Location: Warmwater Aquaculture Research Unit
2021 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
All objectives were planned and completed by the ARS scientists in Stoneville, Mississippi, in collaboration with the scientists at the Mississippi State University. Progress was made on all objectives all of which have a major focus on the ensuring the food safety of catfish, seafood and produce. The third objective also has a focus on the food quality improvement. Production, processing and distribution of fish, seafood and produce are very diverse and extensive, and the system is vulnerable to the introduction of contaminants through the environment, natural processes, and the delivery system.
In support of Objective 1, significance progress was made to optimize the safety of aquaculture products through innovative processes for reducing microbiological, physical, and chemical hazards in seafood/aquaculture products. We continued to renovate our laboratories which included transferring and re-installing equipment from the main Mississippi State University campus to the Experimental Seafood Processing Laboratory. Achievements included installation of an exhaust system for a wet chemistry laboratory, acquisition of $3 million by the Mississippi Agricultural and Forestry Experimentation (MAFES) towards building a Northern Gulf Aquatic Food Research Center (NGAFRC), with an additional $3.8 million pending from the Mississippi Department of Marine Resources for the first phase of building construction for the NGAFRC on a piece of 4-acre land.
We continued to foster our partnership with the USDA-Agricultural Research Service (ARS) and the catfish aquaculture and processing industry to improve the safety and quality of catfish fillet and by-products. A multi-million dollar research project proposal was prepared with a coalition of 15 scientists from MAFES, USDA-ARS, Auburn University and Louisiana State University. We continued to work on the effect of processing, selected chemicals and storage conditions on the spoilage bacteria growth and sensory quality of fresh catfish fillet for extending product shelf-life and demonstrated shelf-life of fillet could be extended for 2-4 days. We initiated a subproject to determine the effect of dry and wet steam on cleaning and sanitation of food processing equipment. Preliminary data showed certain combinations of stream pressure, hot water content and conveyor speed resulted in significant reductions in bacteria and food residues. Using steam for cleaning and sanitation does not require any chemicals, such as chlorine or acids, and would be very useful for improving safety and quality of fish products. Another project has been initiated to determine the effects of high hydrostatic pressure processing to inactivate bacteria in farmed oysters, preliminary data from this project is being analyzed.
In support of Objective 2, we continued to study mechanisms by which certain pathogenic bacteria may be reduced in catfish, seafood and produce including new methods to improve the rapidity, sensitivity and specificity for detecting various pathogens in response to innovative treatments. We completed certification requirements by Food and Drug Administration (FDA) for our Vibrio analysis protocols and are waiting for a FDA visit (delayed due to Covid-19) to certify our laboratory. A novel recombinase-polyermase/dipstick assay was developed allowing more sensitive and rapid detection of pathogenic Vibrio vulnificus in oysters, and this technology is under review for a patent application. This technology will be very useful to oyster aquaculture and processing industries for controlling Vibrio, an important pathogen in shellfish. Further optimization of the method is planned. Significant progress was also made on the development of a rapid system for detecting pathogenic Burkholderia species from fresh vegetables and catfish. Primers-probe combinations have been designed for the detection of pathogenic strains which allow detection of as few as 10 bacterial cells in a sample. We also collaborated with a researchers at the USDA-ARS laboratory in Delaware, on testing how riboflavin, a free-radical initiator, would affect norovirus inactivation by x-ray irradiation. Progress was made on understanding the development of low-level tolerance to fluoroquinolone antibiotic ciprofloxacin in Listeria monocytogenes after sublethal adaptation to quaternary ammonium compound (QAC). Results suggest the potential formation of low-level ciprofloxacin-tolerant subpopulations in some L. monocytogenes strains when exposed to residual QAC concentrations and such cells if not inactivated might create food safety risk.
In support of Objective 3, progress was made on the optimization of the extraction of proteins from catfish by-product, which included heads and bones from the fillet processing industry. Researchers in the Experimental Seafood Processing Laboratory in the Coastal Research and Extension Center of the Mississippi State University continued to investigate how the combinations of the effect of particle size and alkalinity of extraction water could increase the recovery of fish protein from the ground catfish by-products. This research sub-objective was co-supported by an USDA-NIFA competitive grant. Incorporation of whey protein into fish protein isolates improved properties or resulting protein gels. Over-sized catfish are a problem for the industry and have dramatically reduced value, and scientists in the Experimental Seafood Processing Laboratory also determined that adding starch improved the firmness and quality of value-added ‘fish-ball’ products from the meat of oversized catfish. The technologies developed in this project can also be applied to the other types of fish, and will produce a significant effect towards the sustainability of US agriculture and aquaculture. A competitive grant was obtained from the USDA-NIFA-AFRI research programs for enhancing the emulsion stability of the soymilk beverage systems. An international collaboration with Taiwan’s National Kaohsiung University of Science and Technologies led to several publications focusing on the synthesis of butyrate esters of resveratrol, which is a bioactive compound present in grape and other fruits, for enhancing antioxidant capacity and health promotion.
Optimizing efficiency of protein extraction from catfish by-products, containing heads and frames. Catfish by-products (skin, heads and bones), which account for more than 200 million pounds each year and almost 40-50% of the total fish proteins, have been considered as a waste for a long time. Our objective was to enhance the recovery of proteins and improve its food functions through understanding of the protein structures. Our results showed that protein product’s functional performance was related to physical and chemical conditions of the extraction, which subsequently affects the protein molecular structures. Based on our finding of 30% mass recovery, more than 60 million pounds of the value-added protein product could be recovered for making various protein products, such as fish cake or fish sausage for human consumption. The engineering data obtained will pave the foundation for building a protein recovery plant to contribute to the vitality of the rural economy.
Accomplishments
1. Evaluation of dry and wet steam to reduce bacterial contamination on a continuously moving conveyor. Processing equipment cleaning and sanitation are very important to ensure that low bacterial contamination occurs during processing of catfish and other food products to ensure the safety and quality of the products. ARS reseachers in Stoneville, Mississippi, have the objective to use dry and wet steam to spread on the moving conveyer in a continuous manner to achieve the killing of the bacteria and removing catfish residues. A new Clean-In-Place (CIP) technology, Optima Steamer™ SE-II, was tested for its effectiveness for cleaning and sanitizing. Our preliminary results showed that by controlling the steam pressure, water content in the jet stream and moving speed, pathogens can be effectively reduced. The results will be confirmed by conducting more studies. If proven effective, the new steam system can be adopted by the catfish filleting company for improving quality and safety of the fillet products.
2. Enhancing the safety and quality of oyster meat using high hydrostatic pressure processing (HPP). High hydrostatic pressure processing is one of the four FDA-approved post-harvest processing technology for reducing the risk of eating raw oysters. The effect of HPP processing technology on the oysters produced in the Northern Gulf region has not been comprehensively studied. ARS researchers in Stoneville, Mississippi, have the objective to search for the best HPP conditions for processing oysters over a wide range of pressures and processing time intervals. The preliminary results have identified the range of the conditions that could facilitate shucking and to reduce pathogens. More studies are needed. If successfully completed, the oyster processing companies can adopt the processing conditions to preserve the natural quality of oysters with improved safety and to enhance marketing raw oysters to the consumers.
3. Development of a rapid, sensitive, and equipment-free detection of Vibrio vulnificus in oysters. Vibrio vulnificus in oysters and in beach water is very hazardous to human health since it can cause the death of people infected by this pathogen. The official method approved by FDA and NSSP (the National Shellfish Sanitation Program) for Vibrio vulnificus analysis uses culturing method and followed by gene hybridization, and would take 4-5 days to complete. ARS researchers in Stoneville, Mississippi, have the objective to develop a rapid, sensitive and equipment-free method for the detection of this pathogen. Our preliminary results are promising since detection can be accomplished in 30 min. An invention disclosure has been filed by MAFES at the Mississippi State University. If successfully patented, this method will have broad applications in the seafood industries, and will be useful for government agencies for making decisions for beach closure, when this pathogen is detected in the beach water.
4. Decreasing biofilm formation by planktonic cells of Listeria monocytogenes in the presence of sodium hypochlorite. Listeria monocytogenes is regularly exposed to different kind of stresses in the food processing environment. Some processing conditions can exert stress to this pathogen to enhance its persistence in harsh environmental conditions. Along with stress adaptation, biofilm formation by L. monocytogenes is another form of survival mechanism, which makes bacterial elimination from food contact surfaces a serious challenge. ARS researchers in Stoneville, Mississippi, have the objective to understand how sub-inhibitory chlorine in the form of sodium hypochlorite, a commonly used sanitizer, affected planktonic cells and its subsequent biofilm formation ability. The results showed that chlorine decreased L. monocytogenes biofilm formation on polystyrene surface at sub-inhibitory concentration levels. Such anti-biofilm effect was found to be associated with the reduced attachment on polystyrene surface. The research would allow the food processing industry to choose the correct type of equipment materials, which come in contact with foods to facilitate elimination of this pathogen with the aid of chlorine sanitation.
5. Understanding the level of tolerance to fluoroquinolone antibiotic ciprofloxacin in QAC-adapted subpopulations of Listeria monocytogenes. In the food processing environment, even though sanitizers and disinfectants are routinely used at 50-100 times greater than that of their minimum bactericidal concentration (MBC) to kill foodborne bacterial pathogens, both planktonic cells and biofilms cells of these pathogens present in the crevices may be frequently exposed to a gradient of concentrations of biocides in the processing environments. Recent findings showed that such gradual exposure to sublethal concentrations of biocides can co-select for bacterial cells that are tolerant to lethal concentrations of biocides. Therefore, ARS researchers in Stoneville, Mississippi, have the objective to understand the role of sublethal concentrations of biocides in the emergence of heterologous stress-response in L. monocytogenes and if it would lead to the antibiotic tolerance/resistance development. In this project, we tested three approaches for continuous exposure to sublethal concentrations of QAC against actively growing planktonic cells of L. monocytogenes and evaluated the subsequent changes in antibiotic susceptibility against ciprofloxacin by three different methods. Our findings showed that there is a development of low-level tolerance to ciprofloxacin in L. monocytogenes strains after exposure to sublethal concentrations of QAC. These findings are useful in identifying the predisposing conditions for slow emergence of fluoroquinolone-resistant strains of L. monocytogenes, which may create food safety risk.
Review Publications
Kode, D., Nannapaneni, R., Bansa, M., Chang, S.C., Cheng, W., Sharma, C.S., Kiess, A. 2021. Low-level tolerance to fluoroquinolone antibiotic ciprofloxacin in QAC-adapted subpopulations of Listeria monocytogenes. Microorganisms. 9(5):1052. https://doi.org/10.3390/microorganisms9051052.
Tan, Y., Chang, S. 2021. Protein extraction pH and cross-linking affect physicochemical and textural properties of protein gels made from channel catfish by-products. Journal of the Science of Food and Agriculture. https://doi.org/10.1002/jsfa.11126.
Bansal,, M., Dhowlaghar, N., Nannapaneni, R., Kode, D., Chang, S.C., Sharma, C.S., Mcdaniel, C., Kiess, A. 2020. Decreased biofilm formation by planktonic cells of Listeria monocytogenes in the presence of sodium hypochlorite. Food Microbiology. 96. Article 103714. https://doi.org/10.1016/j.fm.2020.103714.
