[Development of enterococci and coli bacteria in Bulgarian yogurt].

The effect of lactic acid fermentation in Bulgarian yoghourt was studied by the development and decline of hygiene level indicating microorganisms--enterococci and coli-bacteriae. It was established that for the first 6 h after production of Bulgarian yoghourt, the quantity of enterococci (Str. faecalis, resp. Str. faecium) increases 5--6 times on the average, after the 12th hour it begins slowly to decrease and the number is reduced two times during storage for 7 days at 7--10 degrees C temperature of 6 days at 18--22 degrees C. The reduction in enterococci number is not fully correlated with the stage of lactic acid fermentation. Coli-bacteriae (E. coli) do not grow in number at the time the milk is turned into yoghourt. Their initial quantity diminishes along with the advance of the lactic acid process and after 24 h of milk storage at 18--22 degrees C or after 48 h at 7--10 degrees C they cannot be detected at all. The conclusion is drawn that enterococci are more suitable as hygiene level indicating microorganisms for hygienic evaluation of Bulgarian yoghourt, as compared to coli-bacteriae, due to their greater viability and longer survival in the product at the time of its production and during storage. It is recommended to perform the investigations on coli-forms not later than the 24th hour after yoghourt productions begins.