Type of Document Master's Thesis Author Melody, Kevin Patrick Author's Email Address email@example.com URN etd-03242008-172028 Title Two Post-Harvest Treatments for the Reduction of Vibrio vulnificus and Vibrio parahaemolyticus in Eastern Oysters (Crassostrea virginica) Degree Master of Science (M.S.) Department Renewable Natural Resources Advisory Committee
Advisor Name Title John Supan Committee Chair Marlene Janes Committee Member Robert Romaire Committee Member Keywords
- Vibrio parahaemolyticus
- Vibrio vulnificus
- high salinity exposure
Date of Defense 2008-03-07 Availability unrestricted AbstractVibrio vulnificus and V. parahaemolyticus are naturally occurring estuarine bacteria and the leading causes of seafood-borne illness in the United States. Multiple outbreaks due to raw oyster consumption in the last decade has lead to much research to remediate these bacteria from oysters destined for the half-shell market. The focus of this research was to investigate the efficacy of icing and high salinity exposure as two post-harvest treatments for the reduction in numbers of V. vulnificus and V. parahaemolyticus in commercial quantities of shellstock oysters.
The icing experiment was conducted in the summer of 2006, and the high salinity trials were done in September 2007. Treatments for the icing experiment include: (1) on-board icing immediately after harvest exposed to minimal handling and shipping; (2) on-board icing immediately after harvest exposed to typical industry shipping and handling practices; (3) dockside icing approximately 1-2 hours prior to docking; and (4) no icing. In most instances during icing and cold storage, there were no statistically significant differences in V. vulnificus and V. parahaemolyticus counts by treatment or time. The only exceptions occurred in August samples, in which case V. vulnificus and V. parahaemolyticus counts in dockside and non-iced oysters were significantly higher than the immediately iced on-board samples. Treated (iced) oysters had significantly higher gaping after one week in cold storage than did non-iced oysters.
For the high salinity exposure research, oysters were relocated to an area of full strength sea water (>30 ppt) to measure change in both V. vulnificus and V. parahaemolyticus. Oysters placed at ambient air temperatures over night had significantly higher numbers of both V. vulnificus and V. parahaemolyticus than when they were first harvested. Due to safety concerns and equipment failure, the experiment could not be completed, but preliminary results indicate a significant decrease in V. vulnificus and V. parahaemolyticus counts after one week of exposure to sea water. However, one week was insufficient time to reduce either V. vulnificus or V. parahaemolyticus to non-detectable numbers.
Overall, post-harvest icing did not substantially reduce V. vulnificus or V. parahaemolyticus in oysters, and icing negatively impacted oyster survival during subsequent cold storage. High salinity exposure showed promise in V. vulnificus and V. parahaemolyticus reduction; however, the logistics of relocating oysters to full strength sea water need to be closely evaluated.
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