Two nearly identical plasma jet-like systems with water misting were investigated for effective pathogen inactivation regimens on Escherichia coli in atmospheric conditions. Although the electrode construction is quite similar, we show that the concentration of active species generated at the exit of the discharge is quite different, and inactivation of bacteria by this treatment also varies. Inactivation and production rates of hydrogen peroxide, nitrate, and nitrite in liquid were higher when a single quartz barrier was utilized in the dielectric barrier discharge and one of the electrodes was open stainless steel.

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Plasma treatment for bacterial inactivation has been studied via the direct application of dielectric barrier discharges or the indirect afterglow of atmospheric pressure plasma jets. Industrial application of this technology is limited to open contact between plasma and bacteria, which limits the potential use of atmospheric plasma for food safety. In this paper, we show that uniform plasma treatment using microsecond-pulsed and nanosecond-pulsed dielectric barrier discharge can be applied directly to a bread surface through two layers of plastic bread packaging material. We show inactivation of Escherichia coli inoculated on the bread surface inside of prevention of mold growth on bread in future studies.