CANNING

CANNING, CANNED GOODS (from Latin conservare - to preserve). Canning is the processing of food and flavoring substances with the aim of preserving them from spoilage for short or long periods. Canned goods usually refer to meat, fish, dairy, fruit and vegetable products sealed in hermetically sealed tin cans and sterilized; in a broader sense, the term canned goods implies all kinds of products specially processed for long-term storage; these include, for example, salted meat, ham, sauerkraut, marinades, etc. C. was already used by ancient peoples, but it began to receive the greatest distribution only in the 19th century, when due to the improvement of C. methods, canned goods began to be used for food supplies for troops and sea transport, and when many food products available in excess in certain areas began to be utilized to improve the nutrition of the population in other areas. Various methods of C. are aimed either at destroying putrefactive and other microbes in the product and preventing new infections, or at creating conditions under which the flora of the product is limited to one degree or another and its effect on the components of the latter is reduced. Depending on the type of product and the tasks set in individual cases, various methods of C. are used, and whenever possible, efforts are made to preserve the external and taste qualities of the fresh product and often to give it valuable taste qualities (smoking, salting, etc.). The cost of the method often plays a large role in choosing the method of C. The most common methods of preservation are: 1) the use of low temperatures (cooling, freezing), 2) the use of high temperatures (pasteurization, sterilization), 3) dehydration (drying, curing), 4) the use of lactic acid fermentation (pickling, brining), 5) the use of chemical agents (salt, vinegar, so-called "preservatives"), 6) smoking. 1. Use of low temperatures. Although low temperature does not kill microorganisms and only delays their development, it is nevertheless a very favorable condition for the long-term storage of food products. Thanks to the use of artificial cold at present, perishable products (meat, fish) are well preserved for many months and even years and transported without any spoilage in hot weather over long distances. With proper management, neither the color nor the taste and nutritional properties of the product undergo significant changes. Preservation with the help of artificial cold is used in the form of cooling or in the form of freezing. Cooling is often used to preserve meat, which after slaughter is placed in the form of dressed whole carcasses for 8-10 hours to cool to 15° in special chambers ("cooling chambers"), and then transferred to proper refrigeration chambers at +2° to +4°. Meat cooled with all precautions can be preserved in refrigeration chambers without any spoilage for about 2 months. When released from refrigeration chambers, the meat gradually warms up and is brought to the external temperature, taking on the appearance of fresh meat. During storage, cooled meat loses about 5-6% of its weight, which is entirely due to "drying out", i.e., loss of water. For longer storage of meat, freezing is used with the help of natural cold in areas where there are cold winters, or with the help of artificial cold. The export of frozen meat is best organized in Australia, where carcasses are frozen at -6° and loaded at night onto ships with refrigeration chambers cooled to -18°. Freezing of fish in the USSR during winter fishing is done with the help of natural cold; in warm weather - with a cooling mixture of ice and NaCl or in special refrigerators. When mixing equal parts of crushed ice or snow with salt, cooling can be achieved to -15° to -18°. In refrigerators, the temperature is lowered by refrigeration machines. In recent years, in some procurement areas, the Ottenzen method of freezing fish has been partially used: immersion in a NaCl solution cooled to -15°, in which small fish becomes completely frozen in 1½-2 hours. Frozen meat before being released from refrigeration chambers must undergo gradual thawing and warming to the external temperature, because with rapid thawing it becomes wet on the surface, acquires a flabby consistency and under ordinary conditions spoils quite quickly. Frozen meat, regardless of the methods of freezing and thawing, is inferior in taste and aroma to freshly killed meat. 2. Use of high temperatures. For preserving products, heating them in the form of pasteurization and sterilization is used. Pasteurization consists of heating the product at a temperature sufficient to destroy the vegetative forms of bacteria and not changing the good properties of the product. Pasteurization is mainly used for C. of liquid products (milk, beer, grape and other fruit-juices). Heating is carried out at 65-70° for 15-20 minutes followed by rapid cooling to prevent the development of spore forms. Pasteurized products do not have great stability during storage. A much more reliable method of C. of products is their sterilization by high temperature; such canned goods can be preserved without spoilage for an indefinitely long time. The idea of sterilization was first implemented in France in 1804 by Appert for the preparation of meat. This method became widespread only after the replacement of the glass vessels used by Appert with containers in the form of tin cans from so-called English tin. The preparation of canned goods consists of two main operations: "canning" the product in the tin and sterilization in an autoclave. The latter operation is carried out at 100-115° depending on the nature of the product. For fish and especially delicate varieties of fruits, lower temperatures are used than, for example, for meat. The preparation of meat canned goods consists of the following. Meat carcasses after veterinary inspection are dressed, and the soft parts of the carcass are separated from the bones, freed from tendons and excess fat and placed in tins, to which pepper, salt, bay leaf, onion and a little fat are added. Tins with meat are sealed with a lid on special machines and then lowered into hot water for testing for hermeticity; those found to be non-hermetic are rejected, and those that have passed the test are placed in autoclaves, where they are kept at 112° for 1½ hours. After sterilization, the tins are placed in thermostatic rooms at 30°, where they are kept for up to 3 weeks. After this period, the tins are inspected, those found to be swollen are rejected. 3. Dehydration. C. by means of drying is based on the fact that the removal of moisture from the product creates conditions unfavorable for the development of microorganisms present in the product. Drying is done by various methods and is used for C. of fish, vegetables, fruits, milk, etc. In summer in a hot dry climate, the warmth of the sun's rays and dry wind are used for drying. The negative side of air drying is the contamination of the product with dust and insects. For drying, certain varieties of vegetables without signs of spoilage are selected. Vegetables are cleaned, chopped and some of them are blanched, i.e., immersed in boiling water or treated with steam. Blanching fixes their natural color and speeds up drying. Drying is carried out in special dryers at different temperatures and for different times depending on the variety of vegetables: cabbage - 8-10 hours at 50-60°, greens - 3-6 hours at 50-75°, beets - 4-8 hours at 80-90°, potatoes - 8-10 hours at 75-80°, etc. Dried vegetables after unloading from the dryer have a moisture content of about 4-6%, but due to hygroscopicity, it increases to 10-12%. For drying fruits, both natural heat from the sun and special dryers of various systems (fire drying) are used. Solar drying of fruits is widely used in Italy, California, Central Asia, Transcaucasia. Often before drying, fruits are fumigated with sulfur dioxide in both solar and fire drying, which on the one hand improves the color of the canned product, and on the other increases its strength. In California fruits, the amount of SO2 sometimes reaches 0.25%. Air drying is also widely practiced in the preparation of various kinds of fish, especially cod, bream, roach, smelt, smelt. Salted fish are dried in the shade under wooden awnings for up to 2½ months. Smelt are dried in special ovens on the floor, where a layer of salt or sand is placed under the fish, and during the drying process they are turned over in the oven several times, which is why salt or sand is often found in the dried smelt for sale. Dry milk, milk powder, is prepared from both whole and skim milk, most often in Krauze apparatus and others. The apparatus consists of 2 metal cylinders rotating towards each other, fixed at a distance of 1-2 mm from each other and heated from the inside by steam. Milk is poured onto the surface of the cylinders in a thin stream and turns into a dry film.

The film is separated from the cylinders and crushed into a fine powder. Another method for preparing dry milk is spraying a thin stream in a vacuum. Dry milk is used in baking and confectionery production. 4. Through lactic acid fermentation, sauerkraut is preserved—a food product widely distributed in the USSR. Fresh white cabbage is finely chopped, placed in wooden utensils with the addition of salt, put in a cellar, and pressed down with a wooden circle with stones placed on it. After a few days, the cabbage gives off much juice, part of which must be removed (otherwise the cabbage will be bitter). Soon the fermentation process begins, caused by yeast and bacteria acting in symbiosis (Bac. brassicae acidae). The yeast form alcohol from sugar, while the bacteria form acids (ethylidene lactic, acetic, and butyric). The interaction of alcohol and acids produces esters that give sauerkraut its specific aroma. During fermentation, gases are also formed: CO₂, H₂, etc. The formation of lactic acid, which has a preserving effect, also occurs when pickling cucumbers, which are poured with a 5% NaCl solution. After 2-3 weeks of pickling, the acidity of the liquid reaches its highest degree (0.49-0.90% in lactic acid). The more lactic acid, the tastier and more durable the cucumbers. Upon reaching maximum acidity, it begins to decrease and after several months may drop to 0, and the brine may even become alkaline; the cucumbers acquire an unpleasant rotten taste. The causative agents of lactic acid fermentation in cucumbers, along with other microbes, are considered to be: Bact. acidi lactici, Bact. coli, Bact. Guntheri. Table salt during the pickling process ensures the correctness of the process and increases the taste qualities and durability of the product. About 5% salt is added; a larger amount (6-8%) impairs the taste and slows down the fermentation process. The preservation of apples, lingonberries, cloudberries, etc., is also based on the development of lactic acid fermentation. Apples or other fruits are placed in clean utensils, poured with boiled water in which a certain amount of sugar, salt, sometimes vinegar is dissolved, cherry or blackcurrant leaves are added, and stored on ice or generally in a cool place where the fermentation process gradually develops. Preserved lingonberries and cloudberries are also well preserved due to the presence of benzoic acid in them. 5. Application of chemical means. Among the methods of treating products with antiseptic substances, salting (meat, fish) holds first place in terms of prevalence and industrial significance. It is based on the removal of water from the meat by salt and its antiseptic properties. Salt is a weak antiseptic; it exhibits an effective anti-putrefaction action only when the meat or fish is saturated with it. In the lower concentrations used under normal salting conditions, it only slows down the development of microorganisms that cause deep decomposition of protein in the product being preserved. Meat is salted in various ways, but dry and wet salting are more commonly used. In the dry method, the meat is cut into pieces, washed in water, and then rubbed on all sides with clean coarse salt. After this, the pieces are placed in barrels and other utensils, arranging them in layers and sprinkling with salt. Salt is taken in amounts of 1.25-1.5 kg per 20 kg of meat. In addition to salt, small amounts of saltpeter (2%), sugar (2%), and various aromatic substances (pepper, cloves, cinnamon, bay leaf, juniper berries, etc.) are used in salting. Saltpeter gives the meat a red color, sugar gives the salted meat a more delicate taste. A weight is placed on the salted meat and the barrel is left in a cold place. After some time after salting, the meat releases juice, with which 15-20% of its components (water, proteins, extractive substances, and salts) are extracted from it. In wet salting, the prepared pieces of meat are placed in a saturated salt solution, which should be prepared in freshly boiled water. Spices broth is added to the brine. It is necessary to ensure that the top pieces are covered with brine and do not come into contact with air, as otherwise the meat will begin to spoil. Salting continues from 2 to 6 weeks, depending on the size of the meat pieces, the strength of the brine, and the temperature of the room. For pork (ham), injection of brine with a hollow needle is often used. After injection, the meat is rubbed with salt again and kept for 10-12 days. The Morgan method is also practiced: pumping brine through the aorta into the circulatory system of the carcass of a freshly killed animal. Butchering is done soon after replacing the blood with brine, which quickly (10-15 min.) and evenly salts the meat. There are many recipes for salting meat, differing in the amounts of substances they contain. The most common recipes are as follows: 1) for 100 parts of salt, take 1 part of saltpeter and 2 parts of sugar; the meat pieces are rubbed with this mixture and placed in vessels; 2) for 20 kg of meat, take 1,000-1,500 g of salt, 125 g of saltpeter, and 125 g each of pepper and bay leaf; 3) for 20 kg of meat, take 3 kg of salt and 125 g of saltpeter; the meat is rubbed with this mixture, placed in barrels, sprinkled with a mixture of pepper, cloves, cinnamon, and other spices; 4) for preparing brine, take 30 parts of salt, 1½ parts of saltpeter, and 1 part of sugar per 100 parts of water; 5) for 60 liters of boiled water, take 6 kg of salt, 200 g of saltpeter, and 100 g each of pepper and bay leaf. With different methods of salting meat, saltpeter (potassium nitrate) is usually added to the salt, which under the influence of complex chemical and bacterial processes is partially reduced to nitrites. The red color characteristic of salted meat occurs only after a sufficient amount of nitrites has accumulated in it. This circumstance, along with the removal of saltpeter reserves for the needs of the military department, led representatives of the German meat industry to consider replacing saltpeter with nitrites; however, by the law of 1916, this replacement was prohibited in Germany from the point of view of protecting public health, as nitrites are harmful to health substances. Subsequently, several scientific works appeared in Germany, which on the one hand confirmed the observation that nitrite salting shortens the duration of salting, and on the other hand proved that while with saltpeter salting the amount of nitrites in the meat increases over time, with nitrite salting the opposite phenomenon is observed. Thus, a certain rationality of switching to nitrite salting was proven from both the economic point of view (acceleration of the salting process) and the sanitary point of view. By order of the health authorities of 5/VI 1927, in Germany, salting of meat with a mixture of table salt and sodium nitrite was permitted on the condition of uniform distribution of nitrite in the salt and nitrite content of 0.5-0.6%_o relative to the salt. Pickling (preservation in vinegar) is used for preserving certain types of fruits (cherries, gooseberries, plums) and vegetables (pickles, beets, carrots, mushrooms, etc.). Vinegar is boiled with spices, sugar, and salt, and the cleaned products placed in jars are poured with this vinegar. Acetic acid changes the chemical composition of the material being pickled and inhibits the development of putrefactive microbes in it. - Application of preservatives. This method of preservation is based on the antiseptic action of a number of chemical substances that are added to products in relatively small amounts and are capable of inhibiting the growth of microbes contained in the products. Most of the chemical substances proposed for preservation are harmful to the health of consumers in the doses necessary for reliable preservation. Therefore, hygienists have a negative attitude towards the use of chemical substances for preserving everyday food products (meat, milk, butter, etc.), and the sanitary legislation of most civilized countries extremely limits their use. - For preserving meat and other products, salicylic, benzoic, boric, sulfuric acids and their salts, formalin and its derivatives, urotropin (hexamethylenetetramine), fluorine compounds, etc., are most often used. The use of these substances is prohibited in Germany, Austria, USSR for preserving meat, meat products, fish, caviar, and other food products and beverages. - Salicylic acid has strong anti-enzymatic and bactericidal properties. In its 1% solution, meat does not spoil for a week; a 0.1% solution inhibits the development of molds. Its use for preserving food products is prohibited in Germany, Switzerland, France, USA, and some other states. - Benzoic acid, C₇H₅COOH, has a weak antiseptic effect. It preserves the color of meat well and therefore can mask decomposition processes in it. It is allowed in some European countries for preserving fruits and juices (England, Germany). In the USSR, it is allowed in marmalade (not more than 0.07%) and pastille (0.04-0.07%) (ost 552,553).

Boric acid, H₃BO₃, and its sodium salt, Na₂B₄O₇ + 10H₂O, possess very weak bactericidal properties. Solutions of them below 2% do not noticeably inhibit the growth and reproduction of microbes, but can suppress the putrid odor at the initial stages of decomposition and therefore should be classified as substances harmful to the consumer, since they are added not so much for C. as for flavoring not entirely high-quality goods. Their addition to food products and beverages is prohibited by the laws of most civilized countries. Sulfurous acid in the form of anhydride SO₂ has found wide application in winemaking for smoking barrels. It is also used for C. of starch, fruits, fruit juices, meat, milk, etc. It has significant preservative action. It is permitted in Germany not more than 0.125% (SO₂) and in England (up to 0.3%). In the USSR, sulfurous acid is permitted in wines in amounts not exceeding 200 mg per 1 liter of wine, including not more than 20 mg free; in marmalade not more than 0.02%, in fruit pastille—in traces, in corn, potato, and wheat starches—not more than 50 mg per 1 kg of starch. 6. C. by smoking is based, on one hand, on drying, and on the other, on the antiseptic action of the smoke obtained from burning wood. The antiseptic action is exerted by the components of the smoke, especially creosote, phenol, carbon dioxide, aldehydes, and among these, formaldehyde. It has been proven that in salted, heavily bacteria-infested meat, after six days of smoking at 22-25°, all bacteria die; in unsalted meat, despite smoking, putrefaction occurs. Therefore, for the success of smoking, the preliminary salting of meat is an essential condition. In smoking, two methods are distinguished: hot smoking, which lasts several hours and takes place in smoke at 70-100° (and higher), and cold smoking, lasting several days or weeks at a temperature of about 25°. For smoking, meat is hung in chambers where smoke develops from the burning of leafy wood, which should not be hot, not above 40°, otherwise fat may render out and a crust may form that poorly allows smoke to penetrate into the product. In the USSR, fish is smoked in consumption areas by hot smoking (herring), and in procurement areas by cold smoking. Cold smoking gives a more stable product. Smoking by the wet method, or "smokeless" smoking, consists in immersing the salted product (ham, sausage, pork belly) for 6-8 hours in a liquid that gives the product a smoked flavor but has no preservative action. The liquid for smokeless smoking is prepared by infusing soot in water, adding wood vinegar there, and filtering the mixture. This smoking cannot preserve the product, and in this respect it can be considered as falsification. Changes in products during C. When brines are used for C., a significant amount of extractive substances, soluble nitrogenous substances, salts of potassium, phosphorus, etc., pass into them, which are thus lost for nutrition. Part of the proteins, when concentrated salt solutions are used, are "salted out," i.e., precipitated. When heated, proteins coagulate, partially change their chemical structure, and depending on the nature of the medium and temperature, part of the molecule is split off. When a protein solution is heated with a strongly acidic reaction (e.g., in the presence of acetic acid), acid albuminate is formed. With strong heating, especially under increased pressure, part of the connective tissue (collagen) turns into glue and dissolves. This explains the disintegration of muscle tissue into individual fibers in sterilized meat preserves. When salting meat by the Morgan method, modified by Dewel (injection into large vessels of a 33% solution of NaCl + 1% NaNO₃), I. A. Smorodintsev and A. N. Adova found that the total amount of nitrogenous substances decreased in the meat from 15% to 9%, the amount of creatinine by 10-20 times. During C. associated with fermentation, a significant part of the carbohydrates is converted into organic acids and partly into substances of an aldehyde nature. Maurer found in salted fermented products (cabbage, cucumbers, pumpkin, and beets): formaldehyde—in cucumbers 0.4-0.5 mg per 1 kg, in sauerkraut 0.08-0.1 mg per 1 kg. The largest amount of formaldehyde is observed at the beginning of fermentation, but these amounts probably do not affect the vital activity of bacteria. Cellulose, during biological C. processes, is partially hydrolyzed and passes into a dissolved state. Effect of C. on vitamins. The amount of lipovitamins (A and D) changes little during C., however, prolonged storage of the product with access to atmospheric O₂ causes their decrease. Vitamin B is more easily destroyed, and sterilized preserves can often be considered devoid of vitamin B. An exception is sterilized tomato puree, in which vitamin B is well preserved. In dried vegetables and fruits, vitamin B is preserved relatively well, with the former better than the latter. In dry egg powder, L. A. Cherkas detected vitamin B after 4 years of storage. The amount of vitamin C sharply decreases during C., since it is the least stable to high temperature, oxidation, and change in reaction medium, which explains the appearance of scurvy when feeding on preserves. Elevated temperature activates oxidative processes; therefore, prolonged heating, even at low temperature, significantly reduces the amount of vitamin C in the finished product. Brief heating of the preserve, especially with limited access to O₂, has a lesser effect on vitamin C. The presence of oxidases in preserves, by enhancing oxidation, reduces the amount of vitamin C; therefore, inactivation of these enzymes, e.g., by "blanching," contributes not only to the preservation of the product's color but also preserves vitamin C by destroying oxidases. Vitamin C is better preserved in preserves with an acidic reaction, as this also causes inactivation of oxidases. This explains the relatively good preservation of vitamin C in canned tomato puree, which has an acidic reaction. Drying products causes a decrease in vitamin C content, with the method of drying and the product itself playing a significant role. Restriction of oxidative processes during drying (vacuum) and significant acidity of the product protect vitamin C from destruction. Ordinary methods of drying vegetables and fruits (in the air, sun, and in ordinary drying chambers) almost completely destroy vitamin C. Condensed sweetened milk preserves vitamin C significantly better than unsweetened, since a lower temperature is used in the preparation of the former. Dried milk partially preserves vitamin C only when prepared by spraying in a vacuum. Traces of copper present in the product, acting catalytically, contribute to the inactivation of vitamin C; therefore, the preparation of preserves in unlined copper vessels or the addition of copper salts for coloring causes a significant decrease in vitamin C. Frozen meat contains significantly less vitamin C than fresh meat. C. of meat and fish products by salting almost completely destroys vitamin C and others, since during this C. vitamins are subjected for a prolonged time to the influence of oxidation, the action of various enzymes, and the influence of complex biochemical processes occurring in the brine and in the product itself. Vessels and containers used for storing preserved products must meet especially strict hygienic requirements, since preserves are in close contact with the vessels for a very long time, and in addition, most preserves contain organic acids that have a corrosive effect on the walls of the vessels. In meat preserves, such an acid is lactic acid; in vegetable preserves, oxalic, malic, succinic, citric, acetic, etc. In preserves poured with oil, fatty acids play the same role. Glassware is considered the best from a hygienic point of view, but it is relatively little used due to its high cost, fragility, and poor resistance to high temperature during sterilization. For fermented preserves, pickles, marinades, fruit purees, etc., wooden containers are mostly used: barrels, tubs, vats, etc. Such wooden containers must first be thoroughly cleaned with a soda solution, hot water, steam, and sulfur dioxide. In domestic use and in small farms, "scalding" is used for cleaning wooden vessels: a little water is poured into the vessel and red-hot stones are thrown into it, with which the water is brought almost to a boil. In large productions, steaming of barrels is done with the help of a special steam generator. Treatment with sulfur dioxide is carried out either by burning sulfur in a wooden vessel covered with a canvas, or by using condensed sulfur dioxide in bombs. Wooden vessels should not be made from coniferous woods, as the resinous substances of these woods can give the preserve an unpleasant taste. Usually, deciduous woods are used for making such vessels: oak, beech, linden, alder, etc. Glazed earthenware should be avoided for storing preserves, especially marinades and pickles, since glaze almost always contains lead (see.

Glaze), which passes into the preserves and is the cause of chronic lead poisoning. Iron, zinc, copper, and aluminum vessels are unsuitable for storing preserves due to their instability with respect to organic acids. Iron vessels are quickly destroyed under the influence of rust and impart an unpleasant taste to the preserves. Zinc and copper dissolve significantly in organic acids, which can cause poisoning. Aluminum vessels also gradually deteriorate during prolonged storage. Enamel-coated iron vessels can impart salts of tin and antimony, which are part of the enamel, into the preserves. Tinplate has wide application for the manufacture of tin cans due to its resistance to sterilization at 100°C, its non-brittleness and flexibility, which make it possible to give it various shapes. A negative property of tin cans is the transfer of tin and lead from the tinplate into the preserves, sometimes to such an extent that it can harm the consumer's health. According to American requirements, the amount of tin passing into the preserve should not exceed 300 mg per 1 kg of preserve, according to the all-Union standards of the USSR - not more than 200 mg per 1 kg. According to section 'g' of the circular of the People's Commissariat of Health of the RSFSR (No. 320/32 of 12/22/1927 - Bull. NKZdr. RSFSR, No. 24, 1927), 'the tin plating for tin cans must contain not more than 0.01% lead, provided that well-polished tin is used for the manufacture of cans, ensuring an even and possibly thin layer of plating. Note 1: In view of the current state of the metal market, it is temporarily considered permissible for the lead content in the plating of tin cans to be not more than 0.07% lead. Note 2: For the preparation of preserves intended for the Red Army, the tin plating of tin cans must contain only traces of lead due to the prolonged storage of these preserves'. Section 3 of the same circular: 'The amount of lead in the external solder of tin cans must not exceed 10%, in the internal solder of tin cans the lead content must not be more than 1%. Note: In the external solder of tin cans, which excludes the possibility of contact between the contents of the cans and the external solder, a lead content of up to 33% is permissible'. The amount of tin passing into the preserve depends on the quality of the tinplate and the properties of the preserve. The tin plating must have sufficient thickness and cover the iron with a continuous layer. In our canning industry, a tin content of 50 g per 1 ft² of tinplate was usually required, but in reality there was always less. With a thin layer of plating, due to the significant brittleness of tin during the manufacture of cans, small cracks form, exposing the iron. At the boundary of two contacting metals (tin and iron) there is a difference in electrical potential, and in the presence of the preserve liquid an electric current is formed, promoting the dissolution of the metals. This process is called 'galvanic corrosion'. To detect invisible cracks in the plating layer, it is recommended to coat the tinplate with a 10% solution of gelatin, to which 3% yellow blood salt is added. In places where this mass comes into contact with the exposed iron, bluish spots appear in the gelatin. The acids of the preserves have a slow corrosive effect on the tin layer. Chloride salts, which have strong oxidizing properties, contribute to the corrosion of the tinplate; this forms basic chloride salts in the form of white spots on the inner walls of the can, sometimes in the form of a white coating on the preserve itself. Very often in cans, 'marbling' of the plating is observed, i.e., the appearance of black-blue spots caused by the action of sulfur compounds of the preserve on the metal. To protect the tinplate from change, the inner surface of cans is sometimes (more often for fruit and vegetable preserves) coated with various lacquers. Lacquers must be harmless, resistant to temperature, acid-resistant, and elastic. In 1894, the Lower Austrian Council for Public Health spoke out in favor of the need to apply such lacquers to all preserves, especially acidic ones. Recipes for lacquers that fully satisfy the above requirements have not yet been developed. Spoilage of preserves. Sterilized preserves can be stored without spoilage for a very long time. In 1824, the polar explorer Captain Perry hid preserves in an Arctic cellar, which were found 8 years later, sent to a museum, and tested in 1911, and were found to be of good quality. Spoilage of tin cans can occur a) from the transfer of tin, lead, and other substances from the container into the preserves, which make the preserves inedible or harmful to health (see above); b) from the hermeticity of the sealing and c) from insufficient sterilization. With strong corrosion of the metal, gases (mainly hydrogen) are formed, which can cause swelling of the can, so-called 'chemical bombage'.-Non-hermeticity of the sealing is most often caused by improper crimping of the can bottoms. To achieve hermeticity when crimping the can, rubber rings are placed between its body and bottoms, or liquid rubber mastic is applied; in recent years, paper rings have also been used. Improper spreading of the ring, as well as its tearing during crimping, do not provide complete hermeticity and cause infection of the preserve with air microorganisms. The same infection occurs through through corrosion of the tinplate during rusting. They are most often observed at the places of crimping of the bottoms and at the side seam, where iron is partially exposed from the tin layer when the tinplate is bent in machines. Local rusting is also observed when using ammonium chloride during soldering, as traces of chloride salts remaining on the tinplate increase the oxidation processes. High humidity and temperature of the warehouse contribute to the rusting of the can and the formation of through holes.-Spoilage of preserves due to the preservation of viable microorganisms and their spores is caused by defects in sterilization. The reasons for the preservation of bacteria and spores in preserves can be: 1) insufficiency of temperature and time of sterilization; 2) 'cold pressure' during sterilization, i.e., the presence of air in the autoclave, which in mixture with water vapor quickly increases the pressure, without giving a corresponding temperature increase according to the manometer reading; 3) rapid increase in pressure in the autoclave; in this case, some types of preserves do not have time to heat sufficiently and are exposed to high temperature for a much shorter time than with a slow increase in pressure; 4) rapid decrease in pressure at the end of sterilization; in this case, a significant difference is observed between the pressure inside the can and in the autoclave, which causes a temporary 'physical bombage', which can be so significant that it sometimes disrupts the hermeticity of the can. After cooling, air containing microorganisms enters such cans and causes spoilage of the preserves. In poorly sterilized preserves, decomposition processes with the formation of large amounts of gas are often observed. With hermetic sealing, these gases cause the so-called 'biological bombage', i.e., swelling of the can. Such bombage is also observed with non-hermetic sealing in cases when particles of the preserve tightly close the existing opening. In canning productions, for testing preserves for sterility, they are stored at a temperature of about 37°C. In cases of can swelling, the unacceptable from a hygiene point of release of gas by piercing the bottoms, soldering the opening with tin, and secondary sterilization is sometimes applied. Spoilage of non-sterilized, protein-rich preserves (for example, salted meat, salted fish, etc.) is most often caused by ordinary putrefactive bacteria. Protein under the action of proteolytic enzymes produced by these bacteria breaks down into amino acids, fatty acids, organic bases, aromatic derivatives; with deeper decomposition, CO₂, H, CH₄, H₂S, mercaptan are formed. The development of putrefactive bacteria is favored by weak concentration of NaCl, the use of old brines (tuzluks), elevated storage temperature, as well as a decrease in the acidity of the brine under the influence of the ammonia formed. To maintain sufficient acidity of the brine, some specialists propose adding sugar to create a favorable environment for lactic acid bacteria, which decompose sugar into lactic acid. Sometimes spoilage of salted meat and fish depends on the development of slime-forming bacteria. In cases of the appearance of slime-forming bacteria, it is necessary to destroy old brines and thoroughly disinfect the vessels.-Salted fish is often affected by the larvae of the cheese fly Piophila casei, 'jumpers'. By resolution of the Scientific Medical Council of 11/13 1925, 'fish superficially affected by the jumper (without damage to the muscle layer, in the absence of a putrefactive odor) may be admitted for sale after thorough cleaning of it from the larvae. Fish more deeply affected by the jumper, upon penetration of the latter into the cavity of the fish, with significant damage to the muscle layer, having thereby lost its nutritional value, is considered unfit and subject to destruction'. To protect against jumpers, the container must be tight, without cracks.

Fresh fish should be processed and covered with brine as quickly as possible to prevent the laying of eggs by the cheese fly. - Spoilage of pickled and salted vegetables and fruits occurs mainly under the influence of molds, butyric acid fermentation, and microorganisms that suppress the vital activity of lactic acid bacteria. The product becomes slimy, acquires flabbiness and unpleasant taste properties. The acidity of the brine in spoiled such canned foods is significantly reduced and is usually below 0.5% when recalculated to lactic acid. Spoilage of fruit and vegetable purees, in addition to molds, is caused by agents of butter and acetic acid fermentation and alcohol-forming yeasts. The puree swells and acquires a wine smell. Spoilage of dried fruits and vegetables is caused by mold, damage by mites and insect larvae. When drying fruits on galvanized nets and sheets, they may acquire a metallic taste and become harmful to the consumer. Poisoning from canned foods. In poisoning from canned foods, Bacillus botulinus (see Botulism) plays a major role, the spores of which are very resistant to heating. Paratyphoid bacteria are less resistant to heating, and poisonings from them are observed mainly when using non-sterilized canned foods. In the literature, a number of cases of poisoning from tin cans containing 103-104 mg of tin in 100 g of canned food are described. Individual types of tin cans. Fish canned foods are prepared in the USSR from 30 different types of fish. By method of preparation, 4 types of fish canned foods are distinguished: 1) in oil, 2) in tomato, 3) in marinade (with acetic acid) and 4) in juice (without additives). In oil are prepared sardines, sprats, mackerel, mullet, etc. In tomato and marinade - beluga, sturgeon, mullet, goby, etc. In juice (salt is added) - mainly salmon fish and red fish: beluga, sturgeon. Fish products sealed in hermetically sealed containers, glass or tin, but not sterilized (for example, anchovies in tins), are called preserves. Fish tin canned foods must meet the following requirements. Sturgeon, beluga and sturgeon in tomato sauce a) must be prepared from completely high-quality, live, chilled or frozen fish; b) the head and internal organs, cartilage, tail, fins, bony scutes and places of injury (bruises) must be carefully removed; c) the amount of fish by weight should be at least 75% of the weight of the contents of the tin; d) the content of inedible parts (spices) should not exceed 0.5% of the weight of the finished canned foods in the tin; e) the acidity of the tomato sauce when recalculated to acetic acid should be in tomato not more than 0.5%, in tomato-marinade - 1.25-2.0%; f) the content of dry substances in the edible part of the canned foods should be from 30% to 35%; g) the vegetable oils (sunflower, mustard and cottonseed) or their mixtures used for making canned foods must meet the requirements of all-union standards for these oils; h) the tomato filling must be made from satisfactory quality tomato puree; the amount of oil, pepper, salt, sugar and other spices is determined by taste; i) vinegar or acetic essence of satisfactory quality is added to the tomato filling; j) canned foods should not contain lead. The tin content should not exceed 150 mg per 1 kg of canned food (GOST 691).--Pike-perch in tomato sauce a) must be made from high-quality fish, pike-perch or zander (of the genus Lucioperca), live, chilled or frozen; b) scales, head, internal organs, tail, fins and spinal bone must be carefully removed; c) the amount of fish by weight should be at least 70% of the weight of the contents of the tin; d) the content of inedible parts (bones, spices) should not exceed 3% of the weight of the finished canned foods in the tin; e) the acidity of the tomato sauce (in acetic acid) should be in tomato not more than 0.5%, in tomato-marinade - 1.25-2.0%; f) the content of dry substances in the edible part of the canned food should be from 25% to 30%. Requirements g), h), i) and j) are the same as for canned foods "sturgeon, beluga, sturgeon in tomato sauce" (GOST 692). Requirements for the canned food "goby in tomato sauce" are in general the same as for "pike-perch in tomato sauce" (GOST 690). Requirements for canned food "goby in tomato sauce" are in general the same as for "pike-perch in tomato sauce" (GOST 690).

Meat canned foods. For meat canned foods ("stewed meat") goes fresh or frozen meat of cattle from healthy animals that have passed veterinary inspection. For one portion of canned food goes at least 280 g of boneless meat, about 40 g of fat, 3 g of salt, 4 g of onion, 2 grains of pepper and a piece of bay leaf. The tin has a height of 9.5 cm and a diameter of 7.5 cm. The finished canned food contains in the tin: 150 g of meat, 50 g of fat and about 130 g of broth. - Vegetable canned foods are prepared from green peas, green bean pods and sugar peas, asparagus, artichoke, cauliflower and Brussels sprouts, carrots, whole tomatoes and ground in the form of puree (tomato puree). Stuffed vegetables (tomatoes, eggplants and peppers) are freed from internal parts and filled with a filling consisting of carrots, white roots, onion, salt, sugar, grain pepper. The filling is fried in sunflower oil. Vegetables are placed in round low tins and covered with a sauce of tomato puree, roots, onion, sugar, pepper and oil. After sealing, they are sterilized at 100° for 35-40 minutes. Requirements for vegetables stuffed with roots: moisture content should not be more than 70%; total acidity, calculated to malic acid, not more than 0.7%. Fat content in tomatoes and peppers not less than 6%, in eggplants - 8%. Vegetables should be tightly packed in tins and covered with tomato sauce to the top of the tin. Stuffed vegetables should not contain lead; tin content should not exceed 200 mg per 1 kg of product. Should not contain preservatives, artificial sweet substances and mineral-origin colorants (copper) (GOST 542). Fruit canned foods, compotes in tins and glass jars are prepared from pears, apricots, quinces, peaches, plums, mirabelles, cherries. The cleaned fruits are blanched in boiling water and after cooling are placed in tins and covered with sugar syrup 18-24° Brix. Sterilization after sealing for a 400-gram tin is carried out at 100° for 12-20 minutes. The canned food should not contain lead, preservatives and artificial sweet substances. The tin content should not exceed 200 mg per 1 kg of product. Coloring vegetable canned foods (peas, beans, gooseberries, etc.) green with copper salts is unacceptable from a sanitary point of view. - Dairy canned foods - see Milk. Examination of canned foods. In sanitary examination of canned foods prepared by different methods, in general the same testing methods are used as for non-canned products, except in cases where new substances are formed in the product during canning or such substances pass from the container into the canned food (tin, lead). Thus, for example, when salting meat with saltpeter, nitrites can accumulate in the canned food in an amount not indifferent to the consumer's health. German sanitary authorities allow not more than 0.015% of nitrites when recalculated to NaNO₂. When examining tin canned foods, testing for hermeticity, testing for sterility, determination of the organoleptic properties of the canned food, determination of its freshness, quantitative determination of tin and qualitative determinations of lead and copper (peas) are carried out.

Assessment of the quality of tin canned foods by inspection presents great difficulties, since it would be necessary to open each tin, which is practically inapplicable. When examining canned foods, attention is paid to the condition of the bottoms of the tins, to the presence or absence of sealed holes, to the mobility of the contents of the tin when shaken, to the integrity of the tins, to the quality of the contents of the opened tin. - When a canned food decomposes, the bottoms of the tins become convex, which occurs from the pressure on the walls of the tin of the gases formed inside it. Detection of such convexity ("bombage") makes one suspect that the canned food is not sufficiently sterilized and has undergone decomposition. On the other hand, a canned food can be spoiled, i.e. contain microbes, but not give bulging of the tin bottoms. This depends on the fact that some microbes, by liquefying part of the canned food and giving it an acute smell and sour taste, do not produce gases at all. Thus, the question of the quality of the canned food can finally be resolved only on the basis of bacteriological research data. When sealing the contents tightly packed in tins, the tin lids are usually crimped with the help of special machines. Previously, the bottoms of the tins were provided with one hole, which was sealed after sterilization. At present in our USSR in the USSR, lids are inserted into the tins whole, and no sealing is needed. Therefore, the detection of one, let alone several, sealed holes in a tin is a suspicious sign. This indicates 617

618 that the canned food spoiled after preparation and that holes were made in the tin can to release gas. Then the tin can was obviously sterilized again and sealed. Such a suspicious sign can also be the mobility of the contents of the tin can when shaken. Usually, the canned food is tightly packed in tin cans, but during decomposition, part of it liquefies (for example, aspic in meat canned foods), and it becomes mobile. Severe denting of tin cans and the presence of a large amount of rust on their surface may be reasons for rejecting canned foods, as dents and rust can lead to violation of the hermetic seal of the tin cans and consequently be the cause of spoilage of the canned food. When inspecting a batch of canned foods, it is necessary to open the most suspicious tin cans in appearance, and if their contents are foamy, have a bad smell (sour, rotten, musty), then such canned foods should be considered spoiled. Tin canned foods should be stored in a dry, well-ventilated place, without sharp fluctuations in temperature. Checking the hermetic seal. A jar with canned food is immersed in water preheated to boiling, taken in such an amount that after immersion of the jar, the water temperature is not below 85°. The appearance of air bubbles in any place of the jar indicates the lack of hermeticity of the said jar.