A Predictive Model for the Decontamination Effect of Lactic Acid and Chitosan on Vibrio parahaeomolyticus in Shrimp

Introduction:  Vibrio parahaeomolyticus is a major causative agent of human gastroenteritis in seafood including shrimp. Lactic acid and chitosan are natural antimicrobials for food decontamination without risk to human health. However, limited information is available on the combined use of these two natural decontaminants to eliminate or reduce V. parahaeomolyticusin shrimp.

Purpose:  The purpose of this study was to evaluate the combined effect of lactic acid and chitosan on reducing V. parahaeomolyticus in shrimp during washing process.

Methods:  A 3-factor response surface model based on the Box-Behnken design was developed to evaluated the effect of lactic acid concentration (1.5, 2, and 2.5% v/v), chitosan concentration (0.8, 1.2, and 1.6% w/v) and washing time (10, 15, and 20 min) on reduction of V. parahaeomolyticus in inoculated raw shrimp. The model was validated with 10 random additional treatments within the model range.

Results:  The result indicated that the model was significant (R² = 0.98, P < 0.001) and achieved 1.35 - 2.42 log CFU/g bacterial reduction in raw shrimp after different treatment combinations. Lactic acid, chitosan, and washing time all exhibited an individual significant effect on bacterial reduction (P < 0.05), and the interaction between lactic acid and chitosan was significant (P < 0.05), indicating improved antimicrobial effect with their combination. Bias factor (B_f) and accuracy factor (A_f) calculated from the validation tests were 1.06 and 1.03, respectively, suggesting a good performance of the model.

Significance:  The combination of lactic acid with chitosan could be an alternative decontaminant for shrimp postharvest washing, and the predictive model could be used to design appropriate combinations of lactic acid and chitosan to achieve desirable V. parahaeomolyticus reduction.