Inactivation of Salmonella biofilms formed on stainless steel surfaces by pulsed light

Salmonella prefers surviving as biofilms on food-contact surfaces, and biofilms could be more demanding to eradicate and pose a risk of cross-contamination. Pulsed light, an emerging nonthermal treatment, has a great potential in inactivating microorganisms. The aim of this study was to evaluate the effect of pulsed light on Salmonella biofilms by investigating flash distances (30, 60 and 90 mm), pulse frequencies (1, 0.5, 0.25 and 0.125 Hz), and simulating the potential stress states (incubation time, sodium hypochlorite, and desiccation) of biofilms in the processing environment. Mathematical equations were used to characterize inactivation kinetics. The results showed that the effect of flash distances, pulse frequencies, and desiccation is weak on the cell reductions. The germicidal efficacy of pulsed light on new biofilms (2 d) was better than that on old biofilms (5 d). Biofilms stressed by sodium hypochlorite were more likely to be inactivated than non-stressed biofilms. The Weibull model was used to fit the inactivation curves of Salmonella biofilms under pulsed light at different voltages. A secondary linear model which combined voltages with the parameter a of the first-order model correlation was further established, demonstrating that it could accurately predict the inactivation of Salmonella biofilms.