Purpose: This study investigated the combined effect of temperature and relative humidity on growth or survival of B. cereus on sirutteok, and also developed predictive growth models.
Methods: Rice cake (sirutteok) samples inoculated with B. cereus were incubated at 5, 15, 25, 35 and 45 °C under different relative humidity (50% and 80%) for different lengths of storage periods, dependent on incubation temperature. Samples were periodically determined for enumeration according to the designed sampling intervals. The experimental data of B. cereus at each combined condition were collected and fitted into the modified Gompertz model to estimate the growth parameters (growth rate and lag time), which were used to develop the secondary models using polynomial equation.
Results: Temperature was much more influential than relative humidity on the growth of B. cereus on sirutteok. The secondary models for growth rate and lag time of B. cereus were developed with high coefficients of determination (0.953 and 0.902). The bias factor, accuracy factor, and the standard error of prediction, which were statistic characteristics for the external validation of the predictive models, were 0.972, 1.10, and 9.03% for growth rate, while 1.05, 1.18, and 17.32% for lag time, respectively.
Significance: The developed models described the growth data of B. cereus on sirutteok, and provided reliable predictions for the purpose of microbiological risk assessment of B. cereus on sirutteok in Korea.