Microbial Food Safety of Fresh and Fresh-Cut Produce

APPROACH: We will design experiments to optimize rapid, real-time PCR-based microbial detection methods for enteric human pathogens and also assess the application of similar methods for spoilage bacteria on fresh and fresh-cut produce. Because of the high organic load in produce wash water, sanitizer applications approved for fresh and fresh-cut preparation often do not provide effective control of human pathogens or may cause adverse effects on produce quality and shelf-life. Sanitation and wash procedures that are more effective in the presence of a high organic load would be developed. We will identify gene families from human pathogens involved in resistance to sanitation agents as well as stress-tolerance which could be used as targets to design novel food sanitation agents. We will develop effective Biocontrol agents such as bacteriophages, yeasts and lactic acid bacteria to enhance food safety by limiting human pathogens on fresh-cut produce without affecting its quality or shelf-life. <P>PROGRESS: 2005/10 TO 2006/09<BR>
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? <BR> Contamination of fresh fruits and vegetables with microorganisms pathogenic to humans has increased in recent years. Due to the increasing consumption of fresh-cut fruits and vegetables, pre-sliced, packaged pieces, the problem only promises to get worse because fresh-cut produce has had its natural barriers to pathogen contamination removed and are often stored in a stressed, sub-optimal condition. There have been many documented cases of foodborne illness due to contamination of fresh fruit and vegetable products with E. coli O157:H7, Salmonella, and Listeria. We need to understand how such contamination occurs, how the human pathogens survive and grow on fresh produce and how we can better devise postharvest systems for eliminating or controlling the growth of human pathogenic microorganisms while maintaining the quality and shelf- life of fresh and fresh-cut produce. The objectives will be achieved through devising better detection methods for pathogens, microbial genome analysis, and developing biocontrol agents. The research undertaken falls under National Program 108- Food Safety and addresses goals 2.1, 2. 2 and 2.5 as described in the National Program Action Plan. <BR> <BR> 2. List by year the currently approved milestones (indicators of research progress)
<BR> Year 1 (FY 2007) Complete studies on optimizing DNA preparation methods suitable for real- time PCR from various produce for enteric human pathogens and complete evaluation of primers for amplification of target sequences from produce spoilage bacteria. Identify fresh-cut processing conditions that influence sanitizer efficacy and complete analysis of enteric pathogens with reference to three acid-stress pathways. Identify effects of fresh-cut preparation methods on microbial growth and complete testing efficacy of bacteriophage cocktail against L. monocytogenes isolates.
<BR> Year 2 (FY 2008) Complete evaluation of antibody-based detection of L. monocytogenes strains isolated from various foods and complete evaluation of PCR protocols for rapid detection of spoilage bacteria. Complete evaluation of the novel compounds on browning inhibition and pathogen inactivation on apples. Complete study on role of glucans in stress tolerance and virulence of Salmonella spp. Complete evaluation of fresh-cut processing environment on produce metabolism and complete burst size study of bacteriophages provided by Intralytix, Inc. <BR> Year 3-4 (FY 2009-2010) Optimize parameters for molecular beacon-based rapid detection methods for Salmonella and Listeria spp. and assays for detection of plant spoilage bacteria. Complete evaluation of the influence of water quality on wash operations and sanitizer efficacy and complete study on functional diversity of rpoS in pathogenic E. coli. Identification of effects of fresh-cut preparation methods on microbial growth and complete testing efficacy of bacteriophage cocktail against L. monocytogenes isolates. Identification of optimal fresh-cut processing for minimal microbial growth and maximum shelf-life and complete study on combining bacteriophages and yeast antagonists on survival of L. monocytogenes. <BR> Year 4-5 (FY 2010-2011) Finish studies and transfer technologies on molecular beacon based rapid detection identification methods and assays for detection of plant spoilage bacteria optimized. Complete evaluation of the novel compound on food quality and safety of fresh-cut pears and lettuce and identify novel gene targets which may have significant role in stress tolerance and survival. Complete studies and transfer technology on optimal fresh-cut processing for minimal microbial growth and maximum shelf life and complete study on combining bacteriophages and yeast antagonists on survival of Salmonella spp. <BR> <BR> 4a List the single most significant research accomplishment during FY 2006.<BR> New project started April 2006, no significant accomplishment this year. The research will benefit the fresh produce industry, as well as increasing the microbial food safety of the Americans food supply. NP 108, component 2.1.1.4. <BR> <BR> 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. <BR> "Fresh-cuts are Popular, any way you slice them: Where Packaging Meet the Product" from the ARS magazine (July 2006) highlighted research done under this project.