Purpose: This study developed a dynamic model to describe the kinetic behavior of E. coli in steamed pig feet at changing temperatures.
Methods: Prepared steamed pig feet samples were inoculated with a five-strain mixture of E. coli strains at 4 log CFU/g. The samples were stored at 10oC for 8 days, 20oC for 6 days, and 25oC for 6 days. Total bacterial and E. coli cell counts were enumerated on tryptic soy ager and 3M PetrifilmTM, respectively. The Baranyi model was fitted to E. coli cell counts data to calculate growth rate (log CFU/g/h) and lag phase duration (LPD; h). The kinetic parameters were further analyzed by a polynomial equation to evaluate the effect of storage temperature, and a dynamic model was subsequently developed, using kinetic models at changing temperatures. The model performance was evaluated with accuracy (A) factor, bias (B) factor, and root mean square error (RMSE) values by comparing observed and predicted data.
Results: Total bacterial counts and E. coli cell counts were increased (P<0.05) in steamed pig feet samples at all storage temperatures (10-25oC). As storage temperature increased, LPD decreased (P<0.05), and growth rates increased (P<0.05). Secondary models were appropriate to describe the effect of storage temperature on the kinetic parameters with 0.897- 0.942 of R2. The developed kinetic models showed good performance with 0.618 of RMSE, 1.02 of B factor and 1.08 of A factor, and the prediction of the dynamic model was also appropriate.
Significance: These results indicate that the developed dynamic model should be useful in describing the kinetic behavior of E. coli in steamed pig feet during storage.