UV light-based interventions to inactivate pathogens on fresh produce through the use of UV-LEDs and water-assisted processing

Germicidal efficacies of a low pressure mercury lamp and UV-LEDs were compared for E. coli, Listeria, and Salmonella. UV-LEDs emitting at 259 and 268 nm were most effective in pathogen inactivation. Synergistic lethality occurred between 259 and 289 nm light applied simultaneously. The efficacy of dry and "water-assisted" UV254 treatment, and treatment with 277 nm UV-LEDs at 4 and 25°C for the inactivation of pathogens on apples and lettuce was examined. An LPM lamp emitting light at 254 nm was more effective in the dry treatment of E. coli O157:H7 on lettuce, while UV-LEDs at 277 nm were more effective against L. monocytogenes on apples. Water-assisted treatment was more effective overall than direct illumination because the majority of bacteria were released into the water and then inactivated by UV light. UV-LEDs have increased power output but similar germicidal efficacy at 4°C vs. 25°C, validating their use in temperature-controlled facilities.