Modeling the dynamic heat inactivation of Vibrio parahaemolyticus in oyster digestive diverticula

ABSTRACT Oysters are a highly valued seafood commodity; however, consumption of raw or undercooked oysters contaminated with Vibrio parahaemolyticus can result in foodborne illness. We evaluated the thermal inactivation kinetics of two virulent V. parahaemolyticus strains (FDA-R2 and TX-2103), representing clinical and environmental sources, in oyster digestive diverticula under dynamic heating conditions at 63°C, 74°C, and 98°C (near boiling). No consistent strain-specific difference was observed in thermal resistance across heating conditions. Although FDA-R2 counts were higher than TX-2103 at 63°C by 0.39 log 10 CFU/g [95% confidence interval: 0.10, 0.69], the 63°C difference varied over time and was not consistent across the heating profiles. Therefore, data from both strains were pooled for kinetic modeling. Dynamic inactivation kinetics were best described by the Peleg-Weibull model, with estimated first decimal reduction times under isothermal conditions of 4.32 min [95% credible interval: 3.37, 5.62] at 63°C, 1.56 min [1.22, 2.43] at 74°C, and 0.34 min [0.19, 0.69] at 98°C. The estimated shape parameter was less than 1.0, indicating rapid initial inactivation followed by a tailing phase. These findings provide quantitative thermal inactivation parameters for V. parahaemolyticus under dynamic heating conditions, supporting science-based evaluation of oyster cooking practices and microbial risk assessments. Vibrio parahaemolyticus is a major seafood-associated pathogen responsible for illnesses linked to oyster consumption. Because V. parahaemolyticus preferentially accumulates in oyster digestive diverticula, this tissue represents a critical target for thermal inactivation during cooking. Although cooking is the primary intervention used to reduce the risk of infection, available thermal inactivation data are largely derived from constant-temperature experiments that do not reflect the changing temperatures experienced during practical cooking. This study is the first to characterize the dynamic thermal inactivation kinetics of V. parahaemolyticus in oyster digestive diverticula under cooking-relevant heating conditions. The fitted model predicted substantially faster inactivation with increasing temperature, with the model-derived isothermal Weibull scale parameter decreasing from 4.32 min at 63°C to approximately 0.34 min at 98°C. These findings demonstrate the importance of considering the full temperature-time profile during cooking and provide quantitative data to evaluate oyster cooking practices and support microbial risk assessments.