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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Research Project #144153

Research Project: Umbrella Project for Food Safety

Location: Warmwater Aquaculture Research Unit

2014 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 new objectives are: 1)Optimize safety of aquaculture products through innovative processes for reducing microbiological, physical and chemical hazards in seafood/aquaculture products. 2)Determine the mechanisms influencing microbial survival of selected pathogens in seafood/aquaculture products. 3)Optimize the market value of seafood/aquaculture products through enhanced food safety and quality.


1b. Approach (from AD-416):
Catfish. Determine optimum rates of microbial reduction through innovative processing in catfish products including evaluation of consumer acceptance. Determine viable methods of hazard reduction (smoking, acidulants, antimicrobials, etc) in catfish products during processing and storage. Determine the methods by which these methods reduce hazards within the products evaluated. Enhance the physical safety of catfish fillets with innovative analysis technology. Seafood/Produce. Determine the efficacy of IQF freezing, irradiation, and high pressure processing and other technologies on the safety and quality of oysters, shrimp and produce. Objective 2: Catfish/ Seafood/Produce. Determine the mechanistic approach by which the certain pathogenic bacteria may be reduced in aquatic species. Utilize PCR analysis and other assays to determine the sensitivity and specificity of various isolates in response to innovative treatments. Objective 3: Catfish. Enhance product value through innovative smoking and further processing of catfish fillets. Value-added analysis will compared products to commodity value for product enhancement addition. Evaluate value-added products to address potential food safety issues. Seafood/Produce. Evaluate consumer acceptance of products enhanced through various processing methods. Preparation techniques, ingredient inclusion, packaging and storage methods will be evaluated at various time frames and inclusion rates to determine specie specific parameters limitations. Analyze economics of various market potentials. Catfish. Determine optimum rates of microbial reduction through innovative processing in catfish products including evaluation of consumer acceptance. Determine viable methods of hazard reduction (smoking, acidulants, antimicrobials, etc) in catfish products during processing and storage. Determine the methods by which these methods reduce hazards within the products evaluated. Enhance the physical safety of catfish fillets with innovative analysis technology. Seafood/Produce. Determine the efficacy of IQF freezing, irradiation, and high pressure processing and other technologies on the safety and quality of oysters, shrimp and produce. Objective 2: Catfish/ Seafood/Produce. Determine the mechanistic approach by which the certain pathogenic bacteria may be reduced in aquatic species. Utilize PCR analysis and other assays to determine the sensitivity and specificity of various isolates in response to innovative treatments. Objective 3: Catfish. Enhance product value through innovative smoking and further processing of catfish fillets. Value-added analysis will compared products to commodity value for product enhancement addition. Evaluate value-added products to address potential food safety issues. Seafood/Produce. Evaluate consumer acceptance of products enhanced through various processing methods. Preparation techniques, ingredient inclusion, packaging and storage methods will be evaluated at various time frames and inclusion rates to determine specie specific parameters limitations. Analyze economics of various market potentials.


3. Progress Report:
The results indicated that more than 5-log colony forming unit (CFU) reduction of Salmonella enterica populations on tuna was achieved using 0.5 kilogray(kGy) X-ray irradiation. Furthermore, 0.6 kGy X-ray reduced Salmonella to less than detectable level. Heating treatment of Listeria (L.) moncytogenes strains showed a diversity of heat tolerance. Exposing to sublethal heat would increase heat tolerance of the pathogen. Pocket size detection kits for detecting food borne are being validated against official methods. The low cost one-tube method was successfully adapted to 96-well microplate system. The next step is to conduct validation study for Vibrio vulnificus and Vibrio parahaemolyticus. A quantitative polymerase chain reaction (PCR) assays was developed and applied to differentiate genetic variants of Edwardsiella (E.) tarda for comparative evaluation of pathology, virulence and dissemination in channel catfish and hybrid catfish. Results showed E. piscicida may be more prevalent in catfish aquaculture than E. tarda. Results showed pegylated gold nanoparticles (AuNPs) could be used as an important platform for studying ligand interactions with AuNps. Researchers at Mississippi State University (MSU) have discovered new primers that can differentiate serotypes of Listeria pathogens. Development of molecular methods to distinguish high-risk serotypes and low-risk serotypes of Listeria would enable determination of the risk associated with the isolation of Listeria monocytogenes from seafood, including channel catfish. A Listeria monocytogenes surface anchor protein was found not to contribute to listerial collagen binding or cell adherence, but appeared to contribute to virulence and intracellular replication. The use of small molecules to block the attachment of LmF2365 to catfish fillet is being continued. Scientists at MSU showed a protein ImoH7858_0396 was a novel virulent factor of L. monocytogenes, and deletion of an alkylated DNA (AlkD)-like genetic determinant affected flagellar motility gene expression, biofilm formation, virulence and stress responses of L. moncytogenes. The physiological functions of deubiquitinating enzymes (DUBs) as potential drug targets in Salmonellosis in catfish and chicken were characterized. Chemical proteomics data showed that activities of host DUBs were regulated during Salmonella infection. Cheddar whey solution (2%, weight/volume) was subjected to nanoemulsification by high pressure homogenization at pressures. The results indicated samples treated with both chedder whey (CW) (subjected to 20,000 PSI of pressure) and chitosan exhibited the best results for storage of the catfish fillet. There was an almost six-fold reduction in oxidative degradation as a result of nano-emulsion coating containing chitosan. The stability and antioxidative activities of a nanoemulsion consisting of a whey protein concentrate and peanut oil were investigated. Based on total radical trapping potentials (TRAP) analyses, the antioxidative potential of the nanoemulsions were significantly enhanced by adding sulfobetaine 3-10, though further addition of Trition X-100 had no significant effect on antioxidative properties. Characterization of phenolic substances and antioxidant capacity of muscadine grape and quality of food grade soybeans have been initiated. Thirteen major varieties bred by ARS researchers at the Cochran Fruit Research Center in Mississippi were analyzed for juice quality and health promotion components. Results showed that black varieties had the highest phenolic substances. However, oxygen radical absorbance capacity was not associated the skin color. Food grade soybeans grown by the ARS researchers in Stoneville, MS, were analyzed for protein quality for making foods. Results showed some varieties have potential to be utilized for foods.


4. Accomplishments
1. Development of X-ray technology for reducing Salmonella pathogens. Researchers at Mississippi State University discovered X-ray at 0.5-0.6 kilogray (kGy) could effectively reduce Salmonella enterica in tuna fillet. Spoilage microorganisms are also significantly reduced. This is important since tuna is eaten raw and the flavor and texture of X-ray irradiated products can be preserved.

2. Development of rapid assays for detection of Vibrios species. Scientists at Mississippi State University (MSU) have improved the sensitivity of the rapid single tube (pocket size) assays for independent detection of Vibrio vulnificus and Vibrio parahaemolyticus strains of bacteria from seafood by converting it to a 96-well pocket size detection systems while maintaining the reliability, sensitivity, and rapidity. The test is still being validated by the Food and Drug Administration (FDA) laboratory in Alabama. One grant proposal has been submitted to National Oceanic and Atmospheric Administration for competitive funding.

3. Development and application of quantitative polymerase chain reaction (PCR) assays for genetic variants of Edwardsiella (E.) tarda. Mississippi State University (MSU) scientists have completed the study on the development and application of quantitative PCR assays for genetic variants of Edwardsiella (E.) tarda for comparative evaluation of pathology, virulence and dissemination in channel, blue and hybrid catfish. Successful primers and molecular methods have been developed to differentiate various types of Edwardsiella species. MSU Scientists, at the National Warmwater Aquaculture Center (NWAC) in Stoneville, MS, have found that E. piscicida is more prevalent than Edwardsiella (E.) tarda in catfish aquaculture in southeastern region of the USA. A journal article has been published, and two presentations were made in scientific meetings.

4. Characterization of attachment factors of Listeria (L.) monocytogenes. Scientists at Mississippi State University (MSU) have identified and characterized an attachment factor of L. monocytogenes. A Listeria monocytogenes surface anchor protein has been found not to contribute to listerial collagen binding or cell adherence, but appeared to contribute to virulence and intracellular replication. The resistance and subsequent adaptation of biofilm cells of foodborne bacterial pathogens to any antimicrobials by a frequent repetitive exposure is a great concern. An internalin-like protein that is involved in the adhesion and invasion of Listeria monocytogenes is also a novel virulence factor. A protein encoded by alkylated DNA (AlkD)-like protein is a bifunctional protein that represses flagellar motility and influnences stress responses through its DNA glycosylase activity. This result provides insides for biofilm formation and virulence of Listeria.

5. Role of physiological functions of deubiquinating enzymes in salmonellosis. Scientists at Mississippi State University (MSU) have identified potential drug targets in foodborne disease salmonellosis and developed a sample preparation method which can be used for tissue-based proteomics in animals to study catalytically active enzymes with important cellular functions.

6. Use of nanoemulsified cheddar whey (CW) and chitosan to reduce oxidative degradation of farm raised retailed cut catfish fillet. The results have potential to lead to the development of natural preservatives with remarkable antioxidative efficacy, that can significantly increase the shelf-life of farm raised retailed cut catfish fillet, without the undesirable health effects resulting from synthetic preservative agents.