Efficacy of Atmospheric Non-thermal Plasma Corona Discharge Under Dry and Wet Conditions on Decontamination of Food Packaging Film Surfaces

Food packaging materials must be sterilized to prevent cross-contamination of the product. Non-thermal plasma (NTP) corona discharge can be an effective alternative sterilization method for packaging films. The inactivation efficiency atmospheric NTP corona discharge under dry and wet conditions against vegetative cells of Escherichia coli, Staphylococcus aureus and Bacillus subtilis, spores of B. subtilis and Clostridium sporogenes and fungal spores of Candida albicans, Penicillium expansum and Aspergillus niger on polymeric packaging films were studied. The maximum inactivation of these microorganisms was 5.58, 0.54, 1.51, 1.06, 2.47, 1.73, 2.80, 3.20 and 3.50 log, respectively. Microbial inactivation by the treatments was greatly enhanced under wet conditions. Gram-negative bacteria were found to be more sensitive to NTP, but spores were more resistant than vegetative bacterial cells. Although fungi were less susceptible than bacteria in dry treatments, they became more sensitive than the Gram-positive bacteria in wet treatments. Overall, plasma treatments under wet conditions achieved higher microbial inactivation and would be favourable over the dry treatment.

Pre-sterilized packaging films were inoculated with test microorganisms, including bacteria and fungi and dried for stabilization. The inoculated films were treated by atmospheric non-thermal plasma corona discharge (ANTP-CD) under dry or wet conditions. The ANTP-CD under wet condition caused a much higher microbial inactivation (4-10-fold) than the treatment under dry condition.image