[Antibacterial activity of milk-fermenting bacteria]

Factors influencing salmonella survival in fermented milk products were investigated. Filtrates of yoghurt and cream cultures and a filtrate from milk precipitated by lactic acid were inoculated by salmonellas. The pH value was adjusted within the range of 7.0 to 4.5. The content of nondissociated lactic acid was determined. The filtrates were incubated 24 and 48 hours at a temperature of 37 degrees C. In comparison with the milk filtrate, great inhibitory (at pH 6.5) and bactericidal (at pH 5.5) effects of the yoghurt culture on salmonellas were proved. The filtrate from the cream culture inactivated salmonellas at pH 4.5, the growth ceased at pH 5.5. The effects of lactic and acetic acids on salmonellas at a concentration of 0.5% and pH 3.3, and acetic acid at a concentration of 0.05% and pH 5.1 were also studied.