Thermal Resistance of Listeria monocytogenes and Vibrio parahaemolyticus in Lab Media and Brown Crab (Cancer pagurus) Meat

The current study investigated thermal resistance characteristics of two key pathogens in ready-to-eat crabs, namely, Listeria monocytogenes and Vibrio parahaemolyticus. Five L. monocytogenes and seven V. parahaemolyticus strains were treated individually in a thermoresistometer at 56-62 °C and 47-53 °C, respectively, in liquid lab media. Data were fitted to inactivation models in GInaFit to select the most heat-resistant strains based on their t_4D-values and z(t_4D)-values. To study the food matrix effect, t_4D-values (58 °C) of the most heat-resistant strains in crabmeat and lab medium were compared. Finally, the selected strains were recovered on nonselective and selective media to evaluate their sublethal injury. Results showed that the Double Weibull model gave the best fit to all inactivation curves. NCTC 13372 was the most heat-resistant L. monocytogenes strain with t_4D-values of 55.80, 25.10, 9.67, and 3.92 min at 56, 58, 60, and 62 °C, respectively (z(t_4D)-value of 5.16 °C). RIMD 2210633 was the most heat-resistant V. parahaemolyticus strain with t_4D-values of 103.20, 34.68, 7.97, and 1.88 min at 47, 49, 51, and 53 °C, respectively, (z(t_4D)-value of 3.41 °C). No significant crabmeat matrix interference effect was observed with a similar t_4D-value of 23.05 min at 58 °C for NCTC 13372 in both MRD and crabmeat. Sublethal injuries occurred for both V. parahaemolyticus and L. monocytogenes at all temperatures. Thermal resistance varies among bacterial strains. L. monocytogenes was more resistant than V. parahaemolyticus. The sublethal injury of L. monocytogenes and V. parahaemolyticus demonstrated that there is an actual risk of recovery of these foodborne pathogens after inadequate thermal treatments.