Response-surface methodologies were used to examine the effects of gamma-irradiation temperature and dose preceded or followed by heating at 60°C for 3 min on the survival of Salmonella typhimurium in mechanically deboned chicken meat (MDCM). The effects of irradiation temperature and dose were significant. Heating the inoculated chicken meat before irradiation did not sensitize the bacteria to the effects of the ionizing radiation. Treating the inoculated chicken meat with gamma radiation made the Salmonella much more sensitive to the effects of heat. For example, 3 min of heat at 60°C followed by a radiation dose of 0.90 kGy at 0°C decreased the number of survivors by 6.4-log units; when the irradiation occurred prior to heating, the decrease was 8.9-log units. Independent studies revealed that the effect of cooking was directly dependent upon the irradiation dose regardless of the order in which the heat and radiation treatments were applied. The effect of irradiation on the survival of the Salmonella was not dependent on the amount of heat applied regardless of the order in which the treatments were applied. There was no evidence of a gamma-radiation, dose-dependent decrease in the thermal D10 value at 60°C of S. typhimurium in MDCM. The increased gamma-radiation, dose-dependent sensitivity of irradiated Salmonella in MDCM to heat did not change even when the irradiated meat was stored for periods of up to 6 weeks at 5°C prior to heating.
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