Use of 254 nm ultraviolet light for decontamination of fresh produce and wash water

Abstract

Fresh produce has been identified as the transmission vehicle for many foodborne illness outbreaks every year. They could be contaminated by pathogens at any point within the farm-to-fork food chain. Washing is often used to remove dirt and pathogens on fresh produce. Moreover, an effective decontamination method is required for wash water to prevent cross-contamination. Our group developed a water-assisted ultraviolet (UV) decontamination system (WUV) which combined washing and UV treatments. We evaluated the influence of turbidity (0–100 NTU) and chemical oxygen demand (COD; 0–2500 ppm) on UV inactivation of Salmonella in simulated wash water with different produce extracts. In the worst condition tested (turbidity of 100 NTU and COD of 2500 ppm), Salmonella in simulated wash water could be eliminated by UV (23–28 mW/cm2; wavelength peak at 254 nm) in 90 s (>6 log CFU/mL reduction), indicating the potential of UV for fresh produce wash water disinfection. Within the ranges tested, the effectiveness of UV inactivation of Salmonella was significantly decreased with increasing COD, but not with turbidity. In addition, ultraviolet lamps were installed in different locations (above and/or in the washing tank).Three WUV configurations showed similar Salmonella reduction on blueberries (1.8–2.0 log) and tomatoes (2.4–2.9 log). However, the Overhead and Dual WUV configurations reduced significantly (P < 0.05) more Salmonella on lettuce than the Submersible WUV configuration.