Thirty eight block samples of minced meat "Kobeba" were divided into three groups to study the effect of different cooking methods (18 samples), nisin (15 samples) and lactic acid cultures (5 samples) on survival of E. coliO157:H7 inoculated into these samples at dose 106 /CFU.The counts of the organism were sharply decreased to 1.25X102 ±0.16X102, 1.43X102 ±0.20X102 and 2.72X102±0.46X102 /g. after 5 ,4 and 2 minutes of boiling, roasting and frying, respectively. Furthermore the frying method had a significant influence on viability of E. coliO157:H7 as compared with the other cooking methods. On the other side, addition of nisin at doses of 10, 25 and 40 ppm decreased the counts of E. coli O157:H7 to 3.54X104±0.45X104, 1.83X103±0.14X103 and 4.83X102±0.42X102 /g. after 18 hours, respectively. Accurately, nisin at doses of 25 and 40 ppm destroyed E. coliO157:H7 after 30 and 24 hours, respectively, while nisin at dose 10 ppm did not destroy all numbers of the organism . Significant differences appeared in E. coliO157:H7 counts as a result of using of nisin at different doses (P≤0.05). Concerning addition of lactic acid cultures, there is a direct relationship between the pH values of inoculated minced meat and the counts of E. coliO157:H7. The mean values of E. coliO157:H7 were 8.59X102±1.36X102 and 1.20X102±0.11X102/g. at pH values of 4.92±0.10 and 4.86±0.13 after 12 and 16 hours, respectively. However, complete destruction of E. coliO157:H7 was occurred after 20 hours at pH value 4.45±0.12. Generally, selection of the accurate time of each cooking method, the best dose of nisin and the effective pH value to control such serious pathogen were discussed. |
