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United States Department of Agriculture

Agricultural Research Service

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Location: Warmwater Aquaculture Research Unit

2010 Annual Report

1a. Objectives (from AD-416)
Research will address methods to determine the presence of pathogens in catfish/catfish products and to maximize elimination methods. Detection techniques will be developed to aid in processing and packaging operations, which should further enhance product safety. Specifically the objectives are: Optimize safety of aquaculture products through innovative processes for reducing microbiological, physical and chemical hazards in seafood/aquaculture products. Determine the mechanisms influencing microbial survival of selected pathogens in seafood/aquaculture products. Optimize the market value of seafood/aquaculture products through enhanced food safety and quality.

1b. Approach (from AD-416)
Develop and evaluate methods for detection and reduction of microorganisms, toxins and contaminants that could affect the safety of seafood/aquaculture products.

3. Progress Report
A series of experiments were conducted in support of the objectives of the in-house research project related 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. A series of projects have been conducted to understand factors influencing virulence of Listeria and reduce its incidence in food products. We determined that low dose X-ray irradiation reduced Listeria but did not have negative effects on sensory characteristics of channel catfish fillets during storage. A series of studies were conducted to determine antibiotic resistance and prevelance of Listeria isolated from catfish processing plants. No Listeria were isolated that were resistant to antibiotics used to treat human listerosis. Listeria were not isolated from catfish skins or intestines, but tanks used to chill fillets were identified as a possible source of Listeria. Results will be used to develop plant-specific cleaning and sanitation procedure to specifically target Listeria. We determined that the generally recognized as safe (GRAS) bacteriophage (Listex P100) was effective for reducing Listeria on catfish and salmon fillets. We demonstrated that whey proteins from cheese processing and muscadine seed extracts had anti-microbial properties when used to treat meat products. We also demonstrated that thermally treating muscadine seed extracts, whey proteins, and tannic acid enhanced their antioxidant capacity and antimicrobial activity on treated meat products. Thermal processing could be useful for enhancing antioxidant capacity and antimicrobial activity of ‘natural’ products. A series of experiments were conducted to determine effects of phosphate treatments on catfish fillet quality. All phosphate treatments increased fillet tenderness, but an agglomerated blend (mono-, di-, and tri-phosphates) of sodium phosphates increased yields and lowered psychrotrophic plate counts of fillets the most. Benefits of agglomerated sodium phosphates were observed for both injected and vacuum tumbled catfish fillets. Refinement of phosphate treatment procedures has the potential to improve yield and product quality of catfish fillets. The ADODR has monitored progress on this project through phone calls, e-mail, and site visits with the Cooperators Principal Investigator and other scientists involved in the project.

4. Accomplishments

Last Modified: 05/22/2017
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