provides a better shelf life than refrigeration, and many frozen foods can be stored for up to a year.

The lower the temperature (from -30 to -35 ° C), the faster the freezing rate, while in the cells and in the intercellular space, tissues are formed small crystals ice and fabrics are not damaged. When frozen slowly, large ice crystals form inside the cell, which damage it, and when thawing, the cell sap is lost.

Microorganisms, depending on their reaction to negative temperatures, are divided into sensitive, moderately resistant and insensitive. Vegetative cells of molds and yeasts are especially sensitive to negative temperatures. Gram-negative bacteria belonging to the genera Psendomonas, Achromobaeter and Salmonella are easily killed. Resistant to low temperatures gram-positive microorganisms and spore forms of bacteria.

The quality of a frozen product is determined by many factors: the condition of the product itself, the presence of biologically active substances, the method, the speed of freezing, the presence of its container and packaging material, etc.

Freeze food products in freezers of various types (chamber, contact, tunnel, etc.). High efficiency is achieved when freezing small or crushed products in bulk on cooling surfaces or in a "fluidized" bed - by the fluidization method. At the same time, a high speed of cold air supplied under pressure is ensured, which washes from all sides the products weighed in the flow.

Freezing in boiling refrigerants (liquid nitrogen, freon, etc.) belongs to ultrafast.

Preserving with high temperatures is carried out to destroy microflora and inactivate enzymes of food products. These methods include pasteurization and sterilization.

Pasteurization is carried out at temperatures below 100 ° C. At the same time, spores of microorganisms persist. Distinguish between short pasteurization (at 85-95 ° C for 0.5-1 min) and long-term (at 65 ° C for 25-30 min). Pasteurization is mainly used to process products with high acidity (milk, juices, compotes, beer). At a pH value below 4.2, the thermal resistance of many microorganisms decreases.

Sterilization is the heating of food products at temperatures above 100 ° C. In this case, the microflora is completely destroyed. Sterilization is used in the production of canned food in sealed metal or glass containers. The sterilization mode is determined by the type of product, time and temperature. The sterilization regime for canned food with low acidity should be more stringent than canned food with high acidity. Lactic acid has a more depressing effect on microorganisms than citric acid, and citric acid is more depressing than acetic acid. The presence of fat reduces the sterilizing effect.

Sterilization is usually carried out at a temperature of 100-120 ° C for 60-120 minutes. (meat products), 40-120 min. (fish), 25-60 min. (vegetable), 10-20 min. (condensed milk) with steam, water, air, steam-air mixture using a variety of equipment (rotary, static, continuously operating, etc.).

During sterilization, the nutritional value of the product decreases, its taste properties as a result of hydrolysis of proteins, fats, carbohydrates, destruction of vitamins, some amino acids and pigments.

The use of high-temperature short-term sterilization with a simultaneous decrease in the duration of the process is promising. Basically, this treatment is used for meat and dairy products at a temperature of 120-125 ° C for 35-45 minutes. in rotary mode. When sterilizing canned food with currents of ultra-high and industrial frequencies, the contents of the can quickly and evenly warmed up throughout the entire volume, the duration of the process is reduced by 5-7 times. This is also a promising way. Microwave sterilization at a temperature of 130 ° C ensures the preservation of amino acids to a greater extent, higher digestibility of proteins and organoleptic properties product. Such processing is based on the interaction of electromagnetic fields with an oscillation frequency of 1 billion Hz and higher with dipole molecules of various substances, primarily water. Flame sterilization reduces the time by 4-5 times heat treatment compared to autoclaving. Heating of the cans is achieved by rotating them in the flame of the burners at a speed of 0.75 s 1 for 10 minutes.

In connection with the introduction into practice of the modern "wow in box" packaging system for food products, aseptic preservation has become widespread. Classic version aseptic preservation of goods in the "wow in box" system consists of three stages:

• - sterilization of the product at a temperature of 130-150 ° C followed by cooling;
• - sterilization of containers by radiation treatment;
• - packaging of a sterile product in a sterile container under aseptic conditions.

Such processing is universal and is used for liquid and viscous products (milk, juices, wines, pasta, etc.).

Preservation by ionizing radiation is called cold sterilization, or pasteurization, since the sterilizing effect is achieved without increasing the temperature. For the processing of food products, b-, c- radiation, X-rays, a stream of accelerated electrons are used. Ionizing radiation is based on the ionization of microorganisms, as a result of which they die. Preservation by ionizing radiation includes radiation sterilization (raappertization) of products for long-term storage with pasteurizing doses.

Irradiation of products is carried out in inert gases, vacuum, with the use of antioxidants, at low temperatures.

A significant disadvantage of ionizing food processing is the change chemical composition and organoleptic properties. In industry, this method is used for the processing of containers, packaging, premises.

Preservation by ultrasound (more than 20 kHz). Ultrasonic waves have high mechanical energy, propagate in solid, liquid, gaseous media, cause a number of physical, chemical and biological phenomena: inactivation of enzymes, vitamins, toxins, destruction of unicellular and multicellular organisms. Therefore, this method is used for milk pasteurization, in the fermentation and non-alcoholic industries, for the sterilization of canned food.

Irradiation with ultraviolet rays (UVL). This is irradiation with rays with a wavelength of 60-400 nm. The death of microflora is due to the adsorption of UV light by nucleic acids and nucleoproteins, which causes their denaturation.

Pathogenic microorganisms and putrefactive bacteria are especially sensitive to UV light. Pigment bacteria, yeast and their spores are more resistant to UV light. The use of UVL is limited due to its low penetrating power (0.1 mm). Therefore, UFL is used for surface treatment of meat carcasses, large fish, sausages, as well as for disinfection of containers, equipment, refrigerator chambers and storage facilities.

Use of suppressing filters. The essence of this method is the mechanical separation of the product from the causative agents of spoilage using filters with microscopic pores, i.e., the ultrafiltration process. This method allows you to save as much as possible nutritional value and organoleptic properties of goods and is used for processing milk, beer, juices, wine and other liquid products.

Home canning methods

Vegetables, mushrooms and other plant products contain 85 percent or more of water (in cucumbers, for example, the amount of water reaches 96%). Thanks to this, all plant products are an excellent environment for the development of various microorganisms.

During growth and development, vegetables and mushrooms are more resistant to microbial contamination. Some protection against infection is the whole, intact skin, which prevents the penetration of microbes into the internal tissues. When collecting, the integrity of the integumentary tissues is disturbed to one degree or another, and at the same time, resistance to infection is significantly reduced, since microbes (yeast, mold, putrefactive bacteria) can penetrate into the inner tissues of vegetables and, rapidly developing, destroy them.

Thus, for a long time to keep plant raw materials in fresh v normal conditions impossible.

However, the terms of consumption of vegetables and mushrooms can be significantly extended if they are previously subjected to some special types of processing, which will create unfavorable conditions for the development of microbes.

These types of processing are collectively called canning. Several canning methods are known. With some, complete destruction of the enzyme systems present in the plant product and the death of microorganisms is achieved, and the possibility of subsequent ingress of microbes into the product is eliminated. These methods are the most radical, and the resulting canned food is stored for a long time.

With other types of canning, canned foods are obtained that can only be stored for a limited time.

The most common storage and processing methods are as follows.

Canning with sugar. When cooking fruits with big amount sugar (about 1 part of the fruit for 1 part of sugar) a product with a high sugar concentration is obtained - 60 - 65% and higher (jam, jam, jam, jelly, etc.) In this case, microbes cannot use sugar for nutrition, therefore, they they cannot develop, but they do not die either. If you add a little water to the resulting jam or jam, favorable conditions will again be created for the development of microbes and spoilage of the product.

Pickling. Acetic acid serves as a preservative for pickling, a small concentration of which is already sufficient to suppress the vital activity of microorganisms. In this case, acetic acid (in the form table vinegar or food vinegar essence) are added to the filling or directly to vegetables prepared for canning and already packaged in containers.

Part marinade filling also includes sugar, table salt, various spices:

• Bay leaf
• black pepper and allspice (peas)
• cinnamon
• Carnation
• coriander
• star anise
• garlic
• dill herb and seeds
• celery leaves
• tarragon
• parsley
• black currant
• basil
• marjoram, etc.

Spices give the marinades a specific aroma and taste. Essential oils, included in their composition, also have preservative properties, prevent the reproduction and development of microorganisms.

High temperature canning. At a temperature of 70 - 100 ° C, most microbial cells die. The most effective preservation method is based on this phenomenon: the products are exposed to high temperatures and then any possibility of subsequent ingress of microbes is eliminated. The latter is achieved by means of a hermetic seal.

When preserving under the influence of high temperature, two options are possible: heating at temperatures below 100 ° C (for example, 80 °, 90 °, 95 °) and heating at a temperature of 100 ° C and above. The first option is called "pasteurization", the second - "sterilization".

It should be borne in mind that sterilization at temperatures above 100 ° C is possible only under factory conditions. The maximum temperature that can be reached at home canning, does not exceed 100 ° C.

Sterilization is a more efficient way of preserving than pasteurization. Pasteurization is allowed only in cases where the temperature of 100 ° C (and above) negatively affects the quality of canned food (for example, they are boiled over) or when canned food has a sufficiently high acidity. In all other cases, sterilization should be used.

Canning under the influence of high temperature at home is carried out as follows. The prepared raw materials are placed in a suitable glass container, which is then placed in a vessel (pan, basin) with warm water. The water is heated to the required temperature, at which the product is kept for a strictly defined time.

Since when canning at home it is impossible to create a temperature above 100 ° C, it is necessary to pay attention to the fact that some types of microbes form spores (compacted formations) - modified living cells, which, when favorable conditions occur, pass into their usual (vegetative) form.

Spores are more resistant to high temperatures, especially those of the causative agent of botulism. These microbes produce a potent poison (called canned poison). They develop only in an oxygen-deprived environment. The presence of acids in the environment prevents their development. Therefore, at home, it is recommended to make canned food only from vegetables that contain a sufficient amount of acid. When processing weakly acidic raw materials, food acids should be added to canned food: citric, tartaric, acetic, lactic, etc.

Some types of vegetables ( tomatoes, sorrel, rhubarb) contain a significant amount organic acids... Such raw materials can be preserved by sterilization without the addition of acid. Some vegetables are low in acidity. Such products (for example, carrots, green peas, etc.) cannot be made at home. natural canned food(without adding acid, salt and other preservatives).

Drying. Drying, that is, removing moisture from vegetables and mushrooms, can also create unfavorable conditions for microbes. It is not necessary to completely remove moisture. When dried, little water remains in the products (12-14 g), so that although microbes do not die, they cannot develop.

When moisture is completely removed from the products, they must be stored in a hermetically sealed container, since otherwise they will re-absorb moisture from the air.

Freezing. Prepared fruits are subjected to quick freezing at a temperature of minus 18-25 ° C and below. Store frozen. Before use, they must be kept at room temperature for 3-4 hours. It is not recommended to wash or defrost vegetables in water, as this deteriorates their taste and loses nutrients. Quick-frozen vegetables are cooked three times faster than fresh ones.

Salting, pickling and soaking. Lactic acid, which is formed in the product as a result of fermentation, serves as a preservative for salting, pickling and soaking. The fermentation of sugar into lactic acid (lactic acid fermentation) occurs under the influence of lactic acid bacteria, which are always present in fresh plant materials. Under favorable conditions, they begin to develop rapidly, converting the sugar contained in the raw material into lactic acid. It is even better with these types of processing to add a pure culture of lactic acid bacteria. Table salt, which is added during these types of processing, also has a preservative effect.