Response Surface Model for the Estimation of Escherichia coli O 157:H7 Growth under Different Experimental Conditions

In this study, a Response Surface Model (RSM) of Escherichia coli O157:H7 as affected by pH levels, sodium chloride and nitrite concentrations, temperature, and aerobic/anaerobic conditions is presented. The standard error of prediction (%SEP) obtained was acceptable for the growth rate prediction (33%SEP), although a bit high for lag time (53.01 %SEP). Mathematical validation demonstrated that the RSM predicts growth rate values on the fail‐safe side in aerobic conditions and within the acceptable range (bias factor [Bf] = 0.99) with acceptable accuracy (accuracy factor [Af] = 1.15), as well as for lag time (Bf = 1.05; Af = 1.25). Temperature was found to have the greatest effect on the kinetic parameters, followed by NaCl concentration and pH. In the experimental range considered here (0 to 200 ppm), NaNO 2 concentration was found to have a significant effect on growth rate but not on lag time.