Oyster production in the Gulf states account for a large fraction of the US production; however, oysters grown in those waters are seasonally susceptible to contamination by Vibrio vulnificus and V. parahaemolyticus. These naturally occurring human health pathogens are a food safety concern for the shellfish industry and consumers. This proposal addresses this concern and seeks to evaluate a non-thermal electrolyzed oxidizing water/controlled temperature post-harvest treatment (PHT) processes to reduce Vibrio contamination in live oysters. The successful development of these processes would provide the oyster industry with additional tools to produce safe oysters for consumption, reduce health risk associated with seafood consumption, and minimize economical loss resulting from foodborne poisoning outbreaks. Our rationale for this project is that the successful development of an electrolyzed oxidizing water depuration process that would reduce levels of potential Vibrio contamination in oysters to safe consumption levels, while at the same time maintaining their quality and sensory characteristics, could significantly reduce the total number of cases of food poisoning resulting from consumption of raw oysters. This project addresses a priority of the Gulf Oyster Industry Program to "develop or investigate new technology, such as ionized water, for depurating oysters of human pathogen."
The goal of the proposed study were to develop and evaluate an electrolyzed oxidizing water (EO water) depuration process to increase quality, shelf-life and safety of raw oysters for consumption. Specific objectives were to: 1) identify the optimal electrolyzed oxidizing water for inactivating bacteria associated with raw oysters; and 2) determine the optimal salinity, temperature, and time for electrolyzed oxidizing water depuration process for reducing bacteria including V. vulnificus and V. parahaemolyticus contamination in oysters. We hypothesized that conditions could be identified using electrolyzed oxidizing water for depuration process to reduce levels of V. parahaemolyticus and V. vulnificus contamination to non-detectable levels in oysters without affecting their food quality.
Initial studies investigated effects of electrolyzed oxidizing (EO) water treatment on reducing both V. parahaemolyticus and V. vulnificus contamination in oysters. Holding oysters inoculated with V. parahaemolyticus or V. vulnificus in EO water (30 pm chlorine) containing 1% NaCl for 4-6 hours resulted in significant reductions of V. parahaemolyticus and V. vulnificus by 1.13 and 1.05 log MPN/g, respectively. However, extended exposure (>12 h) of oysters in EO water containing high levels of chlorine (>30 ppm) was found to be detrimental to oysters. EO water could be used as a post-harvest treatment to reduce Vibrio contamination in oysters. However, treatment should be limited to 4-6 h to avoid death of oysters. Additional research to examine alternative EO treatment processess were underway through 2007 and early 2008.
Currently, one peer-reviewed publication has resulted from this project. In addition, a number of presentations about project results were made at regional meetings.