Purpose: The objective of this study was to evaluate water quality variation during routine operations of fresh-cut produce processing, and analyze multiple factors influencing the effectiveness of antimicrobial washes, with a view toward developing practical guidelines for validation and monitoring.
Methods: Research was conducted in collaboration with commercial processing facilities. We collected in-line water samples during regular operation for three types of leafy-greens (iceberg lettuce, romaine lettuce, and cabbage), and analyzed the water quality on-site, including pH, free chlorine, total chlorine, chemical oxygen demand (COD), turbidity, and total dissolved solids (TDS).
Results: Water quality declined continuously during washing operations. The greatest decrease in water quality occurred during diced cabbage wash, with increased COD (max.14870 mg/L), turbidity (max. 281 NTU) and TDS (max. 4750 mg/L), along with fluctuations in free chlorine, total chlorine, and relatively stable pH. COD values correlated strongly with turbidity and TDS. The best correlation was present in romaine lettuce wash water (Pearson’s r=0.95 for COD vs. turbidity) (Pearson’s r=0.97 for COD vs. TDS). Although free chlorine levels were independent of COD, turbidity and TDS, total chlorine levels correlated well with COD, turbidity and TDS in romaine lettuce wash water (Pearson’s r=0.69, 0.61, 0.73, respectively). Further analysis showed that COD increases linearly with turbidity (R2 =0.9075 for romaine lettuce) and TDS (R2=0.9408 for romaine lettuce).
Significance: The results are useful for regulatory agencies and the produce industry in developing guidelines to maintain the quality and food safety of leafy-greens processed by chlorine-based wash systems.