Purpose: This study was to systematically evaluate how conventional and emerging DBPs may form under fresh-cut produce washing conditions and identify major factors that influence the DBP formation.
Methods: A variety of fresh-cut produce and organic matters extracted from produce were exposed to 0.5-200 ppm sodium hypochlorite (NaOCl) at different contact times (n > 50). The process water and produce were then analyzed for the occurrence of >40 different DBPs using three advanced analytical methods. The impacts of produce type, chlorine dosage, chlorine demand, contact time, reaction pH and temperature on DBP formation were systematically evaluated.
Results: The results thus far show that chlorine demand and DBP formation are highly dependent on the produce type and reaction conditions. Generally, higher total DBP concentration correlates with higher chlorine dose, longer washing time, lower pH and higher temperature, while the distribution among different DBP chemical groups may exhibit different trends. For example, strawberry exhibits greater overall DBP formation potential and faster reaction kinetics than lettuce, likely due to different organic precursor characteristics. Major DBPs include haloacetic acids, chloroform, chloroacetonitriles, chloroacetamides, chloral hydrate and chloropropanones.
Significance: Different organic matter from produce can react with chlorine to generate various DBPs. The yield and rate of DBP formation may vary considerably for different types of produce and washing conditions. A comprehensive understanding of these reactions will help development of safer chlorine sanitation strategies to minimize DBPs and associated risks.