Elimination of coliforms and Salmonella spp. in sheep meat by gamma irradiation treatment

This study aimed at evaluating the bacteriological effects of the treatment of sheep meat contaminated with total coliforms, coliforms at 45 °C and Salmonella spp. by using irradiation at doses of 3 kGy and 5 kGy. Thirty sheep meat samples were collected from animals located in Rio de Janeiro State, Brazil, and then grouped in three lots including 10 samples: non-irradiated (control); irradiated with 3 kGy; and irradiated with 5 kGy. Exposure to gamma radiation in a 137Cs source-driven irradiating facility was perfomed at the Nuclear Defense Section of the Brazilian Army Technological Center (CTEx) in Rio de Janeiro. The samples were kept under freezing temperature (-18 °C) until the analyses, which occurred in two and four months after irradiation. The results were interpreted by comparison with the standards of the current legislation and demonstrated that non-irradiated samples were outside the parameters established by law for all groups of bacteria studied. Gamma irradiation was effective in inactivating those microorganisms at both doses tested and the optimal dose was achieved at 3 kGy. The results have shown not only the need for sanitary conditions improvements in slaughter and processing of sheep meat but also the irradiation effectiveness to eliminate coliform bacteria and Salmonella spp.