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Abstract
Chlorine-based sanitizers are widely used in fresh produce industry. However, the antimicrobial efficacy of chlorine-based sanitizers for fresh produce washing process could be compromised by their reaction with organic matter. Excess amount of residual chlorine can result in a large amount of hazardous disinfection by-products (DBPs), whereas deficiency of residual chlorine may not completely inactivate pathogens on produce. The overall objective of this study was to develop a disinfection strategy to ensure the microbial safety and minimize DBPs formation potential for fresh produce postharvest washing process. In the first study, the correlations between water quality parameters and chlorine demand of different types of fresh produce were determined. It was found that ultraviolet absorbance measured at 254 nm (UV254) was most correlated with chlorine demand of various fresh produce wash waters (R = 0.77) among all the tested parameters. In addition, various types of fresh produce can be divided into two clusters based on the Phenolics-to-Protein/E or PPC ratio with the threshold PPC at 0.6. Chlorine demand of different types of produce in the same cluster was highly correlated with UV254. The second study undertaken revealed that organic load, initial chlorine concentration and sanitizer pH all significantly (P 0.05) affected the chlorine demand of produce wash water. Equations to predict chlorine demand for different types of fresh produce, chlorine-based sanitizers, UV254, initial chlorine concentration and sanitizer pH were developed. In the third study, based on the findings from the first two studies, chlorine dosing strategy to estimate initial chlorine concentration needed to reach a targeted residual chlorine for produce washing process were developed and verified using an automatic produce washer. It showed that 10 mg L-1 of residual chlorine can maintain microbial inactivation efficacy and minimize the initial chlorine concentration. The findings in this project can also be useful for produce industry to enhance the microbial and chemical safety of fresh and fresh-cut produce.