2007 Annual Report
1a.Objectives (from AD-416)
Ensure the safety and quality of catfish and other aquaculture/seafood products to consumers. Continued increase in production, processing and consumption of catfish and other aquaculture/seafood products requires an understanding of microbiological, physical, and chemical hazards to these products. The project is to assess various technologies for reducing microbiological, physical, and chemical hazards in catfish and other aquaculture/seafood products in order to produce high quality products desirable by consumers.
1b.Approach (from AD-416)
Enhance the physical safety of products by determining optimal application parameters for various methods of hazard reduction (smoking, acidulants, antimicrobials, IQF, irradiation, high pressure processing). Determine mechanisms by which the certain pathogenic bacteria may be reduced in specific aquatic species products utilizing PCR analysis. Evaluation of effects of various techniques on products will include both trained and consumer sensory panels and economic analysis of market potential.
This report serves to document research conducted under a Specific Cooperative Agreement between ARS and Mississippi State Universiry (MSU). Additional details of research can be found in the report for the in-house project 0500-00031-001-00S, "Umbrella Project for Food Safety."
A series of experiments was conducted relating to optimizing safety and quality of aquaculture and seafood products, determining mechanisms influencing survival of pathogens in aquaculture and seafood products, and developing methods for identifying pathogens and factors affecting pathogen virulence.
Listeria species are significant food pathogens, but not all strains or species are virulent. The ability to identify virulent strains and virulence associated factors in Listeria will improve our ability to insure safety of aquaculture and seafood products. We obtained DNA sequence information from virulent and avirulent strains of Listeria and found genetic differences between them. We have established methods for culturing and collecting proteins from Listeria allowing determination of differences in protein expression between virulent and avirulent strains. We developed polymerase chain reaction (PCR) assays for rapid, simultaneous confirmation of Listeria identity and virulence potential. We determined the influence of salt concentration and pH on survival of Listeria. This research will have important implications for identifying and controlling this important food pathogen.
Pathogenic strains of Vibrio vulnificus are natural inhabitants of estuarine environments and can be transmitted to humans through consumption of raw shellfish. Most post harvest processes for extending shelf-life of raw oysters have centered on refrigeration, but research to find other processes to eliminate this pathogen has expanded. We used cryogenic freezing to dramatically reduce Vibrio vulnificus in oysters after 7 and 35 days. We also demonstrated that refrigerating oysters for up to 4 days prior to freezing had no impact on V. vulnificus reduction indicating that V. vulnificus did not become more cold tolerant after refrigeration. Establishing specific guidelines for industry partners interested in using individually quick frozen (IQF) freezing technology will maximize the effect of freezing on vibrio reduction in half shell oysters.
Accumulation of algal derived ‘off-flavor’ compounds in catfish meat remains a significant problem for the catfish industry. Methods to reduce or mask these flavors would benefit the catfish farming industry.
The project was monitored by e-mail, telephone calls, and meetings with Mississippi State University and other scientists associated with the project.