Purpose: To establish and compare the thermal inactivation kinetics of Listeria monocytogenes and Vibrio parahaemolyticus in buffer and mussels.
Methods: Five-strain cocktails of each microorganism in phosphate buffered saline (PBS) (2 ml vials) or blended mussels in vacuum-sealed bags were treated at 56, 58 and 60°C (Listeria) or 46, 48 and 50°C (Vibrio) in a circulating water bath with temperatures monitored by thermocouples. At appropriate time intervals, samples were removed, placed in an ice bath, serially diluted and plated on tryptic soy yeast extract agar (Listeria) or marine agar (Vibrio). Colonies were enumerated after 24 h at 37°C (Listeria) or 48 h at 32°C (Vibrio). Each experiment was replicated thrice. D- and z-values were calculated using the first-order model.
Results: D-values for L. monocytogenes in PBS were 4.42 ± 0.16, 1.45 ± 0.22 and 0.58 ± 0.04 min at 56°C, 58°C and 60°C, respectively and for V. parahaemolyticus were 0.86 ± 0.05, 0.51 ± 0.06, 0.12 ± 0.02 min at 46°C, 48°C and 50°C, respectively. D-values were higher in mussels: 12.58 ± 2.80, 5.28 ± 0.65 and 1.46 ± 0.01 min at 56°C, 58°C and 60°C, respectively, for L. monocytogenes and 8.94 ± 0.68, 1.70 ± 0.08 and 0.88 ± 0.09 min at 46°C, 48°C and 50°C, respectively, for V. parahaemolyticus. No significant difference between z-values was observed in PBS, 4.52°C and 4.68°C, and mussels, 4.33°C and 3.98°C, for L. monocytogenes and V. parahaemolyticus, respectively.
Significance: L. monocytogenes had higher thermal resistance than V. parahaemolyticus in buffer and mussels at the tested temperatures. These data will aid the seafood industry in developing appropriate heating processes, such as steaming or microwaving, to eliminate foodborne pathogens.