Behavioural pattern of vegetative cells and spores of Bacillus cereus as affected by time-temperature combinations used in processing of Indian traditional foods

This study was undertaken to evaluate the behaviour of vegetative cells and spores of four potent native toxigenic food isolates of Bacillus cereus as affected by selected time-temperature combinations used in processing of Indian traditional foods. The vegetative cells of B. cereus when subjected to sublethal heat treatments, individually, in different heating menstra showed a sigmoidal inactivation pattern, with D-values in the range of 3.45 min at 60 °C to 10.6 min at 56 °C in saline. Accordingly, the z-values recorded across the heating menstra ranged from 9.3 °C in culture broth to 24 °C in whole milk. Similarly, the inactivation pattern for spores for the same isolates was curvilinear with D-values ranging from 4.4 min at 95 °C in whole milk to 19.45 min at 85 °C in saline. The z-values for spores ranged from 16.6 °C in saline to 38.4 °C in whole milk. The thermal inactivation pattern observed for vegetative cells and spores indicate that the death rate was not constant during the process of heat treatment.