Screening and Prioritizing Conventional and Emerging Disinfection By-products Developed in Fresh and Fresh-cut Produce during Chlorine-based Disinfection

Introduction: Chlorine-containing disinfectants are widely used for cleaning and sanitization in food processing environments. One of the main concerns is the reactivity of chlorine with organic substance to generate disinfection by-products (DBPs) with potential hazards. The side reactions that lead to DBP formation can consume disinfectants and thus lower the efficacy in inactivating pathogens.

Purpose: The purpose of this study is to prioritize DBPs based on screening of their concentrations that can be formed after typical chlorine disinfection processes of produce, including lettuce and strawberries.

Methods: About 50 g of the cut produce were placed into a 200 ml DI water as blank wash and 200 ml NaOCl solution (200 mg/l as Cl₂) as process water, and agitated on a shaker for 30 min at 25°C room temperature. After 30 min, the process water was analyzed for chlorine consumption, and by four analytical methods to screen for the occurrence of around 40 different DBPs including trihalomethanes, haloacetic acids, halonitriles, halonitromethanes, haloacetamides, haloquinones, nitrosamines, and others.

Results: When washed by DI water, 10 and 14 DBPs (out of a total of 27 target DBPs), were detected in wash water from lettuce and strawberries, respectively, at 0.01-0.21 μg/l and 0.03-0.89 μg/l. After washing by 200 mg (as Cl₂)/l NaOCl solution, 22 DBPs were detected in wash water from lettuce at 0.18-1014 μg/l, and 22 DBPs were detected at 0.18-671 μg/l in the case of strawberries. The formation concentrations of some DBPs were also found to be pH dependent.

Significance: The results indicate that residues of chlorine and DBPs are present in produce obtained from the market. Treatment by chlorine can generate a range of conventional and emerging DBPs in produce, and these DBPs may remain in the produce or leach into the wash water.