Mississippi Center for Food Safety and Postharvest Technology

APPROACH: Study the influence of CO2 and ozone gas during refrigerated storage on shelf life and selected pathogens inoculated on catfish. Evaluate the microbial load of fish in a processing line to discern critical point(s) that will enhance the shelf life of iced fillets. Develop effective means of sanitation of catfish processing plants. Study the effect of pre-harvest, harvest, and post-harvest practices on quality and safety of catfish. Conduct experiments to determine the genetic basis for the variation in expression of LLO, PI-PLC, and PC-PLC between the virulent L. monocytogenes strain EGD and avirulent strains. Confirm results using a limited number of L. monocytogenes isolates along with one known virulent strain and one known avirulent strain using a mouse assay.
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PROGRESS: 2005/10 TO 2006/09
Progress Report 1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? This work is a cooperative agreement with Mississippi Center for Food Safety and Postharvest Technology - Mississippi State University. This research directly addresses components of National Program 108 Food Safety, National Program 306 Quality and Utilization of Agricultural Products, and National Program 106 Aquaculture. United States consumers spending on seafood products is currently over $55 billion annually, however, much of this demand is met through foreign imports. The catfish farming industry is the largest segment of U.S. aquaculture with about 600 million pounds of catfish being produced annually. Increasing production and consumption of catfish and other domestically produced seafood will benefit U.S. producers, processors, and consumers. Assurance of safe, high quality products will play a crucial role in expanding domestic production and consumption of catfish and other seafood products. Development and evaluation of technologies that allow identification and reduction of food borne microbial pathogens, spoilage bacteria, physical hazards, and chemical contamination in seafood; and education of processors and consumers on seafood safety are crucial to assuring seafood safety, improving product quality, and developing new products. This research directly impacts and benefits producers, processors, and consumers of catfish and other seafood products. The research will assure consumers receive safe, high quality seafood products, resulting in growth in the industries involved in production and processing of these products. We have addressed issues associated with seafood safety and quality through a multidisciplinary program focused on developing and evaluating technologies for improving seafood safety and quality. The overall goal of this project is to develop technologies useful for assuring safety and improving quality of catfish and seafood products. Specific areas of research have been identified through interactions with industry representatives, extension service personnel, and researchers in other disciplines and states. 2. List by year the currently approved milestones (indicators of research progress) This research project has not been through the OSQR process; therefore, a Project Plan with approved milestones has not been developed at this time. Primary objectives for the project and tentative milestones for FY 2007, FY 2008, and FY 2009 are listed in section 3b. 4a List the single most significant research accomplishment during FY 2006. This accomplishment is related to National Program 108 Food Safety. Listeria monocytogenes is common intracellular bacterium that can cause listerosis in humans, a potentially serious illness that accounts for a significant portion of human foodborne diseases. The virulence of L. monocytogenes varies depending on lineage, with some serotypes causing listerosis in humans while other serotypes do not. An avirulent strain of L. monocytogenes (strain HCC23) was evaluated for its ability to stimulate an immune response and provide protection against subsequent infection with virulent Listeria in mice. Mice infected with strain HCC23 exhibited protection against subsequent infection with virulent L. monocytogenes (strain EGD) and L. ivanovii (strain ATCC 19119). This research has increased knowledge of factors determining virulence of this important food borne pathogen and demonstrated that avirulent L. monocytogenes may have potential as a vaccine against virulent Listeria. 4b List other significant research accomplishment(s), if any. This accomplishment is related to National Program 108 Food Safety. <p>The virulence of L. monocytogenes, a common intracellular bacterium that can cause listerosis in humans, varies depending on genetic lineage. Genetic relationships among L. monocytogenes isolates (36 strains from catfish, 35 strains from seafood, and 37 strains from humans) were determined. Results suggest detected genetic differences in L. monocytogenes isolates can be used to predict their potential for causing listerosis in humans. L. monocytogenes isolates from catfish and seafood pose a low threat of causing illness in humans. This accomplishment is related to National Program 108 Food Safety. Microbrial flora present in raw oysters can pose human health issues and reduce shelf life of product. X-ray radiation was evaluated as a technique for reducing the bacterium Vibrio vulnificus, a potential human pathogen, and other bacterial species associated with spoilage in live, in-shell and shucked oysters. An x-ray exposure of 0.75 kGy reduced V. vulnificus to undectable levels and extended shelf life of oysters by greater than 1 week by reducing spoilage bacteria. X-ray radiation has potential to reduce pathogen and increase shelf life in raw oysters. This accomplishment is related to National Program 108 Food Safety. Attachment strength of microbes influences ability to clean food contact surfaces, and has implications for sanitation of seafood processing equipment and microbial contamination of seafood. A method was developed to quantify attachment strength of common food borne bacterial pathogens. This method allows rapid determination of attachment strength of bacterial pathogens on food contact surfaces. Information on attachment strength of pathogens will be useful in developing and evaluating sanitation of processing equipment and better understanding the transmission of food borne pathogens. 4c List significant activities that support special target populations. Assuring safety and improving quality of farm-raised catfish will benefit operators of small farms by expanding markets for catfish products. The USDA Census of Aquaculture in 2000 classified 84% of catfish farms as small businesses, with annual sales of less than $500,000. Of the 1,370 catfish farms in the United States, 515 farms (38% of the total) reported annual revenues of less than $25,000. Expansion of markets through development safe, high quality catfish products will benefit catfish farmers, a significant portion of which are classified as small farmers. 5. Describe the major accomplishments to date and their predicted or actual impact. The focus of this project is to assure safety and improve quality of catfish and other seafood products, accomplishments relate to National Program 108 Food Safety, National Program 306 Quality and Utilization of Agricultural Products, and National Program 106 Aquaculture. Customers benefiting from the research include producers, processors, and consumers of catfish and seafood products. Specifically, effects of x-ray irradiation, ozonation, UV irradiation, modified atmospheric conditions, hot water pasteurization, and various solutions have been studied to determine effects on food borne pathogens and spoilage bacteria in catfish and other seafood. Specific antimicrobials and methodologies have been developed and are currently being used by catfish processors. Factors associated with virulence of Listeria monocytogenes, a food borne pathogen, have been identified and tests to differentiate between virulent and avirulent Listeria monocytogenes have been developed. Increased shelf-life and safety of catfish have been achieved. Information and technologies have been shared with other scientists, catfish and seafood processors, and consumers. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The benefits of this project will be continued development of technologies and techniques to improve catfish and seafood quality and safety. A better understanding of virulence and control of Listeria, an important food borne pathogen, has been achieved and will lead to safer catfish and seafood products. Processors of catfish and other seafood have inquired about commercial application of technologies being developed and evaluated for improving shelf life of products. Information on current research and seafood safety education has been provided to customers through workshops, meetings, and site visits to processing plants. 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below). Dickson, J.S., Marshall, D.L. 2006. Food microbiology and safety: Basic requirements. In Handbook of Food Science, Technology and Engineering, 4 Volume Set. Hui, Y.H., E. Castell-Perez, L.M. Cunha, I. Guerrero Legarreta, H.H. Liang, Y.M. Lo, D.L. Marshall, W.K. Nip, F. Shadidi, F. Sherkat, R.J. Winger, and K.L. Yam (Eds.). CRC Press, Taylor & Francis Group Boca Raton, FL, Volume IV Food Technology and Food Processing, Chapter 184, pp. 184-1-184-8. Duran, G.M., Marshall, D.L. 2006. Cleaning a processing plant. In Handbook of Food Science, Technology and Engineering, 4 Volume Set. Hui, Y.H., E. Castell-Perez, L.M. Cunha, I. Guerrero Legarreta, H.H. Liang, Y. M. Lo, D.L. Marshall, W.K. Nip, F. Shadidi, F. Sherkat, R.J. Winger, and K.L. Yam (Eds.). CRC Press, Taylor & Francis Group, Boca Raton, FL, Volume IV Food Technology and Food Processing, Chapter 196, pp. 196-1- 196-7. Marshall, D.L., Dickson, J.S. 2006. Contaminants. In Handbook of Food Science, Technology and Engineering, 4 Volume Set. Hui, Y.H., E. Castell- Perez, L.M. Cunha, I. Guerrero Legarreta, H.H. Liang, Y.M. Lo, D.L. Marshall, W.K. Nip, F. Shadidi, F. Sherkat, R.J. Winger, and K.L. Yam (Eds.). CRC Press, Taylor & Francis Group, Boca Raton, FL, Volume IV Food Technology and Food Processing, Chapter 194, pp. 194-1-194-10.