Effect of soiling agents on disinfection efficacy of a pulsed‐xenon UV lamp towards Listeria monocytogenes on stainless steel surfaces

Listeria monocytogenes is a foodborne illness that poses a significant threat to human health in young, old, and immunocompromised persons and accordingly, prevention of Listeria contamination is of the utmost importance. Pulsed xenon ultraviolet radiation (PX‐UV) is a fast method with broad effectiveness against a spectrum of pathogens including Listeria spp. However, the effect of soiling agent present in food preparation environments on the efficacy of PX‐UV inactivation of L. monocytogenes is not well understood. In this work, the effect on PX‐UV treatment for protein‐based (BSA, peptone, and amino acids), carbohydrate (starch, glycogen, D‐lactose, trehalose), and lipid soiling agents (triolein and fish oil) were each evaluated. BSA, D‐lactose, trehalose, glycogen, and triolein were found to increase the amount of colonies recovered on the positive control plates (no treatment) while only trehalose (60% w/v) and fish oil (0.5% w/v) were found to significantly ( p < 0.05) decrease the log‐reduction, while casamino acids (1% w/v) actually increased the efficacy of the PX‐UV treatment. All other compounds had no effect at the concentrations tested. As similar types of compounds had similar UV absorption profiles, it is unlikely that UV absorption plays a significant role in the mechanism of protection exhibited by fish oil and trehalose.