Expansion and validation of a predictive model for the growth of Bacillus stearothermophilus in military rations

Predictive models for the exponential growth rate (EGR) and germination, outgrowth, and lag times (GOL) of Bacillus stearothermophilus previously developed in our laboratory were expanded to include higher salt (1.5%) formulations. The expanded models were validated in 7 military meals-ready-to-eat incubated at temperatures from 45 degreesC to 60 degreesC, and tryptic soy broth incubated from 37.5 degreesC to 70 degreesC. The 95% prediction intervals for EGR were fail-safe in all the military rations tested. The 95% prediction intervals for GOL were fail-safe in 5 of the 7 rations. The TSB results illustrate the dangers of using empirical models to predict microbial behavior outside the range of conditions under which the models were developed.