Validation of a model describing the effects of temperature and water activity on the growth of psychrotrophic pseudomonads

The reliability of the predictive model for the growth of psychrotrophic pseudomonads was evaluated both under controlled laboratory conditions and in industry conditions using various milks, milk-based products, meat and meat products. The validation process involved monitoring the growth of pseudomonads at various temperatures and comparing the observed generation times to those predicted by the model using bias and accuracy factors. For fluctuating temperatures bias and accuracy factors were used to compare the predicted and observed times to reach various population densities. The psychrotrophic pseudomonad model was shown to predict accurately the growth of pseudomonads in the products tested. In some instances knowledge of the lag phase duration was required to maximise the performance of the model.