Consumption of raw oysters, whether wild-caught or aquacultured, may increase health risks for humans. Vibrio vulnificus and Vibrio parahaemolyticus are two potentially pathogenic bacteria that can be concentrated in oysters during filter feeding. As Vibrio abundance increases in coastal waters worldwide, ingesting raw oysters contaminated with V. vulnificus and V. parahaemolyticus can possibly result in human illness and death in susceptible individuals. Depuration is a postharvest processing method that maintains oyster viability while they filter clean salt water that either continuously flows through a holding tank or is recirculated and replenished periodically. This process can reduce endogenous bacteria, including coliforms, thus providing a safer, live oyster product for human consumption; however, depuration of Vibrios has presented challenges. When considering the difficulty of removing endogenous Vibrios in oysters, a more standardized framework of effective depuration parameters is needed. Understanding Vibrio ecology and its relation to certain depuration parameters could help optimize the process for the reduction of Vibrio. In the past, researchers have manipulated key depuration parameters like depuration processing time, water salinity, water temperature, and water flow rate and explored the use of processing additives to enhance disinfection in oysters. In summation, depuration processing from 4 to 6 days, low temperature, high salinity, and flowing water effectively reduced V. vulnificus and V. parahaemolyticus in live oysters. This review aims to emphasize trends among the results of these past works and provide suggestions for future oyster depuration studies.
Background: Some filter-feeding molluscan shellfish can concentrate harmful bacteria in their intestines during feeding, thus posing a potential food safety risk to human consumers. Plasma-activated simulated seawater (PASW) generated from non-thermal plasma may help reduce bacteria in live, molluscan shellfish when used as a disinfectant in depuration systems. This study determined the physicochemical properties of PASW and its antimicrobial efficacy against Escherichia coli DH5α. These results were then compared to similar data from a plasma-activated water (PAW) study.Results: PASW yielded temperatures ranging from 31.0 AE 0.2 to 49.7 AE 1.0 C, pH from 7.21 AE 0.0 to 2.70 AE 0.0, oxidation-reduction potential (ORP) from À15.7 AE 1.0 to 246.0 AE 0.9 mV, and electrical conductivity from 35.4 AE 0.3 to 48.1 AE 1.5 μS/cm after activation by plasma for 1-10 min. Temperature, ORP, electrical conductivity, nitrate (NO 3 À ), and nitrite (NO 2 À ) concentrations of PASW increased while pH decreased with increased plasma activation time. After 2-and 5-min incubations, E. coli treated with PASW5 and PASW10 both resulted in the highest reductions (~3 log CFU/ml). Further, while NO 3 À and NO 2 À concentrations in PASW were higher than in PAW of the same plasma exposure time, PAW yielded higher E. coli reduction values across treatments.
Conclusion:Results from this study demonstrate the potential of PASW as a disinfectant for live, molluscan shellfish depuration to provide a microbiologically safer seafood product for human consumers.
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