Formation of Disinfection Byproducts in Wash Water and Lettuce by Washing with Sodium Hypochlorite and Peracetic Acid Sanitizers

Introduction: Sodium hypochlorite (NaOCl) and peracetic acid (PAA) are being used for cleaning and sanitization in food processing, but their chemical behavior regarding disinfection byproducts (DBPs) formation during washing processes is still largely unknown. Even though PAA is known to have a lower tendency to form chlorinated DBPs than chlorine, the formation potential of DBPs still exists with PAA. Additionally, the side reactions that lead to DBP formation can consume disinfectants and lower their efficacy to inactivate pathogens, thereby increasing the chances of microbial contamination.

Purpose: This study was conducted to obtain a better understanding of the formation potential and distribution of DBPs in the wash water and fresh-cut lettuce after washing by PAA versus by NaOCl. This study also evaluated a wide variety of DBPs including conventional and emerging DBPs (a total of 46 target DBPs).

Methods: Procedures to simulate fresh-cut lettuce washing under produce processing conditions were conducted in the laboratory using three different concentrations of PAA (45 mg/liter, 85 mg/liter, and 100 mg/liter) and one dose of NaOCl (100 mg/liter). The wash water and washed fresh-cut lettuce were extracted and analyzed for the 46 target DBPs.

Results: The results demonstrated that washing by PAA generated fewer DBPs than washing by NaOCl in both wash water and fresh-cut lettuce. The majority of DBPs formed by PAA were aldehydes in the wash water, and aldehydes and trihalomethanes (THMs) in the washed lettuce. The majority of DBPs formed by NaOCl were haloacetic acids (HAAs), nitrogenous DBPs (N-DBPs) and aldehydes in the wash water, and THMs, HAAs, and aldehydes in the lettuce.

Significance: The comprehensive data will facilitate the development of safer produce washing processes and sanitizer applications and guide further research on DBPs in food.