2018 ASHS Annual Conference

Large quantities of spent water heavily loaded with plant-derived organic compounds are generated during fresh-cut produce washing process. The significant chemical oxygen demand (COD) and chlorine demand (CLD) arising from those compounds complicate the safe reuse of the wash water. Thus, identification of the major chemicals contributing to COD/CLD will provide valuable information for improving the overall food quality and safety of fresh-cut produce. This study aims to characterize the chief sources of COD and CLD occurring during fresh-cut produce washing. Water samples, prepared by washing diced cabbages, were fractionated through centrifugation, ultrafiltration, and solid phase extraction. Sugars, organic acids, and phenolics were profiled by HPLC, and proteins and peptides were extracted directly from the wash water. Regression equations were established to predict the time-dependent CLD of each identified compound at their respective concentrations. Results revealed sugars as the major contributor to COD (81.6%), followed by proteins/peptides (5.3%), organic acids (3.6%), and phenolics (0.5%). In contrast, contributions to CLD ranked roughly as proteins/peptides > phenols ~ organic acids > sugars, although this ranking varied over time. Proteins/peptides accounted for approximately 50% of the total CLD during the cabbage washing process. Phenols reacted rapidly with chlorine, contributing to 21% of the total CLD at 5 min, but this percentage diminished over time as other compounds reacted continuously. Organic acids (citric, malic, oxalic, and ascorbic) and sugars (fructose and glucose) exhibited a gradual pattern of reaction, making up for 22% and 16%, respectively, of the total CLD at 2 hr. Collectively, the identified compounds explained for 94% of the total CLD in 2 hr. This is the first systematic report on the sources contributing to COD and CLD in produce wash water. It underscores distinctions between these two parameters, which will influence the development and selection of improved wash water treatment strategies to achieve improved fresh-cut produce safety.