Modeling the Listeria innocua micropopulation lag phase and its variability.

Listeria innocua micropopulation lag phase and its variability have been modeled as a function of growth temperature, intensity of heat stress, and the number of surviving cells initiating growth. Micropopulation lag phases were found to correlate negatively with inoculum size and growth temperature and positively with heat shock intensity. Validation of the models using experimental milk samples indicated that the average lag phase duration predicted is shorter and more variable than the observed, meaning that they should be considered safe for risk assessment. Our results suggest that the effect of inoculum size on the population lag phase has both stochastic and physiological components.