Microbiology of food products of animal and plant origin - document. Microbiology of meat and meat products

Microbiology of food products

animal and plant origin

The quality of any food product (meat, fish, milk, fruits, vegetables, etc.) depends primarily on the quantitative and qualitative composition of the microorganisms contained in it. Under favorable conditions, they develop, causing rapid spoilage of food - rotting, souring, fermentation, etc. To keep products fresh for a long time, special conditions are created in which the development of microorganisms is excluded, slowed down or suspended. For this purpose, various methods of "preservation" are used - long-term storage of perishable products and the development of microorganisms in them. These methods include the impact on microorganisms of various environmental factors (temperature, drying, the use of preservatives, etc.). For the correct choice of ways to influence microorganisms of various factors in order to increase the shelf life of finished food products, it is necessary to know the microbiology of these products, the pattern of development and the nature of the impact of these factors on food microorganisms.

Microbiology of food products of animal origin

Microbiology of meat and meat products

Muscles and blood of healthy livestock do not contain microorganisms. Meat becomes infected with microorganisms during its processing at meat processing plants. In the process of slaughtering livestock, primary processing of carcasses, microbes from the skins of animals, from the intestines, from the slaughter and processing implements get to the surface, and through the lymphatic, blood vessels, along the tendons and bones penetrate into the meat carcasses. The lower the temperature of the carcasses, the fatter, the more fat, in the presence of a drying crust on the surface of the carcasses, the penetration of microbes into the meat is slower. The development of microbes is facilitated by elevated temperature and humidity of the surrounding air.

On 1 cm 2 of the meat surface, up to several hundred thousand microorganisms are found - putrefactive bacteria, salmonella, sarcins, filamentous fungi. All of them cause spoilage of meat with a change in color (bluish, greenish, bright red spots), the appearance of mucus, a sticky surface, and a putrefactive odor. The meat changes its presentation and is not subject to culinary use.

!!! To preserve the quality of meat carcasses, meat pieces, the conditions and terms of its storage should be strictly observed.

Chopped meat more contaminated with microorganisms than pieces of meat, tk. the contact surface of minced meat with air, meat grinder increases, tissue is destroyed, meat juice partially leaks out, which creates favorable conditions for the development of microbes.

!!!Minced meat is stored for a short time and at a low temperature.

poultry meat represents a greater sanitary hazard than animal meat, tk. the bird is often half-gutted: with a head, legs, internal organs, in which there are many microorganisms. In the intestines of waterfowl (ducks, geese) there are a lot of salmonella, which, during processing (removal of the intestines) and pre-slaughter starvation, seed the entire carcass. At catering establishments, special workplaces are organized for processing poultry.

Meat by-products are heavily contaminated with microorganisms as a result of their ingress from the external environment to external organs during the life of animals (legs, tails, heads, ears) and increased moisture content (liver, brains, kidneys). Therefore, by-products are always delivered to catering establishments frozen and processed in the meat shop at separate workplaces.

Sausages contaminated with microbes inside and out. Microbes get inside the loaves with minced meat. During the heat treatment of sausages (steam cooking, smoking with hot smoke), most microbes die. Bacillus spores remain viable, botulinum spores are especially dangerous. On the surface of loaves of sausages, microorganisms are more active (putrefactive and Escherichia coli, filamentous fungi, etc.). They spoil the quality of sausages, causing rotting, mold. The least stable during storage is a group of boiled sausages, jellies, brawns, especially those prepared from lower grades of meat or from raw materials heavily seeded with microbes (trimmings, offal). In addition, these products have high humidity. Semi-smoked, boiled-smoked, smoked sausages are more stable during storage, because produced from less contaminated high-quality raw materials, less moisture, high salt content and treatment with smoke substances during storage.

Microbiology of fish and fish products

Fish is a perishable product, because it is heavily seeded with microbes outside, inside the intestines and in the gills of the head. After the catch, the microbes penetrate the tissue of the fish, causing it to spoil. Micrococci, sarcins, putrefactive sticks are found in fish. Botulinus bacillus is especially dangerous. To prevent botulism, caught large fish (sturgeons) are immediately gutted and frozen. If chilled fish is not properly stored, microbial proteolytic enzymes break down proteins with the formation of foul-smelling substances (rotting).

Freshly frozen fish keeps longer. Sometimes filamentous fungi (mold) develop on the surface. The freshness of the fish is judged by the smell, the color of the gills and the texture of the tissue.

Salted, dried, smoked fish is more stable during storage, because. salt, dehydration process, smoke substances create unfavorable conditions for the development of bacteria.

Non-fish products of the sea (crustaceans, bivalves, cephalopods) are contaminated with microbes of sea water and silt from the intestines of the animals themselves. Therefore, these products are perishable, quickly rotting. When eating raw shellfish (oysters), food poisoning often occurs, cases of food infections (typhoid fever) are known.

Freshly caught fish can contain a large number of micro-organisms. The quantitative and qualitative composition of microorganisms found on fish depends on the fishing season, water temperature, the depth of the fish, the degree of water pollution, and the method of fishing. The number of microorganisms on the surface of freshly caught marine and freshwater fish varies widely: 10 2 ... 10 7 CFU / cm².

The qualitative composition of microorganisms on the surface of the fish is close to that of water microorganisms.

Basically, microorganisms of the seas and oceans are represented by bacteria of the genera Pseudomonas, Micrococcus and Bacillus.

rotting fish is caused by many aerobic putrefactive bacteria - Proteus (Proteus vulgaris), pseudomonads (Pseudomonas fluorescens, P. fradi, P. putrifaciens), bacteria of the intestinal group (Escherichia coli), etc. Among the obligate anaerobes, putrefaction of fish is caused by Clostridium sporogenes, C. putrificum .

Simultaneously with the decomposition of protein in the tissues of fish, hydrolysis of fats and lipoid substances occurs, followed by oxidation hydrolysis products mainly under the influence of staphylococci and other bacteria pathogenic to humans (for example, Pseudomonas aeruginosa Pseudomonas aeruginosa), which have the enzyme lipase.

The main types of vice of salted fish are pink-red staining, the appearance of brown spots, bacterial decay.

The reason for the appearance brown spots ("rusting") on the surface of the fish are filamentous fungi.

On smoked fish, filamentous fungi (Penicillium, Aspergillus, Cladosporium) develop first of all. Sometimes spoilage is caused by yeast (Criptococcus, Debariomyces, Rhodotorula).

Microbiology of sterilized canned food

Hermetically sealed canned food from vegetables, fruits, meat, fish, subjected to sterilization in compliance with the established regime (temperature, time), does not contain microbes and is stable during storage.

Canned food can cause food poisoning if spore bacteria with high resistance to the sterilization regimen are preserved in them: spores of potato bacillus, butyric acid bacteria, causative agents of botulism. These microorganisms cause the process of decay, while gases are released: hydrogen sulfide, hydrogen, carbon dioxide, which cause biological bombing of cans. Such canned food must be destroyed due to the content of the toxin secreted by the botulinum bacillus. The bombing of canned food can be caused by non-spore microbes: cocci, E. coli, yeast, lactic acid bacteria, streptococci.

Some spore anaerobic microbes can spoil canned food without external changes cans (flat souring) - green peas, canned meat and sausages, canned baby food.

Only high-quality raw materials, compliance with the sanitary rules for processing it, observing the sterilization and storage regimen prevent spoilage of canned food and food poisoning by them.

Microbiology of milk and dairy products

IN raw milk even if asepsis rules are followed, a certain amount of bacteria is usually found in the milking process, and 1 cm 3 of freshly milked milk, subject to sanitary rules, can contain no more than 10,000 of thousands, and if these rules are not followed, from 170 thousand to 2 million bacterial cells. The qualitative composition of milk microorganisms also depends on the conditions of its production. With the machine method of obtaining in compliance with sanitary and hygienic rules, micrococci predominate in milk and lactic acid bacteria are present in small quantities. Contaminated milk contains a significant amount of micrococci, Escherichia coli, enterococci, putrefactive, butyric and lactic acid bacteria, yeast and spores of filamentous fungi. Among them there are microorganisms that can cause various kinds of defects in milk (rancidity, foreign taste and smell, discoloration - redness, blue, - ductility). There may also be pathogens of various infectious diseases (dysentery, typhoid, paratyphoid, brucellosis, tuberculosis, etc.) and food poisoning (streptococcus aureus, staphylococcus, salmonella).

For freshly milked milk characteristic antimicrobial (static) phase. All microorganisms that have got into milk do not develop due to the antimicrobial substances that are in milk and delay their development - lysozymes (“lactenins”), leukocytes and many other substances synthesized by the mammary gland and coming from the blood. Milk can only be considered fresh and complete during this phase. A sharp cooling of milk after milking to a temperature of 5 ... 6 0 C can prolong the antimicrobial phase of milk. Chilled milk must be delivered to the dairy in the static phase.

Phase of mixed microflora lasts 12 ... 18 hours. During storage, antimicrobial substances are gradually destroyed. In milk, all microorganisms that have got into it begin to develop. By the end of this phase, mainly lactic acid bacteria develop, and the acidity of the 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 the advantage of lactic acid bacteria comes - lactic acid bacteria phase while the milk is fermented.

Phase filamentous fungi and yeast is final. In this phase, with an increase in the concentration of lactic acid, the development of lactic acid bacteria themselves is suppressed. Their number is decreasing. First of all, lactic streptococci die off. Conditions are created for the development of filamentous fungi and yeasts (Geotrichum candidum, Penicillium, Candida, etc.). They use lactic acid and form alkaline protein breakdown products; the acidity of milk decreases, and putrefactive bacteria (Pseudomonas, Achromobacter, Clostridium, etc.) can again develop in it. The clot of milk disappears, it acquires a liquid consistency, gases accumulate, the product becomes unusable.

The most common defects in butter are staff, rancidity, bitter taste, mold, development of putrefactive and other unpleasant odors.

Staff expressed in a change in color and taste of the surface layer of the oil monolith. The process is caused by the development of putrefactive bacteria, yeast and filamentous fungus Geotrichum candidum. Lipolytic and proteolytic enzymes secreted by these microorganisms decompose fat and protein. Their development can only be prevented by storing the oil in sealed packaging and at low temperatures.

Rancidity oils cause microorganisms that produce lipase. These are, first of all, filamentous fungi Geotrichum candidum, Cladosporium, as well as bacteria Pseudomonas fluorescens, P.pyocyanea, Bacterium prodigiosum. Rancidity begins from the surface of the monolith, gradually penetrating inside. The oil takes on a bright yellow color. Fat hydrolysis products give the oil a characteristic taste and smell of rancid fat. To prevent blemish, cream is pasteurized at a higher temperature to kill lipase-producing microorganisms.

bitter taste the oil is given metabolic products of putrefactive bacteria, micrococci, etc., hydrolyzing proteins to peptones. A measure to prevent the occurrence of a defect is a high sanitary and hygienic culture of production and storage of oil in the refrigerator.

mold caused by mycelial fungus Geotrichum candidum, Penicillium, less often Aspergillus, Alternaria, Cladosporium. Some of them develop on the surface of the oil in the form of spots of different colors. More often than others, Cladosporium develops inside the voids in the form of black dots with a loose packing of the oil block. Mycelial fungi, as well as putrefactive rod-shaped bacteria of the genus Pseudomonas, as well as some spore-forming bacteria and yeast, possessing proteolytic and lipolytic enzymes, decompose lipids and proteins in oil, causing profound changes in it.

Measures to prevent defects in butter are a high sanitary and hygienic level of production, pasteurization of cream at a higher temperature and storage of butter at a temperature of -20 0 C and low relative humidity - not higher than 80%. To prevent oil molding, it is also recommended to treat the packaging material with a solution of propionic or sorbic acid salts.

Milk margarine contains microorganisms of two types: starter microorganisms used to ferment milk, which is part of margarine, and foreign microorganisms that enter during the production process with equipment, communications, water, air, from the hands and clothes of workers and other sources. The development of foreign microorganisms, which can cause defects in the taste and smell of margarine, is possible mainly 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. Unfavorable for the development of putrefactive bacteria is a low pH value (about 5.0). Active reproduction of microorganisms is possible only on the surface of the product or in places where condensation moisture accumulates. If margarine goes bad, it can become rancid, acidic, and moldy.

To protect against microbial spoilage, preservatives (benzoic or sorbic acids or their salts) are introduced into the product or the packaging material is processed.

Microbiology of eggs and egg products

Eggs are a good nutrient substrate for microorganisms. However, the contents of the egg (white and yolk) are protected from their penetration by the shell and membranes. A freshly laid egg from a healthy bird is usually free of micro-organisms. The shell performs a protective function, protecting the egg from the penetration of microorganisms. On top of the shell, when the egg is laid, a layer of mucus is deposited, which, when dried, forms an over-shell film - the cuticle, which includes lysozyme, which has microbicidal properties. The cuticle is easily damaged, so eggs intended for storage should not be washed. When the cuticle is damaged, the microorganisms enter the egg through the pores in the shell. Contamination of eggs with microorganisms can occur in endogenous and exogenous ways.

At endogenous way microorganisms penetrate the egg during its formation in the ovary or oviduct of a sick bird. Often, birds are latent carriers of pathogens of infectious diseases, they carry eggs containing viruses, bacteria, filamentous fungi, pathogens of salmonellosis and tuberculosis.

exogenous Contamination of eggs is associated with contamination of the shell with droppings, soil, bedding, feathers, etc.

Microorganisms that have entered the egg usually first develop near the point of penetration in the shell membrane. The resulting accumulations of them (colonies) are noticeable when candling (transillumination) in the form of spots. Their further reproduction leads to various changes in the proteins and lipids of the egg, to its deterioration. Bacteria multiply in the protein more slowly than in the yolk, due to the content of antimicrobial substances in the protein (lysozyme, ovidine, etc.), as well as high pH (more than 9). The rate of deterioration of eggs depends on the storage temperature, relative humidity, the condition of the shell, and the composition of microorganisms. The condition of the container and packaging material is of great importance. Eggs with dirty and damp shells spoil much faster than those with clean and dry ones.

Bacteria that cause spoilage differ in the composition and activity of their enzymes, and therefore the changes they cause are very diverse.

Bacteria of the genus Pseudomonas (P.fluorescens, P.aeruginosa) hydrolyze the constituent parts of the egg with the formation of specific decay products, due to which the protein becomes green. With the development of bacteria Proteus vulgaris and some representatives of the genus Pseudomonas, black rot appears. The contents of the egg liquefy and turn brown or black. The resulting gases often rupture the shell, and the contents spill onto neighboring eggs and contaminate them. Mixed rot is caused by Escherichia coli, Staphilococcus aureus and other bacteria. The consistency of the protein changes, it becomes liquid, its color changes, most often gray and emits a putrid odor. B. prodigiosum, M. roseus, some yeasts and filamentous fungi, when developing in an egg, stain its contents red. In this case, the protein can be liquefied and viscous. The yolk during these processes may remain unchanged. Some bacteria cause protein liquefaction by causing hydrolytic and oxidative conversion of lipids; in this case, fatty acids, aldehydes, ketones are formed. Often the protein is mixed with the yolk - a homogeneous, cloudy, brown liquid mass with an unpleasant odor is formed. When candling, such an egg does not shine through.

Spoilage of eggs by filamentous fungi has a different character. Fungi grow primarily on the shell membrane and most rapidly near the air chamber. Then they destroy the shell membrane and penetrate into the protein. In the initial stage of molding, when the egg is canned, a dark spot is formed at the place where the fungi develop. As the fungus develops, the size of this spot increases, and the egg becomes completely opaque, as the entire shell inside is covered with mold. Egg spoilage is most commonly caused by Penicillium, Cladosporium, Aspergillus, and the yeast Torulopsis vicola.

Microbiology of cereals

The composition of cereal microorganisms in terms of qualitative composition is close to the microorganisms of the grain from which it is made. However, the number of microorganisms in cereals is less due to the pre-treatment of grain, peeling, grinding, production technology. So in the steamed grain there are fewer microorganisms than in the unsteamed. Erwinia herbicola predominates in groats obtained from non-steamed grains, and spore-forming bacteria (Bacillus subtilis, B.pumilus) and micrococci predominate in groats from grains that have undergone hydrothermal treatment. Mycelial fungi are most often represented by penicilli and aspergillus, sometimes mucosal fungi are detected.

Microorganisms found in cereals are able to decompose protein, lipids, starch, pectin and ferment sugars with the formation of acids. Muscle fungi - produce mycotoxins, among which there may be carcinogenic ones, so cereals during long-term storage can be subject to various types of spoilage under the action of microorganisms, and also pose a danger to human health.

Microbiology of flour

mold, called mainly filamentous fungi genera Aspergillus and Penicillium are the most common types of flour spoilage, which also synthesize carcinogenic mycotoxins. Therefore, moldy flour is an unsafe product. The baking properties of flour during molding are reduced, the flour acquires an unpleasant musty smell, which is usually transmitted to bread.

Souring flour is caused by lactic acid and other acid-forming bacteria. As a rule, they develop into flour when it is moistened.

The rancidity of flour is due to the oxidation of its lipids, both with the participation of atmospheric oxygen and with the activity of microorganisms.

Microbiology of fruits and vegetables

On the surface of fruits, berries and other types of plant materials, they contain a large number of microorganisms that get on them from the soil, water, air, are introduced by insects, birds, etc.

Intact fresh fruits and vegetables have a natural immunity to microbial damage, due to both the anatomical structure, especially the structure of the integument, i.e. peel, and chemical composition (presence of organic acids, essential oils, phytoncides, etc.). Due to the lack of nutrients and moisture, only a few microorganisms, called epiphytes, can develop on the intact surface of fruits and vegetables. The species composition and abundance of these microorganisms depend on the type of plants, geographical, climatic and other conditions of their growth. Epiphytes are typical saprophytic microorganisms that can cause damage to plant materials when the integrity of the integument is violated, in overripe fruits and vegetables, gaining access to deep tissue layers. Epiphytic microorganisms make up a significant part of all microorganisms that inhabit fruits and vegetables. The entire development cycle of these microorganisms can take place in storage.

In the process of storing fruits, vegetables and fruits, their spoilage usually begins with the development of filamentous fungi, which, with the help of released hydrolytic enzymes, damage the skin, penetrate into the tissues and cause their destruction, called rot.

Vegetables that contain more protein and have an acidic juice reaction are most likely to have bacterial rot. Its causative agents are non-spore-forming bacteria of the genera Erwinia and Pseudomonas. Of the spore-forming bacteria, rot pathogens are Bacillus subtilis, B. polymixa, B. macerans. The tissues of fruits and vegetables undergo maceration (decay), darken, soften to liquefaction.

Spoilage of fruits, and especially berries, is also caused by yeast, which ferments sugar into ethyl alcohol and carbon dioxide. At the same time, fruits and berries acquire an alcohol flavor, and sometimes turn sour due to the development of yeast and acetic acid bacteria.

N.G. Ilyashenko, T.V. Pichugina, LN Shaburova Microbiology of food products of animal and vegetable origin. Tutorial. M.: MGUPP, 2009.

Animal and vegetable origin and safety standards for these products. ... quality control of medicines and food products: Directory / V. A. Galynkin and...

Ural State Academy of Veterinary Medicine

Course work

Subject: Microbiology

on the topic: MEAT AND MEAT PRODUCTS

INTRODUCTION

1. MICROFLORA OF MEAT

2. CONTAMINATION OF MEAT CARCASS DURING SLAUGHTERING OPERATIONS

3. MICROFLORA OF MEAT AND MEAT PRODUCTS DURING REFRIGERATION AND FREEZING

4. MICROFLORA OF MEAT AND MEAT PRODUCTS DURING SALT

5. MICROBIAL CHANGES IN THE PRODUCTION OF SAUSAGES

6. MICROFLORA OF CANNED MEAT

Bibliography:

INTRODUCTION

Food products are constantly and quite intensively contaminated with various microorganisms. The study of this microflora has been carried out in different countries for many decades. The studies carried out made it possible to identify a number of regularities in the contamination of food products, the formation of microflora under various technological processes of food processing, its role in the biological and nutritional value of products, as well as the etiological role of certain foods in the transmission of infectious diseases and food poisoning in humans.

It is customary to differentiate the microflora that seed food products into specific and nonspecific. The first includes microorganisms artificially introduced into the product to give it certain properties. Such microflora in the form of starter cultures is introduced into food products during the preparation of all lactic acid products, bread. Specific microflora includes the microflora that forms in individual products at certain stages of their production technology - sauerkraut and other vegetables, cooking sausages, beer, wine, etc. . Being an obligatory technological link in the production of these products, microorganisms provide certain organoleptic properties of these products and, according to a number of parameters, their chemical composition. The microflora formed during the maturation of these products provides certain terms and conditions for the storage of food products. Thus, the specific microflora has a positive effect on food products.

Microorganisms that in vivo seed organs and tissues of animals in case of disease or violation of the barrier functions of the intestine in case of injuries, starvation, overheating or hypothermia of the animal body are nonspecific. If the sanitary conditions for obtaining food products at the stages of harvesting, processing, transportation and storage are not observed, secondary contamination with microorganisms is also possible.

Nonspecific microflora can be represented by saprophytic microbes, food spoilage microbes, potentially pathogenic and pathogenic microorganisms.

Saprophytic microorganisms that enter food products, in some cases, can contribute to the development of certain biochemical processes that are natural for a given food product, which determine its certain properties. In this case, they can be considered as microflora specific for a given food product. By exhibiting antagonistic properties in relation to other microorganisms, saprophyte microbes often ensure the safety and epidemiological safety of food products.

Microorganisms that cause spoilage of food products most often have a pronounced proteolytic activity. Their entry into products is undesirable, since they reduce their biological and nutritional value, and in some cases make it impossible to use products in food. Microorganisms contribute to the accumulation of toxic components that can lead to food poisoning. Among potentially pathogenic microorganisms, one should first of all point out the causative agents of human food poisoning. This is a large group of bacteria, primarily the Enterobacteria family, which, after their death, form toxic substances.

The second group of microorganisms that cause food poisoning in humans belong to the group of toxicoses. Microbial food toxicosis associated with the accumulation of bacterial toxins and toxins of microscopic fungi in food products, and human poisoning can occur in the absence of a toxin-producing microorganism.

Various types of the above microorganisms can multiply in food products, leading to food poisoning of mixed etiology.

Finally, under certain conditions, food products can be contaminated with pathogenic microorganisms that cause dysentery, cholera, brucellosis and anthrax, listeriosis, and yersiniosis. Some rickettsiosis (Q fever) and viral diseases (foot-and-mouth disease, poliomyelitis) and other infections can be transmitted by food.

1. MICROFLORA OF MEAT

Meat and meat products are constantly under the scrutiny of researchers involved in food microbiology. A number of monographs and literary reviews are devoted to the microbiological aspects of obtaining benign meat and products of its processing. Target microbiological installations are used to improve technological processes, which, in turn, are aimed at improving the quality of the products obtained.

According to the FAO classification, it is proposed to divide the microorganisms that contaminate meat at various stages of the technological process into four groups: pathogenic, opportunistic, sanitary-indicative and saprophytes. Through meat, pathogens of infectious diseases (foot and mouth disease, tuberculosis, Q fever, tularemia, leptospirosis, listeriosis, bacterial toxic infections and intoxications, mycotoxicoses, enterovirus diseases) can be transmitted to humans. Among the sanitary-indicative microorganisms include Escherichia coli, group O streptococci. The saprophytic microflora of meat includes about 30 types of various bacteria. All investigators acknowledge that animal meat can be contaminated in two ways. In a living organism there are always microorganisms that, under certain conditions, can penetrate into the blood and muscles. This path is called endogenous, that is, occurring during the life of the animal. Post-mortem contamination of the carcass associated with the entry of microorganisms from the environment is called exogenous.

Studies of the meat of animals slaughtered under non-sterile conditions indicate that in most cases it is contaminated with microorganisms. Some authors believe that most of the deep tissues and internal organs of healthy animals contain a significant number of microorganisms (10 cells 2 /g or more), others argue that deep tissues are sterile, others say that there are single microbial cells only in the liver, spleen in the lymphatics. nodes.

The mechanisms of intravital seeding of the animal body were studied. Meat obtained in the conditions of a meat-packing plant and slaughterhouses is most often contaminated with permanent inhabitants of the gastrointestinal tract of the animal, which is associated with a decrease in the overall resistance of the body. A variety of unfavorable factors can affect the animal: a stressful state associated with a change in the usual environment, a state of hunger and thirst, hypothermia or overheating, fatigue during long distance driving.

Meat obtained from weakened, emaciated and overworked animals will always be contaminated with microorganisms. When fasting for less than a day, there is a slight contamination of organs and tissues of cattle with microorganisms from the gastrointestinal tract. Starting from 48 hours, it increases. After a week of fasting, the contamination of muscles and internal organs with Escherichia coli reaches 100% of the studied samples.

A number of works are devoted to the study of the composition of the microflora of the gastrointestinal tract of animals. In the gastrointestinal tract of animals there is a large number of microorganisms that get there, primarily with food. Their number reaches 10 8 microbes per 1 g of the contents of the rumen. In the acidic environment of the stomach, part of the microflora dies, but viable bacteria, yeasts and molds can remain.

In the small intestine, there is a further decrease in the level of microorganisms to 104 cells/g of content. In the large intestine, due to metabolic processes, the activity of the microflora is activated and its increase to 10 8 cells / g of content. Microorganisms related to gram-negative rod-shaped bacteria, gram-positive enterococci, clostridia, yeasts and molds live here. The composition and ratio of microflora depend on the composition of the feed, the department of the gastrointestinal tract, the time of year and the age of the animal.

In addition, contamination of meat during the life of the animal may be associated with other organs containing microorganisms. These include the upper respiratory tract and the udder. Most of all, this is coccal microflora, less often bacilli, yeasts and molds are found there. Inhabitants of the gastrointestinal tract can be potentially pathogenic and pathogenic microorganisms. In the last 20 years, intestinal yersiniosis has occupied a certain place in the structure of human diseases. The cause of these diseases is most often the meat of cattle and pigs. So, in the study of pig tongues in various stores in Belgium, it was found that 50% of the samples contained the causative agent of this infection. According to the authors, this microorganism is a natural inhabitant of the nasopharynx of animals and eating organs related to the gastrointestinal tract can cause yersiniosis, since the enterotoxin withstands heating at 120°C for 30 minutes and storage in a refrigerator at 4°C. C for 7 months.

The intestines of animals are the habitat of Clostridiosis. The works of G.I. Sidorenko and Yu.P. Pivovarov, back in the 60s, the possibility of intravital seeding of organs and tissues of weakened and sick animals was established.

There are many studies in the literature devoted to the study of microbial contamination of meat from animals with various clinical diseases and clinically healthy animals. Some authors call a very high percentage of seeding in the meat of forced slaughter animals (from 48 to 70%), others give lower values. Thus, the frequency of detection of clostridia in the muscles of cattle with traumatic injuries, according to a number of researchers, was 8.5%, in the lymph nodes - 15.5%, in the liver - 19%; respectively 3.9, 4.2 and 8.5% - in the organs of clinically healthy animals.

When examining pigs, similar results were obtained. From the muscles of sick animals, the percentage of excretion was 12.2%, from the lymph nodes - 16.9%, from the liver - 22.4%; respectively 5.1; 6.4 and 9.9% - from the organs of clinically healthy animals. The data obtained oblige the veterinary service to improve the work on identifying weakened animals.

Microorganism contamination of organs and tissues is observed in animal injuries. In muscle tissue located a few centimeters from the injury site, the amount of glycogen decreases, which leads to more intensive reproduction of microorganisms, most often staphylococci, bacteria of the Escherichia coli group and others.

Without causing disease in the animal, salmonella can be in the intestines for a long time. With a decrease in the protective forces of the animal, they penetrate into the mesenteric lymph nodes, then into the blood and, spreading throughout the body, cause secondary salmonellosis. Many works are devoted to the study of bacteria carrier among animals. Bacteriocarrier is widespread among animals and birds.

In connection with a disease or injury from the intestine or the site of injury, the body of the animal can be infected with pathogenic microorganisms (salmonella, Staphylococcus aureus, pathogens of tuberculosis, foot-and-mouth disease, brucellosis), in addition, the inhabitants of the intestine penetrate into the blood. Of certain importance for endogenous infection of meat is the agonal invasion of microorganisms. Some authors combine it with post-mortem endogenous seeding of organs and tissues, which begins immediately after bleeding, that is, the clinical death of animals. During this period, through the mucous membranes of the nasopharynx and intestines, microorganisms can penetrate into the surrounding tissues.

The exogenous way of contamination of meat is associated with the stages of carcass cutting, subsequent transportation, storage conditions, technology for obtaining meat products and the sanitary condition of the enterprise.

Short description

Microbiology of meat and meat products

Microbiology

111900.62 - Veterinary and sanitary examination

Ways and sources of contamination of meat with microorganisms:

Endogenous
Exogenous

Microorganisms, as a rule, are not contained in the blood, muscles and internal organs of healthy animals, if the rules of sterility are observed.

endogenous

It can occur both during the life of the animal, and after slaughter.
Intravital seeding of meat occurs in animals with infectious diseases, the organs and tissues of which contain the causative agent of the disease.
The spread of the pathogen in organs and tissues depends on the type of infection, its course and the state of the organism of the sick animal.

P with fatigue arising in the process of transporting or driving animals to meat processing plants.

exogenous

Occurs during the slaughter of animals and subsequent carcass cutting operations.

Sources:

Animal skin .
Contents of the gastrointestinal tract .
Air .
Equipment .
Vehicles .
Tools .
Hands, clothes and shoes of workers in contact with meat .
Water used to strip carcasses.

Subject to sanitary and hygienic rules for the production of meat per 1 cm 2 surface area of fresh meat carcasses, there are no more than a few thousand or tens of thousands of bacterial cells.

With a low level of sanitary condition in the shops for slaughter and cutting carcasses by 1 cm 2 surface area of the carcass, the number of microorganisms can reach hundreds of thousands or even millions.

The qualitative composition of the microflora of fresh meat is diverse. . The bulk of this microflora is made up of microorganisms that are permanent inhabitants of the gastrointestinal tract.

Most often found: staphylococci and micrococci, BGKP, various types of putrefactive aerobic bacilli, anaerobic clostridia and non-spore bacteria, yeast, lactic acid bacilli, spores of streptomycetes and mold fungi. Salmonella is sometimes found, less often - other pathogenic microorganisms. Meat is stored refrigerated or frozen. When storing meat in a chilled state, the microflora that has fallen on it goes through four stages of growth: a lag phase, a logarithmic growth phase, a stationary phase, and a dying phase.

Staphylococci

micrococci

Clostridia

Actinomycete spores

Ambient temperature
Humidity.
osmotic pressure.
medium pH.

slime

Occurs during the initial storage period. It usually appears on the surface of meat carcasses in the form of a continuous mucous coating, consisting of various bacteria, yeasts and other microorganisms.

Mucus causative agents :

Aerobic bacteria of the genera Pseudomonas and Achromobacter;
Psychrophilic bacteria of childbirth Lactobacterium, Microbacterium, Aeromonas ;
At temperatures above 5 ° C, micrococci, streptococci, Strepmomyces, and putrefactive ones multiply.

The rate of appearance of mucus depends on the humidity and temperature of storage: than  0 t , the longer the save time.

It can occur under both anaerobic and aerobic conditions.

anaerobic decay : begins in the depth of muscle tissue, which is caused by anaerobic and facultative anaerobic bacteria that enter the meat endogenously from the gastrointestinal tract of the animal. There is a change in color, texture and other organoleptic indicators of meat.

Aerobic decay : under the influence of proteolytic enzymes of putrefactive bacteria, meat proteins gradually decompose with the formation of inorganic end products - ammonia, hydrogen sulfide, carbon dioxide, water, phosphoric acid salts.

acid fermentation

Accompanied by the appearance of an unpleasant sour smell, gray or greenish-gray color on the cut and softening of the muscle tissue.

The causative agents are: psychrophilic lactic acid bacilli of the genus Lactobacterium, bacteria of the genus Microbacterium and yeast, which are able to develop deep in muscle tissue under anaerobic conditions. Reproducing in meat, these microorganisms decompose carbohydrates in muscle tissue with the release of organic acids.

Pigmentation

This is the appearance of colored spots on the surface of the meat due to the multiplication and formation of colonies of microorganisms on the surface of the meat, which have various pigments.

The causative agents are: aerobic or facultative anaerobic microorganisms: Ps.fluorescens, Ps. pyocyanae, Ps. syncyanea, Bact. prodigiosum, sardines, pigment yeast, most often of the genus Rhodotorula.

mold

It rarely appears if the temperature and humidity conditions of storage are observed, since the development of mold fungi is suppressed by actively growing psychrophilic aerobic bacteria. Most often it occurs at low temperatures in conditions of low humidity. Molds, when developing on the surface of meat, as a rule, do not cause deep changes in it, but they can create more favorable conditions for the subsequent development of putrefactive bacteria.

glow

It arises as a result of reproduction on the surface of meat of luminous (photogenic) bacteria that have the ability to glow - phosphorescence. The glow is due to the presence in the cells of these bacteria of a photogenic substance - luciferin, which is oxidized by atmospheric oxygen with the participation of the luciferase enzyme. The group of photobacteria includes various non-spore gram-negative and gram-positive rods, cocci, vibrios. A typical representative of photogenic bacteria is Photobacterium phosphoreum - an immobile coccus-like bacillus. Most of the luminous bacteria live in sea water and on the body of the inhabitants of the sea, including fish. These bacteria get on the meat when it is stored with fish.

GBPOU KK BITT "Belorechensk Industrial and Technological College"

Performed by a student of group 109 "A"

Kremenskaya Albina Israilovna

Lecturer Khachatryan Azatuhi Araovna

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Ministry of Education and Science of the Russian Federation

FEDERAL STATE BUDGET

EDUCATIONAL INSTITUTION

HIGHER PROFESSIONAL EDUCATION

"ORENBURG STATE UNIVERSITY"

Faculty of Chemistry and Biology

Department of Microbiology

COURSE WORK

in the discipline "Sanitary and food microbiology"

Microbiology of meat and meat products

OGU 020209.65.5014.048 OO

Work manager

cand. biol. Sci., Associate Professor, Department of Microbiology

E.A. Drozdova

Executor

student of group 10 MB A.R. Khamidullin

Orenburg 2014

annotation

In this course work, the question of the microbiology of meat and meat products is considered: its contamination with microorganisms, the composition of the microflora of meat products, storage and spoilage.

The first section includes a description of the ways in which meat is contaminated with microorganisms.

In the second section - the microflora of fresh meat and semi-finished products.

The third section is devoted to food poisoning and toxicosis.

The fourth section considers the factors influencing the development of microorganisms during the maturation of meat.

The fifth section describes meat defects caused by microorganisms.

The sixth section is devoted to the storage of meat.

The seventh section includes the microbiology of poultry meat.

And, finally, the eighth section is devoted to the microbiology of sausages.

The work was printed on 24 pages using 8 sources.

This term paper discusses the microbiology of meat and meat products: its colonization by microorganisms, the composition of the microflora of meat products, storage and spoilage.

The content of the course work is as follows.

The first section includes a description of the ways of meat contamination by microorganisms.

The second section - the microflora of fresh meat and convenience foods.

The third section is devoted to foodborne diseases and toxemia.

The fourth section examines the factors influencing the growth of microorganisms during the maturation of the meat.

The fifth section describes the evils of meat caused by microorganisms.

The sixth section is devoted to the storage of meat.

The seventh section includes microbiology of poultry meat.

Finally, the eighth section dedicated microbiology sausages.

Work done by printing 24 pages with 8 sources.

Introduction

6. Meat storage

6.1 Cooling

6.2 Freezing

7. Microbiology of poultry meat

Conclusion

microorganism meat contamination semi-finished product

Introduction

Meat, meat products and poultry products are of great importance in human nutrition, providing the body's needs for protein of high biological value. Meat is a very delicate product that quickly changes its quality characteristics under the influence of microorganisms. In this regard, an important task is to obtain meat with a low content of microorganisms.

In the presence of microbes on the surface or inside the meat, it is necessary to limit their reproduction and enzymatic activity, as well as to reduce their number. These tasks are solved by different methods of conservation using high and low temperatures, salting, smoking, drying, etc. Currently, combined methods of meat preservation are used, which makes it possible to achieve the maximum reduction in the number of microorganisms while maintaining the quality of meat products.

The initial microflora of meat consists of various microorganisms that break down proteins, fats and carbohydrates. A certain level of decomposition of the organic components of meat and, especially, the glycolytic activity of microbes is useful in the manufacture of meat products. The content of beneficial microorganisms in meat is low, and it is the higher, the more hygienic the meat is obtained. The bulk of the microflora are harmful microorganisms that significantly reduce the quality of meat products.

Along with the saprophytic microflora, pathogenic and toxigenic microorganisms enter the meat, causing infectious diseases and food poisoning. Therefore, meat and meat products are subject to strict hygienic control by the veterinary service and sanitary and epidemiological surveillance authorities.

1. Ways of contamination of meat by microorganisms

The meat of healthy animals is usually sterile. But it is a good nutrient substrate for many organisms, and therefore, it is easily spoiled.

There are the following ways of contamination of meat:

1. endogenous (lifetime) seeding - occurs when the physiological state of the animal's body is disturbed. The muscles of animals that have undergone starvation before slaughter, severe overwork, hypothermia of the body are easily seeded with microorganisms as a result of a weakening of natural resistance. Intravital seeding of meat occurs in animals suffering from infectious diseases, the organs and tissues of which contain pathogens;

2. exogenous contamination - can occur during the primary processing and cutting of carcasses. The sources of contamination are the skin of animals, the contents of the gastrointestinal tract, equipment, air, vehicles, tools, hands, clothes and shoes of workers who come into contact with meat. Therefore, the microflora of meat is diverse in number and composition.

Subject to sanitary and hygienic production rules, there are no more than a few thousand or tens of thousands of bacterial cells per 1 cm2 of fresh meat carcass surface area. With a low level of sanitary condition in the slaughter and dressing shops, the number of microorganisms per 1 cm2 of carcass surface area can reach hundreds of thousands or even millions.

2. Microflora of fresh meat and semi-finished products

The qualitative composition of the microflora of fresh meat is diverse. No matter how carefully the meat is processed during slaughter, microorganisms still remain on the surface of the carcass. Among them, E. coli (Escherichia coli), Proteus vulgaris, spore-forming rods (Bacillus subtilis, B. mesentericus, Clostridium sporogenes, Cl. putrificum, etc.) are found. Often fungal spores get on the surface of the meat.

Meat offal (brains, kidneys, heart, etc.), due to the relatively high content of blood and moisture in them, is usually more contaminated with microbes than meat, and therefore undergoes rapid spoilage.

Semi-finished meat products, especially small pieces and minced meat, contain more microorganisms than the meat from which they are made and therefore spoil faster. Meat semi-finished products are infected during the manufacturing process from the outside (from equipment, inventory, from the air). Among these microorganisms, there are many possible pathogens of meat spoilage that can actively affect the proteins, fat and other substances of meat that make up its composition. Poorly bled meat is more likely to spoil.

Microbes penetrate deep into the tissues along the fascia, bones, and blood vessels. The penetration of bacteria into the thickness of the meat indicates a decrease in its quality. This is the basis for bacterioscopic examination of meat, which allows you to quickly determine the degree of its freshness.

For research, pieces of meat are sterilely cut out at different depths and the cut sides are applied to a glass slide to get prints. The smears obtained are Gram-stained and microscopically examined. At the same time, the number of bacteria and the degree of breakdown of muscle tissue are determined.

3. Food poisoning and toxicosis transmitted through meat

Meat can also be infected with toxigenic bacteria.

Toxic infections are caused by salmonella (Salmonella typhimurium, S. dublin, S. cholerasuis), bacteria from the group of opportunistic microflora: E. coli, Proteus vulgaris, cocci and other microorganisms.

Toxicosis is caused only by toxins (staphylococci, streptococci, etc.).

The penetration of Salmonella into the muscles is possible during the life of the animal. Toxic infections occur when eating poorly cooked meat. The causative agents of toxic infections can get on meat from water, from equipment, tools, in violation of sanitary rules. Often the carriers of salmonella are rodents (rats, mice), flies, wild birds, from farm animals - cattle and pigs. Meat infected with salmonella, outwardly, has almost no changes, does not raise suspicions of its unsuitability.

Opportunistic pathogens, among which Escherichia (E. coli) are the most common, persist in meat products for a long time and can cause food poisoning. Common pathogens are bacteria of the genus Proteus, the main representative of which is Proteus vulgaris, which has proteolytic properties. Well-cooked meat, even infected with Proteus, does not cause poisoning.

Botulism is a severe toxic infection that occurs after eating meat containing C. botulinum and its toxins. The causative agent and its toxin in the products are distributed unevenly (locally). Meat from animals with botulism should not be used for food. With botulism, the mortality rate reaches 70-80%.

Toxicosis can be of staphylococcal and streptococcal origin. Certain strains of golden (Staphilococcus aureus) and white staphylococci are able to produce a thermostable enterotoxin that can withstand boiling for 30 minutes. The appearance of meat products containing enterotoxin does not change.

Animal meat can be infected with anthrax, tularemia, typhoid fever, leptospirosis, glanders, tuberculosis, brucellosis. For humans, brucellosis of sheep and goats is of particular danger.

4. Factors affecting the development of microorganisms during meat maturation

The reproduction of microbes in meat depends on the ambient temperature, humidity, osmotic pressure, pH value of the meat and other factors.

Temperature is an important factor contributing to the growth of bacteria. For example, in a piece of meat weighing 2 kg at a temperature of 18-20 ° C during the day, microbes penetrate to a depth of 2-3 cm, at a temperature of 37 ° C during the same time they can be found in the entire thickness of the product. The lower the temperature, the lower the rate of microbial reproduction. But among the microbes there may be psychrophiles that develop at low temperatures. At zero temperature, molds and yeasts develop.

Humidity and osmotic pressure are also of great importance for the development of microorganisms. Reduced humidity delays their development, microbes go into a state of suspended animation, and spores - into the spore stage. A high moisture content leads to an increase in osmotic pressure and the concentration of water-soluble substances, which causes plasmolysis of microbial cells. But not all microbes are equally sensitive to osmotic pressure. Molds and yeasts can withstand very high pressure.

The pH value of meat depends on the amount of glycogen and the lactic acid formed from it. After the slaughter of the animal, the reaction of the meat environment is slightly alkaline (pH 7.1-7.2). During the ripening period of the product, under the influence of enzymes, complex biochemical and physico-chemical processes occur. Glycogen is broken down in muscle tissue, lactic acid accumulates, as a result of which the meat becomes acidic (pH 5.5-5.8). After a day, the pH of the meat decreases, in such an environment the growth of putrefactive microbes stops. Along with an increase in acidity, other changes occur: protein denaturation, loosening of muscle tissue, the formation of substances that determine the taste and aroma of ripe meat. Then the process reverses - the amount of acid decreases and by the end of the fourth day the reaction of the medium in the meat becomes alkaline again.

5. Meat defects caused by microorganisms

It has been established that signs of spoilage of meat appear when bacteria accumulate in it in the amount of 107-108 per 1 g or 1 cm2 of its surface. The time to reach this "threshold" concentration of microorganisms depends mainly on the storage temperature and the initial number of microorganisms on the product.

Various undesirable processes can occur in meat, leading to the loss of its freshness, nutritional and culinary properties. Damage to meat manifests itself in the form of: mucus, rotting, acid fermentation, pigmentation, mold.

Mucus occurs during the initial period of storage. It is observed when storage conditions are violated, especially when temperature and air humidity fluctuate (over 90%) in storage areas. Mucus-forming bacteria resistant to low temperatures develop well even at 0°C. Most often, mucus processes occur throughout the carcass or at the site of blood contamination, in the folds. The surface of the meat becomes sticky, gray-white in color, sometimes with an unpleasant sour musty smell. The number of bacteria in it reaches tens, hundreds of millions and even billions per 1 cm3. Mucus-forming microorganisms do not penetrate into the deep layers of meat, so the defect covers only the surface layer. However, such meat cannot be stored, it must be washed with water or a 15-20% salt solution, followed by drying and airing. Places where mucus or smell is especially pronounced are cleaned. Meat should be quickly used for cooking first courses or sent for processing to meat products, which include exposure to high temperatures in the process of their manufacture. This defect is caused mainly by bacteria of the genus Pseudomonas and Achromobacter. When meat is stored at a temperature above 5 ° C, micrococci, streptococci and other microorganisms multiply. When storing meat with signs of mucus, it further deteriorates, called rotting.

Meat decay is a complex process of protein breakdown. Decay is accompanied by the formation and accumulation of various intermediate and final decay products, among which are poisonous, foul-smelling, and volatile. Rotting is accompanied by a change in the structure of tissues and physico-chemical parameters. Rotting is caused by the vital activity of various putrefactive microorganisms. If hygiene rules are not observed, the greatest microbiological contamination of meat is noted. Meat is a good environment for putrefactive microbes, the development of which occurs under certain conditions. Decay can occur under both aerobic and anaerobic conditions. From aerobic bacteria, E. coli, Proteus vulgaris, B. subtilis, B. mesentericus, cocci, etc. take part in the breakdown of proteins. During aerobic decay, under the influence of proteolytic enzymes of putrefactive bacteria, meat proteins are decomposed with the formation of end products - carbon dioxide, hydrogen sulfide, ammonia, salts of phosphoric acid, water. First, aerobes develop on the surface of the meat, and then penetrate into deep-lying tissues. There are several phases of the putrefactive process. Coccal forms are replaced by non-spore-forming rods, which then give way to spore rods (bacilli). The surface of the meat gradually softens, becomes smeared, acquires a brown or grayish-green color, and an unpleasant odor appears. Anaerobic decay begins in the depths of the muscle tissue, which is caused by anaerobic and facultative anaerobic bacteria that have entered the meat endogenously from the gastrointestinal tract of the animal. They secrete proteolytic and saccharolytic enzymes, resulting in the breakdown of not only proteins, but also carbohydrates and fats. During anaerobic decay of meat, the same changes in the organoleptic properties of meat (color, texture, smell) are observed, as in aerobic decay, but they are accompanied by an even more unpleasant, fetid odor. Of the anaerobic bacteria, meat is decomposed mainly by clostridia: Cl. perfringens, Cl. putrificum, Cl. sporogenes, etc. Under normal conditions, during meat decay, anaerobic and aerobic processes most often occur simultaneously.

Acid fermentation (souring of meat) - more often observed in those meat products that are rich in glycogen (liver). It often occurs due to poor bleeding of animals during slaughter, as well as in cases where the carcasses are not cooled for a long time. The process is caused by lactic acid bacilli of the genus Lactobacterium, anaerobic bacteria Clostridium putrifaciens, sometimes yeast. Reproducing in meat, these microorganisms decompose carbohydrates in muscle tissue with the release of organic acids. The meat acquires an unpleasant sour smell, a pale gray or greenish-gray color on the cut and a soft texture. The resulting fermentation products retard the development of putrefactive bacteria, but create favorable conditions for mold fungi.

Molding of meat is caused by the growth of various molds on the surface of the meat. Their development usually begins with the appearance of an easily erasable cobweb coating of white color. In the future, more or less powerful raids of different colors are formed. Molds in the form of spores fall on the surface of the meat from the environment. Molds can develop in the presence of an acidic environment, at relatively low air humidity (75%), sub-zero temperatures, poor air ventilation and prolonged storage of meat. Molds decompose fats and proteins with the help of enzymes, increase the pH of the environment, release volatile substances, and the meat acquires a musty smell. Molding of meat is caused by fungi from the genus Mucor, Rhizopus, Thamnidium. They cause the formation of white or gray fluffy plaques. Black plaque gives Cladosporium, green - fungi of the genus Penicillium, yellowish - Aspergillus. In addition, some molds found on meat are capable of producing toxic substances (Aspergillus flavus, Penicillium puberulum).

Pigmentation of meat is the appearance of colored spots, a consequence of the development of pigment-forming bacteria on its surface. Thus, the development of the "wonderful stick" (Serratia marcescens) or yeast of the genus Rhodotorula leads to the formation of red spots that are not characteristic of meat, the development of Sarcina flava - yellow spots, Pseudomonas aeruginosa - blue, Pseudomonas fluorescens - green, etc. Most of these bacteria do not cause deep changes in the meat and do not form toxic substances. After examination and removal of pigmented colonies, the meat can be used.

Glow occurs as a result of reproduction on the surface of the meat of luminous bacteria that have the ability to glow - phosphorescence. The glow is due to the presence in the cells of these bacteria of a photogenic substance - luciferin, which is oxidized by atmospheric oxygen. The group of photobacteria includes various non-spore gram-negative and gram-positive rods, cocci, vibrios. A typical representative is Photobacterium phosphoreum - an immobile coccus-like bacillus. Photogenic bacteria develop well on fish and meat, but do not cause any changes in smell, texture and other organoleptic characteristics.

6. Meat storage

Meat is a perishable product. To preserve it, various methods of preservation are used.

The most common way to preserve meat is by exposure to low temperatures: refrigeration and freezing. Low temperature delays the development of microbiological, enzymatic processes and almost does not change the properties of the product.

6.1 Cooling

The microflora of meat stored in the cooling chambers is diverse in composition. By the end of cooling in the deep layers of meat, the temperature reaches 0-4? Consequently, it is mainly psychrophilic microorganisms that survive. But some pathogenic bacteria (salmonella, toxigenic staphylococci) remain viable for a long time at low temperatures. Non-spore-forming gram-negative bacteria of the genus Pseudomonas and Achromobacter, as well as molds and yeasts, multiply on chilled meat under anaerobic conditions. To extend the shelf life of chilled meat, it is possible, in addition to cold, to use additional means of influencing microorganisms:

1. increased content of carbon dioxide in the atmosphere (up to 10-15%);

2. in an atmosphere of nitrogen (90-99%), mucilage of meat occurs 2-3 times slower than when stored in air;

3. ultraviolet irradiation;

4. radurization (treatment with gamma rays), the contamination is reduced hundreds and thousands of times, radioresistant microorganisms are preserved. Storage periods increase several times;

5. periodic ozonation (ozone content up to 10 mg/m3) of storage chambers;

6. surface treatment of meat with a mixture of organic acids (citric, sorbic, propionic, acetic, etc.) and their salts;

7. treatment with a composition of essential oils of various spices;

8. treatment of the surface of the meat with the antibiotic substance pamalin.

The effectiveness of the use of additional means of influencing the microflora largely depends on the degree of contamination of it with microorganisms. If the meat was inoculated in large quantities with multiplying microorganisms, then even under storage conditions that retard their growth, it undergoes spoilage under the action of enzymes secreted by microbes.

Techniques for storing meat and meat products under anaerobic conditions are being developed:

1. vacuum packed;

2. Packed with gas-tight film.

With an increase in the shelf life of such products, the meat is spoiled due to the development of some facultative anaerobic psychrophilic microorganisms.

Microbiological indicators of chilled meat:

1. QMAFANM no more than 1,103 (semi-finished products - 5,105);

2. BGKP are not allowed in 0.1 g (semi-finished products - in 0.001 g);

3. pathogenic bacteria must be absent in 25 g of the product.

6.2 Freezing

During the freezing of meat, a significant number of microorganisms contained in the chilled meat die off. The degree of survival of microbes depends on the method of freezing. So, when meat is frozen in liquid nitrogen (-196? C), more bacteria die than during conventional freezing in air (at t from -18 to 30? C).

During the storage of frozen meat, the microorganisms remaining in it gradually die off. At the same time, the more microbes there were on the meat before freezing, the higher its contamination after freezing.

The microflora of frozen meat is dominated by micrococci. BGKP, Proteus are found, and pathogenic bacteria, such as Salmonella, Listeria, Yersinia, can also survive. So, during long-term storage of frozen meat at t - 18? C, Yersinia survived for 75 days.

Meat should be thawed immediately before use, since the surviving cells do not lose their activity and growth rate. During defrosting, additional contamination of the meat with microbes from the outside should not be allowed.

6.3 Drying, drying, canning, smoking, salting

Drying is one of the oldest methods of preserving meat. The moisture content of meat dried in various ways is below the limit that allows the development of microbes. However, there is always a certain amount of microbes on it, these are mainly micrococci, bacterial spores and molds. With an increase in the moisture content of the meat, they begin to multiply.

In addition to drying, drying is used, during which up to 35% of moisture is removed. During storage, dry and dried meat should be protected from contamination by microorganisms and strictly observe the temperature and humidity conditions.

Preservation of meat by high temperature (canned food) is widely used. Meat intended for long-term storage is subjected to sterilization at t above 100? C (115-120? C). The spores of B. subtilis, B. mesentericus, Cl. botulinum. If spores of bacilli remain in canned food, then some of them can germinate and cause swelling (bombing) of cans.

Smoked meat is also carried out in order to preserve the product. In addition to the loss of water, meat during smoking is exposed to the products of dry distillation of wood, which leads to the death of microorganisms. Gram-negative bacteria are more sensitive to smoke, less - staphylococci, mold fungi, spores. In the process of smoking, meat products acquire a specific taste and aroma.

Meat salting is based on the property of NaCl to increase osmotic pressure, create plasmolysis and thereby inhibit (slow down) microbiological processes. Food spoilage can be caused by gallophiles, bacteria that can withstand high salt concentrations. Also in the brine may be micrococci, enterococci, lactic streptococci, bacilli, less often clostridia and fungi.

7. Microbiology of poultry meat

The microflora of the poultry carcass depends on the production conditions and the method of cooling. Semi-gutted poultry carcasses are usually more contaminated with microorganisms than gutted ones. When half-gutted, intestinal rupture often occurs, which leads to infection of the carcass with intestinal microorganisms. Damage to the skin during feathering also contributes to microbial infection of the muscles.

The microflora of the poultry carcass consists mainly of aerobic non-spore rod-shaped bacteria of the genera Pseudomonas (up to 70-75%), Acinetobacter, Moraxella. There are facultative anaerobic bacteria: Aeromonas, Enterobacter, Escherichia coli, Proteus. Salmonella is often found in poultry meat.

To lengthen the shelf life, the carcasses are cooled:

1. placed in gas-tight films;

2. into the atmosphere with a high content of CO2 (t -2, -3? C);

3. treated with sorbic acid and its salts;

4. irradiated with gamma rays;

5. freeze.

Frozen poultry is stored without microbial spoilage at t not higher than -15? C for months. Frozen chickens can develop yeast and mold, Pseudomonas. The first sign of spoilage is a foreign smell. The types of spoilage are the same as those of animal meat. The degree of freshness of poultry meat is determined by bacterioscopy of imprint smears and freshness is determined by the same indicators.

The quality of chilled poultry meat is evaluated by:

1. QMAFANM (CFU (colony forming unit), no more than 1,104 in 1 g);

2. the absence of pathogenic bacteria, including salmonella and listeria in 25 g of the product.

8. Microbiology of sausages

Sausages are meat products prepared from minced meat with or without a casing, subjected to heat treatment or fermentation until ready to eat. The minced meat (depending on the recipe) includes: meat, bacon, skimmed milk, egg products, spices, seasonings, as binders - flour, starch, etc.

The range of sausage products includes more than 200 items. Sausages are classified according to the type of product and the method of processing into boiled, semi-smoked, smoked, stuffed, sausages and sausages, liver, blood, meat loaves, pates, brawns and jellies. Usually these products are eaten without additional heat treatment. Therefore, increased sanitary requirements are imposed on these products and the technological process of their manufacture.

8.1 Sources of contamination of sausages

In the process of preparing sausages, minced meat is contaminated with microorganisms that enter it from various sources at all stages of the technological process of its preparation: from raw materials, during meat preparation, salting, making minced meat, filling the casing with minced sausage.

The main source of contamination is raw materials. Raw materials must be obtained from healthy animals. Raw materials with various signs of deterioration, as well as with a contaminated surface, contain a large number of microorganisms. Such raw materials can be allowed into production only after a thorough sanitary check. The contamination increases sharply when preparing meat for minced meat. Microorganisms get from the hands of workers, from overalls, from tools, tables, inventory, containers, from the air of industrial premises. Among these microorganisms may be putrefactive. To reduce contamination, it is necessary to speed up the process of cutting meat and carry it out at a low temperature of industrial premises. It is necessary to strictly observe sanitary and hygienic standards.

When salting, the source of contamination by organisms can be salt containing salt-tolerant and salt-loving microorganisms: bacilli, yeast, mold spores, cocci.

In the process of making minced meat, contamination occurs during mechanical operations (chopping meat and processing minced meat in a mixing machine) from equipment, workers' hands, inventory, containers, from indoor air. Practice shows that when chopping meat, its contamination increases by an average of 10 times.

Additional seeding of minced meat is possible by adding bacon and spices. With spices, especially with pepper, a lot of spore-forming bacteria get into the minced meat. Therefore, it is necessary to use sterilized spices. When stuffing sausage sticks, further seeding of minced meat with microorganisms from syringes is possible.

Another source of contamination during this operation is the sausage casing. Apply natural and artificial shells. Artificial casings are more hygienic. Manual stuffing of minced meat into the casing in the manufacture of sausages (puff, tongue) leads to significant microbial contamination. In the study of such sausages, E. coli was isolated in 35.5% of cases, in 20% - Proteus vulgaris.

8.2 Changes in the microflora of minced meat in the manufacture of sausages

The microflora of raw sausage meat usually contains 105-107 bacteria per 1 g, the vast majority of them are gram-negative nonsporing rods. In much smaller quantities, micrococci, spore bacteria, BGKP, and Proteus are found.

After stuffing the shells with minced meat, boiled and semi-smoked sausages are subjected to sedimentation, frying, boiling and cooling. Half-smoked sausages are additionally smoked and dried.

Draft is carried out at a temperature of 2? C and a relative humidity of 85-95% for 2-4 hours. At this stage, the quantitative and qualitative composition of the microflora almost does not change.

Roasting is carried out with hot smoke at a temperature of 80-110? C for 0.5-2 hours. Under the action of antiseptic substances of smoke and temperature, the number of microorganisms on the surface of the loaf is reduced. However, in the depth of the loaf the temperature does not exceed 40-45?C, so the number of bacteria decreases slightly.

Boiling leads to a rise in temperature inside the loaf up to 75 ° C, while up to 90% or more of all microorganisms die. All vegetative cells die. Usually spore-forming rods and the most resistant micrococci persist, and toxin-forming bacteria may also persist.

The more residual microflora, the more it was contained in minced meat before heat treatment. More bacteria survive in high-fat sausages, as the fat creates a protective zone around their cells.

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

Smoking and drying are used in the manufacture of semi-smoked sausages. During smoking, the number of bacteria in them decreases. During storage of sausages, secondary infection of the surface and a gradual increase in the number of bacteria occur.

The number of microflora increases the faster, the higher the storage temperature and relative humidity. Shell-free types of sausage products (meat bread, carbonate) after heat treatment have an insignificant total contamination and should not contain pathogenic and conditionally pathogenic microorganisms. However, since these products do not have a protective shell, if sanitary standards are violated, they can become contaminated with microorganisms. The most common on these products are E. coli, Proteus vulgaris, spore putrefactive bacteria, and cocci.

Smoked sausages are divided into raw smoked and boiled-smoked. Raw-smoked sausages are subjected to long-term draft (5-7 days), cold smoking at a temperature of 18-25? C and drying up to 1.5 months (humidity 25-35%). The composition of the microflora of these sausages is very diverse: gram-negative bacteria, E. coli, Proteus vulgaris, spore aerobic bacilli (B. subtilis, B. mesentericus), anaerobic clostridia, staphylococci, yeast, lactic acid bacilli.

During the ripening of sausages, the composition of the microflora changes. As a result of the release of antibiotic substances by lactic acid bacteria, many bacteria of the original minced flora are displaced.

By the end of the ripening of sausages, the basis of the microflora is lactic acid bacteria and micrococci.

Boiled-smoked sausages are subjected to less prolonged draft (1-2 days), hot smoking at a temperature of 50-60? C, cooking, secondary smoking at a temperature of 32-45? C and shorter drying (7-15 days). The composition of the microflora at the end of drying is almost the same as the microflora of raw smoked sausages.

To improve the quality of smoked sausages, specially selected strains of lactic acid bacteria (Lactobacterium plantarum, L. acidophilum) and denitrifying micrococci are used. They produce dry bacterial preparations "ACID-SK" from acidophilic lactic acid bacteria and "BK-SK" containing a mixture of lactic acid bacilli and micrococci. The bacteria of these preparations have a high acid-forming ability, they produce a large amount of organic acids and other substances that give the product a specific taste and aroma. The preparations have, in addition, antibiotic activity against BGKP, Proteus.

Currently, the possibility of creating preparations containing bifidobacteria in combination with lactic acid bacteria is being considered.

Abroad, raw smoked sausages are produced using molds that are applied to the surface of the loaf. Developing mold covers the loaf of sausage with a thin layer, thereby protecting it from excessive drying, exposure to light and atmospheric oxygen, as well as preventing the development of harmful bacteria and yeast. Metabolic products and mold enzymes penetrate into minced meat and give the sausages a specific taste and aroma.

Subject to sanitary and hygienic requirements in the sausage production and the use of high-quality raw materials, the bacterial contamination of freshly prepared finished products is: for boiled sausages - 103 in 1 g, semi-smoked - 102, liver - 104-105.

The microflora consists mainly of spore-bearing bacteria and coccal forms. The permissible degree of contamination of sausage products with bacteria is standardized.

Boiled sausages, liver sausages, sausages, brawns are especially perishable products. Liver sausages and brawns contain significantly more microorganisms than other sausages. They have a relatively high humidity and are prepared from raw materials that are usually highly contaminated with microorganisms. Although heat treatment destroys many of them, a sufficient amount still remains.

The temperature, shelf life and sale of these products in the distribution network and at public catering establishments are strictly limited. If these requirements are violated, the products are subject to spoilage.

Relatively more stable in storage are semi-smoked and especially smoked sausages, which are distinguished by a low water content, an increased amount of salt and, in addition, treatment with antiseptic substances during smoking.

Types of spoilage of sausages are basically similar to spoilage of meat. Most often it is: souring, mucus, rotting, molding, rancidity, pigmentation.

Souring of sausages is caused by fermenting carbohydrates (introduced into minced meat in the form of flour and other herbal supplements), lactic acid bacteria, and Clostridium perfringens. This type of spoilage is more common in boiled and liver sausages, which are high in carbohydrates and have high moisture content. When carbohydrates decompose, organic acids accumulate, which give the sausages a sour taste and smell. The consistency and color of minced meat do not change. In the future, with the access of oxygen, a grayish-green color of minced meat may appear.

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

The rotting of sausages is caused by the vital activity of putrefactive bacteria: Pr. vulgaris, B. subtilis, B. mesentericum, Cl. sporogenes, etc. The putrefactive decomposition of sausages occurs simultaneously throughout the entire thickness of the loaf. Rotting is accompanied by the release of foul-smelling decomposition products - proteins, fats and carbohydrates; sausage acquires a loose texture.

Molding of sausages appears during storage at high humidity. Molds develop on the casing of sausages, forming dry or wet plaques. With loose stuffing, mold fungi can penetrate into the loaf. Mushrooms are resistant to smoke substances and are able to multiply at elevated osmotic pressure. Molding is the most common type of spoilage of semi-smoked and smoked sausages. To prevent mold, it is recommended to treat the loaves with potassium sorbate and volatile preparations.

Rancidity most often occurs during long-term storage of smoked sausages. It is caused by the decomposition of fat by microbes. The oxidation of fat hydrolysis products is accompanied by the formation of aldehydes and ketones. Sausages acquire a rancid taste, an unpleasant odor, and the fat turns yellow. The causative agents are most often bacteria of the genus Pseudomonas and others.

Pigmentation - the appearance on the shells of boiled and semi-smoked sausages of raids of various colors due to the development of pigment bacteria. Coccal forms of bacteria and yeast sometimes develop on the casings of smoked sausages, forming a gray-brown dry coating in the form of frost. A white coating on the surface of a loaf of raw smoked sausages may be the result of salt crystallization on the casing.

To increase the shelf life of sausages, in addition to low temperatures, it is recommended:

1. ozonation of lockers;

2. storage and transportation of sausages in an atmosphere of gaseous nitrogen.

Other ways to prevent microbial spoilage have been proposed, such as:

1. use of chitosan as a preservative;

2. mixtures of protamine with glycine, sodium acetate and lysozyme;

3. the use of food additive "Amfibakon", which has a bactericidal effect and reduces the number of microorganisms;

4. use of polyamide casings and vacuum bags.

A new direction is being developed - the formation of environmentally friendly protective polymer shells based on latexes directly on the surface of products. With the help of latex coatings, products are protected from unwanted microflora during transportation and sale.

Conclusion

Meat and meat products are the most important food products, as they contain almost all the nutrients necessary for the human body. The main raw materials for the production of meat and meat products are: cattle, pigs, sheep, poultry. The meat of horses, deer, buffaloes, rabbits, meat of wild animals and poultry is also used.

The microflora of meat is random and heterogeneous in composition. It may include various bacteria, mold spores, etc. Under favorable conditions, bacteria multiply rapidly and gradually penetrate into the thickness of the meat, causing it to spoil.

List of sources used

1. Askalonov S.P. Microbiological research and sanitary examination of foodstuffs / S.P. Ascalonov. - Kyiv: Medizdat. - 1955. - 238 p.

2. Verbina N.M. Microbiology of food production / N.M. Verbina. - M.: Agropromizdat. - 1988. - 357 p.

3. Zharikova G.G. Microbiology of food products. Sanitation and hygiene: a textbook for universities / G.G. Zharikov. - M.: Publishing Center "Academy". - 2008. - 304 p.

4. Luzina N.I. Microbiology of meat and meat products / N.I. Luzin. - Kemerovo. - 2004. - 75 p.

5. Mudretsova-Wiss K.A. Microbiology, sanitation and hygiene / K.A. Mudretsova-Viss. - M.: ID "FORUM": INFRA-M. - 2009. - 400 p.

6. Sidorov M.A. Microbiology of meat and meat products / M.A. Sidorov. - M.: Kolos. - 1996. - 395 p.

7. Shevchenko V.V. Commodity science and expertise of consumer goods / V.V. Shevchenko. - M.: INFRA-M. - 2009. - 752 p.

8. Microbiology of meat [Electronic resource]. - Access mode: http://biobib.ru. 11/19/14.

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...

Degree	meat pH	Indicators of bacterioscopy
meat freshness		cal sample (in the field of view
		microscope)
Fresh	5,9	Microorganisms on prepa-
		ratah-prints were not found
		live at all, or
		there are only a few
*		cells of cocci or rods.
		There are no residues on the glass
		meat tissue
Doubtful	6,6	On preparations-prints
freshness		found up to 20-30
		cocci or several papo-
		check. Visible on glass
		traces of muscle breakdown
		fabrics
stale	6,7	On preparations-prints
		there are many microorgan-
		nisms with a predominance
		sticks (field of view dotted with
		them). Lots of glass
		disintegrated muscle
		fabrics

Microbiology of food products of animal and plant origin - document. Microbiology of meat and meat products

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Microbiology of food products of animal and plant origin - document. Microbiology of meat and meat products

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