Jan. 1, 2018 - Dec. 31, 2018Funding Agency
Center for Produce SafetyAmount Awarded
Anita Wright, Ph.D.
University of Florida
Water used for irrigation or processing of produce has been implicated as a source of pathogen contamination that can persist in aquatic systems. Therefore, irrigation derived from surface water sources or flumes of wash water are often sanitized with disinfectants, such as sodium hypochlorite, chlorine dioxide, and peroxyacetic acid. However, these treatments are only marginally effective and have potential toxicity. Thus, development of novel water treatment methods are needed. Proposed research will examine the application of chitosan microparticles (CM) as a possible pre-harvest treatment in irrigation water and/or as post-harvest treatment in produce wash water. Chitosan is derived from chitin as the natural byproducts of seafood waste (shrimp and crab shells) and has applications for industrial waste water treatment as a flocculent. The potential of chitosan as a sanitizer is that it offers an economical, biodegradable and non-toxic alternative to toxic chemicals and that it does not promote resistance to antibiotics. Chitosan is considered “Generally Recognized As Safe” in other food applications, ensuring a high likelihood of acceptance for agricultural water applications. Studies will focus on reducing Salmonella and norovirus on and natural water sources and on produce, and feasibility and cost-effectiveness of practical applications will be assessed.
Water that contacts produce products before harvest or during processing is implicated as a source of pathogen contamination (Danyluk et al., 2007; Pachepsky et al. 2011; CDC, 2012). Currently, pond and wash water is monitored for Escherichia coli levels in order to ensure produce safety. However, metrics that reflect fecal contamination may not accurately ensure the absence of pathogen (McEagan et al., 2013; Luo et al., 2014), particularly those that may be derived from non-fecal sources (i.e. soil, water, foliage). Furthermore, pathogens may persist for extended periods in the environment and be resistant to disinfectants used in water treatment, such as sodium hypochlorite, chlorine dioxide, and peroxyacetic acid. Unfortunately, these compounds show limited efficacy for these treatments, and potential toxicity of these compounds can necessitate additional cost related to their disposal (FDA, 2014). Thus, novel approaches are needed to ensure the safety of agricultural water and provide mitigation for water resources that do not meet current FDA standards. Proposed research will examine the application of microparticles of chitosan as a possible pre-harvest treatment in irrigation water and/or as post-harvest treatment in wash water. Chitosan is derived from chitin, an abundant natural biopolymer and by-product of seafood processing, and has been used for a variety of applications, including food sanitation and also as cost effective treatment for removal heavy metals in wastewater (Tharanathan, 2007). Commercial application of chitosan to irrigation and produce sanitation presents an opportunity to apply biodegradable and non-toxic seafood refuse resources as an economical food safety solution. Feasibility of chitosan applications for sanitizing agricultural water has not been previously assessed. However, established acceptance of chitosan treatment for G.R.A.S. in other food applications ensures a high likelihood of success for subsequent scale-up and associated improvements in processing. The rationale for using chitosan microparticles (CM) in proposed studies is that CM has broader-ranging antimicrobial activity compared to chitosan and does not promote resistance to antibiotics (Ma et al., 2016). Prior research conducted by PI Wright (Fang et al., 2014) and co PI Jeong (Jeong et al., 2011; Jeon et al., 2014) has shown activity against major foodborne pathogens, including Shiga toxin producing Escherichia coli (STEC), Listeria monocytogenes and Vibrio species. Recent studies (Fan, 2016 M.S. thesis University of Florida) by PI Wright’s group demonstrated significant reductions for various serotypes of Salmonella. Proposed research will assess antimicrobial activity of CM in pond water and as film on tomatoes stem scars. Prior reports support antiviral activity of chitosan but not for norovirus (Davis et al., 2012). Therefore, the efficacy of CM toward norovirus will be investigated. Efforts to perform proof of concept for application CM to sanitize agricultural water will include the following
1) Investigate practical pre-harvest application of CM for pathogen reduction in the complex medium of irrigation pond water.
2) Optimize post-harvest application of CM for reduction/prevention of pathogens on produce using CM films.
3) Conduct preliminary experiments to investigate CM activity against norovirus.
4) Assess cost-effectiveness of chitosan application to agricultural water.