Atmospheric cold plasma inactivation of Escherichia coli, Salmonella enterica serovar Typhimurium and Listeria monocytogenes inoculated on fresh produce

Atmospheric cold plasma (ACP) represents a potential alternative to traditional methods for non-thermal decontamination of foods. In this study, the antimicrobial efficacy of a novel dielectric barrier discharge ACP device against Escherichia coli, Salmonella enterica Typhimurium and Listeria monocytogenes inoculated on cherry tomatoes and strawberries, was examined. Bacteria were spot inoculated on the produce surface, air dried and sealed inside a rigid polypropylene container. Samples were indirectly exposed (i.e. placed outside plasma discharge) to a high voltage (70kV_RMS) air ACP and subsequently stored at room temperature for 24h. ACP treatment for 10, 60 and 120s resulted in reduction of Salmonella, E.coli and L.monocytogenes populations on tomato to undetectable levels from initial populations of 3.1, 6.3, and 6.7 log₁₀ CFU/sample, respectively. However, an extended ACP treatment time was necessary to reduce bacterial populations attached on the more complex surface of strawberries. Treatment time for 300s resulted in reduction of E.coli, Salmonella and L.monocytogenes populations by 3.5, 3.8 and 4.2 log₁₀ CFU/sample, respectively, and also effectively reduced the background microflora of tomatoes.