Veterinary rules for conducting veterinary and sanitary examination of milk and dairy products. Veterinary and sanitary examination of milk

Obtaining milk of high sanitary quality is possible only if veterinary measures are observed on farms, milking hygiene is improved, milk quality is monitored and mastitis is prevented in cows.
Milk after milking must be filtered and cooled (not higher than +10 °C), no later than 2 hours after milking.
It should not contain inhibitory, neutralizing substances (antibiotics, soda, hydrogen peroxide, formalin, etc.).
Milk intended for the production of products baby food, must meet the requirements of the highest and first grade, but with a somatic cell content of not more than 500 thousand / cm3.
Upon acceptance of each batch of milk, acidity, purity, density, temperature and fat content are determined.
Bacterial contamination, as well as the mass fraction of protein and the content of somatic cells in milk is determined 1 time in 10 days.
The issue of milk quality is associated with the disease of cows with mastitis, since the inflammatory processes occurring in the mammary gland change the composition of milk and its physical and biological properties. It lacks antibacterial substances - lysozymes, the amount of vitamins decreases. In milk from cows with mastitis, the amount of casein, lactose, SOMO content, titrated acidity decrease.
At the same time, the content of chlorine, sodium, enzymes (catalase, reductase), as well as the number of leukocytes and pathogenic microorganisms (streptococci, staphylococci, salmonella, etc.) increase in it. Therefore, milk from cows with mastitis is dangerous to human health.
To identify cows with latent forms of mastitis, the following methods are used, based on the determination of changes in milk that are present during animal disease:
1. the use of dimastine and mastidin;
2. method of settling;
3. bromthymol test;
4. determination of the number of somatic cells (GOST 23453-794);
5. using devices OSM-70 (hidden mastitis determinant), PEDM (mastitis express diagnostic device).
Test with Mastidine and Dimastin
These substances are surfactants. The method is based on the ability of these substances to destroy cells (leukocytes) and release a nuclear substance - deoxyribonucleic acid, which gives a jelly-like clot of various consistency depending on the number of cells.
Mastidine test
To study milk from a cow, a 2% solution is used, and a 10% solution is used to detect mastitis milk in the team. For this purpose, 1 ml of milk is milked from each share of the udder into the recesses of the milk-control plate and 1 ml of mastidine solution is added. The mixture is stirred with a stick for 10-15 s and the reaction is taken into account by the density of the jelly and the change in color. If the mixture has a protein consistency chicken egg and the color is dark blue, this indicates that the milk is obtained from cows with mastitis. If there are no clots in the mixture and the color is light lilac, this indicates that the milk comes from a healthy cow.
Test with dimastin
For the study, a 5% solution of dimastine is used. The technique of setting the sample is the same as with mastidine. Getting red or pink in the jelly mixture indicates inflammation of the udder in cows. If there are no clots in the mixture and the color is yellow-orange, the milk is from a healthy cow.
It should be borne in mind that the number of cells in milk increases not only during inflammation, but also at the beginning and end of lactation, therefore, to confirm the diagnosis, it is necessary to use a settling test and bacteriological examination.
Settling test
In a test tube, 15 ml of milk is milked from each share of the udder and it is defended at a temperature of 4-5 ° C (in the refrigerator). The test tubes are examined after 16-24 hours. If a sediment more than 1 mm high appears on their bottom, this indicates that this is milk from a cow with mastitis.
Bromothymol test
It is based on the fact that in an alkaline environment the reagent acquires a blue color. To do this, 1 mm of milk is poured into the recess of the milk plate, 2-3 drops of a 0.5% alcoholic solution of bromthymol are added and mixed. Milk from cows with mastitis, depending on the severity of the disease, turns from dark green to dark brown. of blue color. Milk from a healthy cow is characterized by a yellow-green coloration.
To determine the number of somatic cells in milk, the drug "mastoprim" is used, which is a mixture of sulfinol 74% and sodium hydroxide 26% based on dry matter.
1 ml of milk and 1 ml of an aqueous solution of 2.5% mastoprim are introduced into the recess of the milk-control plate. Milk with the reagent is intensively mixed with a stick. The resulting mixture is raised with a stick up and the results of the analysis are evaluated. If a homogeneous liquid or a weak clot is formed, which slightly stretches for a stick in the form of a thread, then in 1 ml of milk there are up to 500 thousand somatic cells.
In the presence of a pronounced clot, when stirred, the notch is clearly visible and the clot is not ejected from the well, from "500 thousand to 1 million cells. When a dense clot is formed, which is ejected from the well of the plate with a stick, more than 1 million cells are contained in 1 ml milk.
The use of devices OSM-70, PEDM is based on the determination of the electrical conductivity of milk. Milk obtained from cows with mastitis has an increased electrical conductivity due to an increase in chloride and sodium ions in it.
Sanitary assessment milk
Milk from cows with a clinical form of mastitis is boiled and destroyed, with a latent form of mastitis, it is boiled and used for animal feed. The clinical form of mastitis is detected during milking by milking the first streams of milk into a special mug. Cows for a latent form of mastitis should be examined once a month.
In farms unfavorable for tuberculosis milk from cows with clinical manifestations is destroyed after adding creolin, lysol or other disinfectants to it. Milk from animals that respond positively to tuberculin, but do not have clinical signs, is boiled and used on the farm. You can use milk from such animals for processing into ghee. From cows that react negatively, milk is pasteurized on the farm at a temperature of 85 ° C for 30 minutes or at a temperature of 90 ° C for 5 minutes.
With brucellosis, cows with clinical forms of the disease do not receive milk.
From cows that react positively, milk is neutralized by boiling and used inside the farm. From negatively reacting cows in a dysfunctional farm, milk is pasteurized at a temperature of 70 ° C for 30 minutes or at a temperature of 85-90 ° C for 20 seconds.
In case of foot-and-mouth disease, milk is processed into ghee, or rendered harmless by boiling for 5 minutes, or pasteurized at a temperature of 80 ° C for 30 minutes.
With leukemia, milk from cows with a clinical form is destroyed. From animals suspicious of the disease, milk is boiled for 5 minutes or pasteurized at a temperature of 85 ° C for 10 minutes.
It is not allowed to sell milk when falsification is established.

Milk after milking must be filtered (cleaned) and cooled on the farm no later than 2 hours after milking, so that during delivery and acceptance at the dairy it has a temperature not higher than 10 ° C. Milk must be natural, freezing it is not allowed.

Milk should not contain inhibitory and neutralizing substances (detergents, disinfectants and preservatives, formalin and hydrogen peroxide, soda and ammonia). The level of content of toxic elements must correspond to hygiene requirements(San Pin 1 1 63 RB 98).

The basic norm of the mass fraction of fat in milk is 3.4%.

Varietal milk, the temperature of which is above plus 10°C, is accepted as "uncooled", with a corresponding discount from the purchase price. If the density is 1026.0 kg/m3, the acidity is 15 and 21°T and the bacterial contamination is over 4x106 CFU per 1 cm3, but meets the requirements of the normative document in other respects, the milk is accepted as non-varietal.

Milk that does not meet the requirements in terms of density and acidity, but not higher than 20 ° T, fresh and whole, is allowed to be accepted on the basis of a control (stall) sample as a varietal one, if it meets the requirements for organoleptic indicators, purity, bacterial contamination and the content of somatic cells THAT. The period of validity of the analysis of the control sample should not exceed 1 month.

Milk obtained from cows in communicable disease-affected farms and approved for human consumption must be received and used in accordance with current disease-specific guidelines. Such milk must not be mixed with raw milk from healthy animals. If such milk is subjected to heat treatment on the farm, and it meets the requirements of the varietal, then the effectiveness of heat treatment is checked and accepted as second-class milk and sent for separation, followed by processing of cream into butter and skimmed milk for feed purposes.

Milk quality control is carried out first on farms after it is received, before being sent to the dairy and upon acceptance at processing plants.

Research begins with the definition organoleptic indicators, temperature, then take samples and determine the density, acidity, purity, mass fraction of fat and the effectiveness of heat treatment (if it was carried out on the farm). All these indicators are determined in each batch of milk.

At dairies, when receiving milk, in addition to the indicated indicators, the content of somatic cells, bacterial contamination and inhibitory substances are also determined (at least once a decade). Neutralizing substances are determined in milk if their presence is suspected.

The organoleptic analysis of milk includes the determination of color, taste, smell, consistency, as well as the presence of defects and falsifications of the product.

Defects in the organoleptic properties of milk can be associated with many reasons: non-compliance with zootechnical and veterinary rules for keeping and feeding cows, conditions for obtaining, primary processing, storage, transportation.

The main types and causes of milk defects:

Consistency defects. 1. Viscous: the development of microorganisms; mastitis; aeration of milk and its storage at 20-25°C; the presence of fibrin and leukocytes that form a mucous substance; passing milk through a cooler (formation of protein films). 2. Mucous: the presence of microorganisms; admixture of colostrum; mastitis, foot and mouth disease, leptospirosis; long-term storage at temperatures below 10°C; eating rotten and moldy feed. 3. Foamy: feeding poor quality silage and excess potatoes; long-term cold storage of raw, pasteurized or boiled milk; coincidence of pregnancy in most cows of the herd. 4. Watery: tuberculosis, mastitis, anthrax; an excessive amount in the diet of stillage, pulp, beets, cabbage, rutabaga tops, turnips, etc .; the period of estrus and hunting; dilution with water and freezing; poor quality roughage. 5. Curd: development of microorganisms, including during storage of uncooled milk; mastitis; admixture of colostrum or old milk; high acidity. 6. Sand: calcification of casein flakes; undermilking of cows; mastitis; metabolic disease; the use of feed and water, poor in calcium.

Color defects. 1. Blue and light blue: the development of microorganisms, some yeasts and molds; eating forest herbs with blue pigment, as well as buckwheat, alfalfa, vetch, forget-me-nots; mastitis, udder tuberculosis; dilution of milk with water; lifting fat; storage of milk in zinc dishes. 2. Yellow: the presence of microorganisms, yeasts and fungi that produce yellow pigment; mastitis, udder tuberculosis; admixture of colostrum; eating carrots, corn, bison, maize, saffron, etc.; giving drugs (rhubarb, acridine dyes, tetracycline, etc.); leptospirosis, foot and mouth disease, jaundice, piroplasmosis, anthrax, mastitis. 3. Bloody: violation of the rules of machine milking; feeding beets, carrots, buttercups, milkweed, horsetail, young shoots of trees, sedges, etc.; piroplasmosis, pasteurellosis, anthrax, mastitis; poisoning; yeast, pigment microorganisms and fungi.

Defects of smell and taste. 1. Ammonia, soda, soap: storage in an unclosed container; adsorbing the smell of manure, ammonia, etc.; badly washed away detergents; development of microorganisms; mastitis, tuberculosis; adulteration with soda, ammonium hydroxide; eating horsetail. 2. Specific: storage next to creolin, turpentine, carbolic acid; improper use of medications and disinfectants; drinking water contaminated with oil products, and their presence in the silo; acetonuria. 3. Smoky: storage in an open container in a smoky room or near paints, varnishes. 4. Sour: storage in insufficiently clean dishes; contamination with microorganisms; eating acidic foods; lack of calcium. 5.3 stale, putrid: moldy; development of putrefactive microflora; feeding rotten, moldy feed, using the same litter; drinking poor-quality water; storage of fresh milk in tightly closed containers; ketosis, acetonemia. 6. Unclean, cow, barn: filtration of milk directly in the barn; ingestion of particles of animal skin, manure, bedding into milk; long-term storage of fresh milk in closed container in the barnyard; feeding with silage, alfalfa, etc.: ketosis, acetonemia. 7. Specific individual plants: feeding wild garlic and onions, mustard, rapeseed, chamomile, cumin, anise, cabbage, beets; moldy and musty food. 8. Silo: Poor quality silo; unsanitary conditions. 9. Bitter taste: eating tansy, vetch, sweet clover, chicory, beet tops, cabbage leaves, wormwood, colza, chamomile, etc., acorns, linseed cake, moldy oat and barley straw, rotten beets, rutabaga, potatoes, large quantities of beans , peas, old malt broth, rancid cakes; development of bacteria, yeast, fungi; admixture of old milk or colostrum; medicines (sabur, rhubarb, aloe, etc.); rusty dishes; long-term storage at low temperatures; foot and mouth disease, protein poisoning, endometritis, mastitis; stage of excitation of the sexual cycle; nymphomania, piroplasmosis, diseases of the digestive system; use of moldy bedding, etc. 10. Fish: storage together with fish; feeding fishmeal, sugar beet leaves; drinking water with algae; grazing on rye, wheat, barley pastures, water meadows; development of microorganisms. 11. Rancid, tart-salty taste: start and start of lactation; stage of excitation of the sexual cycle; abortion, nymphomania, mastitis; microorganisms; exposure to direct sunlight; heat; grazing on swampy pastures; storage of milk in iron, copper dishes; diseases gastrointestinal tract. 12. Pungent taste: eating fresh nettles, hops, water pepper, horsetail. 13. Weakly sweet, bitter-salty taste: an admixture of old-fashioned, mastitic milk or colostrum; brine getting into storage tanks; microorganisms; pulmonary tuberculosis. 14. Oxidized Taste: Feeding beet tops, beet pulp, bard, molasses, alfalfa; excess concentrates; lack of vitamin C; start of lactation; the end of the stall content; water with a lot of iron; copper parts in a system with hot water; storage in iron or copper containers; microorganisms; mastitis.

For laboratory analysis sampling and determination of the quality of milk should be carried out on farms and milk processing enterprises in the presence of responsible representatives of the delivery farms or the owner of the product. After opening the flasks and compartments of the tanks, the fat accumulated on the lids and walls (but not knocked down) is removed with a spatula into the same flasks and tanks and the milk is mixed: in automobile tanks with a stirrer for 3-4 minutes, avoiding strong foaming and overflowing, in flasks - with a whorl, moving it up and down 8-10 times.

A stall sample is taken when there is disagreement about the correctness of determining the quality of milk in terms of density and acidity during its delivery and acceptance. Such a sample is taken on a commission basis, together with a representative of the dairy and the farm, if necessary, with the participation of specialists from the district administration. The results are documented.

The accuracy of the determined indicators can be affected by: insufficient mixing of milk; quick lowering of the probe into the container; sampling is disproportionate to quantity; usage dirty dishes; keeping samples open; violation of conservation rules.

The acidity of cow's milk is characterized by significant fluctuations - from 16 to 20°T. The acidity of milk increases when: grazing cows in wet meadows or meadows with acidic cereals; lack of calcium in the diet; excess concentrates; lack of succulent feed; microbial contamination; with a lack of water during titration, examination of milk earlier than 2 hours after milking, use of non-distilled water, prolonged or improper storage of alkali and standard. Decreases with: excess water during titration; high titration speed; falsification with water, soda; disease with mastitis (up to 5-13°T); pasteurization or boiling at 2-3°T.

Whole Density cow's milk ranges from 1027 to 1032 kg/m3 and is determined by the content of proteins, salts, milk sugar. Colostrum (1038-1040kg/m3), skimmed milk (1033-1035kg/m3) and pasteurized for 10 minutes at 85°C or boiled for 10 minutes (by 0.5-1.4°A ).

The density of milk is determined at a temperature of 20°C. During mass analyzes, it is allowed to rinse the cylinder with milk taken for the next determination of the density of another test milk sample. After preparing the hydrometer, do not touch its working part with your hands.

The density of milk increases with: the presence of mechanical impurities; increase in acidity; incorrect sampling; low milk temperature (less than 15°C). The indicator is underestimated when: the study is earlier than 2 hours after milking; strong agitation with the formation of air bubbles. The accuracy of determining the density is also affected by: insufficient purity of the hydrometer; hydrometer touching the cylinder wall.

The fat content in milk must be known when: converting the actual fat content into the base one, since it is for the amount sold to the state base milk cash payments are made to the deliverer; control of the work of a dairy enterprise or farm; selection for the repair of a herd of cows with the best milk fat content; calculation of dry matter content in milk; establishment of falsification of milk, as well as wages of livestock workers. To convert milk, the actual fat content into the basic amount of milk (kg) is multiplied by the actual fat content and the result is divided by established norm base fat.

When determining the fat content in milk, sulfuric acid dissolves milk proteins, including the protein shells of fat globules, and releases fat in its pure form. Isoamyl alcohol is added to reduce the surface tension of the fat globules. Fat is collected in a compact mass and separated by centrifugation of butyrometers. The discrepancy between indicators in parallel determinations should not exceed 0.1% fat. The final result is determined by the arithmetic mean.

The fat content of milk is overestimated when: incorrect sampling; blowing milk out of the pipette tip; increasing the temperature of the water bath (more than 67°C) and the amount of isoamyl alcohol. It is underestimated if: non-compliance with the density of sulfuric acid (1.81-1.82 g/cm3) and isoamyl alcohol (0.810-0.812 g/cm3); incorrect sampling; inaccurate measurement of the amount of milk; underestimation of the temperature of the water bath (less than 63 ° C); a decrease in the speed of rotation of the centrifuge (less than 1000 rpm) and centrifugation time (less than 5 minutes); violation of the filling sequence of the butyrometer; incomplete mixing of milk, sulfuric acid and isoamyl alcohol.

Determining the degree of purity of milk makes it possible to judge its sanitary condition. The presence of mechanical impurities in milk indicates unsanitary conditions for its production, storage and transportation. Together with particles of feed, manure, hairs, a large number of microorganisms enter the milk, which cause its rapid spoilage, as a result of which sometimes such milk becomes unsuitable for processing into dairy products.

Bacterial contamination of milk is the main indicator characterizing its hygienic and sanitary quality. It is determined by reductase samples with methylene blue or resazurin.

The objectivity of these studies is determined by the correct sampling of milk and the preparation of reagents, strict observance of the sterility of dishes, and the strict fulfillment of other requirements stipulated by the current standards and specifications.

The control of the naturalness of milk is carried out in case of suspicion of its falsification (changing the naturalness of milk for personal gain). It is possible with the removal of the constituent parts of the product (for example, fat) or with the addition of substances unusual for it: water (to increase volume), soda (to reduce acidity), inhibitory substances - antibiotics, hydrogen peroxide, formalin, chromic and other antimicrobial substances, residues various detergents and disinfectants and reagents. Milk with an admixture of abnormal milk, with mastitis, blood impurities, animal diseases, as well as with the addition (impurities) of starch, cottage cheese, vegetable oils and other falsifications.

The suspicion that milk has been boiled or heated is confirmed by methods for determining the presence of peroxidase and phosphatase enzymes in the product.

Peroxidase in milk is inactivated at a pasteurization temperature of at least 800C with a holding time of 20-30 seconds. The presence of peroxidase indicates that the milk has not been pasteurized, or has been pasteurized at temperatures below 80°C, or has been mixed with an unpasteurized product.

Determination of peroxidase: for this, 5 drops of potassium iodide starch and 5 drops of a 0.5% H2O2 solution are added to a test tube with 5 ml of the test milk, the mixture is quickly mixed. The rapid development of a dark blue color indicates that the milk is raw. In a sample of milk pasteurized at a temperature above 800C, the color does not change.

Phosphatase is inactivated at a pasteurization temperature of at least 63°C with a holding time of 30 minutes. The presence of phosphatase means that the milk has been pasteurized at temperatures below 63°C.

Determination of phosphatase: 2 ml of milk and 1 ml of 0.1% sodium phenolphthaleinophosphate are added to the test tube, the test tube is shaken and placed in a water bath at a temperature of 40-45 C. After 10 minutes and after 1 hour, the color of the milk is determined. Raw milk or pasteurized below 63°C is pink. The color of pasteurized milk at a temperature of more than 63°C does not change.

Determination of soda impurities: 5 ml of milk is poured into a test tube and 7-8 drops (0.1 ml) of a 0.04% solution of bromthymol blue are carefully added along the wall. After 10 minutes (without shaking the test tube), observe the color change of the annular layer. At the same time, the yellow color of the annular layer indicates the absence of soda in milk, green of various shades (from light green to dark green) indicates the presence of soda in milk. At the same time, a sample is taken with milk that does not contain soda.

To determine chlorine in milk, add 1 ml of a 5% potassium iodide solution and 1 ml of a freshly prepared 2% starch solution to 10 ml of milk, mix well, then add 10 ml of hydrochloric acid (concentrated) and mix again. In the presence of chlorine, milk turns blue in 3-10 minutes.

The remains of chlorine preparations (bleach, chloramine, sodium hypochlorite, desmol) are determined by pouring 1 ml of pure hydrochloric acid and milk into a thoroughly washed test tube, mix well. Next, 4 drops of a 5% potassium iodide solution are added, mixed again and placed for 5 minutes in a water bath with a temperature of 60-65°C. The tube is then cooled in cold water until room temperature, add 2-3 drops of 1% starch solution and mix well, avoiding direct sunlight. In the presence of chlorine preparations, milk turns blue. A small amount of chlorine can cause pink or mauve discoloration. It is believed that the sensitivity of the test is 5-10 mg of chlorine per 1 ml of milk.

Determination of hydrogen peroxide. To 1 ml of milk (without stirring) add 2 drops of sulfuric acid solution and 0.2 ml of potassium iodide starch solution. The appearance of individual blue spots in the test tube after 10 minutes indicates the presence of hydrogen peroxide in milk. The method is designed to determine hydrogen peroxide in raw milk, its sensitivity is 0.001%.

Determination of ammonia makes it possible to detect ammonia or ammonium salts in raw milk above its natural content (sensitivity 6-9 mg/%), and is carried out no earlier than 2 hours after the end of milking. 20 ml of milk in a glass is heated for 2-3 minutes in a water bath with a temperature of 40-450C and 1 ml of 10% acetic acid and then left for 10 minutes to precipitate the casein. Then, with a pipette (with a cotton wool at the lower end, so that casein does not get in), 2 ml of settled whey is taken and transferred to a test tube, into which 1 ml of Nessler's reagent is added, the contents are immediately mixed. The appearance of a lemon-yellow color within 1 minute indicates the presence of ammonia, orange of varying intensity - the presence of its higher than natural content.

The falsification of milk by the addition of starch is determined by adding 2-3 drops of Lugol's solution to a test tube with 5 ml of well-mixed milk (sour cream, cream). The contents of the tube are thoroughly shaken. The appearance of a blue color after 1-2 minutes indicates the presence of starch in the test sample.

Milk and dairy products are valuable products nutrition of animal origin. However, it should be remembered that milk obtained from sick animals can be a source of human infection with zooanthroponotic diseases, in addition, if sanitary rules and the technology for obtaining and processing and storing milk and dairy products are violated, they can cause food toxicosis and toxic infections. Therefore, one of the most important tasks of the veterinary service is the proper organization of the veterinary sanitary examination of milk in order to control their quality and safety at all stages (receipt, transportation, processing, storage and sale). The procedure for the veterinary sanitary examination of milk and dairy products is determined by the current regulatory documents.

Purchasing requirements for milk

Requirements for natural cow's milk are set out in GOST R 52054-2003, which came into force on 01.01.2004. This regulatory document regulates the quality and safety of milk, and methods for their control, as well as the rules for the acceptance and labeling of this product.

All milk must be obtained from healthy animals on farms free from infectious diseases, in accordance with current veterinary and sanitary rules and the International Veterinary Code. All purchased milk, depending on its organoleptic and laboratory parameters, is divided into three grades, see table. 4. The basic all-Russian norms for the content of fat and protein in milk are 3.4% and 3%, respectively.

Table 1

Milk indicators according to GOST R 52054-2003

It is forbidden to use for food purposes milk obtained from cows in the last 5 days before launch and the first 7 days after calving. If unsatisfactory results of the analysis are obtained for at least one indicator, a second analysis is carried out using a double sample volume from the same batch of milk. The results of the reanalysis are final.

Milk after milking must be filtered and cooled to a temperature of 4±2°C for 2 hours. Milk should be kept at 4°C for no more than 24 hours at the dispenser.

When sending milk, a veterinary certificate form No. 2 (certificate form No. 4 for the region), a certificate of quality and safety and a consignment note (for legal entities) are issued. Milk is transported by specialized vehicles (in tanks for food liquids, metal flasks or other containers permitted by the RF Sanitary and Epidemiological Supervision) in accordance with the rules for transporting perishable goods at a temperature of +2 to +8 ° C for no longer than 12 hours. If the transportation regimes are violated, milk is referred to as off-grade.

Veterinary and sanitary examination of milk

To determine the quality and safety of milk, it is necessary to study the accompanying documents, assess the sanitary condition of containers and transport, and conduct a set of organoleptic, physico-chemical and microbiological studies.

Study of accompanying documents

When milk is delivered to the market by private individuals, they must submit a veterinary certificate form No. 2 or a veterinary certificate form No. 4 (when transported within the district). When studying this document, special attention should be paid to the epizootic state of the settlement from which the milk came, to the timing and results of routine diagnostic tests (for tuberculosis, brucellosis, etc.), vaccinations and tests for latent mastitis. This document is valid for 1 month. In addition, a person selling milk in the market must have a sanitary book of the established form.

If the supplier is an organization, then for each batch of milk a veterinary certificate form No. 2 or a veterinary certificate form No. 4 (when transported within the region) is issued for a period of validity of 3 days, a bill of lading, and a quality certificate indicating the results of milk testing received in the dairy laboratory of the farm. When supplying dairy and milk-containing products and pasteurized milk, a certificate of conformity and a hygiene certificate or their certified copies are additionally required.

Inspection of transport containers

Milk and dairy products are easily contaminated and adsorb strong-smelling substances. Therefore, milk containers must be hermetically sealed. In addition, milk tata must be made from food-grade material approved by the RF Sanitary and Epidemiological Supervision and be sanitary-clean.

Most often, for the transportation of milk, I use special milk tankers, milk flasks made of aluminum and of stainless steel, enameled dishes without chips, containers made of glass and food-grade plastic. In transport, milk cannot be transported together with strongly smelling, toxic and dusty substances.

Taking milk samples and preparing them for analysis

Milk sampling is carried out at the place of its acceptance in accordance with GOST 13928-84 and GOST 26809-86.

An average sample of 500 ml is taken from a batch of milk for the study. Before sampling, the milk is thoroughly mixed, moving it up and down in flasks with a whorl 8-10 times, in road and rail tanks with mechanical mixers 3-4 minutes and 15-20 minutes, respectively. When taking spot samples of milk, mugs with elongated handles with a capacity of 0.25 or 0.5 or samplers (cylindrical tubes with an inner diameter of 9 mm made of stainless steel, aluminum or food grade plastic) are used. When sampling with a sampler, it must be lowered into the container slowly, with the upper end open. The selected samples are placed in a clean container made of a material approved by the Sanitary and Epidemiological Supervision of the Russian Federation, with a hermetically sealed lid.

For preservation of samples, use 1 ml of 10% potassium dichromate solution or 1-2 drops of 40% formalin solution per 100 ml of milk.

Organoleptic study of milk

Taste and smell(GOST 28283-89). The assessment of taste is carried out selectively after boiling the sample, and the assessment of the smell in 10-20 ml of milk heated to 35°C.

Definition appearance, colors and consistency are carried out according to GOST R 52054-2003

Milk color determined in daylight in a colorless glass cylinder.

Consistency milk is determined by pouring a sample of milk into a cylinder of colorless glass. Cow's milk should be a thick homogeneous liquid without sediment and clots. Milk from cows with mastitis may have a slimy consistency and contain clots and flakes. Clots and flakes can form in sour milk, as well as with rapid cooling. fat milk. In order to find out the reason for the formation of flakes and clots, the milk is heated to 30-40˚C. at the same time, flakes of fat, unlike mastitis, dissolve.

Organoleptic indicators of milk, depending on its variety, are presented in Table. 1, organoleptic defects of milk and the reasons for their appearance are presented in table. 2.

table 2

Organoleptic defects of milk

Determination of physico-chemical parameters of milk

In each batch of milk, the following laboratory parameters are determined: titratable acidity, temperature, mass fraction of fat, density or freezing point, purity group and heat resistance group. At least once a decade in the milk under study, the following is determined: bacterial contamination, the content of somatic cells and the presence of inhibitory substances, and the protein content is determined 2 times a month. If it is suspected that milk has been subjected to heat treatment, the presence of alkaline phosphatase in milk is checked. According to the results of organoleptic and laboratory research milk is divided into the highest, first, second grade and off-grade (Table 4).

Determination of milk temperature (GOST 26754-65)

The method of measuring the temperature of milk with a glass liquid (non-mercury) thermometer is based on the change in the volume of liquid in a glass shell depending on the temperature of the medium being measured.

The temperature of milk is measured directly in the tank, flask, bottle, package. When milk is received directly at farms, the temperature is measured in transport containers immediately after they are filled. Before measuring the temperature, milk in tanks and flasks is mixed.

To measure the temperature of milk, glass liquid thermometers are used in a frame according to GOST R 51652-2000. The thermometer is immersed in milk to the lower digitized mark and kept for at least 2 minutes. Readings are taken without removing the thermometer from the milk.

When measuring the temperature of milk with a glass liquid (non-mercury) thermometer, the result of the thermometer reading is rounded off to the nearest whole number. And the results of digital thermometers are determined according to the readings of the digital display of the measuring unit with an accuracy of 0.1˚С.

The arithmetic mean of the measurements is taken as the final result of measuring the temperature of milk in flasks and consumer containers.

Determination of titratable acidity of milk (GOST 3624-92)

The acidity of milk is due to the presence of lactic and other acids in it. The method is based on the neutralization of the acids contained in the product with sodium hydroxide solution in the presence of the phenolphthalein indicator.

In a flask with a capacity of 100 to 250 cm 3, 20 ml of distilled water, 10 ml of analyzed milk, and three drops of 1% phenolphthalein solution are measured. When analyzing sour cream, cream, cottage cheese, 5 g of the product under study and 30-40 ml of distilled water (50 ml warm water for cottage cheese) and three drops of 1% phenolphthalein solution. The mixture is thoroughly mixed and titrated with 0.1 N. sodium hydroxide solution until a faint pink color appears, for milk and cream, corresponding to the control color standard, which does not disappear within 1 min.

To prepare a control standard. In a flask with a capacity of 100 or 250 cm 3, 10 ml of milk (5 g of dairy products) and 20 ml for milk (30-50 ml for dairy products) of distilled water and 1 cm 3 of a 2.5% solution of cobalt sulfate are measured. The mixture is thoroughly mixed. The shelf life of the standard is not more than 8 hours at room temperature.

The acidity of milk and dairy products in Turner degrees is the amount of 0.1 N. solution of sodium hydroxide, necessary to neutralize the acids contained in 100 g of the test product.

The calculation of milk acidity is calculated by the formula: К˚T=V 10,

acidity of dairy products К˚T=V 20

where: V is the amount of 0.1 n. solution of sodium hydroxide used to neutralize acids.

Determination of milk density (GOST 3625-84)

A sample with a volume of 0.25 or 0.50 dm 3 is thoroughly mixed and carefully, in order to avoid the formation of foam, is poured along the wall into a dry cylinder, which should be kept in a slightly inclined position. If foam has formed on the surface of the sample in the cylinder, it is removed with a stirrer. The cylinder with the test sample is installed on a flat horizontal surface, the temperature of the sample is measured. The reading of the temperature readings is carried out no earlier than 2-3 minutes after the thermometer is lowered into the sample.

A dry and clean hydrometer (lactodensimeter) is slowly lowered into the test sample, immersing it until 3-4 mm remains to the expected mark of the hydrometer scale, then leaving it in a free floating state. The device must not touch the walls of the cylinder.

Table 3

Bringing the density of cow's milk to20°C.

The location of the cylinder with the sample on a horizontal surface should be, in relation to the light source, convenient for reading the readings on the density scale and the thermometer scale. The first reading of the density readings is carried out visually from the hydrometer scale after setting it in a stationary position. After that, the hydrometer is carefully raised to the level of the ballast in it and lowered again, leaving it in a free floating state. After establishing it in a stationary state, a second reading of the density readings is carried out. When reading the density reading, the eyes should be at the level of the meniscus. The readings are taken along the upper edge of the meniscus (see Fig. 1).

Reading of indications on hydrometers of types AM and AMT is carried out up to half of the scale division value. In hydrometers of types AON-1 and AON-2, readings are counted up to the price of the name of the division. The temperature of the sample is then measured.

Measurement of sample temperature when using hydrometers of types AM, AMT, AO, AON-2 is carried out using mercury and non-mercury glass thermometers.

The arithmetic mean of the results of two indications is taken as the average value of the temperature and density of the test sample.

Measurement of the density of milk is carried out at a temperature of 15-25ºС. If the sample during the determination of the density had a temperature above or below 20°C, the results of the determination of the density should be reduced to 20°C in accordance with the data in table. 3.

Determination of milk purity group (GOST 8218-89)

The determination of the milk purity group is carried out using a device for determining the purity of milk with a filter surface diameter of 27-30 mm (Record or others) and filters made of needle-punched thermally bonded fiber.

The filter is inserted into the device with the smooth side up. Take 250 ml. thoroughly mixed milk heated to 35 ° C and pour it into the vessel of the device. At the end of filtration, remove the filter, put it on a sheet parchment paper and compare it with a standard. Milk is divided into 3 groups according to purity (see Table 4).

Table 4

Comparison sample for determining the purity group of milk

(when filtering a sample with a volume of 250 cm 3)

Determination of the mass fraction of fat in milk (GOST 5867-90.

Determination of fat content. In a clean milk butyrometer (butyrometer), without wetting the neck, pour 10 ml of sulfuric acid (density 1810-1820 kg / m 3) into a dispenser and, carefully so that the liquids do not mix, add 10.77 ml of milk with a pipette, attaching its tip to the wall of the neck butyrometer at an angle (the level of milk in the pipette is set at the lower level of the meniscus). Blowing milk out of a pipette is not allowed. Then 1 ml of isoamyl alcohol (density 810-813 kg/m 3 ) is added to the butyrometer with a dispenser. To determine the fat content of dairy products, the fat content of which is higher than in milk, a cream butyrometer is used, into which 5 g of sour cream, cream and cottage cheese or 2 g of butter are added, after which sulfuric acid and isoamyl alcohol.

Butyrometers: a) - milk b) - cream

The butyrometer is closed with a dry rubber stopper, introducing it a little more than half into the neck, turned over 4-5 times until the protein substances are completely dissolved and evenly mixed (the butyrometers should be wrapped with a napkin or towel when turning), after which they put the stopper down for 5 minutes in a water bath with a temperature of 65 ± 2 °C. Having taken out of the bath, the butyrometers are inserted into the cartridges (glasses) of the centrifuge with the working part towards the center, placing them symmetrically one against the other.

With an odd number of butyrometers, a butyrometer filled with water is placed in the centrifuge. After closing the centrifuge lid, the butyrometers are centrifuged for 5 minutes at a speed of at least 1000 rpm. Then each butyrometer is removed from the centrifuge and the movement of the rubber stopper adjusts the column of fat in the butyrometer so that it is in the tube with a scale. The butyrometers are then re-immersed, caps down, in a water bath at 65 ± 2°C.

Rice. 3 Automatic pipette for a set of sulfuric acid.

Automatic pipette for a set of sulfuric acid.

After 5 minutes, the butyrometers are removed from the water bath and the fat is quickly read. To do this, the butyrometer is held vertically, the border of fat should be at eye level. By moving the plug up and down, the lower limit of the fat column is set on the whole division of the butyrometer scale and the number of divisions is counted from it to the lower level of the meniscus of the fat column. The interface between fat and acid should be sharp, and the column of fat should be transparent.

The butyrometer readings correspond to the percentage of fat in milk. The volume of 10 small divisions of the milk butyrometer scale corresponds to 1% fat in the product. Fat counting is carried out with an accuracy of one small

dividing the butyrometer. The discrepancy between parallel determinations should not exceed 0.1% fat. The arithmetic mean of two parallel determinations is taken as the final result.

Determination of the freezing point of milk (GOST 30562-97)

This technique allows you to determine the presence of foreign water in the milk.

The thermistor cryoscopic method is used to determine the freezing point of milk.

The essence of the method is that the milk sample is cooled to a predetermined temperature (depending on the device), crystallization is caused by mechanical vibration, after which the temperature is quickly raised to a plateau, which corresponds to the freezing point of the sample.

The cryoscope consists of a thermally controlled cooling bath, a thermistor probe (semiconductor thermistor) with a preset circuit and a galvanometer or digital indicator, a sample stirrer and a crystallization trigger, and sample tubes.

Pour or pipette a test milk sample in the amount of (2.5 ± 0.1) cm 3 into a clean, dry sample tube. Make sure the probe and stirring wire are clean and dry (if necessary, wipe with a soft, clean, lint-free cloth).

Insert a test tube into a calibrated cryoscope. The milk is cooled and crystallized at the set temperature with an accuracy of 0.1 °C. (In some automatic instruments, the temperature can be observed on a digital scale; in other instruments, the necessary accuracy of inducing crystallization is ensured when the galvanometer needle coincides with the corresponding mark).

Determination of milk solids (SOM) and

dry skimmed milk residue (SOOM)

COM% \u003d 4.9 W% + P ° A + 0.5

SOM% \u003d SOM% -W%

where: F% - fat content of milk in%

P ° A - density in hydrometer degrees

(eg density 1028 kg/m 3 =28°A).

Normally, SOM of milk is from 11% to 17%, SOM > 8%.

Determination of heat stability of milk and cream with fat content

up to 40%by alcohol test(GOST 25228-82)

The method is based on the impact ethyl alcohol on proteins of milk and cream, which are completely or partially denatured when mixing equal volumes of milk or cream with alcohol. To determine the heat resistance of the alcohol sample, milk is examined at a temperature of (20 + 2) ° C, and the cream is heated in a glass in a water bath to a temperature of up to (43 ± 2) ° C, mixed and cooled to a temperature of (20 ± 2) ° C.

The thermal stability of milk and cream according to the alcohol test is determined using an aqueous solution of ethyl alcohol with a volume fraction of ethyl alcohol of 68, 70, 72, 75 and 80%.

The density of water-alcohol solutions used for the alcohol sample, kg/m3, at (20.0 ± 0.1) °C should be equal to: for 68% volume fraction of alcohol; for 70% alcohol by volume; 880.5 for 72% alcohol by volume; 872.8 for 75% alcohol by volume; 859.3 for 80% alcohol by volume.

Pour 2 ml of the investigated milk or cream into a clean, dry Petri dish, add 2 ml of ethyl alcohol of the required volume fraction, mix thoroughly in a circular motion. After 2 minutes, observe the change in the consistency of the analyzed milk or cream.

Reaction accounting. If flakes did not appear on the bottom of the Petri dish when the analyzed mixtures of milk or cream with alcohol drained, it is considered that they withstood the alcohol test.

Depending on which solution of ethyl alcohol did not cause the precipitation of flakes in the tested milk and cream, they are divided into groups indicated in Table. five.

Table 5

Milk heat resistance groups

Determination of the mass fraction of protein and mass fraction of total nitrogen (GOST 23327-98)

The Kjeldahl method is based on the mineralization of a milk sample with concentrated sulfuric acid in the presence of an oxidizing agent, an inert salt - potassium sulfate and a catalyst - copper sulfate. In this case, the amino groups of the protein are converted into ammonium sulfate dissolved in sulfuric acid.

The mass fraction of nitrogen in this solution is measured by one of the following methods:

chemical - by alkalizing the solution, distilling ammonia with steam, absorbing it with a solution of boric acid and titrating the latter with a solution of hydrochloric acid with indication of the equivalence point by changing the color of the indicator (manual titration) or using a potentiometric analyzer (manual or automatic titration) ;

electrochemical - by automatic coulometric titration of ammonia directly in the mineralized sample.

The mass fraction of the protein is determined by multiplying the result obtained by the corresponding coefficient.

Taking measurements

Several pieces of glass tubes are placed in a Kjeldahl flask or a test tube, and 10 g of a mixture of salts is added, 1 ml of a pre-weighed product is added, 10 cm 3 of sulfuric acid and 10 cm 3 of hydrogen peroxide or 0.5 g of potassium permanganate are added, after which they are heated on an electric stove until the contents stop violently foaming and until the liquid becomes clear and colorless or slightly bluish. Then the Kjeldahl flask or test tube is cooled to room temperature and the mass fractions of total nitrogen are determined chemically or electrochemically with the indication of the equivalence point.

Chemical way. The mineralizate in a Kjeldahl flask or test tube is dissolved in 20 cm 3 of distilled water and attached to a distillation apparatus (see Fig. 4 (1 - tile, 2 - flask with water, 3 - separating funnel, 4 - drop catcher, 5 - quartz test tube 6 - refrigerator 7 - receiving flask)). In a conical flask with a capacity of 250 cm 3, a 20 cm 3 mixture of a boric acid solution with an indicator solution is measured with a measuring cylinder and placed under a refrigerator for a boric acid solution with an indicator solution (methylene blue or brilliant green). Measure with a graduated cylinder 50 cm 3 of sodium hydroxide solution and carefully, avoiding emissions, pour it through a separating funnel into a Kjeldahl flask or test tube. The faucet of the funnel is immediately closed. Close the clamp on the steam outlet line and open the clamp on the steam supply line from the vaporizing flask to the Kjeldahl flask or test tube. The distillation is carried out until the volume of the condensate reaches 90 - 120 cm 3 (distillation time - 5-10 minutes).

Table 6

Changing the color of a solution during titration

with various indicators

The contents of the conical flask with a solution of the indicator, boric acid and condensate is titrated with a solution of hydrochloric acid with a concentration of 0.2 mol/DM 3 until the color changes indicated in table. 6.

In parallel, put a control reaction without milk.

Processing of measurement results

The mass fraction of total nitrogen X% is calculated by the formula:

X% \u003d 1.4 (V-V 1) C

where: V is the volume of acid used for titration, cm3;

V1 - the volume of acid spent on titration during the control measurement, cm 3

C - concentration of hydrochloric acid, mol / dm 3

m is the weight of the sample of the product, g;

1.4 - coefficient for converting the volume of acid into the mass fraction of total nitrogen

Mass fraction of protein Y%, determined by the formula

electrochemical method. After cooling, the mineralizate is quantitatively transferred into a volumetric flask with a capacity of 50 cm 3, the volume of the solution is adjusted to the mark with distilled water and mixed.

0.2 cm 3 of a neutralizing solution is added to the measuring cell of the titrator filled with an anode solution (100 g of potassium bromide and 240 g of sodium hydroxide are dissolved in 1 liter of distilled water), and then 0.1 cm 3 of the mineralizate solution and the button is turned on "Start" automatic titration. The process of titration of ammonia is carried out automatically. At the end of the process, the device turns off. The readings of the digital indicator correspond to the value of the mass of total nitrogen in the sample.

Determination of the mass fraction of moisture in butter.

An empty weighing bottle is weighed on an analytical balance with an accuracy of 0.001 g, then a weighing of about 5 g of butter is placed in the weighing bottle and reweighed. After weighing, the bottle with butter is heated over the flame of a burner or on an electric stove until all moisture has evaporated from it (boiling oil will begin to turn brown, stop crackling and water bubbles will disappear in it). After heating, the bottle with oil is re-weighed and the mass fraction of moisture is calculated using the formula:

X%=(M-M1) 100%

X% - mass fraction of moisture

M is the mass of the bottle with oil before evaporation of moisture in g.

M1 is the mass of the bottle with oil after evaporation of moisture in the city of

A is the mass of oil in g.

Determination of the main microbiological indicators of milkDetermination of the total microbial contamination of milk

The total microbial contamination of milk is one of the key indicators milk safety. There are two ways to determine the total microbial contamination, direct and indirect.

Determination of the total microbial contamination of milk by direct seeding. Sequential dilutions are prepared from a milk sample in sterile 0.9% NaCl solution from 1:10 to 1:1,000,000. From the last three dilutions, I do 2-3 inoculations (1 ml) in Petri dishes and fill them with melted meat-peptone agar or a special medium. Seeded cups are placed in a thermostat at 37°C for two days when seeded on MPA or at 33°C for 72 hours (special medium). The number of grown colonies is multiplied by the dilution, then the arithmetic mean is calculated, resulting in the number of microbial cells in 1 ml of milk.

Determination of reductase in milk (indirect method). The method is based on the reduction of resazurin and methylene blue by redox enzymes (reductase) secreted into milk by microorganisms. The duration of the color change evaluates the bacterial contamination of raw milk.

Reaction with methylene blue. 1 ml of a working solution of methylene blue (0.0015%), which is prepared from the main solution (0.005%) and 20 ml of the test milk, is poured into a sterile test tube, closed with a cork, mixed by slowly turning the test tube three times and placed in a reducer with a water temperature of 37 -38°С.

In the absence of a reducer, a water bath at a temperature of 37-38°C can be used. The water in the reducer or water bath after immersing the test tube with milk should reach the level of the liquid in the test tube or be slightly higher.

The moment the tubes are immersed in the reducer is considered the beginning of the analysis. Observation of the color change is carried out after 40 minutes, 2.5 hours and 3.5 hours minutes after the start of the analysis. The end of the analysis is considered the moment when the color of the milk becomes discolored, while the remaining small annular colored layer at the top (about 1 cm) or at the bottom of the tube is not taken into account. The appearance of coloring of milk in these test tubes during shaking is not taken into account.

Depending on the time of discoloration, milk is classified into one of four classes according to the degree of its good quality and the approximate bacterial contamination is determined by the number of microorganisms that produce reductase (see Table 7).

Table 7

Accounting for the reaction with methylene blue

Reaction with resazurin. 1 ml of the working solution (0.014%) of resazurin, which is prepared from the main solution (0.05%) and 10 ml of the test milk, is poured into a sterile test tube, closed with a cork, mixed by slowly turning the tube three times and placed in a reducer with a water temperature of 38-40 °C. Accounting for the reaction is carried out after 1 hour and 1.5 hours by color change (see table. 8).

Table 8

Accounting for the reaction with resazurin

Definitions of coli-titer of milk

Coli titer is the smallest amount of milk that contains one bacterium of the Escherichia coli group.

Coli-titer is an important microbiological indicator reflecting the hygiene of milk production.

Minimum allowed values coli-titer for: raw milk - 0.1 ml, for pasteurized draft milk - 0.3 ml, for pasteurized milk packed in consumer containers - 3 ml.

To determine the coli-titer from a sample of raw milk, serial dilutions are prepared in sterile 0.9% NaCl solution from 1:10 to 1:100,000. Then inoculate from each dilution (1 ml) into a test tube with Kessler's medium (lactose and gas). To determine the coli-titer of pasteurized milk in 3 test tubes with Kessler medium

Table 9

Determination of coli-titer of raw milk

Table 10

Determination of the coli-titer of pasteurized milk

inoculate 1 ml of milk and inoculate three test tubes from a dilution of 1:10.

Accounting for the growth of Escherichia coli is carried out by the presence of carbon dioxide in the gas.

Determination of if the titer is carried out according to the table. 9, 10.

Determination of somatic cells in milk (GOST 23453-90)

The method is based on the interaction of the drug "Mastoprim" with somatic cells, as a result of which the consistency of milk changes.

Analysis. 1 ml of thoroughly mixed milk is added to the well of the PMK-1 plate and 1 ml of an aqueous solution of the Mastoprim preparation is added. Milk with the drug is intensively mixed with a wooden, plastic or glass rod for 10 s. The resulting mixture from the well of the plate is lifted with a stick up by 50-70 mm with continuous intensive stirring, after which the results of the analysis are evaluated for no more than 60 s.

Processing of results The number of somatic cells in the test milk is determined by the consistency of the milk.

1. Homogeneous liquid or weak clot, which slightly stretches for a stick in the form of a thread up to 500 thousand times.

2. A pronounced clot, when stirred, a notch at the bottom of the hole of the plate is clearly visible. The clot is not ejected from the hole from 500 thousand to 1 mil.

3. A dense clot that is ejected with a stick from the hole of the plate over 1 mil.

For a more accurate determination of the number of somatic cells, a viscometer is used.

Determination of the quality of milk pasteurization (GOST 3623-73)

The sale of raw milk in the distribution network is prohibited, therefore milk is subjected to heat treatment at dairies. Raw milk must be delivered to dairies. Pasteurization is one of the most common heat treatment methods for milk. Pasteurization reduces the overall microbial contamination of milk by more than 90%, while milk retains most of the vitamins, enzymes and other useful biologically active substances.

In Russia, the following temperature regimes are used for pasteurization:

Low temperature pasteurization 63°C 30 minutes or 72°C 20 seconds.

High temperature pasteurization 75°C 10 minutes, 80°C 30 seconds or 85°C without holding.

During low-temperature pasteurization, alkaline phosphatase is destroyed in milk, and during high-temperature pasteurization, the peroxidase enzyme is destroyed. Therefore, the presence of these enzymes in pasteurized milk indicates that pasteurization was carried out incorrectly.

Determination of peroxidase by reaction

with potassium iodide starch

The essence of the method. The method is based on the decomposition of hydrogen peroxide by the enzyme peroxidase contained in milk and dairy products. Active oxygen released during the decomposition of hydrogen peroxide

oxidizes potassium iodide, releasing iodine, which forms a blue compound with starch.

Preparation of potassium iodide starch. 3 g of starch is weighed with an error of not more than 0.01 g and mixed with 5-10 cm 3 of distilled water. cold water before receiving homogeneous mass. Separately, in a flask, bring to a boil 100 cm 3 of distilled water and, with continuous stirring, add water to the diluted starch, preventing the formation of lumps. The resulting solution is brought to a boil. After cooling, 3 g of potassium iodide is added to the starch solution, stirring until the potassium iodide crystals dissolve.

A solution of potassium iodide starch is an unstable reagent, so it should be prepared in small quantities and stored in a dark cool place no more than two days.

Reaction setting. In a test tube with 5 ml. milk, 5 drops of a solution of potassium iodide starch and 5 drops of a 0.5% solution (2 drops of 1% solution) of hydrogen peroxide are added, the contents of the test tube are mixed with rotational movements after adding each reagent. The presence of peroxidase is then determined by the color change.

If a solution of starch and potassium iodide is used separately, then proceed as follows: 0.5 cm 1% starch solution, 2 drops of 10% potassium iodide solution and 5 drops of 0.5% hydrogen peroxide solution, mix the contents of the test tubes after adding each reagent, then determine the presence of peroxidase by color change.

Evaluation of results. In the absence of the peroxidase enzyme in milk and dairy products, the color of the contents of the tube will not change. Therefore, milk and dairy products were pasteurized at a temperature not lower than 80°C.

In the presence of peroxidase in milk, cream, butter, the contents of the test tubes acquire a dark blue color.

The sensitivity of the method makes it possible to detect the addition of at least 5% of unpasteurized dairy products to pasteurized ones.

Determination of the presence of alkaline phosphatase in milk

The method is based on the hydrolysis of the disodium salt of phenylphosphoric acid by the enzyme phosphatase contained in milk and dairy products. The free phenol released during hydrolysis in the presence of an oxidizing agent gives a pink color with 4-aminoantipyrine.

Preparation of solution A. 1.25 g of the disodium salt of phenylphosphoric acid is weighed with an error of not more than 0.0002 g, dissolved in 100 cm 3 of the main buffer solution (to 348 ml of 25% ammonia solution add 40 g of ammonium chloride, previously dissolved in 100 ml of distilled water, and dilute to 1 liter with distilled water).

Preparation of solution B. 0.8 g of 4-aminoantipyrine, weighed with an error of not more than 0.0002 g, is dissolved in 900 cm 3 of distilled water.

Solutions A and B should be colorless and stored in dark glass bottles in the refrigerator. Shelf life no more than 1 month. Yellowed solutions are unsuitable for work.

The working solution of the substrate is prepared immediately before determining the reaction by mixing solutions A and B (1:9). The working solution is suitable for work for 8 hours when stored in a dark glass bottle.

Preparation of the precipitant of the zinc-copper system. 30 g of zinc sulfate heptahydrate and 6 g of copper sulfate pentahydrate, weighed with an error of not more than 0.01 g, are dissolved in 1 liter of distilled water.

Analysis To 3 cm 3 of milk, add 2 cm 3 of the working solution of the substrate. Then the contents of the tube are mixed and placed in a water bath heated to 40-45 °C for 30 minutes. Add 5 cm3 of a zinc-copper system precipitant to a test tube taken out of a water bath, thoroughly mix the contents of the test tube and place it again in a water bath at a temperature of 40-45ºС for 10 minutes. After removing the test tube from the bath, a visual comparison is made between the contents of the tube of the test product and the control experiment.

A similar reaction with boiled milk is used as a control.

In the absence of the phosphatase enzyme in milk and dairy products, the color of the contents of the tube (solution separated from the precipitated protein) is colorless, i.e., similar to the contents of the test tubes of the control experiment. Therefore, milk and dairy products were pasteurized at a temperature not lower than 63ºС.

Determination of phosphatase by reaction

with sodium phenolphthalein phosphate

The essence of the method. The method is based on the hydrolysis of sodium phenolphthalein phosphate by the enzyme phosphatase contained in milk and dairy products. The phenolphthalein released during hydrolysis in an alkaline medium gives a pink color.

Reaction setting. 2 ml of milk, 2 ml of distilled water and 1 ml of sodium phenolphthalein phosphate in ammonia buffer are measured into a test tube. After that, the contents of the tube are stoppered, shaken and placed in a water bath. The contents of the tube are evaluated after 10 minutes and after 1 hour.

In the absence of the enzyme phosphatase in milk and dairy products, the color of the contents of the test tube does not change. Therefore, milk and dairy products were pasteurized at a temperature not lower than 63ºС. In the presence of phosphatase in milk and dairy products, the contents of the test tube acquire a color from light pink to bright pink. Therefore, milk and dairy products have not been pasteurized, or have been pasteurized at temperatures below 63°C, or have been mixed with unpasteurized products.

The sensitivity of the method makes it possible to detect the addition of at least 2% of unpasteurized dairy products to pasteurized ones.

Then the tube is placed in a water bath with a water temperature of 40 to 45ºС and the color is determined.

Determination of adulteration of milk and dairy products

Milk falsification can be natural or artificial. Natural falsification is understood as the intentional sale of mastitis milk, colostrum or milk obtained from sick animals. In case of artificial falsification, various substances are added to milk in order to increase its volume, the terms of implementation, the prevention of milk souring, etc.

Definition of falsification of milk by water.

To increase the volume of milk, it is diluted with water, while changing the organoleptic and laboratory parameters of milk. The taste and smell of milk of diluted milk are weakened, the consistency is liquid less viscous, the color is bluish, fat<3,2%, СОМ<11%, СООМ<8%, кислотность <16ºТ, плотность < 1027 кг/м.

Determination of the presence of inhibitory substances in milk

(GOST 23454-79)

To increase the shelf life of milk, it is falsified with inhibitory substances (antibiotics, sulfonamides, preservatives, and other substances that inhibit the growth of microflora).

Analysis. 10 cm 3 of the test milk are poured into sterile test tubes and closed with sterile rubber stoppers. The rest of the sample is stored until the end of the analysis in the refrigerator at a temperature of (6±2)°C.

Test tubes with test milk and a control sample are heated in a water bath to (87±2)ºС for 10 minutes, then cooled to (47±1)°С. Then, 0.5 cm 3 of the working test culture St. Termophilus, prepared from a collection test culture.

The contents of the test tubes are thoroughly mixed by inverting three times. Then the tubes are kept for 1 h 15 min at a temperature of (46 ± 1) °C in a reducer or water bath.

1 cm 3 of the main solution of resazurin with a temperature of (20 ± 2) ºС is introduced into the test tubes with the milk under study and the control sample. The contents of the test tubes are mixed by double inversion.

Test tubes with test milk and a control sample are kept in a reducer or a water bath with a thermostat or a water bath placed in a thermostat at (46±1)°C for 10 minutes.

Processing of results. In the absence of inhibitory substances in the test milk (and in the control sample), the contents of the test tubes will be pink or white.

In the presence of inhibitory substances in milk, the contents of the test tubes will have a color characteristic of class 1 milk according to the color scale for determining the class according to the reductase test with resazurin according to GOST 9225-84.

Determination of adulteration of milk with formalin

Place 1 ml of the test milk into a test tube and add 1 ml of Rigel's reagent (a mixture of concentrated sulfuric and nitric acids). In the presence of formalin in milk, a blue-violet ring is formed at the border of milk and Rigel's reagent.

Determination of adulteration of milk with hydrogen peroxide

GOST 24067-80

1 cm 3 of the investigated milk is placed in a test tube, without stirring, two drops of a sulfuric acid solution and 0.2 cm 3 of a 3% solution of potassium iodide starch are added.

After 10 minutes, observe the change in the color of the solution in a test tube placed in a tripod, avoiding shaking it.

The appearance of individual blue spots in the test tube indicates the presence of hydrogen peroxide in milk.

Definition of adulteration of milk

chrompic (potassium bichromate)

1 cm 3 of the investigated milk is placed in a test tube, 5-7 drops of 5-10% solution of silver nitrate are added. Mix the contents of the tube. If there is a chrompic in milk, it acquires a lemon-yellow or red-yellow color.

Determination of falsification of milk by soda.

To prevent souring of milk and dairy products, they are adulterated with soda.

Soda does not dissolve well in milk, so grains of undissolved soda can be found at the bottom of the container.

The admixture of soda in milk and dairy products is determined by adding a few drops of a 0.2% alcoholic solution of rosolic acid to 3-5 ml of the investigated milk or dairy product. In the presence of soda, the contents in the test tube turn pink-red, and in the absence - in orange.

When adding 7-8 drops of alcohol 0.04% solution of bromthymol blue to 5 ml of milk, milk with soda turns dark green, green-blue or blue; without soda - in yellow or salad color.

Determination of adulteration of milk by starch

The falsification of milk, sour cream, cream with starch is determined by adding 2-3 drops of Lugol's solution to a test tube with 5 ml of well-mixed milk (sour cream, cream). The contents of the tube are thoroughly shaken. The appearance of a blue color after 1-2 minutes indicates the presence of starch in the test sample.

Definition of adulteration of sour cream

yogurt or cottage cheese

In a glass of hot water (66-75 ° C), stir one teaspoon of sour cream. If cottage cheese is added to the product, then it settles to the bottom. Pure sour cream does not give sediment.

Milk of cows, sheep, goats, mares, buffaloes, as well as dairy products coming for sale in the markets (including stalls and shops of farms and consumer cooperatives) are subject to sanitary assessment in accordance with the rules for the examination of milk and dairy products in the markets. The sale of milk and dairy products that have not passed the examination in the market laboratory is prohibited (with the exception of state trade). Milk and dairy products are not accepted for assessment without veterinary medical certificates delivered in galvanized and dirty containers.

Samples for research are taken from different layers of the product: milk for a complete study 250_ml (only acidity - 50 ml), butter 10 g, cottage cheese and feta cheese 20_g, curdled milk, boiled milk, fermented baked milk and other fermented milk products 50 ml, sour cream and cream 15 g. samples of milk and dairy products after the study are denatured with surrogate coffee with subsequent disposal in the laboratory of veterinary and sanitary examination.

Milk and dairy products from farms that are free from contagious animal diseases are allowed to be sold at markets. This is confirmed by a certificate issued by a veterinarian (paramedic) for a period not exceeding 1 month. Cow's, sheep's and goat's milk must be not lower than group II in terms of purity and not lower than class II in terms of bacterial contamination, mare's milk - not lower than group I in purity and not lower than class II in terms of bacterial contamination.

In the certificate, the veterinary specialist serving the household (settlement) indicates the date of the examination for latent mastitis, vaccinations against anthrax, examinations for tuberculosis, brucellosis and other diseases provided for by the current instructions. Do not allow for sale milk and dairy products derived from it in the first 7 days after that do not meet the requirements for physical and chemical indicators (density, acidity, fat content, bacterial and mechanical purity), as well as in the presence of neutralizing and preservative substances or foreign odor (petroleum products , onions, garlic, wormwood, etc.), residual amounts of chemical plant and animal protection products, antibiotics and in cases of falsification (milk - fat removal, addition of water, starch, soda and other impurities; sour cream and cream - impurities of cottage cheese, starch, flour, yogurt, butter - impurities of milk, cottage cheese, lard, cheese, boiled potatoes, vegetable fats, cottage cheese, Varenets, matsoni, fermented baked milk, yogurt and other fermented milk products - skim cream, an admixture of soda, etc.).

Cow's milk should be homogeneous in consistency, white or slightly yellow in color, without sediment and flakes, with a specific milky taste and smell, without pronounced flavors and odors unusual for milk. Fat content in milk is not less than 3.2%, density is 1.027-1.033 g/cm 3 , acidity is 16-20 T. It is forbidden to sell milk with acidity below 16 T. If the latter is due to feed factors, then after establishing the reasons for its decrease, milk is allowed for sale as an exception.

Goat's milk is organoleptically close to cow's. It is allowed to sell with a weak specific odor, a fat content of at least 4.4%, a density of 1.027-1.038 g / cm 3, an acidity of not more than 15 T. for purity, density, acidity. In the warm season, 2 hours after being released for sale or at the request of the buyer, the milk is checked for acidity again.

Bacterial contamination and fat content are determined once a month with the systematic sale of milk from the same cow and at least 1 time in 10 days of milk coming from farms.

Milk delivered for sale is initially tested for fat content. When re-delivering milk in large lots (more than ten places), the fat content is determined selectively, but not less than 10% of the total number of places, and in doubtful cases - from each container. If it is suspected that milk obtained from cows that react positively to brucellosis has been submitted for examination, a ring sample is put. Upon receipt of a positive or questionable reaction, the milk is destroyed under the supervision of a veterinarian in the presence of the owner, which is documented in 2 copies, which is kept in the files of the veterinary service. In necessary cases, milk is additionally examined for the content of staphylococcal toxin, for falsification. To test milk and dairy products for pesticides and antibiotics, samples are sent to veterinary laboratories.

Cream, sour cream are examined organoleptically (appearance, texture, taste and smell) and for the admixture of cottage cheese. The fat content, acidity and starch impurity are determined selectively.

Cottage cheese is checked organoleptically and for acidity, and, if necessary, for fat and moisture content.

Ryazhenka, varenets, matsoni, yogurt and other whole-milk products are checked organoleptically, selectively - for acidity and fat content.

Butter and ghee are checked organoleptically, and, if necessary, the content of moisture, fat, concentration of table salt and the presence of impurities (vegetable oil, cottage cheese) are determined.

Bryndza and cheese are checked organoleptically, and if necessary - for the content of fat, salt and moisture.

Koumiss is examined organoleptically, for fat content and acidity. On the container with milk and dairy products, after the examination, there must be a label of the established sample.

Organoleptic research. Determine the color, texture, smell and taste of milk. The color of milk poured into a colorless glass cylinder is determined by reflected daylight. The consistency is determined by slowly pouring milk in a thin stream along the wall of the cylinder. In the trickle and the trace left after it on the glass, it is easy to establish not only the consistency, but also the presence of flakes, impurities, colostrum, etc. The smell is checked in a ventilated room at room temperature at the time of opening the vessel or when pouring milk. The smell is captured better if the milk is preheated to 40-50 ° C. The taste of raw milk is determined if it is obtained from a known healthy animal. During the veterinary and sanitary examination of milk in the markets, the taste is established only after it is boiled, wetting the surface of the tongue with it.

Determination of milk density (GOST 3625-71). It is determined using a hydrometer (lactodensimeter).

Analysis. 150-200 ml of thoroughly mixed milk (temperature 17-23 ° C) is drunk into the cylinder along the wall and the dry and clean hydrometer is slowly immersed, avoiding its contact with the walls. After 1-2 minutes, readings are made on the scales of the thermometer and hydrometer with an accuracy of half the minimum "division. If the temperature of the milk is 20 ° C, then the hydrometer readings correspond to the true density. If the temperature of the milk during the analysis was above or below 20 "C, then density is determined according to a special table (Table 2) or using a correction of 0.2 ° A for each degree difference in temperature. If the temperature is above 20 ° C, then the correction is added to the hydrometer readings, if it is lower, it is subtracted. For example, at a milk temperature of 18 ° C, the hydrometer shows a density of 30 ° A (1.030 g / cm 3). In this case, the temperature difference is: 20-18 = 2, and the correction value is 20.2 = 0.4°A. Therefore, the density of milk, reduced to 20 ° C, is 29.6 ° A (30-0.4), which corresponds to the true density of 1030.4 g / cm 3.

The accuracy of determining the density of milk depends on a number of factors: too low or high temperature of the milk, its poor mixing before testing, a dirty hydrometer or it comes into contact with the walls of the cylinder. An objective assessment of the density of milk is possible only if it is previously known for natural milk obtained on the farm during a given lactation period, under existing conditions of feeding and keeping.

Determination of fat content in milk (GOST 5867 - 69)

Analysis. 10 ml of sulfuric acid are introduced into clean numbered and installed in a tripod butyrometers, strictly following the sequence, with an automatic pipette, 10.77 ml of well-mixed milk is added with a special pipette, pouring it along the wall of the butyrometer and avoiding mixing with acid. The pipette is kept with its tip pressed against the wall of the butyrometer after the milk has drained for another 5-7 s. Do not blow or shake off the remaining milk from the pipette. Then, 1 ml of isoamyl alcohol is added with an automatic pipette and the butyrometer is tightly closed with a dry rubber stopper, holding it only by the expanded part, after wrapping the device in a napkin or towel. The butyrometer with the contents is shaken, turned over several times until the proteins are completely dissolved, then placed with the stopper down in a water bath at a temperature of 65 ± 2 °C for 5 minutes. Putting the butyrometers in the centrifuge cartridges (with the stopper to the periphery), they centrifuge for 5 minutes at a rotation speed of at least 1000 min -1, after which they put them in a water bath at 65 ± 2 ° C for 5 minutes, which is very important, since the scale of the device is designed for this temperature. With the help of helical movements of the cork, a column of fat is set on the divisions of the scale and the percentage of fat is counted from the lower meniscus. The interface between fat and acid should be clear, and the column of fat should be transparent. In the presence of a brown or dark yellow ring (plug), as well as various impurities in the fat column, the analysis is repeated. Fat in milk should be determined in parallel in two or three butyrometers. Differences in the results of parallel determinations of fat should not exceed 0.1% (one small division of the butyrometer).

The arithmetic mean of parallel determinations is taken as the final result. When performing analyzes, safety regulations must be observed. The accuracy of the analysis is affected by violation of the rules for sampling and storage of milk, calibration errors of the butyrometer and milk pipette, poor-quality reagents, insufficient temperature of the water bath or low speed of the centrifuge.

Determination of milk purity (GOST 8218-56). Determined using the device "Record". It is a cylinder without a bottom, narrowed down. The diameter of the narrowed part of the vessel is 27-30 mm. In this part, a grid is fixed, on which special cotton or flannel filters are placed.

Analysis. 250 ml of well-mixed, better heated to 40 ° C milk is poured into the vessel and passed through the filter. After that, the filter is removed and placed on a sheet of paper, slightly dried and compared with the standard, setting the purity group. in milk

Group I mechanical impurities are not detected (the filter is clean),

Group II - sediment is hardly noticeable on the filter, group III - register the sediment of mechanical impurities.

Determination of the acidity of milk. Determined in degrees Turner (T). In practice, a standard method or method for determining the limiting acidity (maximum allowable) is used.

Standard method (titrametric, arbitration), GOST 3624-67.

Analysis. 10 ml of milk and 20 ml of distilled water are poured into a conical flask, then 2-3 drops of a 1% solution of phenolphthalein are added. The mixture is thoroughly mixed and titrated with 0.1 N. sodium (potassium) hydroxide solution until a pale pink color appears, which does not disappear within a minute and corresponds to a color control standard prepared from a solution of cobalt sulfate. The number of milliliters of alkali spent on titration is multiplied by 10 (the amount of milk is brought to 100 ml) and the acidity of the milk is found in Turner degrees. To prepare a control color standard, 10 ml of milk and 1 ml of 2.5% cobalt sulfate are poured into the same conical flask. The standard is suitable for work during the day. The shelf life of the standard is extended if one drop of a 40% solution of formaldehyde (formalin) is added to it.

Determination of bacterial contamination of milk (GOST 9225-68).

Reductase test (arbitration method). The microflora of milk in the process of life secretes enzymes, including reductase, which decolorizes (restores) methylene blue. A relationship has been established between the amount of microflora and the rate of discoloration of milk with methylene blue.

Control of the naturalness of milk. When adding substances unusual for it to milk or removing components (for example, fat), it is considered falsified. To establish the nature and degree of falsification, it is important to know the physical and chemical parameters of natural milk.

Determining the addition of water. The addition of water to milk is determined by the density - its rate decreases. After adding 3% water, the density decreases by 1*A.

A more objective indicator is the amount of dry fat-free substances. It has been established that milk immediately after milking contains at least 8% of them. The amount of added water (%) is calculated by the formula B = 100, where SOMO is the dry fat-free residue of natural milk,%; SOMO 1 - dry fat-free residue of the investigated milk,%.

Determining the addition of skimmed milk (removal of fat). Set to reduce the content of fat and solids and increase the density of milk. The degree of milk skimming (%) can be calculated by the formula O = (F - F 1 / F)100, where F is the fat content in natural milk,%; W 1 - fat content in the studied milk,%.

Definition of double falsification. When milk is diluted with water and fat is removed at the same time (double falsification), the density of milk may not change. In this case, falsification is determined by the content of dry fat-free substances (less than 8%), and the amount of added water and skimmed milk (%) is calculated by the formulas: D = 100-(W 1 / W) 100, where D is the amount of added water and skimmed milk, %; W 1 - fat content in the test sample, %; W - fat content in the stall sample, %; B \u003d 100 - (COMO 1 /COMO) 100, where B is the amount of added water,%; SOMO, - dry fat-free substance in the test milk, %; SOMO - dry fat-free substance in a stall milk sample, %.

The amount of added skimmed milk (%) is determined by the formula O=D-B

where D is the amount of added water and skimmed milk,%; B is the amount of added water, %.

Determination of soda impurity (GOST 24065-80). When soda is added to milk, its reaction becomes alkaline. To determine this type of falsification, an indicator (phenolrot, rosolic acid, bromtimolblau, etc.) is added to milk, which has differences in color in acidic and alkaline environments.

1. Test with phenolrot. Pour 2 ml of milk into a test tube and add 3-4 drops of a 0.1% solution of phenolrot (the indicator is prepared in a 20% alcohol solution). In the presence of soda, the color of the milk becomes bright red. In natural milk, the color is yellow-orange.

2. Test with rosolic acid. 3-5 ml of milk is poured into a test tube and the same amount of a 0.2% alcoholic solution of rosolic acid is added. In the presence of soda, a raspberry-red color appears, in natural milk - orange.

3. Test with bromthymol blue. Pour 5 ml of milk into a test tube and carefully add 5 drops of a 0.04% alcoholic solution of bromtimol blue along the wall. After 2 minutes, the color is determined at the point of contact between the indicator and milk. With a soda content of up to 0.1%, a green color appears, 0.2% or more - blue-green, in natural milk - yellow or salad.

Examination of fermented milk products

The manufacture of fermented milk products is based on the fermentation of milk or cream with pure cultures of lactic acid bacteria, sometimes with the addition of yeast or acetic acid bacteria. The dairy industry produces various fermented milk products (curdled milk - ordinary, Mechnikovskaya, acidophilic, Southern; fermented baked milk; varenets; kefir; acidophilic milk; acidophilus; acidophilic-yeast milk; yogurt; koumiss; Yuzhny and Snezhok drinks; cottage cheese; sour cream, etc.).

Depending on the biochemical processes, there are products of fermentation (curdled milk, cottage cheese, acidophilic milk, sour cream, etc.) and alcohol (koumiss, kefir, acidophilic yeast milk, etc.).

Taking an average sample. The fermented milk product is thoroughly mixed. For all products take an average sample (50 ml). The exceptions are sour cream (cream) - 15 g and cottage cheese - 20 g. In all cases, fermented milk products are examined organoleptically and selectively determine the fat content, acidity. If necessary, they examine for falsification and control the mode (pasteurization or boiling).

Products are examined no later than 4 hours after taking average samples. If the product contains a lot of carbon dioxide and has a pronounced ability to foam (koumiss, kefir, etc.), then it is examined after removal of CO 2 by heating at 40-45 ° C for 10 minutes and subsequent cooling to 18-20 ° C.

Organoleptic research. The color is determined in a clean colorless glass beaker. It depends on the type of dairy product. For some products, milky white (curdled milk, yogurt, matsoni, sour cream, cream, cottage cheese) or with a brownish (creamy) tint (varenets). The consistency (and appearance) is homogeneous, moderately thick, stable, without surface damage, without gas formation pores. There may be a slight separation of whey on the surface (no more than 5% of whey to the total volume of the product is allowed). Matsoni and fermented baked milk should have a slightly viscous clot, yogurt should be viscous (reminiscent of sour cream). For Varents, the presence of milk films is allowed. Koumiss is a homogeneous liquid, foaming with gas formation. Sour cream is moderately thick, without grains of fat and protein (cottage cheese). Cottage cheese is a homogeneous mass, without lumps, non-friable and not coarse. The taste and smell of benign products are sour-milk, without foreign tastes and odors. Fermented milk products that are insipid, swollen, excessively acidic, with gas formation, in the presence of a pronounced foreign smell or taste, with a sour (bitter) taste, unusual color, loose, with mold on the surface and with whey excretion of more than 5% of the total are not allowed to be sold. product volume. Mild defects are allowed in sour cream and cream of the first grade and cottage cheese: aftertastes of fodder origin, wooden containers or slight bitterness.

Determination of fat content in sour cream (cream). To do this, use special creamy butyrometers (GOST 1963-74) with measurement limits from 0 to 40%, with a minimum division value of 0.5%.

Analysis. 3-4 creamy butyrometers are installed (hung) on ​​the scales and balanced. Then, a weight of 5 g is placed on one cup, and 5 g of sour cream (cream) is added with a pipette to the butyrometer fixed on the other cup. Pre-sour cream is heated to 40-45 ° C, so that its consistency becomes liquid. Then the weight is removed, sour cream is poured into the butyrometer until it is balanced (which corresponds to 5 g) and this is repeated until all butyrometers are filled. Then 5 ml of water, 10 ml of sulfuric acid, 1 ml of isoamyl alcohol are added to the butyrometer.

Butyrometers are placed in a water bath at 65 ± 2 °C for 5 minutes, then centrifuged for 5 minutes and again placed in a water bath for 5 minutes, after which the percentage of fat on the scale is set on the lower meniscus. The discrepancy between the results in parallel butyrometers should not exceed 0.5%. If sour cream or cream contains more than 40% fat, then 2.5 g of sour cream is taken, 7.5 ml of water, 10 ml of sulfuric acid are added, and then, as indicated above. In this case, the percentage of fat in sour cream is calculated by multiplying by 2 the readings of the butyrometer.

Determination of the acidity of fermented milk products. The acidity of dairy products, like milk, is determined in conventional units - Turner degrees (GOST 3624-67).

Analysis. In a flask or glass of 100-150 ml, pipette 10 ml of the studied fermented milk product (except cottage cheese). The remains of the product on the walls of the pipette are washed off with 20 ml of distilled water, 3 drops of a 1% solution of phenolphthalein are added to the vessel and titrated with 0.1 N. alkali solution until a pale pink color appears, which does not disappear within 1 min. The amount of alkali used for titration is multiplied by 10 in terms of 100 ml of product.

Determination of the acidity of cottage cheese and fermented milk products of a thick consistency.

Analysis. Weigh 5 g of cottage cheese or a fermented milk product into a porcelain mortar, add 50 ml of water at a temperature of 30-40 ° C and grind with a pestle until a homogeneous mass is obtained. Then add 3 drops of a 1% solution of phenolphthalein and titrate with 0.1 N. alkali solution, stirring and rubbing the contents with a pestle until a pale pink color appears, which does not disappear within 2 minutes. The amount of alkali used for titration is multiplied by 20 (the mass of cottage cheese is brought to 100 g), the resulting value is an indicator of the acidity of the cottage cheese. The discrepancies between parallel definitions should not exceed 4 T. Permissible norms of quality indicators of fermented milk products in the conditions of the laboratory of veterinary and sanitary examination of the market are indicated in the table.

Quality indicators of fermented milk products

Product name Fat content, % Acidity, °T Density, g/cm 3

Cow's milk not less than 3.2 16 - 20 1.027 - 1.035

Goat milk not less than 4.4 not more than 15 1.027 – 1.038

Sour cream at least 25 60 - 100

Cream at least 20 17 - 18

Bold cottage cheese - 9; no more than 240 bold - up to 80%

fatty - 18 no more than 240 fatty - up to 20%

Varenets not less than 2.8 75 - 120

Ryazhenka at least 2.8 85 - 150

Yoghurt at least 6 80 - 140

Butter not less than 78 moisture up to 20% salt - up to 1.5%

Definition of falsification of sour cream and cream. Sour cream is falsified by adding small grated cottage cheese, yogurt, kefir, and starch.

Determination of impurities of cottage cheese or curdled milk.

Analysis. Add a tablespoon of sour cream to a glass of hot water. In the presence of falsification, fat floats to the surface, and casein of cottage cheese or curdled milk and other impurities settles to the bottom. Sour cream should not have sediment or, as an exception, only traces of it are allowed.

Determination of starch impurities.

Analysis. Add 5 ml of sour cream to the test tube, add 2-3 drops of Lugol's solution. Shake the contents of the tube. The appearance of a blue color indicates the presence of starch in the product.

Milk as one of the most valuable food products of animal origin, as well as dairy products, can be the cause of both food poisoning and toxicosis of bacterial etiology in humans. This is observed in cases where various serotypes of Salmonella, botulinus, pathogenic staphylococci with enterotoxic properties, and conditionally pathogenic microflora get into milk or dairy products. In addition, raw milk containing pathogens of brucellosis, tuberculosis, foot-and-mouth disease and other diseases can become a source of the spread of anthropozoonotic diseases.

Everybody cases the occurrence of food poisoning and toxicosis in humans and diseases among animals are investigated by specialists. At the same time, the sources of the disease, the compliance of products with veterinary, sanitary and technological regulatory requirements are established, and the perpetrators are held accountable.

Primary requirements to milk quality. The following requirements are imposed on cow's milk when harvesting according to TU RB 00028493.380-98: it must be whole, fresh and comply with the requirements of sanitary and veterinary rules for dairy farms of collective farms and state farms.

Milk should be clean, without extraneous, uncharacteristic tastes and odors. In appearance and consistency, it is a homogeneous liquid from white to light yellow in color, without precipitation and flakes, with a density of at least 1027 kg / m3 (highest grade - 1028).

Varietal milk has an acidity of 16 - 20 o T ", the degree of purity according to the standard is not lower than the second group and the bacterial contamination according to the reductase test: 3x10 5, 5x10 5, 4x10 6 _ (according to the variety)). It is forbidden to use for food purposes milk with the addition of neutralizing and preservative substances, a residual amount of plant and animal protection chemicals and antibiotics, with a density below 1027 kg / m3, as well as with a pronounced smell and fodder flavor of onion, garlic and wormwood. Therefore, when determining the grade of milk, along with its organoleptic assessment, density, acidity, mechanical contamination, fat content are determined, and once a decade, bacterial contamination of milk is checked using a reductase test.

In the markets, according to the rules of veterinary and sanitary examination of milk and dairy products, approved by the GUV of the Ministry of Agriculture of the USSR on 1. 07. 1976, milk and dairy products from farms that are free from contagious animal diseases are allowed for sale. This is confirmed by a certificate issued by a veterinarian (paramedic) for up to three months. It indicates the dates of the study for subclinical mastitis, tuberculosis, brucellosis and other diseases, vaccinations against anthrax provided for by the current instructions.

In the markets, milk can be sold by persons who have personal sanitary medical books or certificates of medical examinations established for employees of food enterprises. Milk and dairy products with the smell of petroleum products, onions, garlic, the addition of neutralizing and preservative substances, residual amounts of plant and animal protection chemicals, antibiotics, as well as those that do not meet the established requirements for physical and chemical indicators (density, fat content, acidity) and bacterial contamination.

Bacterial contamination, acidity and fat content of milk are determined once a month when it is systematically sold by citizens and at least once every 10 days when sold by collective farms and state farms.

It is prohibited to sell counterfeit milk and dairy products: for milk - fat removal, addition of water, starch, soda; sour cream and cream - an admixture of cottage cheese, starch, flour, kefir; oils - an admixture of milk, cottage cheese, cheese, boiled potatoes, vegetable fats; for fermented milk products - cream removal. To detect adulteration of milk and dairy products, special research methods are used.

Determination of fat in milk is performed by the acid method. In a clean butyrometer, without wetting the neck, pour 10 cm3 of sulfuric acid (density 1.81 - 1.82), add 10.77 cm3 of milk and 1 cm3 of isoamyl alcohol (density 0.810 - 0.813) with a pipette, close with a dry rubber stopper and the contents are mixed until complete dissolution of the protein. After that, the butyrometer is placed with the stopper down for 5 minutes in a water bath (temperature 65 ° C), and then centrifuged for 5 minutes at a speed of 1000 rpm. Then, by moving the cork up and down, the lower limit of the fat column is set on the whole division of the scale and the number of divisions from the lower level of the meniscus is counted from it.

The density of milk is determined to confirm its naturalness or to detect the addition of water to milk. Under the density of milk, it is customary to understand the ratio of the mass of milk of a certain volume, taken at a temperature of 20 ° C, to the mass of water in the same volume, taken at a temperature of 4 ° C. The density of natural cow's milk ranges from 1027 to 1033. It is determined no earlier than after 2 hours after receiving and filtering milk at a temperature of 15 - 25 ° C, and take into account at a temperature of 20 ° C,

Definition technique. 200 cm3 of milk is poured into a glass cylinder with a capacity of 250 cm3 (ml) without foaming and the hydrometer is lowered so that it does not touch the walls of the cylinder. After 1 - 2 minutes, the readings of the hydrometer scale and milk temperature are read using the thermometer of the hydrometer.

If the temperature of the milk is above or below 20 ° C, then an adjustment is made equal to 0.0002 for each degree. At a milk temperature above 20 ° C, the correction is multiplied by the temperature difference and the product is added to the hydrometer density reading. At temperatures below 20 "C, the product is subtracted from the hydrometer reading.

The density of milk is determined to reveal the addition of water to it. It has been established that the addition of 10% water to milk reduces its density by 3 o hydrometers. The last two digits of the milk density index according to the hydrometer are usually called hydrometer degrees and denoted by the letter A.

Example. If 10% water is added to milk with a density of 1027 hydrometers or 27 hydrometers, then its density will be equal. (27 o - 3 o) 24 o hydrometer or 1024 hydrometer density indicators.

Determination of mechanical contamination. Mechanical contamination of milk is determined using the Record device and cotton filters with a diameter of 27–30 mm. Before filtering, 250 cm3 of milk is thoroughly mixed, heated to a temperature of 35 - 40 ° C and filtered. After filtering, the filter is removed, placed on a white sheet of paper and compared with a standard standard indicating the milk group by contamination (GOST 8218 - 89).

If there are no particles of mechanical impurities on the filter, then milk is referred to the first group by purity; if there are individual particles of mechanical impurities - to the second, and if there is a noticeable sediment of large particles of mechanical impurities on the filter - to the third group.

Determination of soda in milk. Soda is added to milk to neutralize acidity, and the development of microbes in such milk does not stop and it can acquire undesirable qualities during storage.

Definition technique. The same amount of 0.2% alcohol solution of rosolic acid is added to 2-3 ml of the test milk in a test tube. The contents are mixed and the reaction is taken into account. In the presence of soda, milk acquires a raspberry-red color, and without soda - orange,

Determination of starch in milk, sour cream and sour cream. Starch paste is added to milk to increase its density, and according to organoleptic characteristics to make milk thicker, in order to hide falsification.

Definition technique. Add 3-5 drops of Lugol's solution to 3 - 5 ml of milk in a test tube, mix and take into account the reaction. In the presence of starch or flour in milk, a blue color appears, and in the absence of them, it does not change.

Determination in sour cream and cream with the admixture of cottage cheese, kefir. In a glass of hot water (66 - 75 ° C), stir 1 teaspoon of sour cream or cream. If cottage cheese, kefir is added to the product, then after stirring it settles to the bottom in the form of small particles, grains or flakes. Pure cream or sour cream does not give sediment. The degree of dilution of sour cream with cottage cheese and sour-milk products is also determined by the actual fat content,

Determination of the form of aldehyde in milk. To detect formaldehyde, which is added to milk during preservation of samples sent for laboratory research or for conservation of skimmed milk, a reagent is prepared consisting of 100 ml of concentrated sulfuric acid and one drop of nitric acid (specific gravity 1.30).

Take 3 cm3 of this reagent into a test tube and carefully layer 3 cm3 of the test milk. In the presence of formalin in milk, after 1–2 minutes, a violet or dark blue ring appears on a yellow background at the place of contact of the reagent with milk. In the absence of formalin in milk, a ring of only a yellowish-brown color appears at the point of contact of these liquids.

Determination of two chromium salts. In a test tube, 3 cm3 of milk is added to 3 cm3 of a 2% solution of silver nitrate, mixed and the reaction is taken into account. In the presence of dichromate salt in milk, the mixture acquires a yellow or reddish-yellow color, and in the absence of it, the color does not change.

Identification of antibio tics in milk. According to domestic and foreign researchers, the use of milk containing antibiotics is dangerous for the health of the consumer and unsuitable for the manufacture of fermented milk products. In accordance with the current TU RB, cow's milk containing antibiotics is not accepted by procurement organizations.

The presence of antibiotics in milk is detected by indication methods based on the suppression of the reproduction of microbial cells and their enzymatic activity in the presence of indicators (resazurin or methylene blue). Thermophilic streptococcus sensitive to antibiotics is used as a test microbe.

Test with methylene blue. Into a sterile test tube add 10 cm3 of the milk under study, 3-4 drops of a fresh test culture of thermophilic streptococcus prepared in skim milk, and 1 cm3 of a working solution of methylene blue (5 cm3 of a saturated alcohol solution of methylene blue in 195 cm3 of distilled water) . Add 10 ml of milk known to be free from antibiotics, 3-4 drops of thermophilic streptococcus culture and 1 ml of methylene blue solution to the control tube. The contents of the test tubes are thoroughly mixed, incubated for 5.5 hours in a water bath at a temperature of 38-40 ° C and the reaction is taken into account. In the presence of an antibiotic in the test milk, thermophilic streptococcus does not. multiplies, the indicator will not recover, the color of the milk will be blue. In the control tube, thermophilic streptococcus will multiply, the indicator will be restored and the milk will become discolored.

Resazurin test. In a test tube, to 10 cm3 of the milk under study, add 1 cm3 of a 0.005% aqueous solution of resazurin and 3 - 4 drops of thermophilic streptococcus. Take 10 ml of milk known to be free from antibiotics, 1 ml of resazurin solution and 3-4 drops of thermophilic streptococcus into a control tube. The tubes are kept for 45 minutes in a water bath and the reaction is taken into account. In the presence of antibiotics, the milk turns steel blue or violet-pink.

Determination of hexachlorane in milk (according to I. N. Gladenko, cited by V. P. Obraztsov, 1986). Introduce into a test tube with a stopper 2 g cream and add 10 - 15 cm3 of solvent (chloroform or benzene), stand for 20 - 30 minutes. Then, 10–15 ml of purified concentrated sulfuric acid is added to the same test tube, mixed without foam formation, and 2–3 g of anhydrous sodium sulfate are added in small portions. The contents of the test tube are allowed to stand until the solvent is completely separated, then the solvent is re-treated with a mixture of concentrated sulfuric acid (1: 1). The acid separated from the solvent is removed, and his treated twice with a 0.5% solution of sodium carbonate, poured into an open bacteriological cup and kept until the solvent has completely evaporated.

20 - 30 flies are planted on the remaining sediment in a bacteriological dish, covered with gauze and transferred under a glass cap. In the presence of hexachloran, after 1; 2; Paralysis of insects is observed at 4 and 6 o'clock.