Alternative Post-Harvest Washing Solutions to Enhance the Microbial Safety and Quality of Organic Fresh Produce

Non-Technical Summary:<br/>
Production of organic fruits and vegetables relies on careful oversight and appropriate inputs at every step in the growth, harvesting, processing, packaging, storage, and transportation. Care must be taken at every point in the supply chain to minimize the risk of produce being contaminated with foodborne pathogens such as, Shiga-toxin producing Escherichia coli (e.g., O157:H7) and non-STEC, Listeria monocytogenes, and Salmonella. Because many fruits and vegetables are consumed with minimal processing, foodborne illnesses caused by these pathogens are threats to the wellbeing of consumers, especially the elderly, infants, fetuses of pregnant women, and the immune-suppressed. This integrated project proposal to the USDA AFRI Organic Agriculture Research and Extension Initiative Program addresses the third priority area to "develop and improve allowable food safety practices to reduce microbial contamination, while increasing shelf-life of organic fresh produce." The long-term goal of this project is to provide safe, alternative, sustainable and effective treatments to prevent or reduce human pathogen contamination of organic produce. To improve microbiological safety of organic produce, there is an urgent need to develop washing practices that not only enhance sanitization effectiveness but also fulfill the requirement of organic sustainability. In this proposal, integrated research and extension objectives are proposed to improve current sanitization/washing practices. These will include fundamental approaches to understand surface properties of fresh produce and implement permitted surfactants in washing solutions to overcome capillary forces to enable more efficacious use of chlorine. In addition, novel sanitization strategies are proposed using organic essential oils to sanitize produce with and without chlorine. Economic feasibility, impacts on shelf-life and sensory properties of sanitization practices will be evaluated. Effective practices developed through research will be rapidly disseminated through extension to organic producers using media, electronic outlets, and on-farm testing. Integrated extension activities will be an important component directly improving microbial safety and quality of organic produce products in two southeastern states. The successful integration of research and extension can be implemented in organic production in other states.
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Approach:<br/>
The integrated project has research and extension components. The first research objective is to probe surface properties of organic fresh produce and develop strategies of improving sanitization effectiveness of washing solutions. Surfactants permitted for organic production will be studied for the potential of overcoming the capillary force on organic fresh produce and improving sanitization effectiveness of chlorine solutions. Cocktails of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella will be prepared from 5 strains associated with outbreaks due to consumption of contaminated fresh produce. The bacteria will be inoculated on organic carrots, cherry tomatoes, cantaloupes, and leafy greens (romaine lettuce and spinach), and the sanitization effectiveness will be evaluated after treatment, along with residual chlorine and surfactant concentrations. The second objective is to study technologies of dissolving plant-derived food antimicrobials as alternative sanitization agent. The solubilized organic essential oil (EO) will be studied for sanitization alone or in combination with chlorine. The third objective is to in-field test the strategies developed in Objectives 1-2. Three research stations with USDA certified organic sites will be used, one located in Tennessee and two in North Carolina, which will utilize organic production standards for growing one cultivar of tomatoes and lettuce. All treatments will be evaluated on site in year three and fully replicated in year four. The fourth objective is to characterize impacts of alternative sanitization agents on sensory and quality. Romaine lettuce and cherry tomato will be used as the test crops for top 6 antimicrobial combinations from Objective 1 (chlorine +surfactant) and top 6 antimicrobial combinations from Objective 2 (EO or EO + chlorine), with comparison to two controls of water only and 150 ppm chlorine. The fifth objective is to conduct economic analysis of the alternative washing solutions. Extension activities will be fully integrated into all aspects of the research, beginning with involvement of organic stakeholders through a Board of Advisors. Their input and guidance on research objectives, success criteria, review of outreach material and media will assure that the research and extension activities are appropriately targeted. The utility of these alternative antimicrobial systems will be shared in several media types to assure appropriate distribution and on-going use for those in the organic fruit and vegetable industry. Varying delivery and means of communication will facilitate a dialogue amongst organic fruit and vegetable industry members that will be ongoing part the project's timeline and emphasize the importance of appropriate food safety interventions during the processing of fresh organic produce.