Development and evaluation of a predictive model for the effect of temperature and water activity on the growth rate of Vibrio parahaemolyticus

The growth rates of four strains of Vibrio parahaemolyticus were measured and compared in a model broth system. The results for the fastest growing strain, based on 77 combinations of temperature and water activity (a(w)) using NaCl as the humectant, were summarised in the form of a predictive mathematical model. The model, of the square-root type includes a novel term to describe the effects of super-optimal water activity, and can be used to predict generation times for the temperature range (8-45°C) and water activity range (0.936-0.995) which permit growth of Vibrio parahaemolyticus. Predicted generation times from the model were compared to literature data, using bias and accuracy factors, for both laboratory media and foods. The model was shown to give realistic growth estimates, with a bias value of 1.01, and an accuracy factor of 1.38.