Purpose: The study aimed to develop a predictive model to evaluate the combined effect of ultrasound and mild heat on reducing V. parahaeomolyticusin shrimps during the postharvest washing process.
Methods: Raw shrimps inoculated with V. parahaeomolyticus were treated with ultrasound (96, 150, and 205 W) combined with mild heat (47, 50, and 53ºC) based on a 3 × 3 full factorial design and the bacterial survival curves were fitted with a Weibull model. The time for a 4-log CFU/g of bacterial reduction (t4d) was calculated based on parameter estimates of the Weibull model to evaluate the inactivation rates and a response surface model was developed to describe the changes of t4d as a function of temperature and ultrasonic power. The model was validated with independent experiments within the model range.
Results: The results indicated that the models were significant (P < 0.05) with high adjusted coefficients of determination (R2-adj = 0.89-0.98). The response surface model showed that t4d was reduced when temperature and ultrasonic power increased and there was a significant positive interaction effect (P < 0.01) between the two factors, indicating thermo-ultrasound treatments accelerated the inactivation of V. parahaemolyticus. Bias factor (Bf = 1.02) and accuracy factor (Af = 1.09) calculated based on the validation data indicated a satisfied performance of the model.
Significance: The developed predictive model could be used to design appropriate regimens of ultrasound and mild heat treatment to achieve desirable V. parahaeomolyticus reduction in shrimps.