Effective pulsed light treatments for inactivating Salmonella enterica serotypes

Abstract

Pulsed light (PL) is a nonthermal treatment that kills microorganisms by exposing them to short-duration pulses of high-intensity broad-spectrum light. This study evaluated the PL inactivation of different serotypes of Salmonella enterica subsp. enterica (Typhimurium, Enteritidis, Heidelberg, and Minnesota) to specifically assess how pulse width and voltage can affect treatment effectiveness. Bacterial suspensions were spread onto solid agar plates, used as a model food surface, and then treated with PL at different treatment parameters (voltage, pulse width, and fluence). Surviving cells were recovered, enumerated, and the proportion of surviving cells were determined. The log-linear model was used to characterize inactivation kinetics. Three independent replicates were performed for all treatments, and data were analyzed statistically. The results obtained with S. Typhimurium highlighted that the inactivation effectiveness of PL treatment could be enhanced by selecting the right combination of parameters within the practical limitations of the equipment. Higher voltages delivered more energy with pulse width, (i.e., a higher irradiance) resulting in a more lethal process. PL was very effective for the inactivation of Salmonella, and a 6 to 7 log reduction was achieved for all four serotypes and their cocktail, after a single light pulse with a fluence of 338 mJ/cm2 and 280 mJ/cm2, at 2500 V (200 μs) and 3000 V (100 μs), respectively. The results demonstrated similar log reductions for individual serotypes and the cocktail.