Modelling the effects of temperature, water activity, pH and lactic acid concentration on the growth rate of Escherichia coli

An extended square root-type model describing Escherichia coli growth rate was developed as a function of temperature (7.63–47.43 °C), water activity (0.951–0.999, adjusted with NaCl), pH (4.02–8.28) and lactic acid concentration (0–500 mM). w model, based on 236 growth rate data, combines and extends previously published square root-type models and incorporates terms for upper and lower limiting temperatures, upper and lower limiting pH, minimum inhibitory concentrations of dissociated and undissociated lactic acid and lower limiting water activity. A term to describe upper limiting water activity was developed but could not be fitted to the E. coli data set because of the difficulty of generating data in the super-optimal water activity range (i.e. >0.998). All data used to generate the model are presented. del provides an excellent description of the experimental data.