Stochastic modelling of the growth of a microbial population under changing temperature regimes

The application of models of microbial growth to the design of food safety systems requires consideration of the effect of arbitrary changes in extern al variables on growth of bacteria. In particular, the effect of changes in external variables, such as temperature, on the probability that the micro bial population size will not exceed acceptable levels at a given time need s to be predicted. This paper presents a method of calculating the time-dep endent probability distribution of the microbial population size under arbi trary changes of temperature through time. To illustrate this method, the e ffect of a sudden temporary increase in temperature on the evolution of the probability distribution of Lactobacillus plantarum population size is pre sented. The effect of this change in temperature on the time taken for the population to reach a critical size, with a given probability, is also calc ulated and the application of this calculation to the design of HACCP proto cols is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.