Influence of the electrode material on the decontamination efficacy of dielectric barrier discharge gas plasma treatments towards Listeria monocytogenes and Escherichia coli

The decontamination efficacy of a dielectric barrier discharge (DBD) gas plasma generator equipped with four different interchangeable electrode materials (stainless steel, brass, silver and glass/brass) was tested towards Listeria monocytogenes 56Ly and Escherichia coli NCFB 555. Bacteria were suspended in sterile saline solutions and placed for 20, 40 and 60 min under the discharge generated at atmospheric conditions by using air as the working gas. Significant differences emerged only for L. monocytogenes (after 40 and 60 min). Highest reductions (up to about 8 log CFU/ml) were observed by using the silver and brass electrodes after 60 min. Differences in terms of electrical parameters (voltage, current, active power) and chemical species generated in the liquid medium (nitrites and nitrates concentrations) were not significant, relevant or directly attributable to the decontamination efficacy of the different electrodes. Ozone production was higher for oxidation-resistant electrode materials. The decontamination effect was influenced by silver and brass antibacterial properties. Industrial relevance The results of the present work, focused on the impact of the electrode material on the decontamination performance, introduced a new aspect in the technology panorama that could improve possible industrial application. The selection of the electrode material played a role in terms of decontamination efficacy.