Thermal inactivation of Bacillus cereus spores formed at different temperatures

The effects of the sporulation temperature in the range 20–45°C on the D and z values of three isolates of Bacillus cereus (ATCC 4342, 7004 and 9818) were investigated. The strains were found to differ in their response. Higher D100 values (around 10-fold) were obtained with isolates 4342 and 9818 when the sporulation temperature increased from 20 to 45°C. With isolate 7004 (the least heat resistant of the three strains), however, the most thermal tolerant spores were obtained at 35°C. The z values were not significantly modified (P>0.05) by the sporulation temperature. Mean z values of 7.46±0.22°C for isolate 4342, 7.80±0.40°C for 7004 and 8.09±0.33°C for 9818 were obtained.