THE PRESENCE AND GROWTH OF YERSINIA ENTEROCOLITICA IN YOGURT PRODUCED WITH DIFFERENT HEAT TREATMENT

In this study, Yersinia enterocolitica (0:3 P41797) was inoculated in three different milk groups (A, B, C) about 2xl07 cfu/ml. Group A treated with heat method before inoculation, group B treated with heal method after inoculation and group C heated with microwave technique before inoculation. These three groups were fermented with Streptococcus thermophiius and Lactobacillus bulgaricus; and stored 5 ±1°C for 7 days. The count of Yersinia enterocolitica and pH value were determined every 24 hours. At the beginning, the pH value of these groups was 6.4. At the end of the 7th day, this value decreased to 4.1, 4.0,4.1. During the storage Y. enterocolitica could not be found in the group A and group C. But, Y. enterocolitica was isolated from the group B at the 1th day 2x 106 cfu/ml, 2nd day 2x 105 cfu/ml. 3rd day Ix 104 cfu/ml. 4'h day 2x I03 cfu/ml, 5th day 4x I02 cfu/ml,  6lh day 1x 102 cfu/ml, in this group, Y. enterocolitica could not isolated at the 7th day.