Factors Impacting Chemical and Microbiological Quality of Wash Water during Simulated Dump Tank Wash of Grape Tomatoes

Abstract

Fresh and fresh-cut tomatoes are high in phytonutrients. However, illness outbreaks associated with contaminated tomatoes have significantly impacted public health and the economic well-being of the tomato industry. Scientific information is needed to develop an effective, practical food safety standard to reduce pathogen contamination. The aim of this study was to assess factors impacting the deterioration of the quality of tomato wash water and the proliferation of indigenous microorganisms during a simulated dump tank washing process. Freshly harvested grape tomatoes were sorted into four groups: prime, defective, underripe, and nontomato debris. Tomatoes with leaf or stem harvest debris, combined or separate, were washed in tap water with or without free chlorine. Water samples were analyzed for total dissolved solids, turbidity, chemical oxygen demand, and chlorine demand. Microbial populations in water and on tomatoes as impacted by chlorine concentration and water filtration (300 μm) were also quantified. Field debris and defective tomatoes were the major contributors to microbial populations in wash water. Field debris, although accounting for <1% of the total weight of harvested material, contributed 37.84% of total dissolved solids, 46.15% of turbidity, 48.77% of chemical oxygen demand, and 50.55% of chlorine demand in the wash water. Water quality deterioration was proportional to the cumulative quantity of tomatoes and debris washed, and free chlorine at ≥5 mg/L significantly reduced the Enterobacteriaceae, aerobic mesophilic bacteria, and yeast and mold populations. These results highlight the importance of minimizing field debris and defective fruits in harvested grape tomatoes to reduce the microbial load and prevent deterioration of wash water quality. This information will be useful for the development of data-driven harvesting and packinghouse food safety practices for grape tomatoes.