PREDICTING THERMOPHILIC SPORE POPULATION-DYNAMICS FOR UHT STERILIZATION PROCESSES

A mathematical model of Bacillus stearothermophilus spore populations during lethal heating treats activation of dormant spores and inactivation mechanisms affecting dormant/activated spores. Rate constants of activation/inactivation processes were determined from isothermal survivor curves of experiments in 105, 110, 115, and 120-degrees-C and corresponding simulations with the model. Variations of rate constants with temperature were incorporated by Arrhenius equations responding to general temperature regimes. Tests demonstrated high correspondence between experimental survivor curves and those generated by simulations with the model for isothermal and dynamic, lethal heating. Tests also indicated Arrhenius rate constants at low lethal temperatures (105-120-degrees-C) and the model may apply to ultra high temperature. The new model was more effective than the traditional model in representing and predicting spore population dynamics during lethal heating.