Using the Streptococcus thermophilus culture to determine the residual content of inhibitory substances in milk
The use of milk containing inhibitors in its composition, due to the suppression of the growth of lactic acid microflora, leads to a strong proliferation of gram-negative bacteria and, ultimately, the development of non-standard fermented dairy products. Of the inhibitors present in the harvested milk, special importance is attached to antibiotics. Along with the noted production difficulties associated with the ingestion of antibiotics in milk, there may also be undesirable consequences for the health of consumers: the possibility of allergies, the appearance of antibiotic-resistant opportunistic or pathogenic microorganisms, the development of dysbacteriosis. This article is devoted to the problem of determining the residual amounts of inhibitory substances in milk and using the microbiological method of reductase testing based on the discoloration of the methylene blue dye in the presence of Streptococcus thermophilus bacterial products to assess the quality of milk from various producers purchased in the retail network of the city of Orenburg. The study revealed that out of 30 milk samples, 53.3 % did not contain antibiotics, 33.3 % probably contained small amounts of inhibitory substances in the milk, and 13.3 % contained inhibitory substances. This method, due to its cheapness and speed, can be recommended for practical use on dairy farms and dairy processing plants.