Purpose: The impact of environmental conditions on spore formation, resistance and inactivation upon various stresses was investigated to further optimize food formulation, industrial process and surface sanitation.
Methods: B.weihenstephanensis KBAB4, a psychrotrophic strain of B. cereus group was chosen as a model. Vegetative cells were grown in BHI broth and spore suspensions were produced in a specific synthetic medium. Survival kinetics upon various stress exposure were fitted using mathematical models to further simulate the impact of environmental conditions on spores and cells inactivation.
Results: Mathematical models describing heat resistance and spore formation as a function of the sporulation conditions were proposed. Higher spore formation and resistance were observed for conditions (temperature and pH) close to optimal growth conditions, yielding an easy screening of production steps at risk for spore contamination and germination. Moreover, acid inactivation of vegetative cells showed the presence of subpopulations with different resistance, more or less pronounced with mild stress pre-adaptation. Similarly, the impact of peracetic acid (temperature, concentration and contact time) was taken into account to further simulate spore inactivation by biocides.
Significance: While already available decision making tools enable the simulation of bacterial growth and heat destruction in food as a function of environmental conditions (pH, temperature, aw), this study proposes several models to simulate bacterial inactivation upon exposure to acid or biocide. Even though further developments are needed to validate these results in food formulations and processes, these observations could be of importance for the food industry to refine safety procedures, as the presence of subgroups with different behaviors may greatly impact the resistance of the whole population.