Abstract: This study aimed to examine the thermal inactivation pattern of Shigella in smoked cooked ham. Shigella (108 CFU/g) were inoculated into smoked cooked ham, cultured at constant temperature and constant humidity and then subjected to thermal treatment at 55 or 63 ℃. The number of surviving cells was counted on selective media. A Logistic model and a 3rd degree polynomial model were separately used to fit the thermal inactivation curve by CurveExpert software. Decimal reduction time (D values) represented the heat resistance of Shigella. The results showed that the curves for 11 Shigella strains fitted by the 3rd degree polynomial model were better, with correlation coefficients (R2) above 0.98. The D values of different Shigella strains were different, ranging from 4.46 to 10.66 min at 55 ℃ and from 0.48 to 3.22 min at 63 ℃ in the inoculated smoked cooked ham. The heat resistance of different Shigella strains were different, and strain S-5 had the strongest heat resistance while S-6 was the weakest.

Key words: Shigella, smoked cooked ham, thermal inactivation, kinetic model, decimal reduction time (D value)