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The overall objective of this proposal is to decontaminate/kill Salmonella and E. coli O157:H7 and extend shelf life of spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes using electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination. <P>The specific objectives are: <OL> <LI>Investigate the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination on the inhibition/killing of Salmonella spp. and E. coli O157:H7 inoculated on the surface and in wounded/torn spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes stored at 4 and 8 degree C and optimize the levels of malic acid, grape seed, green tea extracts alone and in combination by response surface method (RSM). Evaluate the number of survivors at 0, 3, 6, 9, 12, and 15 days of storage (Year 1). <LI>Investigate the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination on the biofilms formed by Salmonella spp./ E. coli O157:H7 and Enterobacter agglomerans (latter will help in biofilm formation) on the surface and in wounded/torn spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes stored at 4 and 8 degree C. Evaluate the number of survivors in the biofilm for 15 days as above. Evaluate the thickness of the biofilm and distribution of Salmonella/E. coli O157:H7 and Enterobacter agglomerans under confocal microscope at 0, 5, 9, and 15 days of storage at 4 and 8 degree C (Year 2). <LI> Investigate the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination on the color and texture of the spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes stored at 4 and 8 degree C. Evaluate color and texture at 0, 5, 9, and 15 days of storage (Year 3). <LI>Investigate the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination on the sensory attributes of the spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes stored at 4 degree C. Evaluate sensory attributes at 0, 5, 9, and 15 days of storage (Year 3). </ol>
NON-TECHNICAL SUMMARY: In light of recent contaminated produce outbreaks, reduction of incidence of food-borne outbreaks related to fresh produce is made a national priority by FDA. Several approaches are in practice to overcome pathogen contamination on fresh produce. However, the commercial methods available do not completely eliminate pathogens attached to the surface and internal tissue. Non-uniform attachment of antimicrobials on the surface leaves blank spots where microorganism can grow and attach to the surface. We are proposing an electrostatic antimicrobial spray to effectively kill/inhibit the growth of pathogens and disrupt bacterial attachments. This research is focused on electrostatic spray for efficient delivery of organic acids, plant extracts, or combinations to kill/inhibit human pathogens Salmonella spp / E. coli O157:H7 on the surface of spinach, lettuce, sprouts, cantaloupe cubes, and tomatoes. These produce will be inoculated with Salmonella / E. coli O157:H7 and sprayed with organic acids/ grape seed/ green tea extracts, or combinations. Log number of survivors will be evaluated during storage. Inhibition of bacterial attachments, disruption of attached bacteria, and killing/inhibiting of internalized pathogens will also be investigated. Treatments will be optimized by statistical method to identify maximum antimicrobial activity. Color, texture, and sensory attributes of the non-inoculated produce will also be evaluated for the treatments that show maximum antimicrobial activity. Success of this study will provide an alternative efficient technology to overcome the outbreaks of Salmonella/E.coli 0157:H7 to the fresh produce industry.<P>APPROACH: Four major activities are covered in this proposal. The first activity will be investigating the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination on the inhibition/killing of Salmonella spp. and E. coli O157:H7 inoculated on the surface and in wounded/torn spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes stored at 4 and 8 degree C and optimizing the levels of these antimicrobials by response surface method (RSM). The second activity will be focused on the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination in the levels optimized by response surface method (RSM) from objective 1 on the number of survivors of Salmonella spp./ E. coli O157:H7 in the biofilm formed on the surface and in wounded/torn produce stored at 4 and 8 degree C. In this activity we will also evaluate the thickness of the biofilm and distribution of Salmonella/E. coli O157:H7 and Enterobacter agglomerans under confocal microscope. The third activity will be evaluating the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination in the levels optimized by response surface method (RSM) from objective 1 on the color and texture of the produce. The fourth activity will be investigating the effect of electrostatic spray containing malic acid, grape seed, green tea extracts alone and in combination in the levels optimized by response surface method (RSM) from objective 1 on the sensory attributes of the produce stored at 4 degree C. All values will be collected and reported as means of three determinations. Analysis of variance (ANOVA) will be conducted using the Statistical Analysis System (SAS 8.1, SAS Institute Inc., Cary, NC, 2000). Duncans multiple-range test will be performed using the SAS program for pair comparison. Significance of difference will be defined at p < 0.05. Successful completion of this project should provide a useful intervention strategy utilizing food acid, natural grape seed and green tea extracts alone or in combination to effectively control Salmonella spp. and E. coli O157:H7 on spinach, lettuce, alfalfa sprouts, cantaloupe cubes, and tomatoes. The cost benefit ratio to adopt new technology will be calculated based on the log reduction of Salmonella spp. and E. coli O157:H7. Major fresh producers will be contacted to discuss the collaboration and application of the electrostatic spray containing malic acid, grape seed and green tea extracts alone or in combination that shows maximum killing/inhibition of Salmonella spp. and E. coli O157:H7. It is anticipated that the initial collaboration will be limited to a pilot plant scale operation to scale up the method without inoculation at the Department of Food Science, University of Arkansas, to serve as a measure of scale-up of the technology.