Validation of sanitizer treatments and their impact on microbial communities associated with agricultural water and fresh produce

Abstract

Harvested rainwater serves as a direct interface between environmental microorganisms and fresh produce safety as foodborne pathogens can be introduced during crop irrigation. Although post-harvest washing can reduce water-mediated cross-contamination, wash water quality is critical for the performance of applied sanitizers. Additionally, while produce surface microbiomes can harbor diverse microorganisms, their composition is influenced by both pre- and post-harvest related factors. Therefore, the overall goal of this dissertation project was to validate sanitizer treatments and their impact on microbial communities associated with agricultural water and fresh produce. The scope of this work extends to both the pre- and post-harvest stages of the produce supply chain and highlights the importance of sanitizer treatments to mitigate pathogen introduction at both stages. Additionally, this work addresses key knowledge gaps in the microbial dynamics associated with both agricultural water and fresh produce. Results from this work support peracetic acid (PAA) as a viable on-farm intervention for reducing foodborne pathogens in harvested rainwater used for crop irrigation. While sanitizer treatments are effective at preventing water-mediated cross-contamination onto clean produce during post-harvest washing, sodium hypochlorite (NaOCl) performance is negatively affected by elevated chemical oxygen demand (COD) levels present during washing. However, results from this dissertation also provide a rapid and field-deployable method to predict COD levels during produce washing by using sugar estimation via a colorimetric assay. Findings from this work highlight how microbial outcomes in produce systems are governed by multiple factors on both the pre- and post-harvest sides of the supply chain. Overall, this dissertation provides actionable, science-based guidance for produce growers, processors, and regulators working to strengthen food safety across the fresh produce supply chain.