How to examine milk in a package for schoolchildren. Project "research of the quality of milk at home"

"Milk is an amazing food,

prepared by nature"

I.P. Pavlov

Milk is one of the most important food products. It contains all the substances without which the human body cannot exist normally, namely: proteins, fats, carbohydrates, inorganic salts, vitamins. Milk is a complete food. Easy digestibility is one of the most important properties of milk as a food product. Moreover, milk stimulates the absorption of nutrients from other foods, the consumption of which adds variety to the diet, improves the taste of other foods. Milk has therapeutic and prophylactic properties. The main significance of milk in nature is to provide nutrition to the born young organism.

Quantity, quality, range of food products consumed, timeliness and regularity of food intake have a decisive influence on human life in all its manifestations. That's why it's important to consume quality foods.

Relevance The chosen research topic, first of all, is connected with the wide consumption of this product and its wide range on the shelves of the city. More than 500 million liters of milk are drunk every year in the world. Milk is given to children at school. In addition, there are various programs to stimulate the consumption of milk and dairy products, as millions of people suffer from a lack of calcium, for example, "School Milk", "Three Dairy Products a Day", "All-Russian Program to Stimulate the Consumption of Milk and Dairy Products".

In this work, I decided to check whether the milk that we drink and buy in stores is of high quality and natural. People's health is the main wealth of any state. Consumption of organic food is a powerful factor in maintaining health and active longevity.

Topic: Determining the quality of milk at home

Target: to determine whether the milk we drink is of high quality and natural

Object of study: milk

Subject of study: the process of determining the quality of milk

Hypothesis: I assumed that the composition of milk may contain impurities that are not declared by the manufacturer and not provided for by the standard. I assume that the highest quality milk of local producers.

Tasks:

To study theoretical material on the composition and types of milk.

To study methods for determining the quality of milk.

Conduct an experiment to determine the quality of milk.

Compare the quality of the researched products.

Research methods:

1. Theoretical: analysis, synthesis, generalization.

2. Empirical: experiment (experience).

3. Generalization.

The practical significance of the work lies in the fact that I conducted experiments to determine the quality of milk at home to determine the possibility of its use or unacceptability in nutrition.

Research period: from January 02, 2017 to January 31, 2017.

CHAPTER 1. STUDYING THE THEORY OF WHOLE MILK

1.1 History of human milk consumption

Milk, like bread, mankind began to use for food more than five thousand years ago. Milk is the only food product in the first months of human life. It is of exceptional importance in the nutrition of an adult. For old, weakened and sick people, milk is an indispensable food.

It has been established that this product contains over a hundred of the most valuable components. It includes all the substances necessary for the life of the body: proteins, fats, carbohydrates, mineral salts, vitamins. These components of milk are well balanced, making them easily and completely digestible.

Milk is one of the most important human food products. Milk and a great variety of dairy products add variety to the diet, improve the taste, increase the nutritional value of our food, and are of great dietary and medicinal value. “If you drink one liter of milk every day for 1200 months, then you will provide yourself with a hundred years of life!” - so jokingly, said the Swedish scientist Nile Gustavson. These words of the Swedish scientist are confirmed by experimental data, because milk contains all the substances necessary for the body.

Since ancient times, milk has also been used as a remedy for many diseases: in the treatment of the heart, kidneys and other organs.

Dairy products (yogurt, koumiss, kefir, etc.) are an excellent remedy for people suffering from gastrointestinal diseases, tuberculosis; they give a good effect in case of poisoning.

The ancient Egyptians used donkey milk for medicinal purposes. Scientists of Ancient Rome and Greece - recommended milk for the treatment of consumption. Hippocrates attributed various healing properties to different types of milk, for example, goat and mare - the ability to cure consumption, cow - to cure gout and anemia, donkey - many diseases.

In our country, whole cow's milk is most often consumed, and dairy products are prepared from it.

Milk is the most valuable product in the universe, since it contributes to both the physical and spiritual development of a person. Milk effectively treats mental disorders - irritability, fussiness, overstrain, pacifies and relieves insomnia. Our grandmothers knew that the best remedy for insomnia in a child is milk. The child was given a glass of warm milk with honey at night, he slept soundly and became calm. If a person drinks milk at night, then he becomes more reasonable, begins to better understand the world around him, acquires the correct vision of good and evil, the Eastern sages believed. They also recommended drinking it either late in the evening or early in the morning, sweetened with honey or sugar, adding spices: fennel, cardamom, turmeric, cinnamon, saffron and licorice. Moreover, milk, which some attribute the ability to increase body weight, in fact, on the contrary, is able to protect the body from gaining excess weight.

1.2. What is the composition of whole milk?

One of the main components of milk is protein, necessary for strengthening muscles and restoring them after hard work. The other is fat, with which energy enters the body. This fat is called milk fat.

Milk also contains sugar, a hydrocarbon that is another source of energy. It's called lactose. It is not as sweet in taste as sugar, but easier to digest by the human body.

Milk supplies the body with important mineral salts. They are required by a person to strengthen bones and produce fresh blood. Especially a lot of phosphorus and calcium are contained in milk, and the latter is more in it than in any other food. In addition, iron, copper, manganese, sodium, potassium, chlorine, iodine, magnesium, cobalt and zinc are present in milk. It contains a high content of vitamins B2, A, B1, C, D. Of course, milk contains a lot of water. However, it is noteworthy that, despite the fact that milk is a liquid product, it contains 110 grams of solid matter for every liter.

1.3. Methods for determining the quality of milk

It is necessary to know some methods for determining the quality of milk.

I. Litmus. You can check the presence of soda or acid in milk using litmus paper. Coloring litmus paper blue will indicate the presence of soda or other alkalis in milk, red litmus will react to an acidic environment resulting from the addition of acid-based bleaches to milk, for example, acetylsalicylic acid. If the color of the litmus strip of paper has not changed, then soda, boric and salicylic acid were not added to the milk.

II. Iodine. The presence of starch, which is added to milk to give it thickness, can be easily and quickly determined using ordinary iodine. A few drops of an alcoholic solution of iodine should be dropped into a small amount of milk. If the milk turns blue, then starch is mixed into it, and a yellowish-orange color indicates its absence in milk.

III.Alcohol. Very often this product is diluted with water. To find out, you need to pour milk into a saucer and add twice as much alcohol. If the product is of high quality, then the liquid will almost instantly (within 5-7 seconds) turn into flakes. Under the influence of alcohol, the milk protein casein tends to coagulate. The more water added to the product and the greater its concentration, the longer this protein will fold. By the time of formation of casein flakes, one can judge the degree of dilution of milk with water. If it took about a minute for the formation of flakes, then 20% of the volume of milk was replaced by water, a time interval of 25-30 minutes will indicate the content of 40% water in milk, and if casein flakes began to appear only after 40 minutes, such milk is diluted with water by half.

IV.souring. At home, it is impossible to check whether the purchased product is natural or made from milk powder. But checking milk for the presence of antibiotics and various substances that slow down the growth of bacteria is very simple. It is necessary to pour milk into a container, cover it tightly and put it where it is warmer. A pure product will begin to turn sour in a day. If there is something extra in the milk, then it will remain unchanged. This means that an agent or antibiotic has been added to the product, which slows down the growth of lactic acid bacteria. In warmth, the increased growth and development of such bacteria begins. Milk, which is made from milk powder, will not sour either. After a certain time, it will smell unpleasant.

V.Vinegar. It happens that chalk is added to milk. This can be tested by adding vinegar to the milk. When chalk interacts with vinegar, foam will appear.

Chapter 1 Conclusion

In the process of studying the theoretical part, I became aware that people began to consume milk as early as the 8th-9th centuries BC. I learned what substances milk consists of, and what types of milk there are. In addition, I managed to find out in what ways you can check the quality of milk at home, which I decided to do.

CHAPTER 2. CHECKING THE QUALITY OF MILK IN DIFFERENT WAYS

2.1. Milk quality research

For the experiment, I took milk from well-known manufacturers in the Udmurt Republic:

For experiments, we used six types of milk.

"Way of Ilyich" village Yakshur, Zavyalovsky district

"Native Lyubava" village of Babino, Zavyalovsky district

"Barbara-beauty", Glazov

"House in the village", Moscow

"Green Village" Kez village

Izhmoloko, Izhevsk

EXPERIMENT No. 1. 2 ml of milk samples No. 1-6 were poured into a cup. Added 4 ml (i.e. twice as much) of alcohol. Under the influence of alcohol, the milk protein casein tends to coagulate. The more water added to the product, the longer it will take for this protein to coagulate - the longer it takes for flakes to appear [Appendix].

EXPERIENCE No. 2. We poured 5 ml of milk into small cups. The samples were allowed to settle for a day at room temperature. The pure product should turn sour, forming a layer of cream on top. If there is no cream, the milk has been defatted. This does not mean that the milk is not of good quality. It just has almost no fat. If the milk has not turned sour, then there is something extra in it - perhaps an antibiotic that slows down the growth of lactic acid bacteria or it is made from milk powder. If the milk turns sour, but becomes a non-uniform consistency, then it is diluted with water [Appendix].

EXPERIENCE No. 3. We add acetic acid, there is no reaction, which means that soda or chalk are absent. Milk curdled in all samples.

2.3.Results of the study to determine the quality of milk

Based on the research, a table was made.

RESEARCH WORK ON HEALTHY NUTRITION

"Determining the quality of milk at home"

INTRODUCTION

Milk is one of the most important human food products. In its composition, the most necessary substances for human health were found. Fats and carbohydrates are sources of energy. Proteins contain all the necessary amino acids, including those that are not synthesized by the human body.

Minerals contained in milk contribute to the formation and absorption of vitamins, are part of human tissues. Milk contains all known vitamins.

The exclusion of milk from the diet can lead to a decrease in the necessary substances in the body.

Currently, a large number of dairy products have appeared on store shelves.

In Novosibirsk, it is not often possible to find natural fresh milk for sale from private producers or peasant farms. Mostly Novosibirsk people use milk from the store in their diet. This project aims to find out the quality of milk from the store and show how you can investigate the quality of milk

object our research becomesmilk , which our parents, and not rarely, you and I buy at a regular grocery store.

Subject research is the process of determining quality milk.

Objective of the project:

Learn to identify a quality product (milk) at home.

Transfer of acquired knowledge, skills and abilities to the public by filming and showing a video about “experimental testing of milk quality at home”.

Show the advantages and disadvantages of a product of a certain sample, to determine the possibility of its use or unacceptability in nutrition.

Tasks project:

• Conduct a theoretical analysis of the literature on this issue;
• Conduct the necessary experiments to determine a quality product;
• Draw conclusions and rationale for the work;
• Make a video on the experimental testing of milk at home;
• Showing a video at the school NPC (scientific and practical conference);
• Placement of the video on the Internet and social networks.

Methods project:

Studying information on the topic;

Experiment;

Observation;

Comparison of facts;

Analysis of results;

Processing of results;

Formulation of conclusions;

Shooting video;

Processing and editing of video files;

Video broadcast.

Project product: determination of the quality of store-bought milk, a video about the methods of experimental study of the quality of milk.

Practical significance project lies in the fact that I conducted experiments to determine the quality of milk and shot a video for parents and students with recommendations for determining the quality of milk at home to determine the possibility of its use or unacceptability in nutrition.

THEORETICAL JUSTIFICATION OF THE PROJECT

Determining the quality of products by smell, taste and color cannot provide complete and reliable information, and sometimes it can be dangerous to health. You can check the quality of milk at home without resorting to the “testing” method. To do this, you do not need to conduct complex laboratory studies, it is enough that you always have at hand.In addition to diluting milk with water, starch, gypsum, chalk, soap, soda, potash, borax, lime, and even chemical products such as boric and salicylic acids are often mixed with it. Some of these substances are mixed in to make the skimmed milk look whole, not skimmed; others - to protect against rapid sourness, in general spoilage, to which milk is subjected to the sooner, the more foreign organic impurities it contains.
In fact, the admixture of these impurities is not able to protect milk from sourness. Moreover, even the most "innocent" of these impurities, for example, bicarbonate of soda, is in fact very harmful, and precisely because, as revealed by direct experiments, the admixture of, by the way, bicarbonate of soda serves as the best condition for the increased reproduction of various pathogenic microbes in milk. - cholera bacilli, tuberculosis and others. ("Encyclopedia of Technologies and Methods" Patlakh V. V. 1993-2007)

There are several methods for determining the quality of milk. Some of them require special laboratory conditions with the necessary equipment and reagents. But some can be done at home. Milk should be checked immediately after opening the package.

Compound

The first thing to check when buying milk is the composition of the product. Currently, in Russia there is a law according to which if powdered milk is added to milk, then the label must say that this is a milk drink and, accordingly, this must also be noted in the composition.

When buying a bag labeled "milk", we expect that we are paying for milk, and not for a milk drink that is made from dry mixes. However, sometimes we are deceived with impunity.

The situation with milk in our country, to put it mildly, is confusing. Despite the existence of GOST, technical regulations and other documents, a method has not yet been developed that would allow determining whether there is powdered milk in drinking milk.

Abroad, if the milk is reconstituted from dry, they write so on the packaging - “reconstituted milk,” explainsLarisa Abdullaeva, executive secretary of the Dairy Union of Russia.- We have come up with the term "milk drink", but no one indicates it on the packaging

(http://www.aif.ru/gazeta/number/379)

If on the milk you bought in the COMPOSITION section it is written that it is:whole milk means good quality milk.

If it is written: reconstituted or normalized, therefore, the milk is made from milk powder, or with its addition.

The amount of protein in milk decreases in winter and cannot exceed 3%. And the packages often indicate much larger numbers. There is no live milk with such indicators in Russia: animal selection has not been carried out for a long time, there are complaints about the quality of feed. If natural milk really contains high protein, the manufacturer will direct such valuable raw materials to cheese or cottage cheese, and will not make ultra-pasteurized milk from it. (from an interviewElena Petrova, OZPP expert).

If the packaging indicates a high protein content, then the milk has most likely been reconstituted.

Determination of impurities

It is quite easy to determine the "purity" of the product, for this you need to strain a certain amount of milk through a dense white cloth, or a cotton pad.

If you notice villi, any grains of a substance, it means that sanitary standards were not observed in the production of milk, and such milk can be dangerous.

"Dirty glass"

During this check, we check the density of milk (fat content), therefore, after stirring the milk in a glass, carefully look at its walls, the “dirtier” your glass is, the better the quality of the milk. It should be noted that the layer of milk on the walls must be uniform.

Litmus.

Sometimes manufacturers, whose product stays on store shelves for a long time, add soda to milk, which slows down the souring process. You can determine the content of soda in milk using litmus papers.

Most likely, not every home has a paper acid-base indicator, but if you set out to check food at home before eating, it is not difficult to get one at a pharmacy.

With the help of litmus papers, you can check the acidic environment of products, in our case, milk.

Pour milk samples into different containers;

It is necessary to moisten one strip of indicator paper in the milk sample;

We wait 1-2 minutes and carefully examine the strip;

We draw conclusions on the color of litmus paper:

With complex adulteration of milk, one should be most careful about chemical impurities, for the detection of which this test can be of no small benefit. Unskimmed, whole milk has a very characteristic double reaction, which is that it is at the same time somewhat alkaline and slightly sour; as a result, a blue litmus paper soaked in whole milk turns slightly red, and a red one turns slightly blue.
On the contrary, if there is an excess of alkali in milk, for example, from the admixture of soda to it, then the red litmus paper turns very blue, while the blue one completely retains its color.
Similarly, if an acid, such as boric or salicylic acid, is mixed into milk, then blue litmus paper, moistened with such milk, turns bright red; red does not change its color at all.

IODINE

The presence of starch, which is added to milk to make it thicker, can be easily and quickly determined using ordinary iodine from a home medicine cabinet.

A few drops of an alcoholic solution of iodine should be dropped into a small amount of milk.

Staining in blue, will show the presence of starch in the product;

A yellow-orange color indicates the absence of starch in the milk.

Alcohol

With the help of alcohol, you can accurately determine whether milk is diluted with water. For this you need:

- to one part of milk, add two parts of alcohol;

- the resulting mixture is actively shaken for 1 minute;

- after shaking, it is necessary to pour the mixture of milk and alcohol into a plate or saucer, carefully observing the state of the mixture and fixing the time after which white flakes appear in it;

- rapid, within 5-6 seconds, the formation of casein flakes released from whey will indicate the high quality of milk;

- if the flakes appear late, then the milk is diluted with water.

By the time of formation of casein flakes, one can judge the degree of dilution of milk with water. If it took about a minute for the formation of flakes, then 20% of the volume was replaced by water, an interval of 25-30 minutes will indicate the content of 40% water in milk, and if casein flakes began to appear onlyafter 40 minutes, such milk is diluted with water by half.

7. Warm water.

By pouring a small amount of milk into a glass of warm water in a thin stream, it is possible to determine with a high degree of probability whether it has been diluted with water.

High-quality milk in the form of a white clot will gather in the upper part of the glass, glass, diluted milk will behave differently - it will almost completely dissolve in water, coloring it in an off-white color.

If milk is poured in quickly, good quality milk will first sink to the bottom of the glass, and then slowly dissolve when diluted with water immediately turns the water off-white.

8. Filter paper

Another way to determine the degree of dilution of milk with water . If you do not have filter paper at home, then you can use a paper napkin or toilet paper. The main requirement is that they must be of a sufficiently high quality.

Having dipped a thin stick, a toothpick or a match into the milk, you need to put a small drop of milk on the surface of the filter paper. It is very important that it be as small as possible and at the same time be as convex as possible, resembling a hemisphere. For the reliability of the result of such drops, it is better to put a few.

Since the filter paper has a finely porous surface structure, it will begin to absorb the water contained in the milk. Therefore, on the surface of the paper, a wet ring will appear around the drop, the width of the ring will be the greater, the greater the amount of water in the milk.

A drop of undiluted milk will create around itself a wet ring no more than 1 mm thick, which will dry at room temperature in about 2 hours.

The water spot around a drop of milk diluted with water by 10% will be noticeably wider and will dry faster - in about an hour. In half an hour, the ring around a drop of milk diluted by 30% will dry, and it will take only 10-15 minutes to dry the ring left by a drop of milk diluted in half.

Checking for antibiotics

The milk that we buy in the store undergoes a special treatment. It is purified from various impurities. In order to destroy microorganisms, pasteurization of milk, ultra-pasteurization and sterilization are carried out.

Pasteurization - heating milk from 63 degrees to a temperature close to the boiling point. Pasteurization destroys vegetative forms of microbes, and sterilization destroys spores at the same time. When boiling, the entire microflora of milk is destroyed, with the exception of spores that are resistant to the boiling point.

Sterilization milk aims to destroy all microorganisms. In this case, milk is first heated to 75 degrees, then heated under high pressure in a fraction of a second. In another method, the milk is sprayed and, at the time of spraying, heated to the temperature of superheated steam. Bacteria are instantly killed. The milk is then cooled and packaged.

Sterilized milk obtained in one way or another does not change its taste. In hermetically sealed containers, sterilized milk can be stored for a long time at room temperature.

UHT It is used to destroy microflora and at the same time preserve the natural properties of milk. Ultra-pasteurization is carried out at a temperature of 105 to 150 degrees with exposure from a few seconds to fractions of a second. Then the milk is quickly cooled in 4-6 seconds.

Unfortunately, at home it is impossible to check whether the purchased product is natural or made from milk powder. But checking milk for the presence of antibiotics and various substances that slow down the growth of bacteria is very simple. Natural and without additives, milk left at room temperature should turn sour in a day.Pasteurized milk turns sour for 2-3 days, ultra-pasteurized and sterilized milk may not turn sour for quite a long time.

PRACTICAL PART

The practical part includes a description of the work on the study of milk quality, in the framework of the above studies.

RESEARCH WORK

ON

HEALTHY FOOD

"Determining the quality of milk at home"

INTRODUCTION

Milk is one of the most important human food products. It contains the most essential substances for human health.

Fats and carbohydrates are sources of energy. Proteins contain all the necessary amino acids, including those that are not synthesized by the human body.

Minerals contained in milk contribute to the formation and absorption of vitamins, are part of human tissues. Milk contains all known vitamins.

The exclusion of milk from the diet can lead to a decrease in the necessary substances in the body.

Currently, a large number of dairy products have appeared on store shelves.

In Novosibirsk, it is not often possible to find natural fresh milk for sale from private producers or peasant farms. Mostly Novosibirsk people use milk from the store in their diet. This project aims to find out the quality of milk from the store and show how you can investigate the quality of milk

objectour research becomes milk, which our parents, and not rarely, you and I buy at a regular grocery store.

Subject research is the process of determining quality milk.

Objective of the project:

Learn to identify a quality product (milk) at home.

Transfer of acquired knowledge, skills and abilities to the public by filming and showing a video about “experimental testing of milk quality at home”.

Show the advantages and disadvantages of a product of a certain sample, to determine the possibility of its use or unacceptability in nutrition.

Tasksproject:

Conduct a theoretical analysis of the literature on this issue;

Conduct the necessary experiments to determine a quality product;

Make conclusions and rationale for the work.

Make a video on the experimental testing of milk at home;

Showing a video at the school NPC (scientific and practical conference);

Placement of the video on the Internet and social networks.

Methodsproject:

Studying information on the topic;

Experiment;

Observation;

Comparison of facts;

Analysis of results;

Processing of results;

Formulation of conclusions;

Shooting video;

Processing and editing of video files;

Video broadcast.

Project product: determination of the quality of store-bought milk, a video about the methods of experimental study of the quality of milk.

Practical significance project lies in the fact that I conducted experiments to determine the quality of milk and shot a video for parents and students with recommendations for determining the quality of milk at home to determine the possibility of its use or unacceptability in nutrition.

THEORETICAL JUSTIFICATION OF THE PROJECT

Determining the quality of products by smell, taste and color cannot provide complete and reliable information, and sometimes it can be dangerous to health. You can check the quality of milk at home without resorting to the “testing” method. To do this, you do not need to conduct complex laboratory studies, it is enough that you always have at hand. In addition to diluting milk with water, starch, gypsum, chalk, soap, soda, potash, borax, lime, and even chemical products such as boric and salicylic acids are often mixed with it. Some of these substances are mixed in to make the skimmed milk look whole, not skimmed; others - to protect against rapid sourness, in general spoilage, to which milk is subjected to the sooner, the more foreign organic impurities it contains.
In fact, the admixture of these impurities is not able to protect milk from sourness. Moreover, even the most "innocent" of these impurities, for example, bicarbonate of soda, is in fact very harmful, and precisely because, as revealed by direct experiments, the admixture of, by the way, bicarbonate of soda serves as the best condition for the increased reproduction of various pathogenic microbes in milk. - cholera bacilli, tuberculosis and others. (© "Encyclopedia of Technologies and Methods" Patlakh V. V. 1993-2007)

There are several methods for determining the quality of milk. Some of them require special laboratory conditions with the necessary equipment and reagents. But some can be done at home. Milk should be checked immediately after opening the package.

Compound

The first thing to check when buying milk is the composition of the product. Currently, in Russia there is a law according to which if powdered milk is added to milk, then the label must say that this is a milk drink and, accordingly, this must also be noted in the composition.

When buying a bag labeled "milk", we expect that we are paying for milk, and not for a milk drink that is made from dry mixes. However, sometimes we are deceived with impunity.

The situation with milk in our country, to put it mildly, is confusing. Despite the existence of GOST, technical regulations and other documents, a method has not yet been developed that would allow determining whether there is powdered milk in drinking milk.

Abroad, if the milk is reconstituted from dry, they write so on the packaging - “reconstituted milk,” explainsLarisa Abdullaeva, executive secretary of the Dairy Union of Russia. - We have come up with the term "milk drink", but no one indicates it on the packaging

(http://www.aif.ru/gazeta/number/379)

If on the milk you bought in the COMPOSITION section it is written that it is: whole milk means good quality milk.

If it is written: reconstituted or normalized, therefore, the milk is made from milk powder, or with its addition.

The amount of protein in milk decreases in winter and cannot exceed 3%. And the packages often indicate much larger numbers. There is no live milk with such indicators in Russia: animal selection has not been carried out for a long time, there are complaints about the quality of feed. If natural milk really contains high protein, the manufacturer will direct such valuable raw materials to cheese or cottage cheese, and will not make ultra-pasteurized milk from it. (from an interviewElena Petrova, OZPP expert).

If the packaging indicates a high protein content, then the milk has most likely been reconstituted.

Determination of impurities

It is quite easy to determine the "purity" of the product, for this you need to strain a certain amount of milk through a dense white cloth, or a cotton pad.

If you notice villi, any grains of a substance, it means that sanitary standards were not observed in the production of milk, and such milk can be dangerous.

"Dirty glass"

During this check, we check the density of milk (fat content), therefore, after stirring the milk in a glass, carefully look at its walls, the “dirtier” your glass is, the better the quality of the milk. It should be noted that the layer of milk on the walls must be uniform.

Litmus.

Sometimes manufacturers, whose product stays on store shelves for a long time, add soda to milk, which slows down the souring process. You can determine the content of soda in milk using litmus papers.

Most likely , not every home has a paper acid-base indicator, but if you set out to check food at home before eating, it is not difficult to get one at a pharmacy.

With the help of litmus papers, you can check the acidic environment of products, in our case, milk.

Pour milk samples into different containers;

It is necessary to moisten one strip of indicator paper in the milk sample;

We wait 1-2 minutes and carefully examine the strip;

We draw conclusions on the color of litmus paper:

With complex adulteration of milk, one should be most careful about chemical impurities, for the detection of which this test can be of no small benefit. Unskimmed, whole milk has a very characteristic double reaction, which is that it is at the same time somewhat alkaline and slightly sour; as a result, a blue litmus paper soaked in whole milk turns slightly red, and a red one turns slightly blue.
On the contrary, if there is an excess of alkali in milk, for example, from the admixture of soda to it, then the red litmus paper turns very blue, while the blue one completely retains its color.
Similarly, if an acid, such as boric or salicylic acid, is mixed into milk, then blue litmus paper, moistened with such milk, turns bright red; red does not change its color at all.

IODINE

The presence of starch, which is added to milk to make it thicker, can be easily and quickly determined using ordinary iodine from a home medicine cabinet.

A few drops of an alcoholic solution of iodine should be dropped into a small amount of milk.

Staining in blue, will show the presence of starch in the product;

A yellow-orange color indicates the absence of starch in the milk.

Alcohol

With the help of alcohol, you can accurately determine whether milk is diluted with water. For this you need:

- to one part of milk, add two parts of alcohol;

- the resulting mixture is actively shaken for 1 minute;

- after shaking, it is necessary to pour the mixture of milk and alcohol into a plate or saucer, carefully observing the state of the mixture and fixing the time after which white flakes appear in it;

- rapid, within 5-6 seconds, the formation of casein flakes released from whey will indicate the high quality of milk;

- if the flakes appear late, then the milk is diluted with water.

By the time of formation of casein flakes, one can judge the degree of dilution of milk with water. If it took about a minute for the formation of flakes, then 20% of the volume was replaced by water, an interval of 25-30 minutes will indicate the content of 40% water in milk, and if casein flakes began to appear only after 40 minutes, such milk is diluted with water by half.

7. Warm water.

By pouring a small amount of milk into a glass of warm water in a thin stream, it is possible to determine with a high degree of probability whether it has been diluted with water.

High-quality milk in the form of a white clot will collect in the upper part of the glass, glass, diluted milk will behave differently - it will almost completely dissolve in water, coloring it in an off-white color.

If milk is poured in quickly, good quality milk will first sink to the bottom of the glass, and then slowly dissolve when diluted with water immediately turns the water off-white.

8. Filter paper

Another way to determine the degree of dilution of milk with water. If you do not have filter paper at home, then you can use a paper napkin or toilet paper. The main requirement is that they must be of a sufficiently high quality.

Having dipped a thin stick, a toothpick or a match into the milk, you need to put a small drop of milk on the surface of the filter paper. It is very important that it be as small as possible and at the same time be as convex as possible, resembling a hemisphere. For the reliability of the result of such drops, it is better to put a few.

Since the filter paper has a finely porous surface structure, it will begin to absorb the water contained in the milk. Therefore, on the surface of the paper, a wet ring will appear around the drop, the width of the ring will be the greater, the greater the amount of water in the milk.

A drop of undiluted milk will create around itself a wet ring no more than 1 mm thick, which will dry at room temperature in about 2 hours.

The water spot around a drop of milk diluted with water by 10% will be noticeably wider and will dry faster - in about an hour. In half an hour, the ring around a drop of milk diluted by 30% will dry, and it will take only 10-15 minutes to dry the ring left by a drop of milk diluted in half.

Checking for antibiotics

The milk that we buy in the store undergoes a special treatment. It is purified from various impurities. In order to destroy microorganisms, pasteurization of milk, ultra-pasteurization and sterilization are carried out.

Pasteurization- heating milk from 63 degrees to a temperature close to the boiling point. Pasteurization destroys vegetative forms of microbes, and sterilization destroys spores at the same time. When boiling, the entire microflora of milk is destroyed, with the exception of spores that are resistant to the boiling point.

Sterilization milk aims to destroy all microorganisms. In this case, milk is first heated to 75 degrees, then heated under high pressure in a fraction of a second. In another method, the milk is sprayed and, at the time of spraying, heated to the temperature of superheated steam. Bacteria are instantly killed. The milk is then cooled and packaged.

Sterilized milk obtained in one way or another does not change its taste. In hermetically sealed containers, sterilized milk can be stored for a long time at room temperature.

UHT It is used to destroy microflora and at the same time preserve the natural properties of milk. Ultra-pasteurization is carried out at a temperature of 105 to 150 degrees with exposure from a few seconds to fractions of a second. Then the milk is quickly cooled in 4-6 seconds.

Unfortunately, at home it is impossible to check whether the purchased product is natural or made from milk powder. But checking milk for the presence of antibiotics and various substances that slow down the growth of bacteria is very simple. Natural and without additives, milk left at room temperature should turn sour in a day. Pasteurized milk turns sour for 2-3 days, ultra-pasteurized and sterilized milk may not turn sour for quite a long time.

PRACTICAL PART

The practical part includes a description of the work on the study of milk quality, in the framework of the above studies.

The naturalness and freshness of milk is not only a problem for those who like to drink it fresh. A high-quality drink is a necessary condition for self-preparation of healthy fermented milk products: yogurt, curdled milk, cottage cheese, and so on. There are several effective ways to check the quality of milk at home.

Quality requirements: what should be a natural product?

GOST establishes the following conditions for the naturalness of milk:

• after milking;
• without extracts;
• without additives of dairy and non-dairy components;
• purified from mechanical impurities;
• chilled to 4°C.

Milk that meets all of the above parameters is called whole milk. Today, it is easiest to find at a farmers' market or buy directly from dairy cow or goat owners. Nevertheless, you should not think that only unnatural milk is sold in the store. You can find a quality product, but manufacturers, before putting the product into retail chains, pre-normalize it - lead to a single fat content standard by adding whole milk or cream to skimmed milk.

Determination of milk freshness

The shelf life of homemade and factory milk is different. A sour product is easy to recognize by its sharp sour smell. If it is not there, but there are suspicions of stale milk, you can confirm or refute the guesses with very simple steps.

Way for the brave

For those who aren't too picky about off-flavours, just try some milk. A sour taste indicates that it is stale.

boiling liquid

A small amount of milk can be poured into a saucepan and brought to a boil. Did the liquid curdle when it boiled? So the product is sour.

Identification of a sour drink with soda

Sour milk releases acid, and soda reacts to it. Pour half a teaspoon of sodium bicarbonate into 100 ml of the drink. Did the liquid froth and bubble? This product is not worth drinking.

Checking the naturalness of the composition

Non-dairy additives in milk are an unfortunate reality in today's dairy market. The pursuit of profit does not imply concern for the health of the consumer. This state of affairs literally forces the buyer to acquire minimal skills to independently determine the quality of products.

Modern additives are very diverse. Basically, their purpose is to preserve the freshness of the product for as long as possible, increase the volume, and add more fat. At home, it is easy to identify a gross fake, although some methods will require chemical reagents, which can be purchased at specialized stores and pharmacies.

Is the milk diluted?

The most common trick for increasing the volume of milk is diluting it with water. Simple manipulations will help to understand whether the product is diluted or not.

Use vodka or alcohol

You will need:

• alcohol or high-quality vodka;
• saucer.

Mix two parts of alcohol (vodka) with one part of milk. Shake well for 1 minute. Then quickly pour the "cocktail" onto the saucer. Wait a little - 5-6 seconds. If flakes form in the liquid during this period, then there is no water in the milk. A slower separation of the alcohol-milk mixture indicates the addition of water to the product by the manufacturer. Depending on the time, the approximate percentage of dilution is established:

• 1 minute - 20% water;
• 15–35 minutes - 40% water;
• 40 and more - 50% water;

The method is not suitable for testing goat milk, since it lacks casein - it is this protein that coagulates during the experiment under the influence of alcohol.

We use the "milk drop" method

You will need:

• paper napkin;
• match.

A match is lowered into well-mixed milk, the resulting drop is taken out and deposited on a napkin. The drying speed of a wet circle formed around a milk drop will tell you whether the liquid is diluted or not:

• whole milk - the diameter of the spot almost corresponds to a drop and dries out for more than 2 hours;
• 10% water - wet circle dries in 1 hour;
• 30% water - the wet border is wide and dries within 30 minutes;
• 50% water - the drop does not hold a convex shape, dries quickly (no longer than 20 minutes).

Testing with warm water

You will need:

• cup;
• warm water.

Pour milk into a glass of warm water in a thin stream. The undiluted product will not immediately mix with the liquid, but will rise to the top. Diluted milk will dissolve easily in warm water.

Is there starch in the liquid?

Unscrupulous milkmen condense skim milk with starch, thereby passing it off as fatter.

You will need:

• tablespoon.

Add a couple of drops of iodine to a tablespoon of milk. The starch present in the product will cause a reaction - the liquid will turn blue. If the color of the milk becomes yellowish, there is no starch in it.

Did the manufacturer add chalk, plaster or soda?

With soda, some businessmen are reinsured from the rapid souring of a healthy drink.

You will need:

Acid method. Half fill the glass with milk, then add half a teaspoon of vinegar or lemon juice. Hissing and bubbles indicate the presence of chalk, gypsum or soda.

Dye method. Pour a small amount of milk into the test tube, then carefully, without shaking the container with the liquid, add 7–8 drops of the indicator along the wall. If soda is present in the composition of the dairy product, the liquid will turn dark green.

Are there any antibiotics in the product?

Antibacterial drugs prevent the growth of pathogenic microorganisms, which increases the shelf life of dairy products. You can tell if an antibiotic has been added to milk by fermenting it. A teaspoon of sour cream or kefir is added to a glass with a drink and left at room temperature for a day. By the end of the mentioned period, the natural product will turn into curdled milk. If the milk does not react to the leaven, the development of lactic acid bacteria is inhibited by antibiotics.

Is there aspirin or boric acid in the drink?

Aspirin in milk is a scam to prolong the product's freshness, which poses a serious threat to the health of people with aspirin intolerance. Additives in the form of salicylic, acetylsalicylic and boric acid are easily detected by litmus paper. The color of the indicator after dipping into milk with the listed components changes to red.

How to detect palm oil?

Palm oil improves the taste of the reconstituted drink, and also increases the shelf life. But no matter how many methods of detecting vegetable fat in milk with improvised means walk on the Internet, it is possible to identify this component only in laboratory conditions using gas chromatography. Therefore, it is more effective to protect yourself from an unnatural product by carefully studying the labeling, being critical of the low price and no less careful choice of a trustworthy manufacturer.

Establishment of fat content and acidity

The fat content of milk bought in bulk or in standard packaging is easy to determine on your own. For this, in addition to milk, you will need:

• ruler;
• a tall glass without a pattern or a test tube.

With a ruler from the bottom you need to measure 10 cm and put a mark. Then you need to pour milk into a glass exactly up to the mark and leave it in a warm place for 8 hours. When the product settles, a layer of cream will appear on top. It must be measured in millimeters as accurately as possible. The calculation is carried out according to the following formula: 1 mm of cream = 1% fat. Therefore, if their height is 5 mm, then the fat content of the entire drink is 5%.

Information about the acidity of milk is necessary for those who are engaged in home cheese making. To determine it, there are special ready-made tests. At home, you can also calculate the acidity of the product using phenolphthalein, distilled water and sodium hydroxide.

Sequencing:

1. Pipette 10 ml of milk into a test tube.
2. Add 20 ml of distilled water and 3 drops of phenolphthalein.
3. Gradually lower into the contents of the test tube 0.1 solution of normal sodium hydroxide until a slightly pink color is obtained.
4. Calculate the amount (in millimeters) of sodium hydroxide used to obtain a faint pink color.
5. Multiply the result by 10 - this will be an indicator of the acidity of milk in degrees.

The acidity of milk is measured in Turner degrees. For a natural product of the highest and first grade, 16–18 ° T is considered the norm; the second grade - from 18 to 20°T; off-grade milk - 21°T.

Is it possible to test dry milk?

Powdered milk is often used in home cooking, baby food and bodybuilding diets. Before evaluating the taste of a reconstituted product, it is advisable to test it dry. Here's what you need to pay attention to first:

1. Texture. The powder of high-quality milk powder is fine, homogeneous. Possible lumps are easily scattered when lightly pressed with a finger. Violation of storage conditions leads to caking of the powder. This product is not worth buying.
2. Color. The powder should be white, a light cream shade is possible. Intense creamy color, brown blotches indicate the burning of milk during the drying process.
3. Smell and taste. In a good product, it is purely milky, sometimes with a taste and smell of boiled milk.

High-quality powder with a high protein content should not precipitate when diluted with water.

Video: How to check the quality of a drink at home?

I would like to believe that in the near future the “milk deception” will end, and consumers will only be interested in the freshness and fat content of the drink, and not in possible additives. In the meantime, you can use proven methods to check the quality of the product.