[Yersinia enterocolitica survival in Bulgarian yogurt and Vita yogurt (experimental studies)]

Laboratory studies were carried out on the development and survival of Y. enterocolitica in Bulgarian sour milk and sour milk 'Vita'. The raw cow milk was contaminated with various amounts of Y. enterocolitica cells. Results showed that the development and survival of the organism in the sour milk was dependent on its count in the raw milk and the running of the process of lactic acid fermentation. Under refrigerator conditions (Bulgarian sour milk contaminated at the rate of 10(4) microbial cells per cm3) Y. enterocolitica retained its viability up to the 24 th hour. When contamination reached 10(5) and 10(5) cells per cm3 the viability of the organism lasted up to 72 hours. Sour milk 'Vita' with a starter of strain of Lb. bulgaricus, producing D (-) lactic acid, possessed stronger inhibitory action on Y. enterocolitica compared with milk with a starter of strain of Lb. bulgaricus, producing L (+) actic acid.