Plasma-treated liquids as an environmentally friendly alternative to conventional disinfectants for the hygienization of food processing facilities - first insights in shelf life characteristics and antibacterial efficacy

Plasma-treated liquids (PTL) are produced using atmospheric pressure plasma and therefore contain reactive nitrogen species and reactive oxygen species. Due to these reactive species, the liquids exhibit an antimicrobial effect. Therefore, their use as disinfectants is being widely investigated, especially for the food industry. However, there are only a few studies on the efficacy of freshly prepared or stored PTLs on their use as surface disinfectants.
In our studies, we produced PTLs from two different base liquids, saline and deionized water, by treatment with an arc discharge plasma jet. The liquids were characterized after production using sum parameters of the reactive species (pH, oxidation-reduction-potential (ORP) and electrical conductivity). Both PTLs were additionally characterized during storage. In microbiological studies, the antibacterial efficacy of fresh PTLs was tested on different surfaces (acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC) and stainless steel). Our studies revealed that all PTL types achieve a reduction over 4 log, even though the characteristics differ. The antibacterial efficacy of PTL from saline was additionally evaluated during storage and decreased slightly, which is accompanied by a change in pH, ORP and electrical conductivity during the first days of storage. However, this PTL though showed good antibacterial efficacy after 8 days of storage, by inactivating up to 4.9 log of E. coli. This illustrates the potential of PTL to be used as disinfectant in food processing and production.