for bacterial contamination of raw milk

Milk and dairy products are valuable foods of animal origin. However, it should be remembered that milk obtained from sick animals can be a source of human infection with zooanthroponotic (common for humans and animals) diseases, in addition, if sanitary rules and the technology for obtaining, processing and storing are violated, milk can cause food toxicosis and toxic infections. .

The source of primary contamination of dairy products with microorganisms is raw milk.

Microbes enter the milk from the external environment through the excretory ducts, the milk cistern and the nipple canal. The nonspecific microflora of milk is made up of bacteria, yeasts, and mold fungi. The contamination of milk with microorganisms occurs already in the process of milking and its intensity depends on the level of hygiene on the farm, the quality of washing and disinfection of milking equipment. A large number of microbes are found on the surface of the skin of the animal. Microbes on the surface of the skin come from food, bedding, manure, air.

Poor milk storage conditions also contribute to the growth of microflora in it. Freshly milked, fresh milk has bactericidal properties, i.e. the ability to delay the reproduction of bacteria entering the milk and even kill them.

To preserve the bactericidal properties of fresh milk, it is cooled. At a temperature of +30°C, bactericidal activity lasts for 3 hours, at +15°C – about 8 hours, at +10°C – about 24 hours. Milk is cooled immediately after milking and stored at +2 to +6°C until dispatch. During storage, the antimicrobial properties of milk disappear, and if the storage rules are not followed, conditions are created in it for the development of undesirable microflora, as a result of which the product deteriorates.

Pathogenic microorganisms may be introduced into milk during its production and transport from the environment, or may be contained in the milk of sick animals.

Especially many different microbes are found in the milk of animals with mastitis (staphylococci, streptococci, etc.). Microorganisms can enter milk through the air and through contact with sick animals with tuberculosis, salmonellosis, etc. And therefore, along with protein, fat and acidity, bacteria content (or QMAFAnM) is one of the most important indicators of milk quality and safety.

Good milk has a correspondingly low bacteria content. However, it must be remembered that raw milk cannot have zero bacteria content. Milk is a living product that is obtained from animals, and bacteria are integral companions of any living organism, and, as a result, the products of its vital activity. Milk containing a large number of bacteria, even non-pathogenic and not changing organoleptic characteristics, cannot be considered complete. An increased bacterial contamination of the product indicates the multiplication of microorganisms, among which there may be pathogens that cause spoilage of the product. High levels of micro-organisms can also cause food poisoning with signs of diarrhea and gastroenteritis.

The requirements for raw milk in terms of bacterial contamination are established by the regulatory documents of the Russian Federation and the Technical Regulations of the Customs Union.

Bacillus contamination of milk is the quantitative content of bacteria in 1 cm³ of raw milk. Microbiological indicators of milk according to TMC (total microbial count) or QMAFAnM (the number of mesophilic aerobic and facultative anaerobic microorganisms) must comply with the requirements of the Technical Regulations of the Customs Union “On the safety of milk and dairy products” (TR CU 033/2013) dated 09.10.2013 and not exceed more than 5.0 × 10 5 (500000) CFU / cm³.

The bacterial contamination of the harvested milk is determined using a reductase test. The method is based on the fact that the reductase enzyme secreted by the microflora of milk decolorizes the methylene blue dye. A relationship has been established between the amount of microflora and the rate of discoloration of milk, to which methylene blue is added. The higher the rate of discoloration, the greater the number of microorganisms in the milk and, consequently, the worse its quality.

In a veterinary laboratory according to GOST 32901-2014 “Milk and dairy products. Methods of microbiological analysis”, to determine the bacterial contamination of raw milk as an arbitration method, the standard cup method of inoculation of certain dilutions of the original milk on a solid nutrient medium is used, followed by cultivation for 72 hours at 30 ± 1 ° C and counting the colony forming units (CFU) of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM).

Thus, the determination of QMAFAnM in milk indicates the sanitary and hygienic state of the product, the degree of its contamination with microflora, makes it possible to judge the state of health of the animal, the state of the udder, the effectiveness of washing and disinfection of equipment, the observance of sanitary and hygienic conditions of production and the rules of personal hygiene of workers, on the conditions of storage, transportation of finished products. Therefore, this indicator is normalized for all dairy products, with the exception of products produced using technically useful microflora (microflora of starter cultures).

IMPORTANT!!! 1 time in 10 days it is necessary to deliver milk to the laboratory for research!!!

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