Control of Enterotoxic Bacillus cereus on Poultry or Red Meats and in Beef Gravy by Gamma Irradiation

The gamma-radiation resistance of five enterotoxic and one emetic isolate of Bacillus cereus vegetative cells and endospores was tested in mechanically deboned chicken meat (MDCM), ground turkey breast, ground beef round, ground pork loin and beef gravy. The D₁₀ values for B. cereus ATCC 33018 were 0.184, 0.431 and 2.56 kGy for logarithmic-phase cells, stationary-phase cells, and endospores at 5°C on MDCM, respectively. Neither the presence nor absence of air during irradiation significantly affected radiation resistance of vegetative cells or endospores of B. cereus ATCC 33018 when present on MDCM. Irradiation temperature (-20 to +20°C) did affect the radiation resistance of stationary-phase vegetative cells and to a limited extent that of spores on MDCM. Impedance studies indicated that surviving vegetative cells were severely injured by radiation. A dose of 7.5 kGy at 5°C was required to eliminate a challenge of 4.6 × 10³ B. cereus ATCC 33018 from temperature-abused MDCM (24 h at 30°C). The radiation resistance of a mixture of endospores of six strains to gamma radiation was 2.78 kGy in ground beef round, ground pork loin and beef gravy, but 1.91 kGy in turkey and MDCM. The results indicate that irradiation of meat or poultry can provide significant protection from vegetative cells but not from endospores of B. cereus .