Application of innovative processing of deep UV-LED to control food-borne pathogens

Abstract

The UV irradiation for treating food has been approved by the U.S. Food and Drug Administration. So far, most UV treatment is performed by low-pressure (LP) UV lamp of 253.7 nm. But these lamps have some potential risks such as possibility of mercury leakage, short life time and requirement of significant amount of energy. As an alternative to UV mercury lamps, deep UV-LEDs (DUV-LEDs) are of great interest for disinfection. The objectives of this study were to examine the basic spectral properties of DUV-LEDs and the effects of UV-C irradiation for inactivating food-borne pathogens on solid medium as well as in water. A cocktail of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes strains was spread-plated onto each selective medium or inoculated to the sample of water. As temperature increased, intensity of LED was slightly decreased while LP lamp showed intensity increasing until it reaches to the peak temperature around 30 °C. As the dose of UV radiation increased from 0 to 1.67 mJ/cm2, all kinds of food-borne pathogens showed great reduction by >5 log. When treatment temperature increases, reduction level of E. coli O157:H7 and S. Typhimurium were gradually increased, but L. monocytogenes showed no significant different (P > 0.05). Only for E. coli O157:H7, the significant reduction (P < 0.05) was observed at 90% relative humidity condition compared with other conditions such as 30 and 60 %. In case of 10 ml of water treatment, levels of surviving cells of all pathogens were reduced to below the detection limit (1.0 log CFU/g). At the scaled-up test, surviving populations of general bacteria were reduced by 5.38 and 4.37 log CFU/ml for 2 L and 3 L of water, respectively, and lowered to below detection limit for 1 L of water at the dose of 3 mJ/cm2. Linear correlation between inactivation and dosage of UV irradiation was indicated at continuous water decontamination system. The result of this study suggests that a novel type of DUV-LEDs applicability was confirmed as an alternative to the lamp type in inactivating food-borne pathogens.