The Optimization and Upscaling of Non-Thermal Atmospheric Plasma for Food Processing ^†

Non-thermal plasma technology is recognized for its strong antimicrobial efficacy on food and food production environment-associated microorganisms and its ability to enhance food safety and food shelf-life [1]. However, the lack of scientific knowledge regarding the differences in physical and chemical processes at various upscaling levels hinders the successful transition of this technology from laboratory settings to industrial applications [2]. Hence, the aim of this study is to study the association between plasma-processed air (PPA) composition and its antimicrobial effects, as well as the underlying mechanism of action. This research focuses on three different air plasma torch devices, each representing a distinct stage of upscaling. A microwave plasma torch operated with compressed air delivers PPA as an antimicrobial-acting process gas. Three air plasma torch devices were applied and optimized to study the association between PPA composition and its antimicrobial effects. By employing advanced analytical methods like Fourier transform infrared spectroscopy (FTIR), a comprehensive analysis of PPA’s characteristics was carried out. Key reactive nitrogen species (RNS) in the PPA were identified via spectroscopic measurements for the lab-size device MidiPLexc. From the spectrum, nitrogen monoxide (NO), nitrogen dioxide (NO₂), and dinitrogen pentoxide (N₂O₅) were detected, where NO₂ took up more than 70 % in a quantity of the key reactive species [3]. Input power and relative humidity were found to have an impact on the species concentration. The findings of this study will provide valuable insights into the physical and chemical factors that affect the scalability of non-thermal microwave plasma for antimicrobial processes. The knowledge gained will accelerate the development and application of non-thermal atmospheric pressure plasma as a highly promising alternative for disinfection and cleaning purposes.