COMPARATIVE STUDY BETWEEN THE EFFECT OF GAMMA IRRADIATION AND OZONE GAS ON THE INCIDENCE OF E. COLI O157:H7 IN BEEF BURGER SOLD IN ASSIUT GOVERNORATE

This study aimed to determine the prevalence of E. coli O157:H7 in beef burger, evaluate the effectiveness of gamma irradiation and ozone gas as an antimicrobial intervention on beef burger and evaluate the effect of both on sensory quality of the product. A total of 125 samples of beef burger were collected from different supermarkets in Assiut City, E .coli was isolated from 24 samples (19.2%), further examination using polymemerase chain reaction (PCR) revealed that only one confirmed to be E. coli O157:H7 with a percentage of 0.8%. Beef burgers inoculated with E. coli O157:H7 at initial level of 106 CFU/g were exposed to different doses of ƴ- radiation (2,4 and 6 KGy) at dose rate 2.32 KGy/h at a constant exposure time. The survival of E. coli O157:H7 was examined post treatments. Irradiation at doses (4 and 6 KGy) significantly decreased the count proportionally to the applied dose without any sensory changes. To explore the effect of ozone on E. coli O157:H7, inculcated samples of beef burger were subjected to 3 different gaseous ozone treatments, 20, 40 and 70 PPM with a time of contact of approximately 3 minutes. It was found that all concentrations significantly reduced the pathogen count without any color or flavor change of beef burger. Gamma irradiation at dose 6KGy is more effective in reduction of E. coli O157:H7 population (a reduction % of 56.o8) than ozone gas at concentration of 70 PPM (a reduction % of 21.14).The public health importance of the organism was discussed and the suggestive measures for safe healthful products were discussed.