Thermal inactivation of Bacillus cereus and Clostridium perfringens vegetative cells and spores in pork luncheon roll

Abstract

The aim of this study was to design a thermal treatment(s) for pork luncheon roll, which would destroy Bacillus cereus and Clostridium perfringens vegetative cells and spores. B. cereus and C. perfringens vegetative and spore cocktails were used to inoculate luncheon meat. Samples were subjected to different temperatures and removal times. The decimal-reduction times ( D-values) were calculated by linear regression analysis ( D=−1/slope of a plot of log surviving cells versus time). The log 10 of the resulting D-values were plotted against their corresponding temperatures to calculate (−1/slope of the curve) the thermal resistance ( z-values) of each cocktail. The D-values for vegetative cells ranged from 1 min (60 °C) to 33.2 min (50 °C) for B. cereus and from 0.9 min (65 °C) to 16.3 min (55 °C) for C. perfringens. The D-values for B. cereus spores ranged from 2.0 min (95 °C) to 32.1 min (85 °C) and from 2.2 min (100 °C) to 34.2 min (90 °C) for C. perfringens. The z-values were calculated to be 6.6 and 8.5 °C for B. cereus vegetative and spores, respectively, and 7.8 and 8.4 °C for C. perfringens vegetative cells and spores, respectively. The D-values of B. cereus and C. perfringens suggest that a mild cook of 70 °C for 12 s and 1.3 min would achieve a 6 log reduction of B. cereus and C. perfringens vegetative cells, respectively. The equivalent reduction of B. cereus and C. perfringens spores would require the pork luncheon meat to be heated for 36 s at 105 and 110 °C, respectively. The results of this study provide the thermal inactivation data necessary to design a cooking protocol for pork luncheon roll that would inactivate B. cereus and C. perfringens vegetative cells and spores. The data may also be used in future risk assessment studies.