Assessment of efficacy and reactive gas species generation for orange juice decontamination using high voltage atmospheric cold plasma

Abstract

While multiple studies have demonstrated atmospheric cold plasma as an effective non-thermal technology for eliminating bacteria, spores, and biological contaminants from food and non-food surfaces1, few report the application of this technique to liquid food within a package2,3. In this study, we use plasma spectroscopy to characterize the high voltage atmospheric cold plasma (HVACP)2 generated by a dielectric barrier discharge (DBD) in orange juice (OJ) within a package containing either air or modified atmosphere (MA65). We also evaluate the effectiveness of HVACP for decontaminating Salmonella enterica serovar Typhi (S. Typhi) in OJ. We exposed 50 ml of OJ both directly and indirectly to 90 kV for up to 120 s and used optical emission spectroscopy (OES) and optical absorption spectroscopy (OAS) to characterize the reactive gas species (RGS). The sample was stored in a refrigerator at 4°C for 24 h following treatment. Conductivity, pH and hydrogen peroxide content was measured before and after the treatments. Treating 50 ml of OJ containing S. Typhi for 120 s with direct treatment resulted in a 2.9 log10 reduction in air and a 4.2 log10 reduction in MA65 24 h after treatment. Using indirect treatment resulted in a 3.8 log10 reduction in MA65. OES and OAS indicated that the levels of OH, N2, N2+, and O− generated in OJ varied with package gas and whether the application was direct or indirect. These differences in RGS between fill gases and contact methods may impact the decontamination efficiency of S. Typhi in OJ. The implications of RGS on microorganism decontamination and potential plasmas systems will be discussed.