Atmospheric pressure plasma treatment of Listeria innocua and Escherichia coli at polysaccharide surfaces: Inactivation kinetics and flow cytometric characterization

Abstract

Non-thermal plasma treatment has the potential to realize the disinfection and sterilization of heat sensitive materials and products. In this study, an rf-driven atmospheric plasma jet was tested for its inactivation effects on Gram-positive Listeria innocua and Gram-negative Escherichia coli inoculated on polysaccharide gel using the plate count method and flow cytometry. An inactivation of L. innocua and E. coli to the detection limit (> 6 log inactivation) was achieved after 4 min plasma treatment with 20 W operating power and sample surface temperatures below 30°C but esterase activity was still detectable for both bacteria tested. Different mathematical models were tested to describe the inactivation kinetics. The best fitted model for all inactivation kinetics obtained was the Weibull model. In a first approach, the membrane integrity and esterase activity was modeled with the Gompertz model, a logistic model or a log-linear model with or without tailing or shoulder. The best fitted models were chosen from the GInaFIT tool according to RMSE. Industrial relevance text: Plasma application shows a high potential in food processing. However, to develop and to design industrial applications for food preservation more data on the interaction of process and target organism are required. Flow cytometric approaches will help to close this gap in future. © 2011 Elsevier Ltd.