Uta Schnabel1, Diana Sydow1, Oliver Schlüter2, Mathias Andrasch1 and Jörg Ehlbeck1

1. Leibniz Institute for Plasma Science and Technology, Germany

2. Leibniz Institute for Agricultural Engineering Potsdam-Bornim, Germany

 

Abstract: Currently used methods for decontamination and sanitation are antimicrobial ineffective, generate high costs with a high consumption of water and chemicals additionally. As an alternative, non-thermal plasma at atmospheric pressure could be a versatile tool. Therefore, an experimental set-up based on a microwave-plasma source which generates plasma processed air (PPA) containing manifold RNS-based chemical and antimicrobial compounds was used. The PPA was introduced into distilled water or tap water to generate plasma processed water (PPW) which can be applied for the decontamination of packaging material and fresh produce. This is a new and innovative method for the generation of antimicrobial active water. In our experiments, PET stripes, fresh-cut lettuce, and fresh sprouts were contaminated with six different bacteria; Escherichia coli K12 (DSM 11250), Pseudomonas fluorescens (DSM 50090), Pseudomonas fluorescens (RIPAC), Pseudomonas marginalis (DSM 13124), Pectobacterium carotovorum (DSM 30168) and Listeria innocua (DSM 20649); in a concentration of 108 cfu ml-1 and subsequently treated with PPW. For PPW production, the plasma was ignited for 5, 15 or 50 s. After a post-plasma treatment with PPW of maximum 5 minutes, a decrease of bacterial load up to 6 log were detected for P. fluorescens (DSM-strain) on PET, P. marginalis and P. carotovorum on salad. For all other bacteria and specimen the inactivation rate was lower. Furthermore, visual examinations after 8 days of storage showed only little influences on the texture and the appearance of the tested specimens. The characteristics of plasma and its generated cocktail of long living chemical compounds in air and in water leading to a high bacterial inactivation and offering a wide range of possible applications.

 

Key words: biological decontamination, fresh food, microwave plasma, microorganism, plasma processed water