Experimental studies and modeling the behavior of anaerobic growth of Clostridium perfringens in cooked rice under non-isothermal conditions

The aim of this study was mainly to develop the dynamic model to evaluate the non-isothermal growth of Clostridium perfringens in cooked rice that is currently popular product in Asian countries. The isothermal growth was measured by culturing C. perfringens in cooked rice stored under anaerobic condition at temperatures from 20 to 48 °C, followed by developing the four different primary models using these observed data. The specific growth rate (SGR, log CFU/h) obtained from each primary model were individually applied in the modified Ratkowky model to estimate the changes in the SGR as a function of temperature. The performances of secondary models developed basing on the different primary model were evaluated by using the validation factors including bias factor, accuracy factor, and mean square error. The resulting validations demonstrate that the Baranyi-based Ratkowky model shows greater performance than those developed basing on other primary models. To predict the non-isothermal growth in two different cooling scenarios of 50 to 19 °C, the Baranyi and Roberts differential equations was developed with the initial physiological state (q0 = 0.16). To validate the dynamic models, the predicted data were compared with experimental data obtained from the non-isothermal experiment. The developed dynamic model provided good prediction of anaerobic growth of C. perfringens in cooked rice under non-isothermal conditions, and it could be used to assess microbial safety of cooked rice during storage and cooling procedure.