Survival of listeria monocytogenes and yersinia enterocolitica in yoghurt

ABSTRACT

For experimental studying of the effect of yoghurt processing and cold storage temperature on survival of food borne pathogens, 2 reference strains of Listeria monocytogenes [F5027] and Yersinia enterocolitica [ATCC 27729] were inoculated into milk in low and high processing of yoghurt, then stored at 4C. The study proved that low and high level inoculum of both organisms slightly reduced due to increase the acidity%, while in the stored product at 4C L. monocytogenes reduced from 2.2 x 10 2 to 1.8 x 10 after 24 hours in the low inoculum, at the same time the high inoculum reduced by two log phase after two days, then completely disappeared after five days. On the other h and, the low level inoculum of Y. enterocolitica reduced to 4.8 x 10 2 starting form 3.2 x 10 3 after 12 hours, while the high level reduced form 7.2 x 10 6 to 8 x 10 2 after two days. The pH of the product during the experiment reduced from 6.3 to 4.0. The public health importance and suggestive control measures were discussed