Inactivation of Escherichia coli on almonds using nonthermal plasma

This study was carried out to investigate the applicability of nonthermal plasma (NTP) technology for the pasteurization of almonds. Almonds were spiked with various levels of Escherichia coli by dipping the almonds in E. coli culture broth followed by drying. The spiked almonds were treated with NTP under different treatment conditions. The pattern of the microorganisms reduction by NTP was analyzed. NTP was found to be effective on reduction of E. coli on almond evidenced by almost 5-log reduction after 30-sec treatment at 30 kV and 2000 Hz. The NTP bactericidal effect on E. coli inoculated on almond increased with the applied voltage and the frequency. The NTP reduction followed the 1st-order reaction kinetics, and the reduction rate constants varied with almond types and grades. The E. coli cells at logarithmic phase were more sensitive to the NTP than those at stationary and declining phases.