Effect of relative humidity on the inactivation of foodborne pathogens by corona discharge plasma jet (CDPJ)

Abstract

In this study, we compared the bactericidal activities of corona discharge plasma jet (CDPJ) at different relative humidities (RHs) against Escherichia coli O157:H7, Salmonella typhimurium, and Staphylococcus aureus. CDPJs were produced at 41–62% RH range. The levels of CO, NO, and NO2 species were increased from 62 to 69 ppm, 271 to 311 ppm, and 15 to 26 ppm, respectively, with increasing RH from 41 to 51%. Thereafter, between 51 and 62% RH, their concentrations were decreased. The inactivation effect of CDPJ on the bacteria at different RHs followed the same trend as the plasma species production. Exposure (300 s) to CDPJ produced at 51% RH had resulted in a decrease of E. coli O157:H7, S. typhimurium, and S. aureus counts by 4.01, 3.65, and 3.31 log, respectively. The inactivation patterns exhibited better fit to a Weibulltail model. The first decimal reduction times (δ values) were decreased with rise in RH from 41 to 51%. The inactivation effect was increased with increasing concentrations of CO, NO and NO2 species. In addition, correlation analysis between individual plasma species and inactivation effect indicated that the concentration of NOx species had the greatest effect on the inactivation. © 2020 Elsevier Ltd