Food products can contain a variety of microflora. The natural and harmless microflora of food products is a complex biocenosis that serves as a biological defense against unwanted microorganisms. However, certain types of microorganisms can affect the quality of food products. In case of violation of the processing, storage or sale of products, these microorganisms can, multiplying to a significant level, lead to product spoilage and food poisoning.

Microbial spoilage of products can occur as fermentation, rotting, molding and decomposition of fats. Milk, cheeses and other dairy products undergo butyric fermentation due to the multiplication of spore-forming anaerobic bacteria in them. In this case, butyric acid is formed, an unpleasant taste and smell appear. Acetic acid fermentation leads to souring of wine and beer. Alcoholic fermentation caused by yeast is used in the production of alcohol, beer, etc. Lactic acid fermentation is used to prepare various fermented milk products.

Putrefaction, the process of decomposition of proteins with the formation of foul-smelling gases, caused by the action of a complex of putrefactive microbes, is the cause of spoilage of many protein products. Mold fungi cause molding of products when they are stored in refrigerators, as fungi are resistant to low temperatures.

Of particular danger is the contamination of food products with pathogenic microorganisms, many of which are able not only to remain viable in products for a long time, but also to multiply intensively in them.

Microflora of dietary fats

There are natural fats of animal and vegetable origin and fatty products of industrial production (margarine, mayonnaise). Rendered animal fats and vegetable oils contain very little moisture and are hostile to most microbes.

Butter contains a lot of moisture, microbes develop both on the surface of the butter and inside it. Putrefactive and other bacteria, yeast, multiplying on the surface of the oil, decompose proteins and fats, leading to the formation of staff (bright yellow layer). With long-term storage of oil, mold fungi (odium, mucor, etc.) develop on the surface. Rancidity of the oil is caused by fat-splitting bacteria, and the products of the breakdown of proteins by proteolytic bacteria and micrococci also give a bitter taste.

Microflora of eggs and egg products

Egg - an excellent breeding ground for microorganisms. With fluctuations in storage temperature, "thermal" respiration is inherent in eggs. An increase in temperature leads to the expansion of the contents of the egg and the displacement of air from the path (air chamber) through the holes to the outside. When the temperature drops, air is sucked into the egg. Together with air, mold spores and various, including pathogenic, microorganisms, E. coli, Proteus bacillus and other putrefactive bacteria penetrate into the egg, which are deposited on the shell membrane, which keeps them from penetrating into the protein.

Eggs obtained from a sick bird become infected endogenously, i.e., the infection enters the contents of the egg before the shell is formed. It is possible for pathogenic microorganisms to enter the egg exogenously (from the outside) through damage to the shell. In the white of a fresh egg, microbes, including salmonella, do not survive due to the bactericidal action of lysozyme.

The presence of Salmonella is most often found in the eggs of waterfowl. In adult ducks and geese, salmonellosis is asymptomatic, but the shell and yolk of eggs are infected with salmonella.

Mold spores usually develop on the surface of the egg shell, forming colonies of various sizes that look like spots when candling or completely cover the egg (“cuff”). Mold gives the egg an unpleasant moldy smell, making it unsuitable for food.

During storage, the protective properties of lysozyme are reduced, and microbes penetrate the egg. The reproduction of putrefactive microflora causes decay processes with the formation of decay products of egg proteins, including toxic ones with an unpleasant taste and smell - ammonia, hydrogen sulfide, etc. This type of egg spoilage is called "putrefactive decomposition". The use of eggs with such a defect is not allowed.

Egg powder may contain an increased number of different microorganisms, including Proteus and Escherichia coli. Salmonella is highly likely to enter it, so egg powder must be subjected to reliable heat treatment. Melange (a mixture of protein and yolk), due to the increased risk of salmonellosis, is frozen and is not used in public catering.

Microflora of canned food

The criteria for the safety of canned foods is the absence of microorganisms and microbial toxins in them that cause food poisoning. The most dangerous food poisonings associated with the use of canned food are botulism and toxicoinfection caused by perfringens bacillus. Botulinum bacillus and perfringens bacillus belong to spore-forming anaerobic mesophilic bacteria from the group of sulfite-reducing clostridia. Spores of Clostridium and other gas-producing bacteria are able to withstand high temperatures during canning and multiply in canned food in the absence of oxygen to produce carbon dioxide and hydrogen, causing cans to bulge (bomb). In canned foods with high acidity (pH below 4.2), Clostridial spores do not germinate or multiply.

Vegetable and meat-and-vegetable canned food can be subject to flat-acid spoilage - souring of the product without swelling of the can. This type of spoilage is caused by thermophilic aerobic and facultative anaerobic acid-forming bacilli.

With abundant infection of raw materials and insufficient sterilization in canned and semi-preserved food (pasteurized, etc.), non-spore-forming microorganisms can remain viable - stakes and molds, molds, yeast, Staphylococcus aureus, etc.

S. aureus belongs to non-gas-producing microorganisms, the reproduction of which in canned food is not accompanied by bombing. In these cases, canned food can cause staphylococcal toxicosis and other food poisoning. Reproduction of staphylococci and accumulation of enterotoxin stops at low pH values ​​in canned food.

Microflora of grain products and bread

Microorganisms (bacteria, mold spores, yeast, etc.) enter the grain from the soil and with dust. The microflora of cereals and flour is determined by the microbial composition of the grain. In 1 g of grain products there can be from several thousand to a million microbes.

Of epidemiological significance is the defeat of grain by mold fungi dangerous to humans - ergot, fungi of the genus Fusarium and aspsrgillus.

Ergot and mold fungi of the genus Fusarium and Aspergillus are capable of releasing mycotoxins into grain, causing severe food poisoning - mycotoxicoses. Mycotoxins can have carcinogenic and other dangerous effects on humans in very small quantities, they are not destroyed in products during heat treatment.

Flour is less resistant to microbial spoilage than grains and cereals. In case of violation of storage conditions, when moistened, an increase in the acidity of flour due to the multiplication of lactic acid bacteria, the multiplication of mold fungi and, as a result, the appearance of an unpleasant taste, smell or lumpiness of flour is possible.

When baking bread, most microorganisms die, but the spores remain viable.

Wheat bread can be affected by "stringy (potato) disease". The reproduction of the causative agent of this disease is bread you. subtilis is favored by the low acidity characteristic of wheat bread.

When cooling bread or when storing in bulk in conditions of high temperature and humidity, the spores of you. subtilis germinate and break down bread starch into dextrins with their enzymes. The crumb first acquires an unpleasant smell of overripe melon or valerian, becomes sticky, then darkens and becomes viscous. Bread affected by "potato disease" is unsuitable for food purposes.

Bread molding is caused by the development of fungi Peniciilium glaucum (green mold), Aspergillus glaucum (white mold), Mucor macedo (capitate mold), the spores of which fall on bread from the air after baking bread.

Microflora of vegetables, fruits and berries

On the surface of fresh vegetables and fruits, there are a large number of various microorganisms that get there from the soil, water and air. The presence of skins, phytoncides, essential oils and organic acids prevents the development of microbes that cause spoilage of fruits and vegetables. Lingonberries and cranberries are particularly resistant to spoilage due to their content of benzoic and sorbic acids.

When the skin of fruits and vegetables is damaged, the microbes that cause spoilage multiply on the surface and get inside the pulp. The processes of microbial spoilage are promoted by overripeness and long-term storage of fruits and vegetables. Rot and other spoilage of vegetables and fruits are caused by fungi (late blight and dry rot of potatoes, black cancer of apples and pears, etc.), bacteria (wet rot of potatoes, black spot of tomatoes), yeast (spoilage of berries). Some species of fungi from the genus Penicillium, propagating on apples, tomatoes, sea buckthorn berries, are able to release patulin mycotoxin, which has a pronounced carcinogenic and mutagenic effect.

As a result of raw consumption of soil-contaminated vegetables, fruits and berries, dysentery, typhoid fever, cholera and other intestinal infections can occur. Familial outbreaks of dysentery have been reported with strawberries. The terms of survival of pathogenic microorganisms and helminth eggs on the surface of vegetables and fruits can significantly exceed the terms of their storage before sale. The use of vegetables, fruits and berries without heat treatment can lead not only to intestinal infections, but also to yersiniosis, geohelminthiasis, amoebic dysentery, etc.

Vegetables can become infected with Yersinia sticks from rodents, from contaminated soil or water. With long-term storage in vegetable stores, Yersinia multiply on the surface of vegetables and accumulate in significant quantities sufficient to cause a human disease. Most often, the cause of jereiniosis is the use of salads from raw vegetables of the old crop in spring or early summer.

Food microflora

1). MEAT. In the first hours after slaughter, the deep layers of meat are practically sterile. On the surface of the carcass, the species composition of the microflora is diverse - ϶ᴛᴏ soil bacteria(cocci, bacilli, clostridia), gut bacteria, and fungi. Reproducing and accumulating on the surface of the carcass, they gradually penetrate into the thickness of the meat and cause spoilage processes.

When storing meat in cooling chambers, the microflora remains unchanged for some time as a result of the formation of a dried layer on the surface of the carcass, which prevents the development of microorganisms. In the future, the microflora undergoes qualitative changes: mesophiles die off and psychrophiles develop, where rod-shaped bacteria that can multiply at a temperature of 0 ¸ -5 0 C become the predominant species, and some species even at -8 ¸ -9 0 C. In aerobic (in the presence of oxygen air) storage conditions of chilled meat, these bacteria are the main causative agent of meat spoilage. At first, separate colonies grow on the wetter surfaces of the product; then a continuous slimy coating of gray, greenish or brown color is formed; the smell and taste of the meat changes.

Mold fungi are the main causative agents of meat spoilage when stored at -4 ¸ -9 0 C. These fungi not only change the appearance and smell of the product, but also cause deep protein breakdown. Due to the active breakdown of lipids, the product becomes rancid. At some negative temperatures, mold fungi grow even on frozen meat.

2) BIRD. A feature of the microflora of poultry meat is the possibility of the presence in it of bacteria from the Salmonella group, which can cause food poisoning. In this regard, carcasses of waterfowl are especially dangerous.

3) FISH. The microflora of fish is represented spore and non-spore bacilli, micrococci, sarcinas, as well as water-dwelling molds and yeasts. As a result of storing fish at low temperatures, mesophilic forms of bacteria die off, and psychrophiles develop. The fish of the northern seas and rivers are more infected with psychrophiles, molds and yeasts. With a sharp drop in temperature, the growth of bacteria stops, and even psychrophiles begin to multiply only after some time. If at 18 0 C the number of bacteria reaches 10 8 - 10 9 per 1 g of fish during the day, then at a temperature of 0 ¸ -2 0 C growth is observed only on the fourth - fifth day.

Ice, sea water and brine are sources of microorganisms. In live-frozen or very fresh fish, microorganisms develop on the surface. They are absent in the thickness of the muscles.

4) MILK AND CREAM. Here, the reproduction of microorganisms occurs faster than on the surface of solid products. As a result of infection, raw milk may contain various microflora: lactic acid bacteria, spore and non-spore bacilli, bacteria of the Escherichia coli group, micrococci and staphylococci.

The development of milk microflora occurs in several phases. Bactericidal phase characterized by the fact that after milking cows, microorganisms in milk do not develop and even partially die off as a result of the action of special substances. Immediate cooling of milk after milking can extend the bactericidal phase up to 24-28 hours. Development phase of mixed microflora characterized by the development of microorganisms that have entered the milk. Considering the dependence on storage temperature, thermo-meso- or psychrophiles begin to predominate in milk. Development phase of lactic acid bacteria characterized by a rapid increase in acidity as a result of the fermentation of lactose into lactic acid. If the environment in milk is alkaline, then conditions will be created for the development putrefactive and butyric bacteria and the milk becomes unfit for consumption.

If milk and cream are stored at low temperatures, the reproduction of lactic acid bacteria is delayed in them. Under their influence, during relatively long-term storage of milk, proteins and fats are split with the formation of bitter and unpleasantly smelling products. Sometimes mucus may appear during refrigeration of milk, most often caused by psychrophiles.

Fruits and vegetables are a source of pathogenic and toxic microflora. Particularly common are pathogens of intestinal diseases that do not die off completely during long-term storage. Products containing little organic acids can be attacked by both mold fungi and bacteria.

When storing frozen fruits, vegetables and berries, the bacteria gradually die off. First of all, non-spore sticks die, incl. bacteria of the intestinal group, micrococci, staphylococci and spores are more resistant. When these products are thawed, they begin to multiply intensively, leading to product spoilage.

In addition, plant products contain phytoncides of various activity. Vegetables such as onion, garlic and horseradish secrete bactericidal substances that kill desinteria, E. coli, staphylococcus, and also cholera vibrios. Phytoncides of the peel and pulp of citrus fruits, bananas, pomegranates and apples, as well as berries, have a detrimental effect on various bacteria, mold fungi.

Microflora of food products - concept and types. Classification and features of the category "Microflora of food products" 2017, 2018.

Microbiology of food products

1. Microbiology of milk and dairy products

2. Microbiology of meat and sausages

3. Microbiology of eggs and egg products

4. Fish microbiology

5. Microbiology of cereals, flour, bread

6. Microbiology of fruits and vegetables

7. Microbiology of canned food

8. Microbiology of culinary products

1. In raw milk, even under hygienic conditions for its production, a certain amount of bacteria is usually found. If the milking conditions are not observed, milk can be abundantly contaminated with microorganisms due to infection with microbes located on the surface of the udder, falling from the ducts of the mammary gland, from the hands of milkers, from milking utensils and equipment, from the air. In combined milk, selected directly from farms, the total number of bacteria ranges from 4.6x10 4 to 1.2x10 6 in 1 cm 3.

The microflora of fresh milk is diverse. It contains bacteria lactic acid, butyric, groups of Escherichia coli, putrefactive and enterococci, as well as yeast. Among them are microorganisms. Able to cause rancidity, foreign tastes and odors, discoloration (blue, redness), ductility. There may also be pathogens of various infectious diseases (dysentery, typhoid fever, brucellosis) and food poisoning (Staphylococcus aureus, allmonella).

Fresh milk contains bactericidal substances - lactenins, which in the first hours after milking retard the development of bacteria in milk, and many of them even die. The period of time during which the bactericidal properties of milk are preserved is called bactericidal phase. The bactericidal activity of milk decreases over time and the faster, the more bacteria in the milk and the higher its temperature.

Freshly milked milk has a temperature of 35 0 C. At 30 0 C, the bactericidal phase of milk with a small initial contamination lasts up to 3 hours; at 20 0 C - up to 6 hours; at 10 0 C - up to 20 hours; at 5 0 C - up to 36 hours; at 0 0 C - 48 hours. At the same holding temperature, the bactericidal phase will be significantly shorter if the milk is heavily contaminated with microbes. So, in milk with an initial bacterial contamination of 10 4 in 1 cm 3, the bactericidal phase at 3-5 0 C lasts 24 hours or more, and with a content of 10 6 bacteria in 1 cm 3 - only 3-6 hours. To prolong the bactericidal phase of milk, it is necessary to cool it as soon as possible to at least 10 0 C.

At the end of the bactericidal phase, the reproduction of bacteria begins and it occurs the faster, the higher the temperature of storage of milk. If milk is stored at a temperature above 10-8 0 C, then already in the first hours after the bactericidal phase, various bacteria begin to develop in it. This period is called phase of mixed microflora.

By the end of this phase, mainly lactic acid bacteria develop, in connection with which the acidity of milk begins to increase. As lactic acid accumulates, the development of other bacteria, especially putrefactive ones, is suppressed. Some of them even die off and come lactic acid bacteria phase. The milk is fermented.

With further storage of milk, with an increase in the concentration of lactic acid, the development of lactic acid bacteria themselves is suppressed, their number decreases. First of all, lactic streptococci die off. Lactic acid sticks are less sensitive to the acidity of the environment and die off more slowly. In the future, yeast and mold growth may occur. These microorganisms use lactic acid and form alkaline protein rampad products; the acidity of milk decreases, putrefactive bacteria can again develop in it.

In milk stored at temperatures below 10-8 0 C, lactic acid bacteria almost do not multiply, which contributes to the development, albeit slowly, of cold-resistant bacteria of the genus Pseudomonas, capable of causing the decomposition of proteins and fats; the milk acquires a bitter taste.

To keep milk fresh, it is cooled at a dairy farm or collection point to temperatures of 6-3 0 C and delivered in a chilled state to processing dairies.

Milk pasteurization is designed to destroy pathogenic bacteria and possibly more complete reduction of the total contamination by bacteria. The efficiency of milk pasteurization depends on the quantitative and qualitative composition of its microflora, mainly on the number of heat-resistant bacteria. Drinking milk is pasteurized at 76 0 C with a holding time of 15-20 seconds. The mode of pasteurization of milk used for the manufacture of fermented milk products is more stringent.

Pasteurization retains a certain amount of vegetative cells of thermophilic and heat-resistant bacteria, as well as bacterial spores. In case of violation of the continuous automated pasteurization cycle (its rupture on the way from the pasteurizer to bottling into containers), milk can be additionally infected with microorganisms. The degree of this secondary contamination of pasteurized milk depends on the sanitary and hygienic conditions of production.

Store pasteurized milk at a temperature below 10 0 C for no more than 36-48 hours from the moment of pasteurization. Flask milk should be boiled before eating.

sterilized milk can be stored for a long time without being subjected to microbial spoilage, since in the process of sterilization its microflora is destroyed.

Sterilized condensed milk produced in the form of canned food. The microflora in this milk should be absent, but spoilage is sometimes observed. It manifests itself more often in the form of bombing (bloating) of cans, caused by heat-resistant, spore-forming, anaerobic bacteria of the genus Clostridium, which ferment lactose with the formation of carbon dioxide and hydrogen and butyric acid bacteria.

Condensed milk with sugar they are also released in hermetically sealed jars, but they will not pull sterilization. The stability of this product is achieved by an increased content of solids, especially a large amount of sucrose. The most common defect of such milk during long-term storage is the formation of "buttons" - seals of different colors (from yellow to brown). The causative agent is more often chocolate-brown mold Catenularia.

Can bombing is sometimes found, caused by yeast fermenting sucrose. At the same time, the sugar content decreases, the acidity increases.

The main dairy products include sour-milk products, butter, margarine, cheeses.

Dairy products play an important role in human nutrition, since, in addition to nutritional value, they have dietary, and some medicinal value. Dairy products are digested better than whole milk, and much faster.

Compared to milk, fermented milk products have an increased shelf life. They are, moreover, an unfavorable environment for the development of many pathogenic bacteria. This is due to their high acidity and the content of antibiotic substances produced by some lactic acid bacteria.

In the conditions of industrial processing of milk in the manufacture of various fermented milk products, it is pre-pasteurized and then fermented with specially selected starter cultures from pure or mixed cultures of lactic acid bacteria. Therefore, the activity of the starter used and the quality of the processed milk are of great importance.

The composition of the starter for the manufacture curdled milk, sour cream and cottage cheese includes lactic acid streptococci and aroma-forming streptococci.

In the manufacture cottage cheese, in addition to sourdough, rennet is used, which activates the process. Sometimes cottage cheese is made from unpasteurized milk. Such cottage cheese is intended only for the manufacture of products that are subjected to heat treatment before use due to the possible reproduction in it of pathogens of food intoxication - staphylococci, which are usually found in raw milk.

When developing kefir they use not pure cultures of microorganisms, but a natural fungal starter - pasteurized milk fermented with the so-called kefir fungus. In the process of fermentation and maturation of kefir, yeast, lactic streptococci, lactic acid bacilli and acetic acid bacteria play a certain role.

Thus, kefir is a product of combined fermentation: lactic acid and alcohol. The alcohol content can be up to 0.2 - 0.6% (depending on the duration of maturation). The resulting carbon dioxide gives the product a refreshing taste. The smell of hydrogen sulfide sometimes appears in kefir. The cause and causative agent of this smell can be putrefactive bacteria. In a clot of kefir, "eyes" can form, which is associated with the excessive development of yeast and aroma-forming bacteria - components of the kefir fungus.

The composition of the leaven for ryazhenka includes thermophilic lactic streptococcus and a small amount of Bulgarian bacillus. Ryazhenka is made from a mixture of milk and cream. The mixture before fermentation is heated to 95 0 C for 2-3 hours, as a result of which it acquires the color and taste of baked milk.

Butter- one of the most important products of milk processing. Butter is made from pasteurized cream. The number of bacteria in them is usually small - from hundreds to several thousand per 1 cm 3. These are mainly spore rods and micrococci.

Microflora sweet cream butter contains residual microflora of pasteurized cream and extraneous microflora, namely, sporeless rod-shaped bacteria and micrococci, among which there are those capable of breaking down milk fat and proteins.

sour cream butter is made from pasteurized cream fermented with pure cultures of lactic acid streptococci. Aroma-forming streptococci are also introduced into the starter culture. Naturally, sour cream butter, compared to sweet cream butter, contains significantly more bacteria, mainly lactic acid, yeast is also present. The number of microorganisms in sour cream butter reaches millions and tens of millions per 1 g. Extraneous microflora is insignificant, its development is delayed by lactic acid, which is formed by lactic acid bacteria.

The most common defect in butter is mold, especially when stored in conditions of high humidity. Molds develop on the surface of the oil in the form of spots of different colors. Sometimes the oil will mold inside the block if there are voids in it that form when the oil is not packed tightly.

Long-term storage of butter at a temperature of -20 to -30 0 C is recommended. At the same time, not only microbiological, but also physico-chemical processes are delayed in it. The type of packaging also matters; oil packed in films made of polymeric materials is preserved better than oil packed in parchment.

Milk margarine It has two types of microflora: a starter microflora used for the fermentation of milk, which is part of margarine, and an extraneous microflora, of non-starter origin. The development of extraneous microflora, which can cause defects in the taste and smell of margarine, is possible mainly only in the water-milk phase of margarine.

Margarine is a highly dispersed emulsion; its water-milk phase is in the form of tiny droplets ranging in size from 1 to 10 microns, which significantly reduces the possibility of reproduction of microorganisms. The low pH value of this phase of margarine (pH about 5) is also unfavorable for many bacteria.

Active development of microbes can only be on the surface of the product or in places where condensation moisture accumulates, which occurs during intensive cooling of margarine packaged in moisture-proof packaging.

If margarine is spoiled, it can become rancid, acidic, moldy.

Cheese- a valuable product of milk processing in terms of taste and nutritional properties. The properties of cheese - taste, aroma, texture, pattern - are formed as a result of complex processes, in which the main role belongs to the world's organisms.

Coagulation of milk (coagulation of casein) is carried out by fermenting it with lactic acid bacteria and introducing rennet.

During all the technological stages of cheese production, lactic acid bacteria accumulate in the cheese mass, which become the main microflora of the ripening cheese.

The maturation of cheeses proceeds with the active development of microbiological processes. In the very first days of ripening, lactic acid bacteria rapidly develop in the cheese, the number of their cells in 1 g of cheese reaches billions. Bacteria ferment milk sugar with the formation of lactic acid, and some also produce acetic acid, carbon dioxide, hydrogen. The accumulation of acids inhibits the development of extraneous microflora.

When ripening hard cheeses Dutch the main role belongs to lactic acid streptococci. In the microflora of ripening Swiss-type cheeses, thermophilic lactic acid sticks predominate, mainly cheese sticks, which play a leading role in the lactic acid process. Thermophilic streptococci also take part in cheese ripening. After milk sugar is fermented, the development of lactic acid bacteria stops and they begin to gradually die off.

In the process of maturation of cheeses, changes occur not only in milk sugar. But also milk proteins. In these processes, lactic acid bacteria also play a significant role.

Develop in ripening cheeses and propionic acid bacteria. They ferment lactic acid to form propionic and acetic acids and carbon dioxide.

Propionic and partially acetic acids, as well as some amino acids and their cleavage products, give cheeses their characteristic pungent taste and smell. The accumulation of carbon dioxide and hydrogen in cheeses as a result of the vital activity of lactic acid and propionic acid bacteria cause cheese eyes, which create a cheese pattern.

During the maturation of hard cheeses, especially at the initial stage of the process, bacteria of the Escherichia coli group can actively develop, and at the end of maturation, butyric ones. The growth of these bacteria is accompanied by an abundant release of carbon dioxide and hydrogen, which results in an irregular cheese pattern and even swelling.

There is also such a defect as the bitterness of cheese, due to the development of microorganisms that actively decompose proteins, the resulting peptides have bitterness. This defect can cause some lactic streptococci.

Significantly reduces the quality of cheese an anaerobic spore bacterium of the genus Clostridium putrificum, which has a pronounced activity. At the same time, the cheese softens, its consistency becomes smeared, a putrid smell and an unpleasant taste appear. However, spoilage, especially of hard rennet cheeses, is more often manifested in mold.

When developing soft, so-called mold cheeses In addition to lactic acid bacteria, molds are of great importance, with which cheeses are specially infected. The peculiarity of the taste of these species is due to a change not only in milk sugar and protein substances, but also in milk fat, which is broken down by molds with the formation of volatile fatty acids.

Processed cheeses produced mainly from mature cheeses. Their microlora is mainly represented by spore-bearing bacteria, there are also lactic acid and coli, and streptococci, preserved during the melting of cheese. The number of bacteria in these cheeses is relatively small, thousands of cells per 1 g. During refrigerated storage (up to 5 0 C), no significant changes in the microflora are observed for a long time. At higher temperatures, the number of bacteria increases more or less rapidly depending on the temperature. Butyric acid bacteria are the most dangerous causing swelling of cheeses. To avoid this type of spoilage, the antibiotic nisin is introduced into cheeses.

General bacterial contamination smoked sausage cheeses usually does not exceed hundreds of cells per 1 g. These are mainly spore bacteria. The main type of spoilage of these cheeses is molding.

2. Microbiology of meat and sausage products. Meat is a good nutrient substrate for many microorganisms, in which they find all the substances they need - sources of carbon and nitrogen, vitamins, mineral salts. The pH of the meat also favors the development of micro-organisms, and as a result, the meat spoils quickly.

The muscles of healthy animals are usually sterile. The muscles of sick animals that have undergone starvation before slaughter, severe overwork, may contain microorganisms. In addition to lifetime infection, muscles can be contaminated with microbes after the slaughter of an animal: during the primary processing and cutting of carcasses, from tools, from the hands of workers, etc. Therefore, even freshly processed meat is not sterile and, mainly on the surface, it contains one or another number of microorganisms.

The contamination of freshly processed chilled meat with microorganisms can vary depending on the degree of maturation of the meat, the temperature and humidity conditions of cooling, the sanitary and hygienic conditions of production, etc. The composition of the microflora is diverse. These are mainly aerobic and facultative anaerobic, sporeless, gram-negative rod-shaped bacteria, bacteria of the Escherichia coli group, lactic acid micrococci. In smaller quantities, aerobic and anaerobic spore-forming bacteria, yeasts, and mold spores are found.

Meat can also be infected with toxigenic bacteria, the genus Clostridium, Salmonella. Salmonella often cause intestinal diseases in cattle, after which the animals are bacillus carriers for a long time.

Meat by-products (brains, kidneys, heart, etc.) are usually more contaminated with microbes than meat, and therefore spoil more quickly.

Reproducing under favorable conditions on the surface of the meat, microorganisms gradually penetrate into its thickness.

Chilled meat is a perishable product. Temperature is decisive for the rate of microbial growth and hence for the spoilage of chilled meat. The spoilage of chilled meat can manifest itself in different ways and depending on the storage conditions.

rotting meat starts at the surface and gradually spreads to the depth. At a storage temperature above 5-8 0 С putrefactive processes are caused by aerobic and anaerobic microorganisms. In the initial stages of the process, mainly coccal forms of bacteria are involved, then they are replaced by rod-shaped bacteria. The spoilage of meat at these temperatures occurs very quickly - within a few days.

When storing meat at temperatures below 5 0 C, the composition of its initial microflora gradually changes and becomes more uniform. After a few days of storage, non-spore Gram-negative bacteria of the genus Pseudomonas (up to 80% or more of the entire microflora) show greater activity.

With putrefactive spoilage of meat, its color becomes gray, it loses its elasticity, becomes slimy, softens. First, a sour, and then an unpleasant, putrid smell appears, which intensifies as the process deepens.

slime- the earliest common type of spoilage of cooled and chilled meat, especially if it is stored in conditions of high relative humidity (over 90%). This defect is caused mainly by bacteria of the genus Pseudomonas; often mucus is also caused by micrococci. Mucus is expressed in the formation of a continuous layer of mucus on the surface of the meat. It has been established that abundant mucus formation in these bacteria occurs at temperatures from 2 to 10 0 С; mucus accumulates (albeit slowly) even at -2 0 C.

acid fermentation accompanied by the appearance of an unpleasant sour smell, the formation of a gray or greenish-gray color on the cuts and the softening of the meat. This process can be caused by anaerobic bacteria of the genus Clostridium. Acid fermentation of meat often occurs due to poor bleeding of animals during slaughter, as well as in cases where carcasses are not cooled for a long time.

meat pigmentation- the appearance of colored spots - is associated with the development of pigment microorganisms on its surface. Thus, the development of the “wonderful stick” (Serratia marcescens) leads to the formation of red spots unusual for meat. In the case of the development of non-pigmented non-spore-bearing yeast, a white-gray coating appears on the meat.

mold due to the growth of various fungi on the surface of the meat. Mold development usually begins with the appearance of an easily washable cobwebbed or powdery coating of white. In the future, more or less powerful raids are formed. On chilled meat, many mucor fungi (Mucor, Rhizopus) can develop, forming white or gray fluffy plaques. Black plaque gives Cladosporium, green - appears with the development of fungi of the genus Penicillium, yellowish - with the development of Aspergillus.

In addition, some molds found on meat can produce toxic substances.

The optimal storage conditions for chilled meat are considered to be temperatures from 0 to -1 0 C and relative humidity of 85-90%, but even under such conditions, meat is stored for no more than 10-20 days.

Meat semi-finished products, especially small pieces and minced meat, deteriorate faster. They usually contain more microorganisms than the meat from which they are made.

To prolong the shelf life of chilled meat, it is possible to use means of influencing microorganisms additional to cold: increasing the content of carbon dioxide in the atmosphere, ultraviolet irradiation, ozonation of storage chambers. Significantly increases the shelf life of chilled meat in a nitrogen atmosphere. Under such conditions, mucilage of meat occurs 2-3 times slower than when stored in air.

To increase the shelf life of meat, it is frozen and stored in this form for a long time. During the storage of frozen meat, the microorganisms remaining in it gradually die out, but some, including toxigenic ones, can remain viable. The microflora of frozen meat is dominated by micrococci. At a temperature not higher than -12 0 C, frozen meat is preserved for months, and the growth of microorganisms does not occur on it.

Microflora of poultry meat poultry meat, like cattle meat, is a favorable environment for the development of microorganisms. The species composition of microflora, types of spoilage of poultry meat are similar to microorganisms of meat of slaughtered animals, however, in poultry, especially in waterfowl, salmonella, the causative agents of food toxic infections, can be more common in the muscles.

For the development of spoilage processes, the method of slaughter and cutting of poultry is important.

Half-gutted poultry carcasses are usually more heavily contaminated with microbes than gutted ones. With half-gutting, intestinal rupture often occurs, which contaminates the cavity of the carcass with intestinal microorganisms.

Damage to the skin during the removal of feathers also contributes to infection of the muscles by microbes. The microflora of poultry kept at 1 0 C, by the time the sign of spoilage (foreign odor) appears, consists mainly of aerobic non-spore rod-shaped bacteria, mainly of the genus Pseudomonas (up to 70-75%).

Frozen poultry is stored without microbial spoilage at a temperature not higher than -12, -15 0 C for a long time, for months. On frozen chickens stored for a year at -7-10 0 C, yeasts and molds develop, and at -2.5 0 C - Pseudomonas, bacteria and yeasts.

Microflora of sausages Sausage products are usually eaten without additional heat treatment. Therefore, these products and the technological process of their manufacture are subject to increased sanitary requirements. As a rule, during the manufacture of sausages, the content of microbes in meat increases compared to their original amount. Already during the primary processing of meat (during deboning and trimming), the number of meat microflora significantly increases as a result of its contamination with microbes from the hands of workers, tools, equipment and from the air. The number of microorganisms in meat significantly increases during its grinding, as well as due to the microflora of the auxiliary materials and spices used (if they are not previously sterilized). Practice shows that grinding meat increases its contamination by an average of 10 times.

The contamination of minced meat also depends on the type of meat used. Stuffing minced meat into casings by hand can lead to infection with undesirable microorganisms. The vast majority of these are gram-negative non-sporing rods, micrococci, spore-forming bacteria, bacteria of the Escherichia coli group are found in much smaller quantities.

After stuffing minced meat into shells, boiled and semi-smoked sausages are fried and then boiled; half-smoked sausages are still smoked.

When roasting with hot smoke, the temperature inside the loaf is not more than 40-45 0 С, therefore the number of microorganisms decreases only on the surface of the loaves due to the action of antiseptic substances of smoke and temperature. In loaves of small diameters, the number of bacteria slightly decreases in the thickness. During the cooking of sausages (until reaching 70-72 0 C in the depth of the loaf), the content of microorganisms in sausages decreases by 90-99%, but still quite a lot of them can remain, especially in the depth of the sausage mass. Usually spore-bearing rods and the most resistant micrococci are preserved. Some toxin-forming bacteria may also persist.

After cooking, sausages are quickly cooled to avoid the reproduction of residual microflora in them.

In the process of smoking sausages, the number of bacteria in them decreases.

In the manufacture of smoked (raw-smoked, dry-cured) sausages, prepared minced meat after being stuffed into casings is subjected to maturation. To do this, the loaves are kept at low positive temperatures for several days, after which they are smoked and dried for a long time until the required moisture content of the product (25-35%) is reached.

During the maturation of minced meat, complex physicochemical, biochemical and microbiological processes take place in it, as a result of which the characteristic taste, aroma and consistency of the product are formed.

At present, raw smoked sausages are produced using molds (Penicillium candidum), applying them to the surface of the loaf. Developing mold covers the loaf of sausage with a thin layer, protecting it from excessive drying, exposure to light and oxygen, and also prevents the development of harmful bacteria and yeast. Metabolic products and mold enzymes penetrate into minced meat and contribute to the formation of a specific aroma and taste of sausage.

Boiled, liver sausages, sausages and brawns are especially perishable products. They have relatively high humidity and. in addition, they are prepared from raw materials that are usually highly contaminated with microorganisms. Although heat treatment destroys many of them, there are still a sufficient number of them.

Relatively more stable in storage are semi-smoked and especially smoked sausages, which are distinguished by a low water content, a high salt content and a significant treatment of smoke with antiseptic substances (during smoking).

Types of damage to sausages:

Souring in boiled and liver sausages is caused by fermenting carbohydrates introduced into minced meat in the form of flour and other herbal supplements, lactic acid bacteria, and the bacterium Clostridium perfringens.

The mucus of the membranes is usually due to the growth of non-spore-bearing rod-shaped bacteria and micrococci.

Molding of sausages appears during their storage at high humidity. Molds develop on the casing of sausages, and with loose stuffing, they can also be inside the loaf. Mostly smoked sausages are moldy. Potassium sorbate treatment is recommended to prevent mold development.

The rancidity of sausages is caused by the decomposition of fat by microbes. Sausages acquire a rancid taste, an unpleasant odor, and the fat turns yellow. The causative agents are most often bacteria of the genus Pseudomonas.

Pigmentation - the appearance on the shells of boiled and semi-smoked sausages of raids of various colors due to the development of pigment bacteria. On the casings of smoked sausages, coccal forms of bacteria and yeast often develop, forming a gray-white dry coating in the form of frost.

3. Microbiology of eggs. Eggs are a good nutrient substrate for microorganisms. However, the contents of the egg are protected from their penetration by the shell and shell membranes. An egg, freshly laid by a healthy bird, usually contains no or very few microbes.

The sterility of the egg can be preserved for some time, as it has a natural immunity. A significant role in immunity is played by the bactericidal substances contained in the egg (lysozyme, ovidin). During storage, the egg ages and the faster, the higher the temperature. Its immunity is reduced, and conditions are created for the penetration and reproduction of microorganisms in it. Some microbes mechanically penetrate through the pores of the shell; others, especially molds, grow through the shell.

The microflora of eggs is mainly of exogenous (after laying) origin due to contamination of the shell from the outside. However, it can also be of endogenous (lifetime) origin (in sick birds, pathogens enter the egg during its formation in the ovary and oviduct).

The bacterial flora of the egg surface is diverse. These are bacteria of the Escherichia coli group, spore bacteria, various types of pseidomonas, micrococci, mold spores. Pathogenic microorganisms, such as salmonella and staphylococci, can also be found.

Microorganisms that enter the egg usually develop near the point of penetration; their resulting accumulations (colonies) are visible during transillumination (ovoscopy (from Latin ovum - egg and Greek skopro - I look), determining the quality of eggs by translucent them with an ovoscope) in the form of spots. Some bacteria liquefy protein. They give it an unusual color (redness, greening, blackening) and an unpleasant smell (putrid, musty, cheesy). The yolk may remain unchanged; a large amount of gases (ammonia, hydrogen sulfide) can accumulate inside the egg, sometimes tearing the shell. Other bacteria cause liquefaction of the yolk, oxidative conversion of lipids, with the formation of fatty acids, aldehydes, ketones.

Often, the protein is mixed with the yolk and a homogeneous, cloudy, brownish liquid mass with an unpleasant odor is formed. With ovoscopy, such an egg is not translucent. The “sour egg” defect caused by Escherichia coli is not detected during ovoscopy, and when opened, the egg emits a pungent odor.

Molds grow primarily on the shell membrane and most rapidly near the air chamber. Then they destroy the shell membrane and penetrate into the protein.

To avoid additional contamination, eggs are recommended to be washed with disinfectant solutions before use.

Eggs are stored at a temperature of -2 0 C and a relative humidity of 85-88%. With sharp fluctuations in temperature, the shell is moistened, which contributes to the development of microorganisms.

Microflora of egg products Made from chicken eggs melange – frozen mixture of protein and yolk. The egg mixture usually contains a significant amount of various microorganisms, and during its manufacture pathogenic and opportunistic bacteria can enter. In the process of freezing and subsequent storage, the microorganisms in the melange partially die off, but a sufficient amount of them can still be preserved, especially if the melange was not immediately frozen after production.

Melange is a perishable product, it can only be stored frozen. When melange is thawed, microorganisms multiply intensively in it, so the thawed product must be sold within a few hours, keeping it chilled. To reduce the contamination of the egg mixture, it is often pasteurized for a short time (1-3 minutes) before freezing at relatively low temperatures (about 60 0 C), which do not change the physical state of the melange.

In the manufacture egg powder By drying the egg mass, not all microorganisms die. Under proper storage conditions, microorganisms cannot develop in the powder, since it has a low moisture content (3-9%), but many remain viable for a long time.

4. Microbiology of fish. Fish meat has a looser texture than the meat of warm-blooded animals, since there is less connective tissue in the muscles of fish, and this contributes to the spread of microorganisms in the body of the fish. The amount and composition of the surface microflora of freshly caught fish can vary significantly depending on the breed and type of fish, the nature of the reservoir, season, area and fishing technique. Among them, aerobic, sporeless, gram-negative rod-shaped bacteria of the genus Pseudomonas, spore-forming bacteria, and yeast predominate.

Fish caught from polluted waters may contain E. coli, salmonella and enterococci. Gills and intestines are the most contaminated with microorganisms. The causative agents of botulism are found, especially in the intestines of sturgeons. On sea fish there is a causative agent of poisoning such as toxic infections.

Fresh chilled fish- a product of short-term storage (several days) even at a temperature of about 0 0 C. At the same time, small fish deteriorate faster than large ones. On chilled fish, bacteria first multiply on the surface and gills, from where they then enter the body. In the tissues of the body of the fish, bacteria multiply less intensively.

The development of microorganisms is accompanied by significant changes in the chemical composition of fish meat. Putrefactive processes develop, as a result of which a volatile compound, trimethylamine, is formed, a substance that causes the appearance of a specific unpleasant odor that is characteristic of perishable fish.

For longer preservation, the fish is frozen or subjected to other methods of preservation: salting, smoking, pickling, drying.

Frozen fish can be stored for a long time (months) without microbial spoilage at a temperature not higher than -12-15 0 C. Covering the fish with glaze and storing at -18 0 C is a good protection. This temperature excludes the development of microorganisms.

Frozen fish may contain various micrococci, rod-shaped spore-forming and non-spore-forming bacteria, and mold spores are found in small quantities.

When defrosting, especially slow, some microbes die, but the remaining microbes begin to multiply rapidly. In this regard, the product should be thawed immediately before use.

Ambassador is one of the old ways of preserving fish. The preservative effect of salting is due to the high osmotic activity of the salt solution. Table salt inhibits cell reproduction. Predominant in salted fish are salt-resistant micrococci, spore-bearing rods, and mold spores. Therefore, various defects may appear in salted fish during storage. Some of them are due to the development of microorganisms. Red aerobic bacteria develop, causing "magenta" - red slimy plaque with an unpleasant odor. Spoilage of salted fish is caused by salt-tolerant micrococci that form a red pigment.

It is also possible to develop brown mold, which, like the magenta pathogens, gets on fish with salt. With mold damage, brown spots and stripes appear on the surface of the fish. This defect is called "rusting". Brown molds do not develop at temperatures below 5 0 C.

Slightly salted herring can be subjected to “saponification” under the influence of the development of aerobic cold- and salt-resistant bacteria. At the same time, the surface of the fish is covered with a dirty white smeared coating. The fish acquires an unpleasant taste and putrid smell. Toxigenic bacteria can also survive in salted herring: salmonella, Staphylococcus aureus, botulinum.

Lightly salted fish products from small fish (sprat, herring, anchovy), produced in hermetically sealed containers - preserves- in addition to a small amount of salt contains sugar and spices. Preserves are not subjected to heat treatment; to protect against spoilage, an antiseptic is introduced into them - sodium benzoate (0.1%). Good results instead of it or in combination with it are given by sorbic acid and the antibiotic nisin. The process of salting and ripening is carried out for 1.5-3 months. At temperatures from -5 to 2 0 C. Salt also provides some preservative effect. However, in preserves, an inhabitant of the intestines of fish from the genus Clostridium is often found. The active development of this bacterium can lead to the bombing of jars. To increase the stability of preserves in storage, it is recommended to use sterile spices.

Unlike sterilized canned fish, preserves are not long-term storage products even in the cold.

IN marinated fish the main factor inhibiting the development of bacteria, including putrefactive ones, is an acidic environment (due to the presence of acetic acid). Some preservative effect is exerted by salt, sugar added to the marinade, as well as spices containing essential oils and having phytoncidal properties. However, spices are often heavily contaminated with microbes. Molds can develop on pickled fish, which reduces the acidity of the product and creates the possibility of growth of putrefactive bacteria. Storing marinated fish in hermetically sealed containers and in the cold prevents it from molding.

Fish drying and curing- old ways of preserving it as a food product. When water is removed from fish up to a certain limit, unfavorable conditions are created for the development of microbes. Salt also has a preservative effect in dried and salted-dried fish.

With an increase in the humidity of the product and a favorable temperature, molds develop first. To prevent mold, these fish products must be stored in the cold and at a relative humidity of 70-80%.

Preservative start in smoked fish are mainly antiseptic substances of smoke (or smoking liquid). In addition to the effect of antiseptics, when hot smoking, high temperature has a detrimental effect on the microflora of fish, and when cold, the presence of salt and drying of fish. When smoked, a certain amount of microorganisms is preserved in the thickness of the fish. Bacteria of the genus Pseidomonas are very sensitive to the bactericidal substances of smoke; the most resistant are spores of bacteria and molds, as well as many micrococci.

The microflora of hot and cold smoked fish is similar to each other and is represented by up to 80% of various micrococci. There are spore-bearing and non-spore-forming rod-shaped bacteria, yeasts, and mold spores.

Hot smoked fish, compared to cold smoked fish, is richer in moisture, contains less salt, which is the reason for its faster spoilage. It is recommended to store hot-smoked fish at low temperatures (from 2 to -2 0 C) and for a short period of time.

5. Microbiology of cereals, flour, bread. Microflora of cereals. First of all, the microflora of cereals is determined by the composition of the microflora of the processed grain. The degree of contamination by microorganisms of freshly harvested grain of cereal crops, as well as grains of the same crop, can vary significantly. The environment of bacteria is dominated (up to 80-90%) by the non-spore, facultative aerobic rod-shaped bacterium herbicol.

As the grain is stored under conditions that do not allow the development of microorganisms, their number on the grain decreases due to the death of the herbicola bacterium, although it remains the predominant form. It is generally accepted that a large number of these bacteria on the grain is an indicator of its good quality. The composition of the fungal flora changes significantly. The dominant components are penicillium and aspergillus fungi (called "storage molds"), and typical representatives of freshly harvested grain, "field molds", are stored in single quantities.

Some molds found in cereals produce toxic substances. Therefore, cereals during long-term storage can be subject to various types of spoilage under the influence of microorganisms and enzymes in the cereal.

The possibility and intensity of the development of microbes are determined primarily by the moisture content of cereals, which changes during storage of products depending on the relative humidity of the air. The storage temperature also matters: the higher the moisture content of the cereal, the wider the temperature range for the possible development of microorganisms.

On cereals made from steamed grain, molds develop more intensively than on cereals from unsteamed grain. At low positive temperatures (4-5 0 C), molding of cereals is detected several months earlier.

flour microflora. The microflora of freshly ground flour, like cereals, is mainly represented by microorganisms of processed grain. The bulk consists of bacteria, among which herbicol prevails. In second place are spore-forming bacteria, the dominant of which are potato and hay sticks. Among the molds, species of the genera Penicillium and Aspergilus predominate, and mucor fungi are also found. The microflora of flour is quantitatively poorer than the microflora of processed grain. Since when it is cleaned before grinding and during the grinding process, a significant number of microorganisms are removed along with contaminants and grain shells, which are rich in microbes.

The degree of contamination of flour with microorganisms varies widely and is determined not only by the degree of contamination of the processed grain, but also by the nature of its preparation for grinding, cleaning method, grinding method, flour yield and its grade.

The lower the grade of flour, the more peripheral grain particles get into it, the more microorganisms it contains. The number of mold spores in flour of all varieties (the lower the grade, the more) exceeds their content in processed grain. The grinding products passing through the machines are contaminated with mold spores as a result of the contact of flour particles with the separating grain shells, with production equipment, with the air flow used in the production process.

Flour is a product less resistant to microbial spoilage than grains and cereals, the nutrients in it are more accessible to microorganisms. However, their development under the correct storage regime (at a relative air humidity of not more than 70%) is prevented by a low moisture content in the flour; there is even a gradual death of vegetative cells of bacteria.

With an increase in the relative humidity of the air, the microorganisms that were in the flour in an inactive state begin to develop, and molds develop first of all, since they are able to grow at a lower moisture content than bacteria. Baking properties of flour during their development are reduced. They acquire an unpleasant musty smell, which is usually transferred to bread.

molding flour- the most common type of damage to it. Moldy flour is not safe: Aspergillus and penicillium are found on it, capable of producing mycotoxins, many of which are heat-resistant and can persist in bread.

Many food products are a favorable environment not only for preservation, but also for the reproduction of microorganisms.

The entire microflora of food products is conditionally divided into specific and nonspecific.

The specific microflora includes strains of microorganisms used in the process of technological production of food products (lactic acid products, bread products, beer, wine, etc.).

Nonspecific microflora refers to random microflora that enters food products during their preparation, delivery, processing and storage. The source of these microbes can be raw materials, air, water, equipment, animals, people.

Infection of food products with microorganisms can lead to food poisoning and other diseases in humans.

Microbiological criteria for food safety are divided into four groups:

1. Sanitary-indicative microorganisms: BGKP, bacteria of the genus Escherichia, Klebsiella, Citrobacter, Enterobacter, Serratia are taken into account.

2. Potentially pathogenic microorganisms: coagulase-positive staphylococci, bacteria of the genus Proteus, sulfite-reducing clostridia, B. cereus.

3. Pathogenic microorganisms, including salmonella.

4. Microorganisms - indicators of the microbiological stability of the product (yeasts, molds).

Sanitary and bacteriological examination of food products

Sampling. Sampling is carried out sterile, with sterile devices, in sterile dishes. Samples are placed in the appropriate container, sealed. Transportation is carried out in cooler bags as soon as possible.

Sanitary and microbiological assessment of food products includes the determination of the total microbial number and titer of sanitary indicative microorganisms.

Determination of the total microbial number (TMC)

TMC - the total number of microorganisms contained in 1 g (cm 3) of the product. To determine it, use the method of multiple dilutions.

Multiple dilution method. In the study of dense substrates, the sample is crushed in a homogenizer or ground in a mortar with quartz sand and the initial suspension is prepared at a dilution of 1:10. A series of subsequent dilutions is prepared from the obtained suspension or initial liquid material so that from 50 to 300 colonies grow in agar when the last two dilutions are sown on a Petri dish. From the last two dilutions, 1 cm 3 is added to the cup and 10-15 ml of melted and cooled to 45 0 C MPA are poured. The dishes are incubated at 37 0 C for 48 hours, the number of grown colonies is counted. TMC is determined taking into account the dilution of the test material.

The method of limiting dilutions (titer). From the initial liquid material, a series of tenfold dilutions is prepared until the presence of one bacterial cell can be assumed in the last test tube. Sowing is done in a liquid selective medium, followed by the isolation of microorganisms on a solid nutrient medium and the study of their characteristics.

The titer is taken as the smallest amount of substrate in which one individual of the desired microorganism is found.

Determination of sanitary-indicative microorganisms

Sanitary-indicative microorganisms characterize the product in terms of epidemic danger.

The main sanitary-indicative microorganisms are BGKP and for quantitative accounting they use methods for determining the amount and titer. At the same time, the quantity is understood as the determination of the most probable number (MPN) of BGKP in a unit of mass or volume of the product.

Definition of HF BGKP.

To determine the NPs from a liquid product or an initial dense suspension, dilutions of 10 -1 , 10 -2 , 10 -3 are sequentially made, of which 1 cm 3 is inoculated into three test tubes with Kessler medium for each dilution. After 24 hours of incubation at 37 0 C, changes in the color of the medium and gas formation are recorded in the test tubes. Depending on the number of germinated test tubes, NPs of coliform bacteria are determined.

Determination of the titer of BGKP

Tenfold dilutions of the analyzed material are prepared and sown on Kessler's medium to identify the smallest amount of the product in which E. coli is present. The inoculations are thermostated at 43 0 C for 18-24 hours. Each tube is inoculated onto Petri dishes with Endo medium so as to obtain the growth of individual colonies. The inoculations are incubated at 37 0 C for 18-24 hours, after which smears are made from the grown colonies, stained according to Gram. When gram-negative rods are detected in smears, the colonies are subcultured on Hiss media with glucose. The presence of gas formation in test tubes with crops indicates the presence of BGKP.

The titer is set according to the smallest amount of the product in which BGCPs are found or according to standard tables.

In assessing food products by microbiological indicators, it is necessary to take into account the possibility of detecting pathogenic and opportunistic microorganisms. Food products are analyzed for the presence of salmonella, sulfite-reducing clostridia, staphylococci, and proteus. In a broader study, products are examined for fungal flora.

To study for Salmonella, a suspension is prepared from the analyzed products and inoculated on accumulation media (selenite, magnesium chloride broths). After daily incubation at 37 0 C, re-seeding is carried out on Endo, Levin, Ploskirev media or bismuth-sulfite agar. Further, the colonies are identified by taking into account the growth characteristics on the media of Giss, Ressel, Olkenitsky and in the agglutination reaction with monoreceptor sera.

To identify sulfite-reducing clostridia, the test material is inoculated into 2 test tubes with Kitt-Tarozzi, Wilson-Blair or casein-mushroom medium. One test tube is heated at 80 0 C to destroy the accompanying microflora. Crops are incubated at 37 0 C for 5 days. In the presence of characteristic growth, it is sufficient to ascertain the specific microflora in smears and, if necessary, to check toxin formation in a bioassay on white mice.

To detect staphylococci, the test material is inoculated on yolk-salt agar. The inoculations are incubated in a thermostat for 24 hours. Suspicious staphylococcal colonies are stained by Gram, they are reseeded onto milk agar, and the isolated culture is further identified.

To identify the proteus, the test material is sown on a slant agar by the Shukevich method. After daily incubation, smears are made from the upper edge of growth and, if they contain gram-negative polymorphic bacteria, a conclusion is made about the isolation of Proteus, if necessary, biochemical and antigenic typing is used.

microflora of medicinal plants,

Food products can contain a variety of microflora. The natural and harmless microflora of food products is a complex biocenosis, which serves as a biological defense against unwanted microorganisms. However, certain types of microorganisms can affect the quality of food products. In case of violation of the processing, storage or sale of products, these microorganisms can multiply to a significant level, lead to product spoilage and food poisoning.

Microbial spoilage of products can occur as fermentation, rotting, molding and decomposition of fats. Milk, cheeses and other dairy products undergo butyric fermentation due to the multiplication of spore-forming anaerobic bacteria in them. When ϶ᴛᴏm, butyric acid is formed, there will be an unpleasant taste and smell. Acetic acid fermentation leads to souring of wine and beer. Alcoholic fermentation caused by yeast is used in the production of alcohol, beer, etc. Lactic acid fermentation is used to prepare various fermented milk products.

Putrefaction, the process of decomposition of proteins with the formation of foul-smelling gases, caused by the action of a complex of putrefactive microbes, is the cause of spoilage of many protein products. Mold fungi cause molding of products when they are stored in refrigerators, as fungi are resistant to low temperatures.

Of particular danger is the contamination of food products with pathogenic microorganisms, many of which are able not only to remain viable in products for a long time, but also to multiply intensively in them.

Microflora of dietary fats

Distinguish between natural fats of animal and vegetable origin and fatty products of industrial production (margarine, mayonnaise). Melted animal fats and vegetable oils contain very little moisture and will be an unfavorable environment for most microbes.

Butter contains a lot of moisture, microbes develop both on the surface of the butter and inside it. Putrefactive and other bacteria, yeast, multiplying on the surface of the oil, decompose proteins and fats, lead to the formation of staff (bright yellow layer) During long-term storage of oil, mold fungi (odium, mucor, etc.) develop on the surface. Rancidity of the oil is caused by fat-splitting bacteria, bitter taste is also given by the products of protein breakdown by proteolytic bacteria and micrococci.

Microflora of eggs and egg products

Egg - an excellent breeding ground for microorganisms. With fluctuations in storage temperature, "thermal" respiration is inherent in eggs. An increase in temperature leads to the expansion of the contents of the egg and the displacement of air from the path (air chamber) through the holes to the outside. When the temperature drops, air is sucked into the egg. Together with air, mold spores and various ones, incl. pathogens, microorganisms, Escherichia coli, Proteus coli and other putrefactive bacteria, which are deposited on the shell membrane, which keeps them from penetrating into the protein.

Eggs obtained from a sick bird become infected endogenously, i.e., the infection enters the contents of the egg before the shell is formed. It is possible for pathogenic microorganisms to enter the egg exogenously (from the outside) through damage to the shell. In the protein of a fresh egg, microbes, incl. salmonella, do not survive due to the bactericidal action of lysozyme.

The presence of Salmonella is most often found in the eggs of waterfowl. In adult ducks and geese, salmonellosis is asymptomatic, but with ϶ᴛᴏm, the shell and yolk of eggs become infected with salmonella.

Mold spores usually develop on the surface of the egg shell, forming colonies of various sizes, which look like spots when candling or completely cover the egg (“cuff”). The mold gives the egg an unpleasant musty smell, makes it unsuitable for food.

During storage, the protective properties of lysozyme are reduced, and microbes penetrate the egg. The reproduction of putrefactive microflora causes the processes of decay with the formation of decay products of egg proteins, incl. and toxic, with an unpleasant taste and smell - ammonia, hydrogen sulfide, etc. This type of egg spoilage is called "putrefactive decomposition." The use of eggs with such a defect is not allowed.

Egg powder may contain an increased number of different microorganisms, incl. Proteus and Escherichia coli. There is a high probability of Salmonella getting into it, so egg powder must be subjected to reliable heat treatment. Melange (a mixture of protein and yolk), due to the increased risk of salmonellosis, is frozen and is not used in public catering.

Microflora of canned food

The criteria for the safety of canned food products will be the absence of microorganisms and microbial toxins in them that cause food poisoning. The most dangerous food poisoning associated with the use of canned food will be botulism and toxic infection caused by perfringens bacillus. Botulinum bacillus and bacillus perfringens ᴏᴛʜᴏϲᴙ tend to spore-forming anaerobic mesophilic bacteria from the group of sulfite-reducing clostridia. Clostridia spores and other gas-forming bacteria are able to withstand high temperatures during canning and multiply in canned food in the absence of oxygen to produce carbon dioxide and hydrogen, causing jar inflation (bombing). multiply.

Vegetable and meat-and-vegetable canned food can be subject to flat-acid spoilage - souring of the product without swelling of the can. This type of spoilage is caused by thermophilic aerobic and facultative anaerobic acid-forming bacilli.

With abundant infection of raw materials and insufficient sterilization in canned and semi-preserved food (pasteurized, etc.), non-spore-forming microorganisms can remain viable - stakes and molds, molds, yeast, Staphylococcus aureus, etc.

S. aureus refers to non-gas-forming microorganisms, the reproduction of which in canned food is not accompanied by bombing. In these cases, canned food can cause staphylococcal toxicosis and other food poisoning. Reproduction of staphylococci and accumulation of enterotoxin stops at low pH values ​​in canned food.

Microflora of grain products and bread

Microorganisms (bacteria, mold spores, yeast, etc.) enter the grain from the soil and with dust. The microflora of cereals and flour is determined by the microbial composition of the grain. In 1 g of grain products there can be from several thousand to a million microbes.

Of epidemiological significance is the defeat of grain by mold fungi dangerous to humans - ergot, fungi of the genus Fusarium and aspsrgillus.

Ergot and mold fungi of the genus Fusarium and Aspergillus are capable of releasing mycotoxins into grain, causing severe food poisoning - mycotoxicoses. Mycotoxins can have carcinogenic and other dangerous effects on humans in very small quantities, they are not destroyed in products during heat treatment.

Flour is less resistant to microbial spoilage than grains and cereals. In case of violation of storage conditions, when moistened, an increase in the acidity of flour due to the multiplication of lactic acid bacteria, the multiplication of mold fungi and, as a result, the appearance of an unpleasant taste, smell or lumpiness of flour is possible.

When baking bread, most microorganisms die, but the spores remain viable.

Wheat bread can be affected by "stringy (potato) disease". Reproduction of the causative agent of the ϶ᴛᴏth disease of bread Do not forget that you. subtilis is favored by the low acidity typical of wheat bread.

When cooling bread or when storing in bulk in conditions of high temperature and humidity, spores should not be forgotten. subtilis germinate and break down bread starch into dextrins with their enzymes. The crumb first acquires an unpleasant smell of overripe melon or valerian, becomes sticky, then darkens and becomes viscous. Bread affected by "potato disease" is unsuitable for food purposes.

Bread molding is caused by the development of fungi Peniciilium glaucum (green mold), Aspergillus glaucum (white mold), Mucor macedo (capitate mold), the spores of which fall on bread from the air after baking bread.

Microflora of vegetables, fruits and berries

On the surface of fresh vegetables and fruits, there are a large number of various microorganisms that get there from the soil, water and air. The presence of skins, phytoncides, essential oils and organic acids prevents the development of microbes that cause spoilage of fruits and vegetables. Lingonberries and cranberries are particularly resistant to spoilage due to their content of benzoic and sorbic acids.

When the skin of fruits and vegetables is damaged, the microbes that cause spoilage multiply on the surface and get inside the pulp. The processes of microbial spoilage are promoted by overripeness and long-term storage of fruits and vegetables. Rot and other spoilage of vegetables and fruits are caused by mold fungi (late blight and dry rot of potatoes, black cancer of apples and pears, etc.), bacteria (wet rot of potatoes, black spot of tomatoes), yeast (spoilage of berries) Certain types of fungi from the genus Penicillium, multiplying on apples, tomatoes, sea buckthorn berries, they are able to secrete the mycotoxin patulin, which has a pronounced carcinogenic and mutagenic effect.

As a result of raw consumption of soil-contaminated vegetables, fruits and berries, dysentery, typhoid fever, cholera and other intestinal infections can occur. Familial outbreaks of dysentery have been reported with strawberries. The terms of survival of pathogenic microorganisms and helminth eggs on the surface of vegetables and fruits can significantly exceed the terms of their storage before sale. The use of vegetables, fruits and berries without heat treatment can lead not only to intestinal infections, but also to yersiniosis, geohelminthiasis, amoebic dysentery, etc.

Vegetables can become infected with Yersinia sticks from rodents, from contaminated soil or water. With long-term storage in vegetable stores, Yersinia multiply on the surface of vegetables and accumulate in significant quantities sufficient to cause a human disease. Most often, the cause of jereiniosis is the use of salads from raw vegetables of the old crop in spring or early summer.