A response surface model to describe the effect of temperature and pH on the growth of Bacillus cereus in cooked rice.

This study was performed to develop a predictive model for the growth rate of Bacillus cereus in cooked rice. A response surface methodology (RSM) was used with a combination of storage temperature (10 to 40 degrees C) and pH value (5.4 to 6.8). The growth curves generated under different conditions were fitted using a modified Gompertz equation, and the relationship of the growth rate to the growth curves was modeled using an RSM quadratic polynomial equation. The predictive model was significant (P < 0.01), and the predicted values of the growth parameters obtained using the model equations were in close agreement with experimental values (R2 = 0.9864). The RSM evaluation for describing the growth rate of B. cereus involved both a bias factor (Bf) and an accuracy factor (Af). Both the Bf value (1.006) and the Af value (1.011) approached 1.0 and were within acceptable ranges. Therefore, the adequacy of the predictive model for B. cereus in cooked rice was verified by the validation data.