Location: Warmwater Aquaculture Research Unit
2013 Annual Report
Objectives
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.
Approach
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.
Progress Report
The results indicated that the 0.1 and 0.2 kGy X-ray treatments significantly reduced the Salmonella populations on tuna samples. Biomarkers on Vibrio vulnificus and Salmonella were discovered and optimized on its expression in 24 hours. Researchers at Mississippi State University (MSU) have been successful in developing polymerase chain reaction (PCR) primers that can differentiate serotypes of Salmonella. New primer sets are currently being tested to differentiate serotypes 1/2a and 3b.
Identification and evaluation of attachment of Listeria monocytogenes on the surface of ready-to-eat products have been started. Scientists at MSU have screened 32 genes encoding surface proteins and lipases of the strain to find highly expressed genes on lettuce leaves. Results showed that transcription levels of five genes were significantly up-regulated on lettuce leaves. It was a hypothesized one of these genes involved in an attachment to vegetables and the gene was named Listeria cellulose-binding protein (LCP). Scientists at MSU constructed a LCP mutant (LCP) by deleting the LCP gene and this mutant lost its ability to attach on the surfaces of leafy vegetables and cantaloupe skin. Results strongly suggest that LCP plays an important role in an attachment to vegetables and fruits.
Scientists at MSU investigated the effects of essential oils of thyme and oregano and their antimicrobial phenolic constituent carvacrol were evaluated for their ability to inhibit biofilm formation and inactivate preformed Salmonella biofilms. The presence of nonbiocidal concentrations of thyme oil, oregano oil, and phenolic carvacrol at 0.006 to 0.012% suppressed Salmonella spp.
Scientists at MSU are using novel proteomic techniques to discover new biomarkers in chicken and catfish relevant in foodborne disease, such as chicken salmonellosis. ARS Scientists are also discovering new active enzymes (kinases and deubiquitinases) and have developed and optimized an animal tissue processing method, which is compatible with the chemical proteomics to uncover these enzygmes. Techniques to identify novel enzygmes through mass spectrometry have been developed and have discovered a gene in animal macrophage cells (UCHL5) involved in bacterial survival in macrophages.
The quality attributes, descriptive sensory characteristics, and muscle proteomes (sarcoplasmic and myofibrillar) of normal and reddish channel catfish (Ictalurus punctatus) fillets were evaluated. Reddish fillets had greater redness and yellowness values and less lightness than normal fillets, but no differences existed in cooking loss and instrumental texture. The reddish fillets were more bitter, earthy, grassy, metallic, and oxidized, and had more off-flavor than normal fillets. Analyses of the sarcoplasmic proteome revealed higher abundance of hemoglobin (beta) in reddish fillets. Scientists at MSU identified the protein biomarkers responsible for redness in catfish fillets.
Accomplishments
1. Development of single tube assays for detection of Vibrios species. Scientists at Mississippi State University (MSU) have developed single tube (pocket size) assays for independent detection of Vibrio vulnificus and Vibrio parahaemolyticus strains of bacteria from seafood by using the unique biochemical features found in each of these organisms. The test is still to be validated by the FDA laboratory in Alabama. At the conclusion of another segment of this project, ARS Scientists anticipate developing a multiplex quantitative polymerase chain reaction (PCR) assay for detection of all high-risk Listeria monocytogenes (LM) serotypes. ARS Scientists have already shown that multiplex PCR with primers from LMOF2365_0088 and LMOF2365_2059 will detect isolates in serotypes 1/2a, 1/2b, 1/2c, and 4b. In the currently proposed project, ARS Scientists will develop primer/probe combinations that will allow this assay to be quantitative. ARS Scientists also anticipate improving this assay to allow distinction of serotypes 3c, 3b, 4d, and 4e from the high-risk serotypes.
2. Development and application of quantitative polymerase chain reaction (PCR) assays for genetic variants of Edwardsiella tarda. Mississippi State University (MSU) scientists have begun 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. ARS Scientists have developed and validated a set of PCR primers to distinguish between various phenotypically indistinguishable Edwardsiella's and have identified that of the three (E. tarda, E. piscicida and E. piscicida-like), E. piscicida is predominant in catfish aquaculture. A manuscript has been submitted to the Diseases of Aquatic Organisms and is currently under review.
3. Characterization of attachment factors of Listeria (L.) monocytogenes. Scientists at Mississippi State University (MSU) have identified and characterized an attachment factor of L. monocytogenes. This study helps understand how L. monocytogenes attaches on the surface of vegetables and fruits and the information may help to prevent the initial attachment. The resistance and subsequent adaptation of biofilm cells of foodborne bacterial pathogens to any antimicrobials by a frequent repetitive exposure is a great concern. This work shows that the essential oils of thyme, oregano and carvacrol show strong antimicrobial activity against Salmonella biofilm cells that are present on polystyrene or stainless steel coupon surfaces. Essential oils are made up of several antimicrobial constituents, so there is less chance of adaptive resistance and these compounds can serve as a hurdle response to bacterial cell adaptation.
4. Role of physiological functions of deubiquinating enzymes in salmonellosis. Scientists at Mississippi State Univeristy (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.
5. Factors related to development of red fillet in catfish. From the study on determining the relationships between environment factors, catfish, physiology, rigor mortis and meat quality, a method was developed to characterize the proteome of catfish fillets with red color defect.
