GAMMA-IRRADIATION AS A MEANS TO ELIMINATE LISTERIA-MONOCYTOGENES FROM FROZEN CHICKEN MEAT

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D-10, dose required for 10% survival-0.15 kGy) at 0-5 degrees C. The cells showed higher radiation survival when irradiated under frozen condition, with a D-10 of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre(-1)) was evidenced by even higher D-10 values (0.5 kGy) at both 0-5 degrees C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 x 10(3) colony-forming unit (cfu) g(-1) and high (5 x 10(6) cfu g(-1)) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2-4 degrees C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10(3) cfu cells of L monocytogenes g(-1) from air-packed frozen chicken meat.