Predictive microbiology and food safety

The evaluation of risk in food safety requires knowledge of the probability that microbial population sizes will not exceed defined levels. This proba bility is evaluated assuming that the growth of the microbial population ca n be described by the Gompertz equation with the variance of growth dependi ng on the population size. It is shown that the probability density associa ted with this phenomenon is skewed, so that the risk of a high microbial po pulation is greater than that which would be estimated using a symmetrical probability distribution such as the Gaussian. Maximum likelihood estimates of the parameters of the Gompertz equation based on the derived probabilit y density are calculated using data published by Zwietering et al. [23] for the growth of Lactobacillus plantarum under different temperatures. The pr obability that a microbial population of a given size will exceed an unacce ptable level within a given time is calculated for growth at two temperatur es, 10 and 25 degrees C. The implication of these theoretical results for t he management of risk in food safety and in the design of hazard analysis c ritical control point procedures is discussed. (C) 2000 Elsevier Science B. V. All rights reserved.