Microbiology of egg products. Food microflora
100 r first order bonus
Choose the type of work Graduate work Course work Abstract Master's thesis Report on practice Article Report Review Examination Monograph Problem solving Business plan Answers to questions creative work Essay Drawing Compositions Translation Presentations Typing Other Increasing the uniqueness of the text Candidate's thesis Laboratory work Help online
Ask for a price
Eggs are a nutritious food product, as they contain proteins, fats, carbohydrates, mineral salts, and vitamins. At the same time, they are a very good nutrient medium for the development of microorganisms.
However, the shell and shell membranes prevent the free penetration of microbes into the contents of the egg. The eggshell is permeated with tiny pores, through which the air necessary for the egg to breathe penetrates from the outside, and carbon dioxide and water vapor are released from the inside.
A freshly laid egg from a healthy bird is immune and usually does not contain microbes, that is, it is sterile. During storage, the egg gradually ages and loses its immunity, as a result of which favorable conditions are created for the development of microorganisms that have penetrated into it.
The penetration of microbes into the egg occurs through the pores of the shell, the surface of which is usually contaminated with a large number of different microorganisms: up to several hundred thousand and even millions of cells can be found per 1 cm2 of the shell.
The microflora of the surface of eggs most often includes various intestinal bacteria of birds, bacteria from the soil and air, spores mold fungi and etc.
Microorganisms that have entered the egg from the outside, under favorable conditions, begin to develop intensively and cause rapid spoilage.
The rate of deterioration of eggs depends on the temperature, humidity in the storage room and the condition of the shell. When stored, eggs with dirty and damp shells deteriorate much faster than those with clean and dry shells.
However, in no case should you wash eggs laid for storage, as this will lead to their rapid deterioration due to the abundant penetration of bacteria through the shell along with moisture.
The causative agents of egg spoilage are mainly bacteria - Proteus, E. coli, hay bacillus, micrococci, as well as molds - penicillium, aspergillus, etc.
Bacteria cause rotting of egg white, accompanied by the release of gases - hydrogen sulfide, ammonia and others, sometimes tearing the shell. When candling, a rotting egg is not translucent, and its contents emit an extremely bad smell.
Mold fungi develop primarily on the shell film. In the initial stage of mold, candling shows a dark spot at the site of mold development. Then this spot grows and finally the egg becomes completely opaque. Further, the molds destroy the shell membrane and penetrate into the protein.
Eggs of waterfowl (ducks, geese) often contain pathogenic paratyphoid bacteria that cause food poisoning. Therefore, the sale of such eggs in the trading network and their use in catering establishments is prohibited. They can be used in bakery and confectionery production for the manufacture of well-baked small pieces of dough. During baking, under the influence of high temperature, paratyphoid bacteria die.
Send your good work in the knowledge base is simple. Use the form below
Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.
Posted on http://www.allbest.ru/
1. Microbiology of eggs
1.1 The structure and composition of the egg
Depending on the type of bird, chicken, duck, goose, turkey, quail eggs, etc. are distinguished. Mainly chicken and quail eggs are sold.
A chicken egg consists of a shell (12%), protein (56%) and yolk (32%). The egg is a good nutrient substrate for microorganisms. But not all components of the egg have the same resistance to microorganisms.
Fresh eggs from healthy birds are free of germs. The sterility of the egg remains for a long time, as it has immunity. A significant role in immunity is played by the bactericidal properties of the shell and egg white. The shell performs a protective function, protecting the egg from the penetration of microorganisms. Insemination occurs through pores, the number of which reaches about 100 per 1 cm2 of area.
On the surface of the shell, when the egg is laid, a layer of mucus is deposited, which, when dried, forms an over-shell film - the cuticle. The composition of the film includes lysozyme, which acts bactericidal on many microorganisms. The cuticle is easily damaged, so eggs intended for storage should not be washed.
Shell membranes: outer - tightly adjacent to the calcareous shell, the inner covers the protein.
Egg protein has the strongest antibiotic effect. The antibiotic properties of the protein are due to the presence of bactericidal substances - lysozyme, ovidine, etc., which inhibit the growth of microorganisms. The content of lysozyme in the egg white of chickens is 5.71 mg / ml, in the protein of ducks - 1.8 mg / ml, geese - 0.38 mg / ml. The reproduction of microorganisms is also constrained by high pH.
Quail eggs weigh 10 - 12 g, with a thin fragile shell and various colors. Contain more biologically active substances compared to chicken eggs. 1 g of a quail egg contains more vitamins: A - 2.5, B1 - 2.8 and B2 - 2.2 times. In five quail eggs, equal in mass to one chicken, the level of phosphorus and potassium is 5 times higher, and iron is 4.5 times higher. Much more copper, cobalt, and amino acids in quail eggs. According to the content of such essential amino acids like tyrosine, threonine, lysine, glycine and histidine, quail eggs are superior to chicken eggs. The increased content of vitamins, minerals and essential amino acids leads to an increase immune protection organism. The high content of B vitamins contributes to improved functioning of the nervous system. The high content of phosphorus, potassium, iron improves memory. Use quail eggs increases tone, stabilizes the work of the kidneys, heart, pancreas. Quail eggs are stored for a long time, due to the high content of lysozyme. At room temperature they can be stored for up to 30 days, and in the refrigerator - up to 60. Quail eggs never contain salmonella. This is because they have a very strong shell membrane and small breathing holes in the shell, which prevent the penetration of pathogenic bacteria. Due to the high body temperature (42 ° C), quails are resistant to infectious diseases. Quail eggs do not cause allergies in children and adults. On the contrary, the ovomucoid protein present in them is able to suppress allergic reactions. 100 g of quail eggs contain: 13.6 g of protein; 12.8 g fat; 1.2 g carbohydrates; energy value 174 kcal.
1.2 Ways and sources of contamination of eggs with microflora
With endogenous (lifetime) infection, microorganisms penetrate the egg during its formation in the ovary or oviduct of a sick bird. Infection of eggs with pathogens of various infectious diseases can occur during their formation. Such pathogens are viruses, bacteria, fungi, pathogens of salmonellosis, tuberculosis. Often, birds can be latent carriers of pathogens of infectious diseases and carry eggs containing these microorganisms. Often the occurrence of toxic infections in humans is associated with the consumption of eggs and egg products.
Exogenous seeding of eggs is associated with contamination of the shell with droppings, soil, bedding, feathers, etc. Eggs are seeded during collection, storage and transportation. The seeding of eggs increases with the unsanitary condition of nests, containers for storing eggs and packaging material.
The rate of penetration of microbes into the egg is influenced by temperature, high humidity, the degree of freshness of the eggs, the presence of organs of movement in bacteria, etc. Wet shells are the most permeable to microorganisms. Fluctuations in air temperature especially contribute to the penetration of microorganisms into the egg, at which the seeded air is absorbed through pores, the number of which reaches about 100 per 1 cm2 of area.
At a temperature of 20°C and a relative humidity of 80-85%, Pseudomonas and Proteus bacteria penetrate from the surface of the shell into the egg on days 2-5, Salmonella typhimurium - on days 8-11, E. coli - 13-15, Aspergillus - on 5-9 day. The rate of penetration of mesophilic microbes at temperatures below 15°C and humidity of 60-65% slows down, and below 10°C it almost stops. Psychrophilic bacteria of the genus Pseudomonas and fungi pass through the pores of the shell and at 0o.
Shell cleanliness is an important indicator of quality food eggs. To obtain eggs with a clean shell, they should be properly collected and stored, all equipment in the premises should be kept clean. It is necessary to comply with the sanitary and hygienic requirements provided for by the egg production technology. Contaminated shells not only spoil them marketable condition but also drastically reduces the storage time. Depending on the contamination of the shell, the number of microorganisms on it varies widely. Per 1 cm2 surface of fresh clean eggs there are tens and hundreds of bacteria, and polluted ones contain tens of thousands and even millions of microbial cells. Contamination of the egg shell with pathogenic and conditionally pathogenic microflora occurs most often with the floor system of keeping chickens in poultry houses with poorly equipped nests, with poor quality litter and microclimate disturbance.
1.3 Main types of egg spoilage
Eggs are perishable products. With prolonged or improper storage, the activity of lysozyme gradually decreases, the physicochemical properties of their contents change, the integrity of the shell is violated, and the egg may undergo microbiological spoilage.
The spoilage rate depends on: storage temperature, relative air humidity, shell condition, composition of microflora.
Among bacteria, the most common spoilage agents are Pseudomonas fluorescens, Proteus vulgaris, Micrococcus roseus, Bacillus subtilis, Clostridium putrificum, Cl. sporogenes, etc. Bacteria - causative agents of spoilage differ in biochemical properties and activity, therefore, the changes they cause are very diverse.
Some bacteria act on the protein, others on the yolk.
Rotting is the process of splitting egg white by proteolytic enzymes of bacteria with the formation of specific decomposition products with the release of ammonia, hydrogen sulfide, carbon dioxide. The protein acquires an unusual color and an unpleasant odor. The yolk does not change. There are the following types of decay.
Green rot appears as a result of penetration into the egg of bacteria of the genus Pseudomonas, which form a green pigment that turns the contents of the egg green.
Red or pink rot is caused not only by bacteria of the genus Pseudomonas, but also by Micrococcus roseus, Serratia marcescens, etc. They give red and pink color to the decay products.
Black rot appears during the reproduction of Proteus vulgaris and some representatives of the genus Pseudomonas. The contents of the egg liquefy and take on a brown or black tint. The resulting gases often break the shell.
Mixed rot is caused by E. coli, Staphylococcus aureus and other bacteria. In this case, not only the consistency of the protein changes, but also its color, which becomes gray, and an unpleasant odor appears.
Other bacteria act on the yolk, causing hydrolytic and oxidative transformation of lipids, thus forming fatty acid, aldehydes, ketones.
Molding of eggs is most often caused by fungi of the genus Penicillium, Aspergillus, Cladosporium, and less often others. Molds get on the surface of the shell from the soil or from contaminated objects. At high humidity, fungal spores germinate and penetrate into the pores of the shell, and then onto the shell membranes. They find the most favorable conditions near the air chamber. When ovoscopy of the affected eggs, dark spots are visible - colonies of fungi.
- "Small spot" is formed during the development of mold fungi on shell membranes. Mycelium appears different color, clearly visible during ovoscopy. For example, penicilli give dotted spots of yellow-green or blue-green, Cladosporium - dark green or black, Aspergillus - black, Sporotrichum - red or pink.
Then the fungi penetrate the protein, diluting it. As the fungus develops, the size of the spot increases, and the egg becomes completely opaque, because. the whole shell is covered with mold from the inside.
“Bacterial cuff” and “drying” are caused by putrefactive bacteria that thin the protein, which most often acquires a greenish color. The yolk floats up and dries to the shell membrane ("drying"), the yolk membrane is torn. Foul-smelling gases come out through the pores of the shell, under the pressure of which the shell can burst.
defect " sour egg are caused by many bacteria, including E. coli. When determining the light transmission of such an egg, the defect is not detected, and when opened, the egg emits a pungent odor.
1.4 Infections transmitted through eggs
Infection of eggs with pathogenic microorganisms also occurs exogenously and endogenously.
Of particular danger are waterfowl eggs, which are often infected with salmonella. Salmonella entering the egg develop freely in it, since lysozyme does not act on them. The most dangerous among Salmonella are: S. enteritidis, S. cholerae suis, S. typhimurium, S. newport, S. dublin, S. anatum, etc. In this regard, sell duck and goose eggs in grocery stores, markets and sell their raw form through the catering network is prohibited.
Of the salmonellosis in chickens, pullorosis is most often noted. The main source of infection in pullorosis are bacterial carriers, from which eggs infected with S. pullorum and S. gallinarum are obtained. Chickens sick with pullorosis are hatched from such eggs, which release the pathogen into the external environment. Previously, these salmonella were considered safe. Eating eggs infected with S. pullorum and S. gallinarum is now known to be one of the causes of foodborne illness in humans. The most favorable environment for the development of Salmonella is the yolk.
In addition to salmonella, Vibrio cholerae and other pathogenic microorganisms, including tuberculosis pathogens, can enter the egg through the pores of the shell. Most often, M. avium is found in chicken eggs. Eggs obtained from tuberculosis patients and chickens suspicious of this disease are used for food purposes only at industrial food industry enterprises after preliminary heat treatment. The sale of such eggs through the trading network and public catering establishments is prohibited.
The causative agent of mycoplasmosis (Mycoplasma galhsepticum) is transmitted mainly by the transovarial route. Endogenous infection of eggs is also noted by pathogens of plague, cholera, etc. Endogenous infection of food eggs with viruses can also be observed when birds are immunized with live virus vaccines used in industrial poultry farming.
In addition, endogenous infection of eggs is possible in diseases of the ovaries and oviducts of various etiologies. In this case, eggs can be infected with staphylococci, Escherichia coli, Proteus bacillus, Pseudomonas aeruginosa, fluorescent bacilli and other microorganisms.
2. Microbiology of egg products
Melange and egg powder are made from chicken eggs.
Melange - a frozen mixture of protein and yolk, sold only in frozen form. It is necessary to store at a temperature of -5 ... -10 ° C, a shelf life of 10 months. Melange can also be made either from the yolk mass or in the form of egg white.
For the production of any kind of melange, only good-quality eggs are used that meet the requirements of the current technical specifications. Do not use duck, goose and limed chicken eggs, food defective eggs, as well as eggs from farms that are unfavorable for infectious diseases of birds.
Egg mixture usually contains a significant amount of various microorganisms. During manufacture, pathogenic and opportunistic bacteria can get into it. In the process of freezing and subsequent storage, the microorganisms in the melange partially die off, but can still be preserved. enough them, especially if the melange was not immediately frozen after manufacture. For example, the number of salmonella for 6 months. storage of melange can decrease by 1000, E. coli - by 100, total contamination - by 40 times. However, microorganisms never die completely.
Melange is a perishable product, it is allowed to store it only frozen. When thawing in melange, microorganisms multiply intensively, so the thawed product must be sold within a few hours, keeping it chilled.
To reduce microbial contamination egg mixture sometimes, before freezing, they pasteurize for a short time (1-3 minutes) at relatively low temperatures (about 600), which do not change physical state melange. As a result of pasteurization, the contamination of the egg mixture is reduced by 90-95%. To increase the effect of pasteurization, it is recommended to add hydrogen peroxide (up to 1%) or substances that increase the pH of the mixture to 10-11 to the egg mixture before heating. Sometimes mixed with sugar in a ratio of 1:1. In saccharified melange, Salmonella die off already after 2-3 months at room temperature of storage. In some cases, yeast, streptococci, clostridia are isolated from sugared and pasteurized egg melange.
Bacterial contamination of melange is normalized: the number of mesophilic aerobic and facultative anaerobic microorganisms (MAFAM) should be no more than 5 105 per 1 g of product; the presence of BGKP in the amount of 0.1 g is not allowed; Staphylococcus aureus and Proteus in 1g; salmonella should be absent in 25g.
Currently, the freeze-drying method is widely used. food products, at which 75 ... 90% of moisture evaporates in vacuum at a negative temperature.
Egg powder obtained by drying the egg mass by spraying it at 600C in special chambers. To do this, use chicken table eggs (except for limed ones) and egg frozen melange that meets the relevant requirements. Properly prepared egg powder absorbs water well and has the properties of fresh eggs. Benign egg powder has a light yellow color, taste and smell characteristic of a dried egg. The advantages of egg powder are reduced volume and weight, the ability to store in an uncooled room, and good transportability.
Drying only kills part of the bacteria. In egg powder, spore-forming bacteria, staphylococci, streptococci, Escherichia coli, and sometimes salmonella are found in a viable state. During storage, the microflora gradually dies off.
The shelf life of egg powder at a temperature not higher than 20 ° C and relative humidity not higher than 75% is about 6 months; at a temperature of 2 ° C and below and a relative humidity of 60-70% - up to two years.
The quality of egg powder is evaluated by the same microbiological indicators as melange. If the titer should not be lower than 0.1 g.
Sanitary and microbiological studies of egg products and eggs are carried out under the control of poultry farms of food production, as well as in the presence of epidemiological and epizootic indications. If pathogenic microorganisms are found in egg products, then such products cannot be used for food purposes.
Sanitary and microbiological control is subjected to incoming raw materials (chicken eggs), finished products: egg melange, egg powder, as well as monitoring compliance with technological and sanitary-hygienic regimes for the production of egg products.
Eggs for microbiological analysis are selected from different places of the batch by random sampling in the amount of 30 pieces (in some cases, at least 5-10 eggs). The selected sample is packed in a clean container and transported under conditions that exclude their damage and secondary contamination (contamination).
A feature of the sanitary and microbiological study of eggs and their products is the simultaneous study of the microflora on the surface of the shell and the contents of the egg.
In the microbiological examination of the surface of the egg shell, swabs are made, obtained by a) the swab method or b) the rinsing method or c) the grinding method.
When a wash is obtained using a swab, the egg is immersed in a mortar containing 10 ml of sterile saline and the surface of the egg is washed with a sterile swab for 2-3 minutes, the resulting wash is examined.
When receiving flushing by rinsing into a sterile dish or plastic bag pour 10 ml of sterile liquid into which the egg is immersed and shaken for 5 minutes. The resulting wash is examined.
Upon receipt of the flush by grinding, the shell and shell membrane of three eggs are separated from the contents and placed in sterile mortars. The contents are ground with a pestle, pour 90 ml of sterile liquid. After 3-5 minutes of settling, the supernatant is examined without dilution or tenfold dilutions are prepared, depending on the degree of contamination of the shell surface.
The total bacterial contamination of the egg surface (i.e., the amount of MAFAnM) is determined by conventional methods by inoculating 1 ml of the wash or its 10-fold dilutions in parallel into two Petri dishes, which are poured into 15 ml of MPA melted and cooled to 500C, cultivated at 300C. in a thermostat for 48-72 hours. All colonies that have grown in depth and on the surface of a dense nutrient medium are counted, the arithmetic average number of colonies is determined for two cups of one dilution, multiplied by the dilution value and divided by the surface area of the egg shell. As a result, the number of microorganisms (CFU/cm2) per 1 cm2 of eggshell is obtained.
Before microbiological examination of the contents of the eggs, the surface of the shell is washed with a warm 0.2% solution of caustic soda or a 0.5% solution of soda ash for 2 minutes. Rinse the egg after washing tap water, allowed to drain and immersed in 70% alcohol for 10 minutes, after which they are burned in a flame.
On sharp end eggs make a hole with a diameter of about 1 cm and fire again, the contents of one or more eggs are poured into a flask and homogenized with beads or pipettes until uniform consistency. The study is carried out immediately, for this, 10 ml of the egg mass is transferred into a flask containing 90 ml of sterile saline - this is the initial dilution of 1:10, from which 1 ml is transferred into a test tube with 9 ml of saline, obtaining a dilution of 1:10, 1:100, etc. .d. to the desired final dilution.
Microbiological examination of the contents of the eggs is reduced to the determination of MAFAnM, the identification of BGKP, Staphylococcus aureus, Proteus, Salmonella, in some cases B.cereus.
To determine MAFAnM (CFU/g or CFU/ml), 1 ml of the obtained dilutions is added in parallel to Petri dishes (2 cups for each dilution) and poured molten and cooled to 450C MPA. Thoroughly mix, after solidification, incubate at 300C for 72 hours. All grown colonies are counted, and the arithmetic mean of the number of colonies from all inoculations of one dilution is determined from the counting results.
The number of CFU in 1 g of egg products is determined by the formula:
X \u003d A x 10n / V
where A is the arithmetic mean of the number of colonies in the cup; n- degree of tenfold dilution of the product; V- volume seed added to the cup. The research results are recorded as follows: the number of mesophilic aerobic and facultative anaerobic microorganisms is 1.0 x 10 CFU / g.
To detect BGKP, inoculation is carried out in 1 ml of a natural product, and from dilutions of 1:10, 1:100 in Kessler's medium, the inoculations are cultivated for 24 hours in a thermostat at 370C. Test tubes with signs of growth are inoculated on Endo medium and incubated for 24 hours at 370C. Then the crops are viewed and the growth of colonies characteristic of CGB is noted, preparations are prepared from at least three characteristic colonies, Gram-stained and microscoped. The results are evaluated for each sample separately. Detection on Endo medium of colonies with characteristic features growth, the presence in smears of gram-negative lactose-fermenting rods indicates the presence of CGB in the product.
The result is recorded as follows: not detected (or detected) CGB in 0.1 ml of liquid (in 0.1 g of dry) egg products.
To indicate Salmonella, 25 ml of a natural product is added to a flask containing 225 ml of enrichment medium (Kaufmann, magnesium or selenite), shaken, thermostated at 370C for 20 hours. Ploskirev, Levin), kept in a thermostat. The results are recorded on the ICA after 48 hours, and on the Ploskirev, Levin media - after 24 hours. At least three colonies typical of Salmonella are taken and inoculated into test tubes with MPA, MPB, and Krumvide-Olkenitsky or Kligler differential medium). Krumvide-Olkenitsky or Kligler media are inoculated with a stroke on a sloping surface, and then with an injection into the depth of the column. The cultures are incubated in a thermostat at 370C for 24 hours.
The grown colonies from the surface of the differential media are used for setting up RA and preparing smears. The resulting cultures are studied for morphological, tinctorial, enzymatic properties, the ability to form hydrogen sulfide and other properties characteristic of bacteria of the genus Salmonella.
Microbiological indicators of eggs and egg products regulated Sanitary regulations and norms are presented in table 9. egg microbiological contamination of microflora
Table 1 Standards for microbiological indicators of eggs and egg products
Additional material.
During the microbiological examination of frozen egg products (mélange, protein, yolk), to check the quality of frozen egg products with the requirements of the current regulatory and technical documentation, 3% of the boxes, but not less than six, are selected from different places of the batch. From the total number of selected boxes, one package, a can, is selected from each box selected in the sample. From different places of each package, jars are taken with a sterile oil probe at least four columns of the product into a sterile dish. Before microbiological examination, the samples are thawed in a water bath at a temperature not exceeding 450C to a temperature inside the product not higher than 1-50C.
The selected samples are combined, thoroughly mixed and a combined sample weighing no more than 0.5 kg is obtained, which is placed in a sterile container with a ground stopper. 100 g of the product is taken from the combined sample for microbiological analysis, the rest is used for organoleptic and physico-chemical methods of analysis.
To assess the sanitary and microbiological quality of dry egg products, 3% of the packaging units, but not less than 3 units, are selected from different places of the batch under study. At least three point samples taken in equal numbers are taken from different places of the packaging unit selected for the sample.
Sampling is carried out with a probe, scoop, spoon, metal tube, spatula or other device, which each time before use is sterilized by flaming or in advance in an autoclave.
The mass of the sample taken from each barrel, bag, box or jar should be 200 g. From a batch of dry egg product packed in bags, three bags are taken from different places in each box selected in the sample. The samples are combined, thoroughly mixed, quartered and a combined sample weighing 0.5 kg is obtained.
The combined sample of egg powder is divided into two equal parts, which are placed in clean sterile glass jars with ground stoppers or plastic bags.
One part of the sample is sent to the laboratory for research, the other is sealed, labeled and stored for one month at a temperature not exceeding 200C and a relative humidity of 65-75% in case of disagreement when determining the quality of a dry egg product. On the label indicate: the name of the manufacturer; Product name; production date; lot number and size; date and place of sampling; the name of the person who took the sample; designation of the current regulatory and technical document.
100 g of dry egg product is taken from the combined sample into a sterile container for analysis, the rest of the sample is used for organoleptic and physico-chemical analyzes.
To prepare dilutions, a weighed portion of dry egg products weighing 10 g is added to a flask with 90 ml of sterile saline, following the rules of asepsis, and a series of tenfold dilutions of egg products is prepared, depending on the expected contamination of the product.
If the quality of eggs and egg products does not match according to microbiological indicators, they are sent to the production of heat-treated products.
Hosted on Allbest.ru
...Similar Documents
Microbiological standards drinking water and cleaning methods. Characteristics of intestinal bacteriophages, their significance as sanitary indicative microorganisms. Major foodborne infections. Effect of drying and freezing fish products on microorganisms.
test, added 08/06/2015
Characterization of pathogenic microorganisms. Infection, ways and sources of its transmission. Diseases transmitted to humans through meat products. Immunity and its types. Decomposition of proteins by microorganisms. Damage to bakery products.
test, added 01/13/2011
The role of microbes in nature and human life. The use of microbiological processes in industry and agriculture. Personal hygiene of employees of a public catering enterprise. The structure, the essence of the processes of digestion. Ways of infection with helminths.
test, added 02/23/2009
Historical information about the use of starter cultures in the dairy industry. Isolation of pure cultures of lactic acid bacteria and determination of their production value. Methods of preparation and use of starter cultures, microbiological control of their quality.
term paper, added 12/14/2010
Analysis of pathogenic bacteria, ways of their entry into the body. The role of bacteriophages in the fight against them. Classification of lesions by location. Diseases caused by pathogenic microorganisms transmitted through milk. Bacteria are the causative agents of diseases.
presentation, added 11/20/2014
Types of aphids that are harmful in protected ground, the use of entomophages against them in greenhouses. Microbiological control of protected ground pests. Methodology for breeding vetch aphids. Evaluation of the effect of microbiological preparations on spotted greenhouse aphids.
thesis, added 02/05/2011
The nature and assessment of the influence of various factors external environment on microorganisms: physical, chemical and microbiological. The importance of microorganisms in cheese making, the development of appropriate processes in the production of the final product, the stages of maturation.
abstract, added 06/22/2014
Characteristics of microbiological and physical stimulants and their role in the life of plants. Biological features of sunflower, characteristics of seeds of the "Pioneer" variety. Determination of the effect of stimulants on germination, growth and development of seeds.
term paper, added 09/13/2015
Morphology of bifidobacteria, their cultural and biochemical properties. Products with bifidobacteria. Dietary and medicinal properties dairy products from the point of view of nutritional physiology. Microbiological control of the production of fermented milk products.
term paper, added 12/18/2010
Brief historical reference and classification of microorganisms causing food toxicosis. Cultural properties of this class of microorganisms. Sources of product contamination with staphylococci, diagnosis and treatment of diseases caused by them.
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 shell membranes. An egg freshly laid by a healthy bird is usually free of germs.
The sterility of the egg can be preserved for some time, as it has immunity. A significant role in immunity is played by the proteins contained in the egg (lysozyme, ovidin, etc.), which have bactericidal properties.
During storage, the egg ages and the faster, the higher the storage temperature, so the eggs are quickly cooled after removal. With a decrease in immunity, 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. Moisturizing it favors the germination of mold spores. Hyphae of the fungus, penetrating the shell and shell membrane of the egg, contribute to the penetration of bacteria.
The microflora of eggs can be of endogenous, or lifetime, origin (in birds with tuberculosis and salmonellosis, pathogens enter the egg during its formation in the ovary and oviduct) and exogenous (contamination of the shell from the outside after laying).
Eggs with contaminated shells are not allowed for retail sales; they must be washed. For washing, use high-quality water with the addition of detergents and disinfectants permitted by the Ministry of Health of the Russian Federation. washed eggs unstable, therefore, to prevent rapid deterioration, it is advisable to treat them with film-forming substances.
Microorganisms that enter the egg usually develop near the point of penetration; their resulting accumulations (colonies) are visible during visual ovoscopy (transmission) in the form of spots. Further reproduction of microbes leads to various changes in the proteins and lipids of the egg, to its deterioration.
Egg products.
Made from chicken eggs melange- frozen mixture of protein and yolk. Egg mixture usually contains a significant amount of various microorganisms. During manufacture, pathogenic and opportunistic bacteria can get into it. 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 is allowed to store it only frozen. When thawing in melange, microorganisms multiply intensively, so the thawed product must be sold within a few hours, keeping it chilled.
To reduce microbial contamination, the egg mixture is often pasteurized for a short time (1-3 minutes) before freezing at relatively low temperatures (about 60 ° C), which do not change the physical state of the melange.
Microbiology of fish, fish products and commercial invertebrates
The fish is fresh.
Freshly caught fish can be heavily contaminated with microorganisms. The level of contamination and the qualitative composition of microorganisms depend on a number of conditions: the fishing season, water temperature, the depth of the fish, the degree of water pollution, and the method of fishing.
The qualitative composition of the microflora on the surface of the fish is close to the microflora of water. In fish caught in cold and temperate regions and in cold weather at any latitudes, representatives of psychrotrophic and psychrophilic, sporeless, gram-negative bacteria belonging to the genera Pseudomonas, Achromobacter, Flavobacterium. In the warm season and in warm waters, the surface microflora of the skin of fish is represented by mesophilic microflora - various types micrococci, corynebacteria. Many of these bacteria have proteolytic, fat-splitting, acid-forming properties.
Most microorganisms are in the gills. The gill apparatus, filled with blood, is easily seeded with microflora of water and natural silt.
Of particular importance is the isolation of fish pathogenic microorganisms for humans. Due to the unsatisfactory sanitary condition of coastal marine areas and inland waters due to incoming untreated sewage, representatives of the bacteria of the group of Escherichia coli (including enteropathogenic), genera Salmonella, Schigella, Listeria, Staphylococcus aureus, Cl. botulinum(especially type E). Over the past two decades, in the water (Japanese, less often the White, Baltic and very rarely Black Seas), as well as on fish, it has been found V. parahaemolyticus- halophilic vibrio, the causative agent of poisoning (Yu. I. Grigoriev).
Freshly caught fish quickly dies (falls asleep - sleep). After the death of a fish, a number of complex changes occur in its body: mucus separation, rigor mortis, autolysis, and microbiological processes.
These changes contribute to the penetration of microorganisms into muscle tissues. Microorganisms penetrate into the tissues of dead fish from the surface, from the intestines, from the blood of the gills. The higher the contamination, the greater the number of microorganisms will be in the thickness of the tissues.
Freshly sleeping fish begins to spoil quickly. The organoleptic indicators of fish quality change significantly: the body loses its elasticity, the eyes become sunken, the gills are gray, the mucus of the surface increases, the mucus is cloudy, slightly liquefied, and an unpleasant odor is felt. The main cause of spoilage is the breakdown of protein and extractive substances by microorganisms, hydrolysis and oxidation of fat.
The temperature of fish kept under ice is slightly above 0 °C. During long-term transportation, this temperature can rise up to 6 ºС.
The contact of fish with ice leads to a significant change in the quantitative and qualitative composition of the microorganisms seeding it. The use of ice made from clean water and not kept long time in bunkers, does not cause an increase in the number of fish microflora.
The disadvantage of the method of storing fish under ice is its rapid contamination with mucus, scales, which contributes to bacterial contamination ice. To increase the effectiveness of the action of ice on the microflora, preservatives, such as the antibiotic nisin, are added to it.
The reproduction of bacteria leads to a deterioration in quality, therefore, the shelf life of chilled fish in trade and public catering establishments at temperatures from 0 to -2"C is 48 hours.
For longer storage, the fish is frozen or subjected to other methods of preservation: salting, smoking, pickling, drying.
Frozen fish.
It can be stored for a long time (months) without microbial damage at a temperature not exceeding -12 ° C. Glazing and storage of fish at -18 ° C and relative humidity not exceeding 80% are good protection.
During the freezing process, many micro-organisms on the fish are killed. The contamination of fish after freezing ranges from 10 2 to I0 3 in the first year. At the same time, the higher the contamination before freezing, the more microorganisms remain on frozen fish.
Different microorganisms exhibit unequal resistance to destructive action. low temperatures. Some microorganisms gradually die off during subsequent storage, others remain viable for a long time, while microbes remain the greater, the lower the storage temperature.
Salted fish.
Salting is one of the oldest ways to store fish. The preservative effect of salting is due to the high osmotic activity of the salt solution and a decrease in water activity. (a to) environment. In ch. 4 it was noted that the salt tolerance of microorganisms is different. Table salt not only inhibits cell reproduction, but also affects their biochemical activity.
Immature fish species are salted for preservation as a semi-finished product used in the manufacture of dried, dried, smoked and other types of fish products.
With any method of salting fish, changes occur in the quantitative and qualitative composition of its original microflora. Psychotrophic species typical of fresh fish Pseudomonas gradually die off or remain in a small amount in a plasmolyzed state. Halophilic and salt-resistant micrococci become predominant in salted fish and brine; spore-bearing rods are found in smaller numbers; there are lactic acid bacteria, yeast, mold spores. The number of bacteria in brine varies from 10 3 to 10 6 in 1 cm 3.
Marinated fish.
The main factor inhibiting the development of bacteria in pickled fish, including putrefactive ones, is acidic environment. Salt, sugar added to the marinade, as well as spices containing essential oils and possessing phytoncidal properties. However, often the spices themselves are significantly seeded with microbes. Molds can develop on pickled fish. This reduces the acidity of the product and creates the possibility of growth of putrefactive bacteria. Storage of marinated fish in hermetically sealed closed container and prevents it from molding in the cold.
Fish dried and dried.
When water is removed from fish meat up to a certain limit, unfavorable conditions are created for the development of microbes. In dried and salt-dried fish, salt also has a preservative effect.
Some microorganisms remain on these products for a long time in an anabiotic state. The microflora consists mainly of micrococci. There are spore-forming bacteria, lactic acid, mold spores.
With a subsequent increase in the humidity of the product and a favorable temperature, molds begin to develop first. To prevent mold, such fish products must be stored in the cold and at a relative humidity of 70-80%.
Smoked fish.
The preservative effect of smoking fish is mainly due to the antiseptic substances of the smoke (or smoking liquid). In addition to antiseptics, the hot method of smoking has a detrimental effect on the microflora of fish. heat, and when cold - salt and drying the fish. When smoked in the thickness of the fish, one or another number of microorganisms is still preserved. Bacteria of the genus Pseudomonas; resistant spores of bacteria and molds, as well as many micrococci.
The microflora of hot and cold smoked fish is similar and is represented mainly (up to 80% or more) by various micrococci. There are spore-bearing and non-spore-forming rod-shaped bacteria, yeasts, and mold spores.
Preserves.
lightly salted fish products from small fish(sprat, herring, anchovy, etc.), produced in hermetically sealed containers - preserves, contains, in addition to salt, sugar, spices, vegetable oil. Preserves are not subjected to heat treatment; to protect against spoilage, an antiseptic is introduced into them - the sodium salt of benzoic acid (benzoate) (0.1%). Instead of this salt or in combination with it, it is recommended to use sorbic acid and the antibiotic nisin, which also gives good results. Salt also provides some preservative effect.
The microflora of preserves in the first days of their production is diverse: it includes microorganisms of fish, salt and spices. The latter are often to a large extent (10 4 -10 6 / g) seeded with spore-forming aerobic and anaerobic rod-shaped bacteria and micrococci, among which there are salt-resistant and cold-resistant putrefactive forms. In the process of ripening preserves, the composition of their microflora changes. Bacteria of the fam. Mcgossaceae, as well as lactic acid.
Unlike sterilized canned fish, preserves are not subject to long-term storage even in the cold. The proposed (E, N. Dutova, M. M. Goftarsh) radiation treatment (radiurization) of preserves allows not only to increase their shelf life, but also to exclude the use of an antiseptic.
Caviar.
The caviar of many fish is a valuable food product. To receive high quality product caviar is extracted from live or freshly sleeping fish.
The microflora of caviar consists of psychrophilic microorganisms, which belong to the natural microflora of fish. The further technological process of caviar processing at all stages is associated with the use of manual labor. In this case, staphylococci, bacteria of the Escherichia coli group, spores of bacteria and filamentous fungi, and yeast can enter. Therefore, in the production of caviar products, it is necessary to comply with high sanitary and hygienic requirements: cutting tables, inventory, utensils, hands of processors must be immaculately clean. Of great importance are the purity of the air, the quality of the water used to wash the eggs.
The species composition of the caviar microflora is very diverse. It is dominated mainly by rod-shaped mesophilic saprophytes. In addition to bacteria, actinomycetes, yeast, filamentous fungi were found in freshly salted caviar.
Properly stored granular caviar at temperatures from -2 down to -4 ºС, a decrease in the number of microorganisms contained in it is observed. Under the influence of low temperature, salinity, low humidity and acid reaction, the species composition of caviar microorganisms becomes more uniform and is represented by various species of the genus micrococcus.
Spoilage of caviar is expressed in sourness and rancidity. The main causative agents of caviar spoilage are bacteria of the group E. coli and close to it in properties B. lactis aerogenes, and B. ruberw Pseudomonas fluorescens. They cause souring of caviar. Cocci and filamentous fungi contribute to the formation of a rancid taste.
Commercial invertebrates.
Shellfish (shrimp, crabs, lobsters, spiny lobsters) and shellfish (scallops, mussels, oysters, squid) are highly perishable food raw materials. In addition to microorganisms, the reason for their rapid deterioration is the active influence of the enzymes of the animal itself.
Most commercial invertebrates are demersal animals, so their primary microflora corresponds to that of marine sediments, silt and water.
The qualitative and quantitative composition of the microflora of even the same species of crustaceans or molluscs varies depending on the place, season, and method of fishing.
The microorganisms of the shell covers, gills, and viscera of crabs are typical of the microflora of the marine soil; spore-forming bacteria predominate. The meat of live crabs, not caught in the nets, contains few bacteria - from units to several hundred per 1 g.
In freshly caught shrimp and crabs, pathogenic and opportunistic microorganisms are usually absent or occur in small quantities. However, during processing, contact with contaminated deck and equipment, crustaceans can become infected with these microorganisms.
Spoilage of oysters and mussels is caused mainly by Pseudomonas and lactic acid bacteria; spoilage of scallops - bacteria of childbirth Moraxella And Acineiobacter.
To extend the shelf life of chilled products, it is recommended to treat them with chemical preservatives (solutions of sodium metabisulfite, sorbic, benzoic, citric acid), as well as radiation treatment.
Freezing invertebrates - The best way their conservation before processing and sale. Shelf life is measured in months, depending on the type and quality of the product, the mode of freezing and storage. During the period of freezing and subsequent storage, up to 90% or more of the original microflora dies off. The residual microflora is dominated by coccal bacteria and gram-negative rods. Glazing the product allows you to extend the shelf life.
Eggs are a good nutrient substrate for microorganisms, according to experts from the Central Research and Production Veterinary Radiological Laboratory, as they have high nutritional and biological qualities. Fresh eggs from healthy birds are sterile. Sterile eggs remain for quite a long time and during storage. The reason for this is the presence of an immune substance in them - a specific protein of lysozyme, as well as the fact that the egg shell, a film of dried mucus on it and shell membranes prevent the penetration of microbes.
However, with prolonged or improper storage of eggs, the activity of lysozyme gradually decreases, the physicochemical properties of their contents change, the integrity of the shells is violated, and the egg may undergo microbiological deterioration. The rate of spoilage of eggs depends on the storage temperature, relative humidity, shell condition, composition of microflora. 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.
Spoilage microorganisms are: Escherichia coli, staphylococci, mold fungi, butyric bacteria (clostridia), micrococci.
Sometimes eggs from waterfowl contain salmonella. Salmonella-infected eggs can cause food poisoning. Therefore, the consumption of raw duck and goose eggs directly as food is limited, and it is prohibited at catering establishments. It is forbidden to use duck and goose eggs for the manufacture of confectionery products with cream, ice cream, mayonnaise, melange, egg powders. Such eggs are used in the production of confectionery, where they are exposed to high temperatures.
Types of damage to eggs are: mold and decay.
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. In the initial stage of molding, when ovoscopy of the egg, a dark spot is observed at the site of mold development. As the fungus develops, the size of this spot increases and the egg becomes completely opaque, since the entire shell is covered with mold from the inside. Egg spoilage is most commonly caused by Penicillium, Cladosporium, Aspergillus, and the yeast Torulopsis vicola. Hyphae of the fungus penetrate the shell and shell membrane of the egg, and further facilitate the penetration of bacteria. Manifested by the appearance of raids of various shades.
Among bacteria, Pseudomonas fluorescens, Proteus vulgaris, Micrococcus roseus, Bacillus subtilis, Clostridium putrificum, Clostridium sporogenes are the most common causative agents of putrefaction.
The microflora of eggs is mainly of exogenous, after laying, origin due to contamination of the shell from the outside. It may also be of endogenous, intravital origin; in sick birds, pathogens enter the egg during its formation in the ovary and oviduct. On 1 cm2 of the surface of fresh clean eggs there are tens and hundreds of bacteria, and on a contaminated shell there are hundreds of thousands and even millions of cells. Microorganisms that enter the egg usually develop near the point of entry; their resulting accumulations (colonies) are visible during ovoscopy (transmission) in the form of spots. 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, as well as the high pH value (more than 9.0). Rotting, as a type of spoilage, is manifested by the appearance of turbidity, dark spots.
The rate of spoilage of eggs depends on the storage temperature, relative humidity, shell condition, composition of microflora. 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.
MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS
EE "BELARUSIAN STATE ECONOMIC
UNIVERSITY"
Department of commodity science of food products
on the topic: Microbiological processes of spoilage of eggs and egg products
Performed
FEUT student
3 course, DGH-2
Checked by N.E. Svireyko
INTRODUCTION 4
1. EGGS AND EGG PRODUCTS 5
1.1 general characteristics eggs 5
1.2 Characteristics of egg products 6
2. MICROBIOLOGY OF EGGS AND EGG PRODUCTS 7
2.1 Chemical composition of eggs 7
2.2 Microflora of eggs 7
2.3 Ways and sources of contamination of eggs with microflora 9
2.4 Microflora of egg products 10
3 SPELL PROCESSES 12
3.1 Rotting 12
3.2 Mold 13
4 STORAGE AND QUALITY OF EGGS AND EGG PRODUCTS 14
4.1 Quality assessment 14
4.2 Storage of eggs and egg products 14
CONCLUSION 16
LIST OF USED SOURCES 17
APPENDIX 18
INTRODUCTION
Egg products are valuable food products, because they contain complete proteins that are well absorbed by the body and have high calorie. In their composition, they contain fats, minerals, vitamins. Egg products are a supplier of lecithin, which is necessary for the nutrition of the human nervous system and is involved in metabolism.
A bird's egg is a complex biological complex, which includes all the nutrients and biologically active substances necessary for the life of the body, enclosed in protective shells.
During storage of eggs, microorganisms that have entered them can multiply and cause spoilage. For long-term preservation of quality, egg products are preserved by freezing or drying. During the preparation of egg products for canning, microorganisms from various sources of the external environment enter them. In the process of freezing and drying and subsequent storage, the composition of the microflora of egg products changes.
The relevance of the chosen topic is expressed by the need to control the quality of eggs and egg products according to various indicators, including microbiological ones.
1. EGGS AND EGG PRODUCTS
1.1 General characteristics of eggs
Eggs are a valuable food product. An egg consists of three parts: yolk, white and shell. On average, the protein is 56%, the yolk - 32% and the shell - 12% of the mass of the egg.
The shell protects the contents of the egg from external influences. Outside, it is covered with an over-shell membrane, and inside - with elastic under-shell and protein films.
The surface of the shell is permeated with pores necessary for gas exchange and the release of moisture from the egg. Through these pores, microorganisms can enter the egg and cause deterioration of the protein and yolk. At the blunt end of the egg, between the shell and protein films, there is an air chamber (puga), by which the freshness of the egg is determined.
The egg white is a viscous, transparent liquid and consists of four parts: outer and inner - liquid, middle - denser and densest hailstones (hailstones are dense twisted strands that hold the yolk in the center of the egg).
The yolk is a yellow opaque mass, the color of which is due to the presence of carotene and xanthophyll pigments in it. The yolk is enclosed in a shell, and the germinal disk is placed on its surface.
The shape of the eggs is different: from spherical to ellipsoid-elongated; color - from white to yellow-brown.
The chemical composition of eggs depends on the type and breed of the bird, the conditions of its maintenance, feeding, time of laying, etc. The closest in chemical composition chicken and turkey eggs. Duck, goose and quail eggs contain more lipids than chicken and turkey eggs.
Depending on the expiration date and quality, eggs are divided into types: dietary and table. Diet eggs include eggs whose shelf life does not exceed 7 days, not counting the day of demolition. Table eggs include eggs, the shelf life of which does not exceed 26 days from the date of sorting, not counting the day of demolition, and eggs stored in refrigerators for no more than 120 days.
1.2 Characteristics of egg products
In the process of storing eggs, their quality deteriorates and marriage is formed. To reduce the loss of eggs during storage, to increase their durability, frozen and dry egg products are produced. Dry egg products have a higher energy value than fresh eggs and frozen egg products due to more content they contain proteins, fats and carbohydrates. For industrial processing, food chicken eggs are used that meet the requirements of the standard, with a shelf life of no more than 25 days, and eggs stored in the refrigerator for no more than 120 days. Egg processing products include chilled or frozen melange, frozen yolk and protein, dry egg powder, dry protein and yolk, dry omelet.
Frozen egg products. Freezing is the best way to preserve eggs, as the original natural properties of the product are preserved. Depending on the part of the egg used, there are frozen egg melange, frozen egg yolk and m-born egg white.
Frozen egg white has a whitish-yellow color, a solid consistency, after thawing the consistency is liquid, it may not be completely homogeneous. There should be a characteristic bump on the frozen surface; if there is no bump, then the product may have been thawed.
Frozen egg yolk has a pale yellow color, after thawing - from yellow to pale yellow.
Frozen egg melange is a mixture of proteins and yolks in a natural proportion, to which table salt or sodium citrate or sugar to prevent coagulation from the same parts of the egg. The raw materials for the production of frozen egg products are high-quality table and refrigerated chicken eggs of the first and second categories.
Egg powders are the most stable in storage. They are produced in the form of egg powder (a mixture of yolk and protein), dry yolk and dry protein. The chemical composition of egg powder differs from the composition of a whole egg by the ratio of nutrients. Egg powders are obtained by spray drying and film drying. The consistency of egg powders is powdery, without lumps. The color of dry yolk is light yellow, dry protein is yellowish-white, uniform throughout the mass. Taste and smell are characteristic of this product, without foreign tastes and smells. Humidity - no more than 9%.
Dry omelette - differs from egg powders, dry pasteurized whole or skimmed milk is added to it in a ratio of 1: 1.
2. MICROBIOLOGY OF EGGS AND EGG PRODUCTS
2.1 Chemical composition of eggs
The egg protein contains,%: 87.9 water, 10.6 proteins, 0.9 carbohydrates, 0.6 ash; in the yolk - 48.7 water, 16.6 proteins, 32.6 fats, 1.0 carbohydrates, 1.1 ash. Quail eggs contain, %: 73.3 water, 11.9 proteins, 13.1 fats, 0.6 carbohydrates, 1.1 ash. Of the fat-soluble vitamins - vitamin A (in chicken yolk 0.30 mg%, quail - 0.47 mg%), vitamin E (in chicken yolk 2.0 mg%) and water-soluble vitamins (B1, B2, B6, PP ). All this indicates that eggs are a good breeding ground for the development of microorganisms. However, the contents of the egg (white and yolk) are protected from their penetration by the shell and shell membrane. In a freshly laid egg, there are practically no microbes, or there are very few of them.
The sterility of the egg is preserved for some time, since it has natural immunity, in which bactericidal substances play a significant role. Egg protein has the strongest bactericidal effect, it is able to kill many microorganisms, especially gram-positive rods, molds and yeasts.
The bactericidal ability of the protein is due to the presence of antibiotic substances in it: lysozyme, avidin, ovoalbumin, ovomucoid, ovomucin and carbon dioxide, which kill or inhibit the growth of microorganisms. In addition, the multiplication of microbes in the protein is suppressed by its high pH (9.2) and the resistance of protein proteins to the action of proteolytic enzymes of microorganisms. The inner layer of protein adjacent to the yolk has a stronger antimicrobial effect. The shell, shell membranes and egg white of freshly laid eggs have the most pronounced antimicrobial properties.
2.2 Microflora of eggs
The egg ages especially quickly at a storage temperature above the established norms. Its immunity decreases, and rather favorable conditions are created for the penetration and reproduction of micro-organisms in it. Some microbes mechanically penetrate through the pores of the shell, others, especially molds, grow through the shell. Moisturizing it favors the germination of mold spores. Hyphae of the fungus, penetrating the shell and shell membrane of the egg, contribute to the penetration of bacteria.
Microbiological processes are the main cause of egg spoilage. For microorganisms, the shell of the eggs is under-shell, proteinaceous and partially over-shell, impermeable. A freshly laid egg is usually sterile. After laying, microorganisms enter the egg through the pores of the shell. By dissolving the shells of the egg with enzymes, the bacteria get inside the egg. During the development of bacteria, the contents of the egg decompose (putrefaction) and unpleasant-smelling substances are formed.
A sign of bacterial seeding of eggs is the appearance of a putrefactive odor, the appearance of green colonies on the shell of the egg and the liquefaction of the protein. With the development of bacteria, the hailstones are destroyed, the yolk floats up and dries to the shell. If the process is deeper, then the yolk shell is torn, the yolk is mixed with the protein and a cloudy-dirty liquid is formed. The content of such an egg becomes opaque, the shell becomes gray. Through the pores of the shell, molds penetrate the inside of the egg. At first, they develop on the shell and protein films in the form of separate colonies of various colors (dark green or black, yellow or blue, red or pink), depending on the type of mold. Growing molds destroy the films, penetrate the protein and change its contents with the release of decomposition products, which give the eggs a musty smell and a bitter-sour taste.
During storage, the physicochemical properties of the contents of the egg gradually change (it dries out, the pH of the protein rises); the antimicrobial effect of protein, shells and shell membranes is weakened, since lysozyme and other bactericidal substances are inactivated; shell pores become more permeable. All this creates favorable conditions for the penetration and reproduction of microorganisms in the egg. Processes, as well as dehydration. TO microbiological processes damage sausages...
Commodity research and examination of certain types of goods in the field of production and circulation of agriculture
Abstract >> Culture and artAND microbiological processes, as well as the preservation of dairy products. Thermal... egg products. The dough is made from wheat flour with eggs, egg...and persistence. Microbiological processes cause damage goods, significantly...
Microbiology products plant origin
Book >> BiologyOnly chicken eggs. Waterfowl eggs ... g, salmonella - in 25 g product. Egg powder. This raw material is subject to increased... microbiological processes leak during storage of fruits and vegetables? 6. What groups of microorganisms are involved in processes damage ...
Expertise and assortment eggs
Abstract >> Culture and artAir humidity - occurs damage eggs microorganisms. After demolition ... mechanical damage, development microbiological processes, egg anomalies... . PRODUCTS PROCESSING eggs TO products processing eggs include frozen and dry egg products. ...
Loading...
