Purpose: We identified major chemical compounds and functional groups in various leafy green vegetable latex, investigated their effects on sanitizer degradation, and explored new approaches for reducing organic load and maintaining sanitizer efficacy.
Methods: Wash waters collected during fresh-cut produce processing were treated with chlorine solutions containing a range of free chlorine concentrations. The treatment solutions were examined with Raman and infrared spectroscopy, and/or subjected to chemical analysis. Several flocculants over a range of concentrations followed by filtration through activated carbon and ozone were used to treat the simulated produce wash water. Turbidity, pH, chemical oxidation demand (COD), total soluble solids, total suspended solids, and chlorine demand were then determined.
Results: Chlorine concentrations influence the transformation of different functional groups in the wash water as shown by Raman and infrared spectroscopy. High molecular weight flocculent significantly reduced wash water turbidity. Flocculation followed by filtration further reduced turbidities from 50 to <1 NTU, but with limited reduction in COD. With activated carbon filtration, COD was reduced 45% from initial 1270 mg l-1 to 700 mg l-1.
Significance: This study provides critical information on the chemistry of produce wash water during chlorine replenishment. Research findings can be used by the produce industry to develop strategies for maintaining sanitizer concentration required to prevent pathogen survival and cross-contamination during commercial produce washing operations.