Why milk quickly sours in the refrigerator. Research work "why sour milk"

Tomko Alena Sergeevna

Milk is the very first product that humans and all mammals try in their lives. It has a unique composition, because during the first months it must meet the needs of the body in all the elements necessary for growth. Milk contains proteins, fats, sugars, trace elements, vitamins, enzymes, hormones, and much more.

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Tomko Alain "Why does sour milk?"

Municipal budgetary educational institution

"Smorodinskaya Secondary School"

Research

"Why does sour milk?"

Section: inanimate nature

Grayvoronsky district of Belgorod region

Supervisor:

Tomko Tatyana Viktorovna, primary school teacher, Smorodinsky Secondary School, Graivoronsky District, Belgorod Region, Municipal Budgetary Educational Institution

with. Smorodino 2016

Introduction ................................................. .................................................. ................ 3
I. Why does milk turn sour? . ………………………………………………………… 5-6

Ii. In what environment is milk souring faster? ………………………………… 7-8

Conclusion ................................................. .................................................. ............9
Bibliography................................................ ................................................ten
Applications ................................................. .................................................. ... 11-12

Introduction

Milk is the very first product a person tries in his life and everythingmammals . It has a unique composition, because during the first months it must meet the needs of the body in all the elements necessary for growth. Milk contains proteins, fats, sugars, trace elements, vitamins, enzymes, hormones, and much more.

After standing for some time in the warmth, the milk curls and acquires a sour taste.Why is milk sour? I was interested in this question, and I decided to choose this topic for my research.

therefore the purpose of my research:find out why milk sours.

Tasks:

study the literature on this topic;
find out the cause of souring milk;
explore what can increase and slow down the souring of milk;
prepare a presentation of the work.

Relevance: Milk is considered to be a wonderful product. It serves as the only food for a newborn person, therefore it is intended to satisfy all the needs of the body. It is not by chance that nature has generously provided milk with biologically active substances, and in the most useful combinations. According to modern data, milk contains over 200 of the most valuable components - all kinds of vitamins and minerals. Milk has everything you need to build blood in the nervous tissue, muscles and bones.

Hypothesis: the milk turns sour due to the fact that bacteria and other microorganisms multiply in it.

Research methods: analysis, comparison, synthesis, observation, experiment.

I. Why does milk turn sour?

All children love to drink fresh milk, including me. But the milk turns sour after a while. Therefore, it became interesting to me: “Why does milk turn sour and how can it be kept longer?” I decided to answer this question.

The first who saw the microflora of dairy products was the famous French scientist Louis Pasteur. He became interested in the process of fermentation, began to study its causes.

Exploring the sour milk under a microscope, Pasteur found in it very small "balls" and "sticks". Observing them, Pasteur made sure that the balls and sticks in sour milk grow and their number increases rapidly. “Therefore, they multiply,” Pasteur decided. By adding an insignificant amount of sour milk containing balls and sticks to fresh milk, Pasteur caused it to ferment, that is, lactic fermentation. Thus, Pasteur established that fermentation processes are caused by microbes, and fermentation itself is a source of energy for these microbes.

Even good milk is considered to be normal milk by lactic acid bacteria, yeast. In warm milk, the bacteria multiply very quickly: every half hour it can split in half and give two new ones. Thus, in a short time, the number of bacteria in 1mm of warm milk can reach several million.

About 35% sour milk is composed of lactic acid. It is under the influence of lactic acid milk sour and curtailed.

From the literature, I also learned that some dairy products are made by souring milk, adding to it different types of microorganisms, each of which is able to change milk and give it new flavor properties (cream, sour cream, kefir, cottage cheese, ryazhenka, yogurt). Fermented milk products contain a huge amount of live bacteria and other microorganisms.

After standing a day or two, the milk turns sour. But you can make him turn sour and turn into cottage cheese not in two days, but in two seconds. To do this, add a little vinegar to the milk. Cottage cheese immediately stand out.

Cottage cheese is casein, milk protein. It is dissolved in milk, like sugar in water. But it is worth adding acid to the milk to make casein stand out, taking fat with it.

But no one pours milk into the milk. Why does it still sour?

Ii. In what environment is milk souring faster?

I decided to check in which medium milk is souring faster?

To determine this, I delivered milk for souring under the following conditions:

1 EXPERIENCE which we spent: put a glass of milk at home on the table. The next day, the milk sour.

Conclusion: the milk turns sour after standing a day or two.

2 EXPERIENCE: In fresh milk, we added vinegar, and at the same time the milk sour, and then turned into cottage cheese.

Conclusion: cottage cheese is casein, milk protein. It is dissolved in milk, like sugar in water. But it is necessary to add acid to milk, and casein begins to stand out, taking with it fat.

3 EXPERIENCES: We decided to check the environment in which milk is souring faster?

For the experiment we needed:

Milk,

Kefir,

4 glasses

We numbered the glasses and poured milk in them in the following order:

№1. Boiled milk;

№2. Unboiled milk;

Number 3. Unboiled milk, adding kefir as a starter;

№4. Also unboiled milk.

Glasses numbered 1, 2, and 3 I left at room temperature (+ 20 ° C), and put glass at number 4 in the refrigerator (+ 4 ° C).

During the experiment, the milk sour in the following order:

1. The quickest acid is milk with kefir leaven at room temperature.

2. Then sour boiled milk at room temperature.

3. The third in a row is acid boiled milk from the refrigerator.

4. The last is boiled milk.

We checked whether the milk was raw or not, heating it up. If the milk "rolled up", then we considered it sour.

Conclusion

Thus, as a result of the study, we have completed the tasks and I believe that the goal has been achieved. I learned that milk contains: water, fat, sugar, protein, salts, vitamins. Vinegar can increase the souring of milk, and boiling - slow down. So that the milk does not turn sour, you need to boil it, because the bacteria die from boiling.

During the study, I came to the conclusion that the results confirmed the hypothesis put forward by us:milk turns sour under the influence of dairy bacteria.

Bibliography

Mikhail Ilyin. Stories about things. - Selected works in three volumes. -Goslitizdat :. M, 1962
Ivan Dubrovin “Everything about ordinary milk” - Eksmo-Press, Yauza, Moscow
Wikipedia
http://www.kakprosto.ru
www.topautkor.ru
www.prozagadki.ru
www.pkmoloko.ru

Gomov Ilya

The research work was conducted by a student in grade 2. The work is educational in nature. In the course of work, the student learns not only to conduct experiments, but also to draw up his research.

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Ministry of Education and Science of the Russian Federation

Municipal autonomous educational institution "Lyceum No. 6"

Educational research work

Why does milk sour?

Completed: Gomov Ilya Igorevich,

Pupil 2 class B

Head : Gordenkova Nina Vasilyevna,

primary school teacher

tambov

2016

Introduction …………………………………………………………………………… 3

Literature review ……………………………………………………… 4-6

Milk history ………………………………… ................................. 4

1.2. Milk composition ……………………………………………………………… .4

1.3 Benefits and harms of milk ……………………………………. ………… 4-5

1.4. Lactic acid bacteria …………………………………………… ..5

1.5. Lactic acid products ………………………………………… ..5-6

2. Research Methods …………………………………………… 6-7

2.1. Stages of research ……………………………………………………… .6

The results of the study ……………………………………………… 7

Conclusions …………………………………………………………………………… 8

Conclusion …………………………. ……………………………………… ..9

Resources used ……………………………………………………… ..10

Applications ……………………………………………………………………… 11

Introduction: Both humans and mammals, from mice to elephants and whales, begin their feeding with milk. This is a wonderful, tasty and healthy drink, a real elixir of growth, which nature itself has invented. A newborn, no matter who he is - a boy or a girl, a kitten or a puppy - until a certain age, the stomach cannot digest any food other than milk. But in it there are all useful and nutrients necessary for a small being to grow faster and develop properly.

Relevance: It is important to be attentive to yourself, to your health, to be able to protect your body from the harmful effects, because human life is invaluable, and muscles, skin, bones, teeth are built from the nutrients that exist in milk. In addition, milk is also a medicine, because thanks to a set of useful substances in it, doctors prescribe it to many patients. Children should drink milk every day.

Hypothesis:

Purpose:

Tasks :

Subject of study: milk

Place of research:apartment (kitchen)

February 2016

Research methods:

Literature review

1.1Mistory of milk

Since ancient times milk used to feed infants unable to digest solid food and to feed the sick. The composition of cow's milk contains many beneficial elements, is a rich source of calcium and vitamins, is well absorbed by the body. Milk was drunk in ancient times, as evidenced by the vessels found during archeological excavations in the caves of primitive people. In the ancient temple, discovered near Babylon, found wall drawings depicting the process of milking a cow. It is believed that this temple is about five thousand years old. The Bible has many references to milk. Abel, the son of Adam, fed the sheep and probably drank the milk. Sayings about milk. (see Appendix №1)

1.2. Composition of milk

The composition of cow's milk is largely determined by its origin. It has a multicomponent composition in the form of a polydisperse system with a liquid consistency. Cow's milk is the most popular type of milk from all mammals, and occupies the largest portion of all types of milk produced in the livestock industry of world agriculture. Cow's milk consists of protein, fat, carbohydrates, water, ash, organic acids, minerals and vitamins. It contains almost the entire line of B vitamins, vitamins E, D, H, ascorbic acid, beta carotene, vitamin PP, choline, nucleic acids, monounsaturated fatty acids, lactose, essential amino acids. Of the mineral elements, perhaps the most valuable and essential element of the composition is the macro element.calcium . It is included in the chemical composition of cow's milk in the optimal form for easy digestion by the body, in an amount of on average from 100 to 150 mg%. It also includes potassium, phosphorus, chlorine, sulfur, magnesium, sodium, various chlorides and citrates, a number of trace elements. The amount of mineral elements and vitamins, as well as the percentage of fat content in the composition of milk can vary depending on the season, conditions of keeping, health and diet of cows, age and other factors affecting lactation.

1.3 The benefits and harm of milk

The benefits of cow's milk for the body is undeniable - it is the richest source of vitamins and minerals. The lactose contained in the composition is good for the heart. However, milk should be used with caution. People with lactose intolerance are contraindicated. People with diseases of the gastrointestinal tract, liver or pancreas should also refrain from the use of milk and choose for the diet.dairy products .

1.4. Lactic acid bacteria

Fresh milk contains many important nutrients. But the most wonderful substance found in milk is milk sugar. Its name is lactose. “Protects” milk from souring precisely lactose. If the fresh (that is, just-milked) milk stays for a while, then it starts to acquire a sour taste. Why it happens? Who "steals" milk sugar? (These are lactic acid bacteria - big “gourmets.”) They love various sugars, cannot live without many vitamins and some other compounds. Where do lactic acid bacteria get into milk? It turns out that they live in those places where milk is formed - on the surface of the mammary glands, where droplets of milk linger. Only a small droplet, which remains outside, "sours", it "diluted" in sterile milk and the sour taste will not be noticeable. But it is necessary to wait a little, the bacteria will have time to multiply and will certainly make themselves felt.DAIRY-ACID BACTERIA, a group of microorganisms that ferment carbohydrates to form mainly lactic acid. The classification of the DAIRY BACTERIA is not sufficiently developed.In milk, there is not only milk sugar, but all sorts of substances that other types of bacteria feed on. However, lactic acid bacteria are beneficial. Other types of bacteria can cause various types of ailments.

1.4. Lactic products

Fermented milk products contain a huge amount of live bacteria and other microorganisms. It turns out that milk can be pre-processed before it starts to turn sour. Thus, you can get lactic acid products.

Sour milk If you take the most fatty part of milk - cream, then the same types of lactic acid bacteria will turn them into sour cream.

Ryazhenka

Matsoni, matsun, katyk

Jugurt

Kurunga

Airan

"Kiselo mleko"

Chal (shubat)

Cottage cheese - Another fermented milk product. Cottage cheese is a protein product obtained by souring milk with the subsequent removal of whey.

Cheese - a highly nutritious food product made from coagulated (sour) milk.

2. Research Methodology

2.1. Stages of research

Stage 2 Stage

2.2. Description of experiments

Experience 1. Watching fat droplets

Fat floats in milk in the form of many small droplets. Since fat is lighter than water, it gradually floats to the top - a layer of cream is formed. Knocking the cream, get the oil: the droplets of fat from the shocks merge together and separated from the water.

Experience 2. Milk souring

I decided to check where the milk is souring faster - at room temperature or in the refrigerator. In the room all the milk sour on the second day. In the refrigerator, rustic boiled milk sour on the 5th day of the experiment, boiled on the 5th day was not sour.

Test 3 Acid

Using the example of experiment No. 2, I saw that unboiled and boiled milk starts to turn sour from the second day of the experiment. I decided to speed up this process. In the word lactic acid products. Two roots, milt and sour. And I thought that if you add acid, the milk will turn sour. Added a little acetic acid in one glass and lemon juice in another. Milky-colored flakes formed on the surface of the milk. From the literature, I found out iscasein (lat. caseus - cheese) - difficultprotein , formed from the precursor of casein - caseinogen during the spreading of milk. Casein (caseinogen) is present in milk in a bound form as a calcium salt (calcium caseinate). It is dissolved in milk like sugar in water. But it is worth adding acid to milk to make casein stand out, taking fat with it. This experience helped me see the effect of acid. It means that lactic acid bacteria also separate casein, and lactic acid products are obtained.

Experience number 4 Milk fermented with a piece of rye bread

In the room, in a glass with village milk, in which there was a piece of bread, milk sour the next morning. Boiled milk acidity later. In the refrigerator, pasteurized unboiled and boiled milk with pieces of rye bread on the 4th day of the experiment went cold, but not sour. From this experience, we can conclude that the presence of yeast under certain conditions (temperature conditions) also causes souring of milk. My grandmother in the village uses this method for quick souring of milk. And then she gets cottage cheese.

3.Results of research

Findings:

People with lactose intolerance have milk contraindicated.

Conclusion

Resources used:

1. Sushansky A. G., Liflyandsky V. G. Encyclopedia of healthy nutrition. T. I ,. Health Nutrition / St. Petersburg: “Neva Publishing House”; M .: OLMA-PRESS, 1999

2. Sharygina A. M., Kalinina L. V. General technology of milk and dairy products, Moscow: Koloss, 2007

3. https://yandex.ru/images/

4. https://ru.wikipedia.org/wiki/Milk

5.http: //sostavproduktov.ru/produkty/molochnye/moloko/korove

7. http://www.woman-lives.ru/

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Appendix №1

Milk Tips

The doctor Hippocrates called milk a medicine.

Academician Pavlov called milk food prepared by nature itself.

Avicena argued that milk is the best food for people.

But is it always good when sour milk? Not! If you need to keep the milk in an unchanged form, how to make sure that the lactic acid bacteria do not multiply and do not “change” the taste of milk? To destroy the germs you can use simple boiling of milk.

One of the most common technologies is milk pasteurization. Milk is kept at 61–63 ° C for 30 minutes or at 72–73 ° C for only 15 s. This does not impair the taste of the product, but kills pathogenic bacteria.

The use of storing food in the cold has long been known. At temperatures just below zero, bacteria continue to multiply, but very slowly. Therefore, milk can be frozen and stored and stored in this form for a long time.

When there were no refrigerators, milk was stored in the winter in the form of frozen circles and even sold as such in the markets. The first mention of frozen milk belongs to 1792

Other known methods for storing milk include drying. On spray units milk is dried at a temperature of 150-180 ° C.

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Appendix № 3

Sour milk - it is a fermented milk drink made from pasteurized milk by fermenting it with starter, prepared on pure cultures of lactic acid plants.

Ryazhenka - creamy color, to taste and texture resembles sour cream, but has a peculiar taste. Sweet taste reminds stewed milk. Fat content Ryazhenka 6%. For its preparation, pure cultures of lactic streptococcus are used. Caloric ryazhenka significantly higher caloric yogurt of other varieties.

Matsoni, matsun, katyk - in fact, they are different names for approximately the same type of southern sour milk, produced from cow, buffalo, sheep, camel or goat milk.

Jugurt produced in the North Caucasus (mainly in Kabardino-Balkaria). It is squeezed sour milk, looks like sour cream or pasta.

Kurunga - it is a fermented milk drink widely distributed in Northeast Asia among Buryats, Mongols, Tuvans and other peoples.

Airan - a very common drink among the peoples of Central Asia, in the Caucasus, in Tatarstan, Bashkiria. Cooked from cow, goat, sheep milk.

"Kiselo mleko" - Bulgarian sour milk, prepared with the use of "Bulgarian sticks", opened at the beginning of our century by Stamen Grigorov

Chal (shubat) - fermented milk, highly foaming drink with a pure fermented milk taste and yeast odor, made from camel milk.

2. Research Methodology

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I.I. Gomov

Pupil 2 class B

Why does milk sour?

Hypothesis: the milk turns sour due to the fact that bacteria and other microorganisms multiply in it

Purpose: find out why sour milk

Tasks :

To study the scientific and educational literature and Internet resources on the topic.
Conduct research on the process of souring milk.
Investigate what can strengthen and slow down the souring of milk.
Draw conclusions, summarize and systematize the material.

Subject of study: milk

Place of research:apartment (kitchen)

Dates of the study: February 2016

Research methods:

Theoretical (analysis of facts from literary and Internet sources, compilation of the material, generalization);
Empirical (experiment and observation, photographing)

Since ancient times milk used to feed infants unable to digest solid food and to feed the sick. The composition of cow's milk is largely determined by its origin. It has a multicomponent composition in the form of a polydisperse system with a liquid consistency. The benefits of cow's milk for the body is undeniable - it is the richest source of vitamins and minerals. However, milk should be used with caution. Fresh milk contains many important nutrients. But the most wonderful substance found in milk is milk sugar. Its name is lactose. “Protects” milk from souring precisely lactose. Where do lactic acid bacteria get into milk? It turns out that they live in those places where milk is formed - on the surface of the mammary glands, where droplets of milk linger. Only a small droplet, which remains outside, "sours", it "diluted" in sterile milk and the sour taste will not be noticeable. But it is necessary to wait a little, the bacteria will have time to multiply and will certainly make themselves felt. Fermented milk products contain a huge amount of live bacteria and other microorganisms. It turns out that milk can be pre-processed before it starts to turn sour. Thus, you can get lactic acid products.Stages of research: Stage 1- the study of literature and Internet resources. Stage 2 - conducting experiments and research.For the experiments, I took the village milk, boiled and boiled. Poured it into glasses (volume 200 ml) and watched him for five days. At the same time one part of glasses with milk was in the room, and the other in the refrigerator. In one of the glasses I added a slice of rye bread, and in the other two acid. In one acetic acid, in another lemon juice.

3.Results of research

1. Fat floats in milk in the form of many small droplets.

2. Milk quickly sours in heat.

3. Casein can be separated with acid (complex protein)

4. The presence of yeast accelerates the process of souring milk.

Findings:

Milk-valuable power source.
Lactic acid bacteria are a source of milk souring. They are useful for intestinal work.
People with lactose intolerance are contraindicated.

Conclusion

I performed this work together with the teacher, N.V. Gordenkova. I consider it relevant, as it is necessary to know about the benefits and dangers of milk. It is interesting to study, what you do not know and find out the reason for what is happening. In the course of my work, I deepened my knowledge of the presence of lactic acid bacteria, which are necessary for the formation of lactic acid products.

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Annotation.

The research work "Why sour milk" is designed for students of grades 2-4. In the course of work, children learn to observe and draw conclusions comparing observations. Work teaches children to observe, draw conclusions, defend their point of view. Develops curiosity and interest.

"Curdled milk". This is the state of the product in which the milk thickens and also stratifies - it is divided into a denser mass and liquid, called serum. There are several factors that can trigger this process. First, the milk may curl up due to the souring process. In the composition of any milk there are special lactic acid bacteria. If the milk is cooled, they are in a kind of dormant state. When the product is at a temperature close to room temperature, the bacteria begin to actively proliferate. As a result of this process, the milk changes its properties - consistency and taste. The reason for souring is usually improper storage. And the consumer is not always to blame for this - if at the factory or in the store milk remained for a long time at an unsuitable temperature, it can sour very quickly. To prevent similar processes in milk, except for storage in the cold, can pasteurization sterilization. In both cases, the milk is heated to a certain temperature. Pasteurized milk can be stored in the refrigerator for several days, and sterilized milk - even for several months, provided that the factory packaging is not opened. Secondly, the milk changes its properties even with special human exposure. For example, in order to get cottage cheese or cheese, the milk is heated to a boil together with sourdough. As a result, chemical processes are accelerated, and milk can curdle in a few minutes. If you continue to cook it, the density of milk will increase, and you can get cottage cheese. After squeezing off excess water, it will be grains of coagulated milk. However, this product will have its own specific taste, which is what people seek when preparing.

Milk - This is a drink that both adults and children love. It is good for health and quenches thirst. But to store milk is difficult enough - it can sour, change its structure and taste. Why does this happen and how to avoid it?

In order to understand the causes of souring milk, you need to understand what this drink is. Milk contains a lot of nutrients. Its important component is animal protein, it also contains dissolved fats and sugar. All of these components can serve as food for lactic acid bacteria. When bacteria begin to multiply, various chemical reactions occur in the milk, including protein folding. That is why the milk turns sour, that is, thickens, and is also divided into two parts - whey and a thicker curd. Does it cause bacteria to multiply? First of all, it is the storage temperature. Room temperature is enough to provoke a reaction. Therefore, milk should be stored in the refrigerator or in another cool place, if you want to keep it fresh. You can also reduce the risk of souring of milk using a special heat treatment. There are two types of such processing - pasteurization and sterilization. During pasteurization, the milk is heated to 60-80 degrees Celsius and is in such a temperature range from thirty minutes to an hour. After this process, the milk storage period is increased by several days due to the fact that a significant part of lactic acid bacteria dies. Another way to preserve milk is sterilization. In this case, the liquid is heated to the boiling point. Such milk can be stored in an airtight

Milk has long been a product from which animals, mammals, and people begin their diet. This is not only delicious, but also incredibly healthy drink, which is created by nature itself, it can be called a real elixir of growth. Most newborns of any kind - kittens, puppies, babies - the stomach is simply not adapted to the digestion of any other food, except milk, which has a huge amount of nutrients and useful substances that help a small, fragile body to grow and develop faster.

Today, milk is simply a huge variety of products, and milk production has grown into a fairly large industrial sector.

The Institute of Nutrition of the Russian Academy of Medical Sciences even developed approximate consumption rates of dairy products for a person per year, and in terms of milk (in kilograms), it turns out as much as 392 kg of milk! Of course, it is not pure milk; these are cheeses, and butter, and cottage cheese, and other dairy products. However, according to statistics, the average person in Russia consumes about 200 kilograms of milk per year, which is almost two times less than the recommended volumes.

Milk composition

Before we talk about what makes milk sour, we need to understand what it consists of, what is contained in this drink.

The content of various substances in milk depends largely on its origin. Cow's milk is the most popular type of milk of all; it is this milk in the livestock industry of the entire world agriculture is produced in the largest volumes. As for the composition of this type of milk, you can find an incredible amount of vitamins in it: this is almost the entire line of B vitamins, as well as vitamins E, D, PP, H, ascorbic acid, nucleic acids, lactose, monounsaturated fatty acids and amino acids. And of course, milk contains a large amount of calcium, which is simply necessary for human health, for the development of the body and the strength of bones. In cow's milk, this macro is contained in the most optimal form for easy absorption by the body. On average, this amount is 100-150 mg%.

Also in cow's milk contains magnesium, sulfur, chlorine, sodium, potassium, and in addition to them - a variety of citrates, chlorides and trace elements. For the most part, the amount of all vitamins and minerals, as well as the percentage of fat content of milk, depends largely on many factors:

cow ration;
her state of health;
cow age;
season;
other factors affecting cow lactation.

By the way, milk producers resort to some tricks to “fit” a huge amount of milk to a certain percentage of fat content, which is indicated on the package. Milk of different fat content is simply mixed together until, for example, 3.2% is obtained, which is indicated on the package. Also, the manufacturer usually writes that the percentage of milk fat may vary slightly.

From all of the above, it is clear that the benefits of milk are not in doubt, however, this product is not equally useful for all people. So, for people with lactose intolerance, milk is simply contraindicated (but lactose-free milk can be found on store shelves, although it will cost much more). People suffering from diseases of the intestinal tract, diseases of the pancreas or liver, too, should be wary of drinking milk, but it is better - and completely abandon it in favor of fermented milk products.

Touching the topic of fermented milk products, you first need to decide what is lactic acid bacteria and why they are needed, what function they perform. As already mentioned, milk is just a storehouse of various useful substances. Milk also contains a truly wonderful substance - lactose, in other words, it is milk sugar. It is lactose that is the substance that prevents milk from souring immediately, protecting it from such a fate. But if you leave fresh milk for a while, it will get a sour taste, which means it will turn sour. Why it happens? The fact is that lactic acid bacteria live on the surface of the mammary glands. It is there that the droplets of milk linger. It is only one drop under the influence of lactic acid bacteria to sour and get into the rest of the milk - the milk begins to turn sour. Of course, this will not be immediately noticeable, as one sour drop is diluted in a large amount of “good” milk. But lactic acid bacteria tend to multiply rapidly, and one has only to leave the milk unboiled, and it will sour completely.

To keep the milk from souring too quickly, simply boil it, and after the boiled milk has cooled, pour it into a clean dish and put it in the refrigerator. When boiling milk can "run away". To prevent this, grease the inside of the top 5 centimeters of the pan.

Lactic acid bacteria themselves are the kind of bacteria that ferment carbohydrates to form lactic acid. Of course, milk contains not only lactose, but also many other substances that other bacteria “feed on”, but it is lactic acid bacteria that are of use; the rest of the bacteria can bring mainly diseases.

Fermented milk products contain a huge amount of live bacteria and various other microorganisms. If before the milk starts to turn sour, it is processed in a special way, in this case, you can get fermented milk products. Different nations have their own kinds of such products, sometimes repetitive, but still bearing different names. The following is a characteristic of most types of fermented milk products of different nations.

Sour milk Prepared by souring pasteurized milk with ferment, which is prepared on pure cultures of lactic acid plants. If you do not sour milk in the same way, but the fattest part of it is cream, then you get sour cream.
Ryazhenka. This product resembles sour cream to its taste and consistency, but it still has a peculiar taste and differs from sour cream in its color — cream rather than white. Ryazhenka has a sweetish taste, than she resembles baked milk. Usually on the shelves you can find ryazhenka one fat - 6%. Yes, and preparing ryazhenka a little differently - for this you need to use lactic streptococcus. It is also worth noting that ryazhenka is much more caloric than yogurt of other species.
Katyk, matsun or matsoni. Yes, all this is one product that is called differently by different nations. Most know it called matsoni. This is a kind of sour milk that is made from camel, goat, sheep and cow milk.
Jugurt - squeezed sour milk, which apparently resembles sour cream. This product is produced mainly in the North Caucasus.
Ayran. Quite common and popular drink in the countries of Central Asia, which is prepared from different types of milk - both cow and goat or sheep.
Kurunga - also refers to fermented milk drinks that are drunk in Northeast Asia.
Shubat - also a sour-milk drink, which is loved in Asia. It is made from camel milk. The main difference from other sour-milk beverages is that shubat tends to foam strongly.
Cheese. It is made from sour milk, nutritious, high-calorie and healthy product.
Cottage cheese- one of the most famous dairy products. Prepared by souring the milk, after which the whey is removed.

How is the souring of milk?

As mentioned above, milk becomes sour under the influence of lactic acid bacteria. When they multiply in milk, various chemical reactions start to occur, one of which is protein folding. As a result, the milk thickens (sours) and is divided into two parts. The first part is liquid, this is whey, and the second is actually sour and thickened milk itself.

For such a multiplication of bacteria, which resulted in sour milk, an important factor is the temperature. For example, at room temperature, milk will be enough for a couple of days to completely sour, and in the refrigerator, on the contrary, fresh milk can be stored for up to 5-7 days.

In order for milk not to turn sour so quickly, you can conduct a special heat treatment. For example, during pasteurization, the milk should be heated to about 60-80 degrees Celsius. At this temperature, the milk should be about half an hour. As a result, the shelf life of milk is increased by several days, mainly due to the fact that lactic acid bacteria are killed.

There is also a more radical method of preserving the freshness of milk - sterilization. This method is used by most milk producers. This method is to bring the milk to the boiling point. If sterilized milk is stored in a sealed package, where neither air nor bacteria can get, the milk can be stored for up to several months. Of course, even this method has a minus, which for some consumers is quite substantial - the benefits of milk, the shelf life of which is extended in this way, is greatly reduced.

If lactic acid bacteria act during the natural souring of milk, then artificial acids can use various acids, such as vinegar. When vinegar gets into the milk, milk protein is released, and accordingly, the milk becomes sour. At the same time, artificial souring occurs much faster than natural, it takes not a few days, but just a few seconds.

If necessary, prepare a home-made kefir or yogurt, which means artificially sour milk, you can buy a special leaven in the pharmacy. A package of such a starter will cost about 60 rubles.

There is a very common belief among the people, who asserts that milk sours much faster during a thunderstorm. Of course, only if it is not in the fridge at this moment. According to belief, this is due to the fact that it is during a thunderstorm that a certain effect of magnetic pulses of long frequency can occur. There is another version, according to her, milk protein and calcium interact in a special way during a thunderstorm, which leads to this result.

If, however, you do not have time to process the milk, and it is sour, you can make very tasty pancakes from it. To do this, take:

200 ml of sour milk
a glass of flour
3 eggs
sugar and salt to taste
half a teaspoon of soda
a quarter cup of vegetable oil

Mix all the listed ingredients and whisk with a whisk or mixer at low speed to prevent the appearance of lumps. Lightly grease the pan and cook pancakes as usual.

How to choose milk in the store

It has long been no secret that a huge number of artificial substitutes for almost any product, including milk, have appeared. How is it possible, by eye in the store, to determine if real milk is on the shelf or not?

Pay attention to the composition. Good milk cannot boast of a long composition, usually only “pasteurized milk” or “normalized milk” can be written in this section. In packs on which you see a long list in the composition, in which you can find both dried milk and vegetable fats, margarine, oils and similar products, there is no way for real milk to be found.
Look at the expiration date. With real milk it usually takes 3-5 days, after which the milk starts to turn sour right in the package. Some manufacturers, despite the excellent composition indicated on the packaging, milk can be stored for up to six months, and most likely it is sterilized milk. As mentioned above, although this milk is real, it is no longer as useful as pasteurized milk.
Price. Nowadays, no matter how sad it is, good, real milk can in no way cost less than 60 rubles per liter. Of course, many retail chains have their own milk production and sell it like a real one, for only 20-30 rubles per liter. But, as practice shows, such milk does not resemble the properties, nor taste, the present, which costs 60 rubles and more. Most likely, if you want to cook porridge, when boiling it will roll up or flakes will appear, despite the fact that on the package, where the production time is, is the current number. Even when boiling, it may not change externally, but the taste will clearly resemble the taste of kefir. Of course, such milk can not be called real, tasty and healthy.

Why sometimes shop milk does not turn sour?

Sometimes you will notice that if the store milk with a long shelf life is left in the refrigerator and “forgotten” about it, it will not turn sour. Many immediately sin on the milk producer, saying that supposedly natural milk can not fail to sour in a few days, even in the refrigerator. In part, they are right, but do not forget that when lactic acid bacteria are sterilized, all the lactic acid bacteria disappear from it, and without them the milk simply cannot sour.

But, no matter how sterilized the milk is, in an open package after a few days in the refrigerator or outside it, the milk may start to deteriorate, or simply “go out” even a couple of months before the expiration date. Such a "behavior" of milk may even frighten the ordinary man in the street, but this is not the fault of the manufacturer.

The fact is that if milk-souring is mainly guilty of lactic acid bacteria, then milk begins to "rotten" due to the fact that bacteria that get into the milk from the air cause the destruction of milk protein, or, in other words, its rotting. This process is popularly called “rancid”.

Thus, even if the milk that you purchased in the store is not in a hurry to turn sour even in the open, this does not always mean that it is not of high quality or not real.

Hello, dear readers of the site "AS"! It is not uncommon that beginning herders face the problem of the preservation of milk, and it is not uncommon to ask why the milk has spoiled and what reasons have led to a reduction in the shelf life? The answer to these questions will be devoted to this article.
If, after 2-3 days, homemade milk begins to “drown” by itself, gives a sediment at the bottom, then first of all you need to check the sanitary condition of the room where the cow is located, and the condition of her udder. Sweep her udder daily before each milking and wipe with a clean rag or towel (). After each milking, the bucket in which you milk the cow, as well as the dishes into which you pour the milk, should be well and efficiently washed with warm water and soda.
Pay attention to this can be observed from the spoiled feed and its toxicity. Much depends on the diet and frequency of feeding, method and grazing on pasture, or animals.
It is also important to know the age of the cow, how much calving she had, whether she was sick (and what it was) before, whether she was vaccinated against infectious diseases, whether your veterinary service carries out diagnostic tests for the most common diseases. All this can be found in the district or district veterinarian. Having all the data, you can specifically advise how to treat the animal and carry out so that it does not get sick.
Milk, which stands in the refrigerator for several days, may be due to germs.
If fresh gives a precipitate, it can be assumed that it is clogged with pathogens that release toxins and enzymes, from which milk sugar breaks down to form lactic acid. This is also the reason for its collapse.
Catarrh in animals occurs during all periods of lactation, start-up and, most often, is limited to inflammation of one-quarter of the udder. This happens when irregularities and violation of the rules of manual milking, incomplete delivery, milking with a pinch, as a result of micro-flora from the external environment through the nipple canal, for unsanitary conditions of livestock. It can also be observed in case of supercooling of the udder, damage to the tips of the nipples, the introduction of a non-sterile catheter and drugs, and the introduction of microbes and toxins with blood and lymph during inflammatory processes in other organs and tissues.
When a sick animal is detected in a cow, it is necessary to gently milk the fist every 2-4 hours with a break for the night. Milk from affected udder should be dispensed into separate dishes and destroyed after boiling. From unaffected - after boiling for fattening. From the diet of the animal should be excluded acidic feed, reduce by half juicy, 3-4 times - concentrated with replacing them with hay. The amount of water is not limited.
It is forbidden to feed not benign, moldy, frozen. Do not make a sharp transition from one type of food to another. Adhere to hygiene, periodically disinfect the room where there is cattle, clean it, clean the manure in a timely manner. A clean litter should always be in the stable.
And do not self-medicate. At the slightest signs of disease cattle urgently call a veterinarian.