Modelling Bacillus cereus growth.

The aim of this study was to model the growth, in a model system, of toxigenic strains of Bacillus cereus as a function of temperature, pH and water activity. Optical density (OD) values were transformed into numbers of colony-forming units (CFU) by the use of a 'calibrating' relation. The growth curves were then fitted to the Gompertz function which allowed the estimation of the lag-time (lambda) and the growth rate (mu). These two parameters were then modelled according to the controlling factors which were pH and water activity at 20 and 30 degrees C.