Design and application of a portable atmospheric cold plasma jet for food safety and air quality improvement

Non-thermal technologies that can inactivate microorganisms without producing harmful gases, heat damage or chemical residues can contribute largely to food safety and environmental applications. This study reports the design, preliminary characterization, and application of a portable atmospheric cold plasma (ACP) jet intended for local food surface decontamination and indoor air pollutant degradation. The device was constructed with a dielectric-barrier configuration (6.58 mm electrode gap) and operated using filtered ambient air at 1.1 L/min. Electrical behavior was assessed via oscilloscope measurements, while reactive gas species (RGS) were evaluated using optical emission spectroscopy (OES) and colorimetric quantification of ozone and NOx. Additionally, methylene blue (MB) discoloration was performed to confirm oxidative activity and functional validation of the reactor. The plasma jet demonstrated peak-to-peak voltage and current reaching up to 11.8 kV and 87 mA respectively. The produced mean ozone and NOx concentrations were up to 50 ppm and 41.5 ppm, respectively, depending on operating voltage. Plasma treatment at 4.5 kV for 5 min numerically delayed Aspergillus flavus (A. flavus) growth by up to 4 days under refrigerated storage and reduced colony counts relative to controls. For the volatile organic compounds (VOC) treatment, maximum reductions of 92.17% (formaldehyde (HCHO)) and 91.89% (Total VOC or TVOC) were achieved at 4.5 kV after 38 min. Overall, the proposed handheld ACP jet demonstrated the feasibility of localized fungal growth suppression and VOC reduction while highlighting areas requiring further optimization.