Understanding the Salmonella Inactivation Mechanisms of 365, 395 and 455 nm Light Pulses Emitted from Light-Emitting Diodes

Abstract

Salmonella is a foodborne pathogen responsible for several outbreaks in low-water activity (aw) foods. Treatment using light pulses emitted from light-emitting diodes (LED) is an emerging decontamination method to inactivate foodborne pathogens. The objective of this study was to understand the antibacterial mechanisms of light pulses with 365, 395 and 455 nm wavelengths against Salmonella Typhimurium in low-aw conditions. The 365 nm light pulses showed better inactivation efficacy against low-aw S. Typhimurium than the 395 nm light pulses. For instance, the 365 nm LED treatment with an ~217 J/cm2 dose produced a reduction of 2.94 log (CFU/g) in S. Typhimurium cell counts, as compared with a reduction of 1.08 log (CFU/g) produced by the 395 nm LED treatment with the same dose. We observed a significant generation of intracellular reactive oxygen species (ROS) in S. Typhimurium cells after treatments with the 365, 395 and 455 nm light pulses at low-aw conditions. The LED treatments also showed a significant membrane lipid oxidation of S. Typhimurium cells after treatments with 365, 395 and 455 nm light pulses. Overall, a major role of ROS generation was observed in the inactivation efficacy of the 365, 395 and 455 nm light pulses against S. typhimurium at low-aw conditions.