Inactivation of foodborne pathogens on food packaging and in cow milk by exposure to a Nd:YAG laser

Abstract

This study demonstrates the inhibition of selective foodborne pathogenic bacteria by exposure to a 355 and 266 nm Nd:YAG laser. In baseline assay P. aeruginosa showed maximum inhibition followed by Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, and Listeria monocytogenes grown on agar surface. Cell lysis was confirmed by confocal microscopy for all pathogens. In liquid media, P. aeruginosa was irradiated with the third harmonic of a Nd:YAG laser pulse energy of 185 mJ, which was able to reduce the population of 1.65 × 105 by 4.7 logs, while P. aeruginosa could only be reduced by 0.73 log/cm2 on packaging material surface. In the final phase, the laser’s potential was preliminarily tested for sterilization of raw cow milk. The reduction patterns of E. coli, Salmonella sp. yeasts and Lactobacillus sp. were 30%, 25%, 47%, and 30%, respectively, in raw milk, moreover, laser exposure had no significant impact on physio-chemistry of milk. Therefore, results indicate the potential application of laser in packing materials and milk sterilization at the industrial level.