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Abstracts
Workgroup: Public Health and Processing
Development of Commercial Oyster Marinades for Vibrio vulnificus Control in Gulf Coast Oysters
Principal Investigator(s):
Dr. Marilyn B. Kilgen, Department of Biological Sciences, Nicholls State University, Thibodaux, LA, Marilyn.Kilgen@nicholls.edu
Co-Investigator(s):
Chef Kenneth Perry, and Chef Carol Gunter, Chef John Folse, Culinary Institute, Nicholls State University
Funding Period: Oct. 1, 1999 - June 30, 2001
Six prototype commercial acid marinades (pH 4) that would appeal to a wide range of regional United States ethnic taste preferences and capable of reducing the ambient levels of Vibrio vulnificus to non-detectable (<3 MPN/g) in gulf oysters within 24 hours at 35OC were developed in the Chef John Folse Culinary Institute at Nicholls State University (NSU). The six prototype marinades were Pacific Rim, Hawaiian, South Louisiana, Caribbean, Midwest, and Southwest. These six prototype marinades were evaluated for flavor and textural changes in sensory studies using NSU staff, faculty and students following the guidelines of the NSU Human Subjects' Institutional Review Board. The marinades were seasonally evaluated (summer (August) - fall (November) - winter (February) - spring (April) for microbiological effectiveness in reduction of V. vulnificus to non-detectable limits in the microbiology laboratory at NSU. Sensory evaluation at NSU during the summer and fall sensory evaluations selected South Louisiana, Caribbean, Southwest and Midwest ethnic marinades as the top four for flavor preference. The Louisiana Oyster Task Force sponsored "The Ship's Galley Featuring a Taste of Louisiana" at the Annual Boat Show in the Louisiana Superdome. A total of 1,399 individuals sampled the South Louisiana marinade at this event for a central location testing. Of these 1,116 rated the marinade as "Excellent" in flavor ratings of 1-10 to delineate "undesirable," "average," or "excellent."
All six marinades were tested microbiologically in the summer (August) and fall (November) evaluations. After selection of the top four marinades, only those were used in the winter (February) and spring (April) microbiological and sensory evaluations. The base of the six marinades was originally vinegar. This base was used in the summer and fall trials. The base was changed to lemon juice in the winter and spring trials. Acid marination in all six prototypes at pH 4.0 or less (vinegar base) at 35OC reduced levels of ambient V. vulnificus from 240,000 MPN/g in the summer trial to non-detectable (<0.3 MPN/g) in 24 hrs. (The U.S. Food and Drug Administration defines "non-detectable" levels of V. vulnificus as <3 MPN/g). Samples were evaluated microbiologically at 6, 12, 18 and 24 hrs. post marination. In the fall trial the vinegar base formula for all six marinades reduced level of ambient V. vulnificus (only 200 MPN/g) to non-detectable by 18 hours. In the winter samples, the formulas were changed to a lemon juice base and only the four marinades selected by sensory evaluation in the first two seasons were evaluated. Since the levels of V. vulnificus in the control oysters was <0.3 MPN/g the microbiological analysis, and the 6, 12, 18 and 24 hr. analyses were all <0.3 MPN/g V. vulnificus in all four ethnic marinades. In the spring (April) sample, the ambient V. vulnificus levels were >24,000 MPN/g in the control oysters. At 24 hrs. the South Louisiana, Midwest, and Southwest showed non-detectable levels. However, the Caribbean marinade had 75 MPN/g V. vulnificus after 24 hrs at 35OC. The results indicated that citric acid in the lemon juice was not as effective as the acetic acid of the vinegar.
IMPACTS and/or BENEFITS:
The intended benefactors of this new oyster product development will be the Louisiana oyster industry and related industries such as restaurants, caterers, and oyster consumers. Restaurants and caterers could offer the product as an appetizer. Consumers could benefit because of increased confidence in a value-added, safety-enhanced product.
No comprehensive studies utilizing low acid marination of raw oysters for internal reduction of naturally occurring V. vulnificus have been conducted previously. The development of a value-added product that reduces V. vulnificus to non-detectable (<3 MPN/g) in raw Louisiana or Gulf coast oysters will greatly enhance efforts to regain markets and consumer confidence in gulf oysters. It could result in a significant economic benefit to the State of Louisiana and the entire Gulf coast oyster industry.
PROJECT PUBLICATIONS:
There are no publications currently from this project, but an invited presentation was made to the annual meeting of the Louisiana Oyster Industry Convention in New Orleans, LA.
Kilgen, M.B., K. Perry and C. Gunter. 2001. Evaluation of Acid Marinades for Vibrio vulnificus Control in Oysters. Presented to the annual meeting of the Louisiana Oyster Industry Convention. March 24, 2001. New Orleans, LA
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