[Inactivation kinetics of Vibrio parahaemolyticus in peeled shrimp treated with organic acids].

ABSTRACT

OBJECTIVE: To establish the kinetic inactivation models of Vibrio parahaemolytius in saline and peeled shrimp treated with acetic acid, lactic acid and citric acid for guidance of their potential application in shrimp decontamination. METHODS: To determine the survival rate (P) of V. parahaemolyticus in saline and peeled shrimp treated with organic acids, dose-response in peeled shrimp between P and concentrations of organic acids was modeled directly. Logit (P) was transformed from survival P with the formula ln [P/(1-P)] for linear modeling. Both linear models were used to interpolate 50% and 90% effective inhibitory concentrations (EC50 and EC90), which were then used to compare the difference of inhibitory potency between saline and peeled shrimp. RESULTS: Organic acids in saline were more inhibitory to V. parahaemolyticus in saline than in peeled shrimp, seen as 160 to 200-fold increase of EC50 and EC90 for lactic acid and citric acid, and more than 70-fold increase for acetic acid. These results indicate that food matrix had significant impact on the antimicrobial activity of organic acids. We also found that EC90 of the tested organic acids in peeled shrimp was far below the 2.5% limit for use as food ingredients regulated by USDA. With equimolar concentration in the test solutions, the order of inhibitory potency is citric acid > lactic acid > acetic acid. CONCLUSION: Food matrix could have negative impact on antimicrobial activity of organic acids. Concentrations of organic acids around 2% could lead to significant reduction of V. parahaemolyticus contamination of peeled shrimp for improved food safety.