Purpose: The objective of this study was to develop a dynamic model to describe the kinetic behavior of E. coli in diced white radish kimchi at changing temperatures.
Methods: Prepared diced white radish kimchi samples were inoculated with a five-strain mixture of E. coli at 4 log CFU/g. The samples were stored at 4°C (16 days), 15°C (4 days), and 25°C (2 days). Total lactic acid bacterial and E. coli cell counts were enumerated on de Man, Rogosa and Sharpe agar and 3M Petrifilm, respectively. The data of E. coli survival were fitted to the Baranyi model to calculate death rate (log CFU/g/h) and shoulder period (h). The kinetic parameters were further analyzed by a polynomial equation as a secondary model, and dynamic model was subsequently developed with changing temperatures. The model performance was validated with observed data, and root mean square error (RMSE) was calculated.
Results: Lactic acid bacteria in diced radish kimchi grew at all storage temperatures. However, E. coli growth was not observed at 4-25°C, and their cell counts were decreased during fermentation. As storage temperature increased, shoulder period decreased and the death rate increased (P<0.05). The developed kinetic models showed good performance with 0.480 of RMSE, and the prediction of the dynamic model showed also appropriate performance.
Significance: These results indicate that the developed dynamic model should be useful in describing the kinetic behavior of E. coli in diced white radish kimchi fermentation.