sterilized milk. Thermization, sterilization, UVT-treatment of milk: purpose, modes, efficiency, influence of modes on changes in the components and properties of milk

It is unlikely that there are those who have not tried milk and would not know about it. useful qualities. It is difficult to imagine such a person, whether he is a farmer, a resident of a rural area or an inhabitant of a metropolis. The very word "milk" is associated with health, satiety, cheerfulness.

From childhood, we hear that milk is extremely useful, it helps babies grow strong and healthy, cures diseases and promotes good health.

Since ancient times, cows in the village were considered breadwinners, favorites. Without milk, life is bad.

In the modern world, striving for the maximum beneficial use of its time, to obtain certain benefits, the technology of pasteurization, ultra-pasteurization and sterilization was invented.

Let's try to figure this out.

What it is?

Consider what sterilization means. It turns out that everything is simple, and sterilization is boiling. That is, to obtain sterile milk, it is necessary to boil it and leave it in this form at a temperature of about 150 ° C for 30 minutes.

According to GOST, certain types of milk can serve as raw materials for the manufacture of a sterilized product:

• whole, from the farm;
• fat normalized;
• fat free.

And:

• cream;
• buttermilk.

But GOST also allows the use of some stabilizer salts: sodium and potassium citrate; potassium and sodium phosphate. In general, these components are present in milk in a natural form. Additionally, they are introduced in order to slow down or even stop the souring process for a long time.

To ensure the quality of goods sold on supermarket shelves, safety food products controlled in our country by the Technical Regulations. It regulates the permitted level of substances and microorganisms hazardous to human health in the composition of food products.

Not all milk is taken to the dairy for further processing. It must be selected for compliance with high quality requirements. Appearance should not contain lumps, flakes, impurities. Consistency is uniform. The color allowed is white, shades of blue and pale cream are possible. Milk should not be transparent, viscous. Odor other than natural is not allowed. All these characteristics are called organoleptic.

But also, before entering further production, technologists take samples and check the chemical composition of raw materials, evaluate its physical parameters.

We hasten to refute the existing myth about the addition of antibiotics to the composition of sterile milk.

Today it is strictly prohibited.

Technological process

In industry, milk is sterilized either by heat or chemicals or ionized radiation. The choice of method depends on the specifics of the technologies in each production. In our article, we mean exactly the thermal type of sterilization.

In the dairy industry, the technology for manufacturing sterilized milk is usually carried out according to several schemes.

• The liquid is poured into an absolutely sealed package and sealed. Then subjected to heating to 120°C and incubated for 20-30 minutes. This is a single-stage sterilization.
• Liquid raw materials for the manufacture of dairy products are pre-sterilized in a stream at 150 ° C, the exposure time is only 10 seconds, then the same procedures are carried out as in one-stage sterilization. Therefore, a two-stage sterilization is obtained.
• Both direct and indirect sterilization of milk can be performed by heating at 135-150°C for several seconds. Next, the resulting product in a disinfected atmosphere is packaged in sterile containers. This method is called single-stage sterilization with aseptic filling.

At what temperature does the procedure take place?

On average, products are sterilized at a temperature of 120-150°C. Exposure to high temperature lasts up to 30 minutes.

How is it different from pasteurization?

The main difference is that pasteurization uses lower temperatures (up to 65°C). With this heating, the raw milk is kept for about 30 minutes. This is called long pasteurization. But there is also short-term and multi-link pasteurization, temperature regime rises (but not above 90°C), the time of exposure to milk is reduced accordingly.

The purpose of pasteurization and sterilization is the same- increase the shelf life of milk and protect it by destroying pathogenic bacteria. In order to be able to eat it without fear for health, all technological processes must be strictly observed.

How many useful substances lose milk during sterilization?

As you know, with prolonged heating, all pathogenic and toxicogenic microorganisms that exist in the liquid, bacteria - almost the entire microflora, die. In addition, enzymes are inactivated. The resulting product is absolutely safe for health. Sterilized milk is very long term storage, its taste and smell do not differ from the usual.

It is believed that it will not bring great health benefits.- when processed at high temperatures, beneficial bacteria will die along with harmful ones. In addition, in the process of boiling milk, the amount of vitamins B1, B2, B12 and C decreases in it.

And also polyunsaturated fatty acids, lysine and cystine are destroyed during sterilization.

Few people know that vitamins A, D, B2, B3, PP, H, as well as carotene are preserved during sterilization, only a small part of the total is destroyed by high temperature.

Therefore, sterilized milk is quite suitable for adult consumption. because it contains mineral salts and proteins necessary for the body. Such a product can be given to children, but the children's diet should be additionally enriched with vitamin C.

But sour sterilized milk is unsuitable for further use due to its characteristic bitter taste. It will not turn out yogurt and the like dairy products.

Benefit and harm

Of course, milk is good for you. After all, this is not just a drink - it is a unique biological fluid. Entire encyclopedias have been written about the vitamins and microelements contained in dairy products - we will not repeat ourselves.

Let's just say that sterilization destroys a substantial amount of bacteria that are beneficial to humans and some of the vitamins, but not everything that was mentioned above. In addition, milk remains useful due to the proteins, fats and carbohydrates that remain in its composition. At balanced diet, the richness of the diet of modern man, the body receives the missing in the sterilized dairy product vitamins from other foods.

Contraindication for the use of sterilized milk is individual lactose intolerance ( milk sugar) is a congenital feature that occurs in people of different ages.

IN this case fermented milk products, of which a truly great variety is currently produced for every taste, can become a substitute.

Is it possible to sterilize milk at home?

Wanting to keep the purchased farm product a little longer, as well as protect your health when buying whole milk, you can boil it in the atmosphere of an ordinary city apartment. If you do not want to lose the beneficial properties and vitamins that are destroyed by boiling, use the home pasteurization method.

For it glass container must be carefully prepared. One way is to heat it in the oven to 100 ° C, and the holding time is 20 minutes. Now you need to continuously stir the liquid for about half an hour (to evenly heat the entire volume).

To save time, you can heat the milk liquid up to 73°C. In this case, it will take only 15 minutes to stir continuously.

Then you should place the chamber with milk in a container with ice water. Do not stop stirring until the temperature of the liquid reaches 4°C.

Pour the resulting milk into the prepared dishes. Close the lids as carefully as possible and store in the refrigerator. So in a simple way You can extend the shelf life of milk up to two weeks.

As far as sterilization is concerned, it is impossible to sterilize milk at home: it requires a special industrial sterilizer and an absolutely sterile aseptic atmosphere. Such conditions are possible only on large industrial farms and factories.

The difference is only in terminology - for home use and absolute sterility of milk is not required, because the goal is not sale, but own consumption.

Terms and conditions of storage

One of the indisputable advantages of sterile milk is its long shelf life - it can be from 6 to 12 months. It is also undemanding to environmental conditions: hermetically sealed sterilized milk cartons may well be stored, remaining fresh when room temperature. Opened packaging is still safer to put in the refrigerator. This milk cannot turn sour, but it cannot go rotten.

You will learn more about sterilized milk in the following video.

Milk is one of the most popular and nutritious foods. Everything mass is usually accompanied by fiction. We asked our expert Olga Sokolova, Junior Researcher, to debunk some myths about milk. Central Laboratory of Microbiology of the State Scientific Institution VNIMI of the Russian Agricultural Academy.

Milk has always been considered useful product. Please tell us who and how it can help in solving health problems? For example, due to its potassium content, milk is believed to reduce puffiness, remove waste, and is a superfood for the prevention of osteoporosis. It is also believed that it is useful to drink it for people with heart failure, hypertension, people with diseases of the gastrointestinal tract, gallbladder, etc.

Milk contains substances with unique properties. Each of these substances can have an effect on the body. positive influence. Especially if one or another property is strengthened. By itself, milk is not in all cases an unconditionally useful product.

Let me give you an example: a person has a gastrointestinal disease. It is prescribed to drink milk. What if the person is lactose intolerant? In this case, you need to use only fermented dairy products, fermented milk products with bifidobacteria, they do not contain lactose.

IN dairy production There is also a promising direction - the development of specialized nutrition. For example, for the elderly, or for people with certain diseases, children of different ages, people from different social groups, athletes, and so on. This is not enrichment with vitamins and microelements, this is really a separate direction.

What is the unique composition of milk?

Rather, it is not the composition of milk that is unique, but its properties as a whole and the properties of its individual components. Milk is the only biological fluid that a person can eat throughout his life. Now various fractions of milk can be isolated and used in other areas of knowledge, and not just in nutrition. First of all in medicine.

If we talk specifically about the composition of milk, then milk is 87.5% water and 12.5% ​​solids. But the composition of these dry substances is very diverse. Milk is a multicomponent and multifactorial liquid. For example, only milk fat contains more than 140 fatty acids. And each substance of milk is useful in its own way. If you list all these substances and the benefits that they bring to the human body - enough for a whole encyclopedia.

Does the milk from the store retain at least some healing properties?

Undoubtedly yes! Most consumers forget that the benefits are not only vitamins. It also contains proteins, fats and carbohydrates. All these substances are stored in milk. If we talk about sterilized milk, there are no vitamins in it, but vitamins are preserved in pasteurized milk. Otherwise, the composition of pasteurized and sterilized milk is identical.

To be honest, I don’t really understand the noise about the fact that there are few vitamins in sterilized milk. If a person eats well, he will receive vitamins from other sources.

By the way, there is a lot of debate about the properties of pasteurized and sterilized milk. What is the difference?

In the beginning, I will make a reservation that sterilized and ultra-pasteurized milk are one and the same. Now I will answer the question. Technology difference. If we omit the stages of preparation of raw milk (these stages are the same for any dairy products) and some intermediate operations, then the technology can be described as follows:

Pasteurized milk:

1. preparation of raw materials;
2. normalization (bringing to the same fat content);
3. homogenization (bringing to a single consistency - so that the cream does not settle);
4. pasteurization (various modes up to 99 degrees);
5. intermediate storage (if necessary);
6. bottling.

Sterilized milk:

1. preparation of raw materials;
2. normalization;
3. adding stabilizer salts;
4. homogenization;
5. sterilization (temperature over 100 degrees, most often around 120 degrees);
6. cooling;
7. immediate bottling.

With the technology of pasteurized milk, I think everything is clear. But regarding sterilized questions arise.

What are stabilizer salts and why are they needed? These are citrate or phosphate salts. They are present in milk in a native (natural) form. Their additional introduction ensures that the milk does not turn sour for 6-8 months. Their job is to control acidity. There is such a thing as a "buffer zone". What it is is rather difficult to explain. But if it is very simplified, it is like emptiness. If this “void” is occupied by acid, the milk will turn sour. Salts-stabilizers forcibly "occupy" the buffer zone, do not allow milk acid to penetrate there.

Sterilization of milk is carried out in absolutely sterile conditions. Filling is carried out immediately in closed facilities (pasteurized milk can also be filled in open facilities). Packaging for sterilized milk does not let in light, air, microbes, water and is completely hermetic. Milk in the process of sterilization is disinfected. All these factors ensure the safety of milk for a long time.

There is a myth that antibiotics are added to sterilized milk. This is wrong. Until a certain time, antibiotics could only be present in pasteurized milk. This was allowed by GOST. However, now GOST has been revised, and antibiotics are prohibited in any milk.

Is reconstituted milk inferior to raw milk in terms of enzymes and vitamins?

If we talk specifically about raw milk, then - of course. Raw milk is full of everything. Both good and bad. And even to compare such milk it is impossible. They are just two different products.

But if we talk about liquid drinking milk and the restored one is another matter. Properly restored powdered milk indistinguishable from pasteurized milk, both in taste and chemical characteristics. Moreover, neither a simple buyer, nor a specialist, nor a laboratory analysis will be able to distinguish it.

Another myth: skimmed milk drinking does not make sense, it is not useful, it has little calcium. How would you comment on it?

Skimmed milk is milk with reduced content fat. Calcium is found in the protein part of milk, not fat. So the amount of calcium and skimmed milk are completely unrelated things.

They have the opportunity to use it immediately from under the cow. But the townspeople buy useful and indispensable product in the shop. This milk necessarily undergoes heat treatment, which extends the shelf life of the product. This article will focus on milk sterilizers: their device and purpose.

The benefits of milk

From the very first days of birth, a person feeds on milk, first breast milk, and later - cow's. This product is rich in vitamins and minerals, enzymes and proteins, milk fats and sugar. Useful substances are easily absorbed by the human body.

Milk is especially useful for babies, because protein is so necessary for building muscles, skin cells, nails and hair. For normal bowel function, there must be a sufficient amount of milk sugar in the body. It helps to normalize the microflora, removing purulent foci and infection. Milk saturates the body with calcium, which nourishes bones, teeth, promotes the production of hormones and enzymes.

The product contains many vitamins that contribute to the normalization of all life processes in the human body. Especially good for calming down nervous system relieves stress and relieves depression.

Periodic table in the composition of milk

This useful and delicious product rich in minerals: calcium and potassium, magnesium and phosphorus, sodium, chlorine and sulfur. All of them are macronutrients. The greatest value in milk is calcium. It is easily absorbed by the human body. For example: cow's milk contains one hundred to one hundred and forty milligrams of the element per percent of the product. The amount of calcium in milk is directly related to the diet of the animal, its breed. The stage of lactation and the time of year matter. So, for example, in summer there is less calcium in milk than in winter.

Milk is useful in micronutrient content. Their concentration is small, hence the name. This group of minerals includes copper and iron, manganese and zinc, iodine and cobalt, aluminum and fluorine, selenium and silicon, chromium, lead, chromium, tin and others. They are part of vitamins and enzymes. The amount of these minerals in milk depends on water, soil, composition nutrient mixtures for animals, their state of health, methods of processing and storage conditions of the product. Possessing a set of elements of almost the entire periodic table, can milk not be useful? Of course not. Milk is the very first food. Humans consume milk throughout their lives.

Which sterilizer to choose: steam or cold?

With the advent baby in the house there is a need to often boil nipples, bottles, toys. They quickly deteriorate because of this, and the method of cleaning accessories is not very convenient: you need a saucepan, trays, potholders. For this, there is a specially designed device that is simple and easy to use. This is a milk sterilizer. After getting acquainted with the parameters of the devices, everyone will choose the best for themselves. Sterilizers are:

When buying a sterilizer, a passport is always enclosed in the packing box indicating the technical characteristics and parameters of the device. You need to pay attention to the following:

• How many bottles does it fit.
• The presence of a time indicator. Without it, you will have to constantly monitor the process.
• Possibility to sterilize other accessories.
• Device power. Released models with different periods sterilization: from five minutes to twenty.

This device is intended for heat treatment. Sterilized milk is purified from pathogenic bacteria and microbes. They simply die due to exposure to high temperatures. The disadvantage is that part of the sterilized breast milk useful substances necessary for the formation of the child's immunity is lost. That's why heat treatment not recommended for continuous use.

Sterilize baby's milk only when necessary. For example, a woman who has given birth does not have her own milk or it is not enough. Then the donor product must be processed. Sterilizer for breast milk at home is very simple. To do this, it is enough to adapt a large enamel pan, prepare glass or plastic bottles. The procedure is:

• Breast milk is bottled.
• The pan is filled with water so that the container stands stably, does not float in the water and does not fall.
• Gas or electric stove turns on. The pot is put on fire, the water is brought to a boil. Then the heating is reduced, and boiling continues. Five to eight minutes is enough.
• The hob turns off.
• The bottles are carefully removed from the pan using a towel so as not to burn yourself.

Baby food sterilizer

Babymoov installation - indispensable assistant for every mom. This baby milk sterilizer is equipped with steam holes not only on the central tube, but also on the bottle holders, which have removable mechanisms. If necessary, breast pumps can be treated. The central part of the installation is also removed, you can dry the container on it. As you can see, these operations are done without touching the dishes with your hands. The installation holds six bottles with nipples dressed on them. By the sound signal, you can know that the sterilization is over. Philips sterilizers are also very popular, however, they are quite expensive. There is also an alternative - the Belarusian sterilizers "Buslik", which many mothers buy with pleasure, since their quality is not bad, and the price is more than affordable.

Product processing methods

Sterilized milk is a sterile product. It does not contain the bacteria present in the raw product, which prolongs the shelf life and does not change the taste. There are different types of milk:

• Single stage. It is used for the manufacture of sterilized milk in bags. The product is heated to a high temperature - one hundred forty - one hundred and fifty degrees for one second. Then cooled, homogenized and poured into sterile bags.

• Two-stage. This method is used when not bags, but glass containers are used as packaging. Milk is heated to the same temperature as in the first case, only kept for five seconds, not one. The product is cooled, poured into glass containers and re-sterilized. But the temperature is lower - one hundred and twenty degrees, and the processing time is longer - twenty minutes.

In the production of sterilized milk, the first method is better preserved biological value product. The taste of milk does not differ from fresh.

Sterilized milk production technology

• Raw materials are being prepared.
• Milk is normalized - fat content is reduced to a single figure.
• Homogenizes - the consistency must be homogeneous so that the cream does not exfoliate.
• Stabilizer salts are added.
• Sterilized - heating temperature of one hundred degrees and above.
• Cooling down.
• Spills immediately.

Why do we need salt stabilizers? They control acidity. Their presence in milk does not allow the product to turn sour for a long time- six to eight months. There is the concept of a buffer zone. If it is occupied by lactic acid, the product will turn sour very quickly. Salts dissolve and forcibly fill this void, preventing the acid of the product from penetrating there.

For processing in industrial environment using a milk sterilizer. The process is carried out under conditions of absolute sterility. For bottling this particular product, closed installations are used so that microbes do not get in. therefore milk is insured against harmful effects external environment.

Device for processing milk at the place of its milking

A farm milk sterilizer is essential in every farm where livestock is bred. The product is sold for sale to the public after special processing. But, if there are newborn calves on the farm, for the first time after they are born, they are given milk. Before it needs to be processed so that the kids do not become infected. Use a light milk sterilizer for mini-farms "SSM".

It is a gas discharge lamp with a powerful stream of ultraviolet rays. There is no ozone exhaust, which does not allow milk fat oxidize, resulting in the milk not having bad smell. The sterilizer is powered. Its warm-up time is four minutes. It must be taken into account in the course of work. To check that the milk sterilizer is ready for use, a red object is brought up to it at a distance of one meter. If it turns brown, the device is ready for full power operation.

The sterilizer in the flask is placed so that it does not touch the surface of the milk, which must be constantly stirred. Samples are taken at intervals of ten minutes using a masttest. When it shows a negative reaction, the milk is ready for use. The ultrasonic milk sterilizer is widely used for milk processing in modern farms.

Sterilizers tubular

These units are designed for heat treatment of milk, cream, various juices. Applied in industrial production where it is necessary to carry out long production cycles. on a milk sterilizer takes a short period of time, and the product retains its beneficial properties. These sterilizers are characterized by a high level of sanitation, good thermal efficiency, low maintenance cost, which has a lot of advantages. importance on the scale of production.

Advantages of tubular sterilizers

• There is no possibility of infection with pathogenic microbes.
• It is easy to take a sample to check the readiness of the product.
• Flushing of the installation with a solution is carried out automatically. The control panel is equipped with switches for flushing time, temperature, concentrate dosage and others.

• All production lines are automated, which ensures complete sterility.

Diseases transmitted through milk

This product is obtained from animals. If they are healthy, no harm even from eating fresh milk will not be. But if the animals are sick, the chance of infection is high. A person can get tuberculosis, foot-and-mouth disease, brucellosis, or coccal infections. That is why it is so important to sterilize milk. Thanks to this procedure, the product is cleansed of microbes and bacteria, while retaining its valuable properties.

Introduction

Sources of contamination of milk by microorganisms

Spore form of microorganisms

Spore microorganisms that die during milk sterilization

1 Botulism

2 Clostridia perfringens

Milk sterilization methods

Milk quality assessment

Conclusion

Introduction

Sterilization is a heat treatment process in which, as a result of exposure to high temperatures (above 100 ° C), all microorganisms die, and the shelf life of milk increases. Both vegetative and spore forms of microbes are destroyed. The higher the heat treatment temperature, the greater the sterilizing effect and the more noticeable changes in the color and taste of the milk. With an increase in temperature, the spores are destroyed much faster than the change in color and taste of milk. Its color change depends on various methods sterilization. Compared to pasteurized, sterilized milk has a higher stability and can withstand long-term storage and transport even without refrigeration. Sterilized milk is convenient and economically advantageous to use to supply the population of remote areas that do not have a sufficient raw material base, as well as large industrial centers and new camps. After sterilization, milk retains valuable nutritional qualities and well absorbed by the body. In the dairy industry, one-stage sterilization is mainly used with a single heating of milk in a stream to 135–140 ° C, followed by cooling and bottling. .

The purpose of this abstract is to study the types of microorganisms that die during the sterilization of milk.

1. Sources of contamination of milk by microorganisms

Two ways of contamination of milk with microorganisms are known: endogenous and exogenous.

In the endogenous way, milk is seeded with microorganisms directly in the udder of the animal.

Exogenous contamination occurs from external sources: animal skin, bedding materials, feed, air, water, milking equipment and utensils, hands and clothing of dairy farm workers.

endogenous seeding. Udder milk always contains a certain amount of microorganisms. In the glandular part of the udder, microorganisms can be found inconsistently and in a single number of cells. In the excretory ducts and milk cistern, the number of bacteria can reach several tens or hundreds of cells per 1 cm. These microorganisms are udder commensals. These include enterococci, micrococci, sometimes mastitis streptococci, corynebacteria (Figure 1).

Figure 1 - Corynebacteria and Enterococci

Endogenous seeding of udder milk can occur with mastitis, septic infectious diseases, injuries and inflammation of the teat canal and udder.

exogenous seeding. The most important source of bacteria in raw milk is the skin of the animal and especially the skin of the udder and teats, which are worn in the teat cups.

The milk film formed during milking between the skin of the teats and the teat cups, the presence of coarse and fine folds on the skin, as well as relatively high temperatures create favorable conditions for the development of microflora.

Bedding materials from straw and hay are a significant source of contamination of the skin of the animal, and then milk with E. coli, butyric acid bacteria, enterococci, putrefactive spore-forming yeasts, molds, lactic acid bacteria.

Feed also contains a wide variety of micro-organisms. In freshly cut grass there are more lactic acid bacteria, in roughage - putrefactive spore-forming aerobic bacilli.

Since milk is currently produced and stored predominantly in closed systems, raw milk contaminated mainly by hand milking. However, when changing milk lines, outside air is always sucked in.

2. Spore form of microorganisms

Bacterial spores are a dormant, non-reproducing form of bacteria. They form inside the cell, they are formations of a round or oval shape. Sporulation is a genetically determined trait, encrypted in the genetic code of a microorganism. Bacteria, predominantly gram-positive, rod-shaped with aerobic and anaerobic respiration in old cultures, as well as in adverse environmental conditions (lack of nutrients and moisture, accumulation of metabolic products in the medium, changes in pH and cultivation temperature, the presence or absence of atmospheric oxygen, etc.) can switch to an alternative development program, resulting in the formation of one spore. This indicates that sporulation in bacteria is an adaptation for the preservation of the species (individual) and is not a way of their reproduction.

The process of sporulation occurs, as a rule, in the external environment within 18-24 hours. Outwardly, it begins with the concentration and compaction of the cytoplasm and nuclear substance in some part of the cell. At the same time, a zone of cytoplasm differentiates around this site, which, condensing, turns into a spore shell. The cell at this stage is called prospore. Prospore, like a vegetative (reproducing) cell, is easily stained with aniline dyes.

During the formation of a prospore, DNA is divided into two nucleoids, the cytoplasmic membrane grows inside the cell, enclosing one nucleoid and not a large number of cytoplasm. Around the formed prospore, the cellular cytoplasmic membrane of the mother cell begins to grow, developing two petals, from which two shells will subsequently form: outer and inner. In the gap between the petals of the membrane, mucopeptides, calcium salts of dipicolinic acid accumulate, which provides the spore with high thermal stability.

As the prospore matures, it decreases in size and becomes denser. From the petals of the cytoplasmic membrane, two shells are formed - the outer (exine) and the inner (intine). Subsequently, the formed spore is covered with a thick layer of several proteins similar to keratin, which are part of feathers, nails, and skin. Dehydration of the spore occurs, the vegetative part of the cell is destroyed. The outer shell becomes impermeable to water and various substances. Therefore, a mature spore loses its ability to be stained by conventional methods. The bacterial cell wall is formed from the inner layer during spore germination.

A mature spore is approximately 0.1 of the volume of the mother cell. Spores in different bacteria differ in shape, size, location in the cell.

Microorganisms in which the spore diameter does not exceed the width of the vegetative cell are called bacilli, bacteria. Having spores, the diameter of which is 1.5-2 times greater than the diameter of the cell, are called clostridia.

Inside the microbial cell, the spore can be located in the middle - the central position, at the end - the terminal and between the center and the end of the cell - the subterminal position. Clostridia with terminal spores are called plectridia.

By chemical composition and the presence of enzymes, spores and vegetative cells from which they are formed do not differ from each other. The difference lies in the quantitative ratios of chemical compounds. In a spore, unlike a vegetative cell, it contains twice less water, which is mostly in a bound state. In the spore, the concentration of calcium, magnesium, as well as lipids and picolinic acid noticeably increases, which largely determines the resistance of spores to the effects of adverse physical and chemical factors. As a result, spores can remain in the soil for decades, withstand boiling for 60 minutes and even several hours, and also the action of high concentrations of disinfectants. The stability of spores makes it difficult to fight against spore-forming putrefactive, butyric and other microorganisms that enter milk and dairy products that withstand milk pasteurization regimes.

Spores, when they enter the nutrient substrate and favorable conditions of existence, can germinate into the original vegetative form. At the same time, the spore swells, the size increases significantly, and biochemical processes are activated. The germination of the spore ends with the formation of a hole in the shell and the appearance of a sprout, which then stretches into a stick. The germinating spore can be stained with common aniline dyes.

The spore germ can occur polarly, equatorially, and between the pole and the center of the cell. In the first case, the sprout appears at one of the ends of the spore; in the second case, it emerges in the middle part, prependicular to the long axis of the spore. The process of spore germination is carried out much faster than its formation, and ends after 4-5 hours.

Sporulation is a constant feature that is important for identification, i.e. determining the type of bacteria. The difference between a bacterial cell and a spore cell is shown in Figure 2.

Figure 2 - Spore formation

Spore microorganisms that die during milk sterilization

At a temperature exceeding the optimum, a slowdown in the reproduction of microorganisms is observed, and at a temperature above the maximum, their development completely stops and microbial cells die. The resistance of microorganisms to high temperatures is called thermal stability or thermal resistance. It is not the same for different groups of microorganisms. The spores of bacilli and clostridia have the greatest heat resistance. They withstand boiling from a few minutes (Bac. subtilis) to 6 hours (Cl. Botulinum) or more. Spores are not rendered harmless under milk pasteurization regimes (65-90 º WITH). Vegetative forms and sporeless bacteria are thermolabile; they die at 65 º C for 5-30 min.

Spore-forming. The putrefactive aerobes include Bac. Subtilis - hay stick, Bac. Mesentericuc - potato stick, Bac.megatherium - cabbage stick, Bac. Mysoides - mushroom bacillus, etc.

Spore-forming putrefactive aerobes include bacteria of the genus Clostridium. All spore-forming putrefactive ones are rather large thick sticks, reaching sizes of 0.5-2.5 * 10 (in clostridia - up to 20) microns, they stain positively according to Gram, are mobile until the moment of spore formation, do not form capsules.

sterilization milk microorganism

3.1 Botulism

Botulism is a food poisoning, one of the most severe diseases associated with eating food, infected with the bacteria Cl. Botulinum and containing botulinum neurotoxin.

The causative agent of botulism belongs to the genus Clostridium. Known such pathogen serovars as: A, B, C, D, E, F, G, differing in antigenic structure, formed by toxins and a number of other features.

Clostridia are large sticks 3.4-8.6 µm long and up to 1.3 µm wide. The causative agent is mobile until the moment of spore formation, peritrichous, stains positively according to Gram, does not form capsules. Spores are located subterminally in the cell. A stick with a spore in appearance resembles a tennis racket, a spoon, a boat (Figure 3).

Figure 3 - Clostridium Botulinum

Clostridia ferment glucose, fructose and some other carbohydrates, but saccharolytic properties are unstable. Serovars are heterogeneous in terms of proteolytic properties. Proteolytic strains are able to melt pieces of the liver or minced meat on Kitt-Tarozzi type media.

The causative agent of botulism produces two main types of toxins: neurotoxin and hemolysin.

Neurotoxin (botulinum toxin) produces all serovars, it determines clinical picture intoxication in botulism.

The spores of the pathogen are resistant to the external environment. They remain viable under conditions when all other living organisms perish. Spores withstand boiling for 5-6 hours, remain viable in alcohol for 2 months, resist the action of acids and formalin, and are resistant to freezing.

Unlike benign foods, foods containing the causative agent of botulism may have a specific odor. rancid butter, "pinching" taste, become pale in appearance, loose texture. A person becomes infected when eating food containing a toxin and living microbes, with the reproduction of which the amount of the toxin increases.

2 Clostridia perfringens (Cl.perfringens)

Toxic infections caused by Cl.perfringens take the third place after food poisoning salmonella and staphylococcal origin. The name of the pathogen is associated with the ability to form a large amount of gas that breaks the surrounding dense nutrient medium. The term "perfringens" in Latin means "breaking through", "breaking through". Clostridia are large non-motile Gram-positive rods. In the body of humans and animals form a capsule. Slowly form spores (Figure 4).

Figure 4 - Cl.perfringens

Perfringens develops at a temperature of 15 to 50 º WITH. Optimum temperature for the fastest growth is 37 º C. A feature of Cl.perfringens is the ability to reproduce rapidly. The pathogen ferments glucose to form salts of lactic, acetic and butyric acids, ethyl alcohol, carbon dioxide and hydrogen, can ferment fructose, galactose, mannose, lactose, sucrose, ribose, starch, dextrin and glycogen.

4. Milk sterilization methods

Sterilization of milk is carried out in order to obtain a product that is safe in sanitary and hygienic terms and to ensure its long-term storage at ambient temperature without changing its quality. There are many ways to sterilize milk (chemical, mechanical, radioactive, electrical, thermal).

For example, sterilization of milk by means of radiation treatment completely eliminates energy costs, since sterilization in a gamma plant occurs due to the radioactive decay of radiation sources. In addition, the milk is not heated, which eliminates the change palatability and basic physical and mechanical properties, there is no need for cooling.

However, the most reliable, cost-effective and widely used in industry is the thermal method.

In the dairy industry, raw milk is sterilized according to three principles:

one-stage in the package - after pouring milk into the package and hermetically sealing it at a temperature of 115-120 ° C with an exposure of 15-30 minutes;

one-stage with aseptic filling - indirect or direct sterilization of milk raw materials at a temperature of 135-150 ° C for several seconds, followed by aseptic packaging in sterile containers.

Depending on the characteristics of the production and packaging of the finished product, raw milk is sterilized by periodic and continuous methods.

Periodic sterilization is carried out by placing the product in a package (glass or plastic bottles) into an autoclave and creating a vacuum of 0.08 MPa in it, which corresponds to a temperature of 121°C. At this temperature, the product is kept for 15-30 minutes. The temperature is then reduced to 20°C. Milk comes to sterilization normalized, homogenized, preheated.

Sterilization in a continuous way in the package is carried out in hydrostatic tower sterilizers. The bottled product will be fed into the first tower of the sterilizer, where it is heated to (86 ± 1) °C. In the second tower, the bottled product is heated to a temperature of 115-125°C and kept for 20-30 minutes, depending on the volume of the bottle. In the third tower of the sterilizer, the bottles are cooled to a temperature of (65 ± 5) °C, in the fourth - to (40 ± 5) °C. Further cooling takes place in the product storage chamber. The entire processing cycle in the tower sterilizer is approximately 1 hour. Such milk is stored at a temperature of 1-20 ° C for no more than 2 months. from the time of production.

In the dairy industry, sterilization of milk and dairy products is carried out in containers and in a stream.

When sterilizing a dairy product in a container, the taste changes and its nutritional value due to the fact that with a fairly long thermal exposure, the components of the product are destroyed, which determine its taste and nutritional properties.

Sterilization in a stream. The most progressive is the sterilization of the product in the stream at ultra-high temperature mode (135-150°C with exposure for several seconds) followed by its packaging under aseptic conditions in a sterile container.

Ultra-high temperature (UHT) processing allows you to increase the shelf life of products up to 6 months. When packing dairy products under aseptic conditions, a package made of a combined material is used, plastic bottles, plastic bags, as well as metal cans and glass bottles.

Milk sterilized in a stream at ultra-high-temperature modes with a short exposure, but its quality indicators are close to pasteurized milk.

In the process of in-line sterilization, the product is heated to the sterilization temperature, maintained at this temperature for the required time, and cooled to the packaging temperature under aseptic conditions.

The ratio of temperature and processing time is determined by the required sterilization efficiency and is of greater importance for the quality of the product. The upper temperature limit for the sterilization of milk in a stream is 150°C, since even a short exposure at this temperature can lead to undesirable changes in the quality of the product. At the same time, it is technically difficult to carry out very rapid heating to this temperature and subsequent rapid cooling. The lower temperature limit is 135°C, since at temperatures below 135°C, sterilization efficiency is insufficient for short-term exposure. Increasing the exposure time is also undesirable in order to avoid deterioration of the quality of the product.

Thus, in-line sterilization of milk is the most efficient method of heat treatment of milk.

5. Evaluation of milk quality

The determination of microbiological indicators is carried out by the methods provided for by regulatory documents, and according to the methods approved by the bodies and institutions of the State Sanitary and Epidemiological Service of Russia.

The product is manufactured in accordance with the requirements of this International Standard. technological instructions approved in the prescribed manner. According to organoleptic characteristics, the product must meet the requirements of Table 1.

Table 1 - organoleptic evaluation milk

Indicator nameCharacteristic AppearanceOpaque liquid. For fatty and high-fat products, a slight settling of fat is allowed, which disappears when stirred. Consistency Liquid, homogeneous, non-viscous, slightly viscous. Without protein flakes and lumps of fat that have strayed Taste and smell Characteristic for milk, without foreign tastes and odors, with a slight aftertaste of boiling. For baked and sterilized milk - a pronounced taste of boiling. For reconstituted and recombined, a sweetish aftertaste is allowed Color White, uniform throughout the mass, for melted and sterilized - with a creamy tint, for fat-free - with a slightly bluish tint

Sterilized milk must meet the requirements of industrial sterility. Industrial sterility requirements for sterilized and ultra-sterilized milk:

After thermostatic exposure at a temperature of 37 degrees Celsius for 3-5 days, no visible defects and signs of deterioration (bloating of the package, change in appearance, etc.), no changes in taste and texture.

After thermostatic exposure, changes are allowed:

a) titratable acidity not more than 2 degrees Turner;

b) QMAFAnM not more than 10 CFU/cm3 (g).

Conclusion

Milk contains more than 200 substances readily available to microorganisms, so they multiply intensively in it. Milk contains proteins, peptones, polypeptides, globulins, albumins, casein, amino acids. Milk contains fatty acids, lipids, milk sugar(lactose), vitamins, hormones, enzymes and mineral salts. And always in natural milk microorganisms exist.

During sterilization, milk is freed not only from the vegetative microflora, but also from the spore one. Such a product has absolute reliability from a sanitary and hygienic point of view, allows transportation over long distances without refrigeration, and eliminates the need for daily delivery to trade. From year to year, consumer demand for long-term storage dairy products in all countries of the world is growing, their range is expanding, shelf life is increasing, and ways to increase storage stability are being improved.

List of used literature

1. Tverdokhleb G.V. Technology of milk and dairy products / G.V. Tverdokhleb, G.Yu. Sazhinov, R.I. Ramanauskas. - M.: DeLi print, - 2006. - 616 p.

Stepanenko P.P. Microbiology of milk and dairy products / P.P. Stepanenko. - M .: LLC "All for You-Podmoskovye", - 1999. - 415 p.

Solyanik T.V. Microbiology. Teaching aid / T.V. Solyanik, A.A. Glaskovich. - Gorki: BSHA, - 2014. - 104 p.

Course work. The process of milk sterilization and devices for its implementation / AltSAU: Faculty of Engineering, - 2011, - 26 p.

Course work. Microflora of milk and dairy products / Pavlodar State University them. S. Toraigyrova, -2012. -31 s.

GOST R 52090-2003. Drinking milk. Specifications; Entered.01.07.04.-M.: Publishing House of Standards, 2008.-5 p.

the federal law Russian Federation dated June 12, 2008 N 88-FZ " Technical regulation for milk and dairy products.

Milk is a wonderful product that is one of the staple foods, but it can be fraught with danger. Milk itself is a favorable environment for bacteria and microbes, and if it was obtained from a sick animal, it can cause many dangerous diseases: tuberculosis, brucellosis, staphylococcal and streptococcal infections, etc. Before getting on the table in the form of various dairy products , it must undergo a special treatment - sterilization. You can carry out the procedure with a special tool - a light sterilizer for milk (CCM).

The existing milk disinfection technologies that are used today in the dairy industry and at home are based on heat treatment:

1. Pasteurization performed for 30 minutes at 65°C. The shelf life of this product is 2 weeks.
2. Process sterilization lasts for 30 minutes at a temperature of 130-150°C. Under such conditions, all microorganisms die, including lactic acid ones. The shelf life of products that have undergone such processing lasts up to 1 year.
3. At UHT milk is exposed to a very short-term effect, literally, within 4 seconds. But the temperature here reaches 135°C. The product is then gradually cooled to low temperatures, up to about 4-5°C. Such milk retains a maximum of useful properties, and its shelf life reaches 2 months.

The light sterilizer performs disinfection without the use of high temperatures, but with the help of ultraviolet radiation, which is harmful to pathogenic bacteria and microorganisms.

The principle of operation of the SCM

The basis of the SSM is discharge lamp that produces a powerful beam of ultraviolet radiation. Devices based on UV rays have long been used to disinfect rooms, reservoirs, and individual objects. Scientists have found that ultraviolet radiation with a wavelength of about 254 nm has a destructive effect on the DNA of microorganisms, depriving them of the ability to reproduce.

How to apply

The light sterilizer is designed for milk processing in industrial conditions and is necessary in every livestock farm. What do you need to know about it to be successful?

1. The CCM is powered by a 220V power supply.
2. The device is ready for use 4 minutes after connecting to the network. There is a way to check readiness for work. If a red object brought to it at a distance of one meter turns brown, then the device can be used.
3. The device is placed in a container with milk at a distance of 50 cm from the surface.
4. The sterilization process must take place with continuous stirring of the milk. UV radiation cannot penetrate into the deeper layers of milk due to its opacity.
5. Every 10 minutes of exposure, samples are taken for the presence of pathogenic microflora.
6. The process is considered complete when the samples are negative.

How to sterilize milk at home

At home, we most often use the familiar and accessible way sterilization - boiling. Of course, this method does not retain all the beneficial properties of milk.

Modern devices invented to help mothers allow sterilization that is more gentle on milk. For example, a sterilizer based on hot steam. Moreover, it can also be used as a sterilizer for breast pumps, bottles and small toys for babies.

Conclusion

Milk that has undergone heat treatment is certainly inferior in terms of useful properties cold processed product. Due to its high cost, a light sterilizer is most often used only in industrial conditions, but it can also be used at home.