Application of plasma-activated fog (PAF) in postharvest treatments to reduce spoilage by fungal pathogens and pesticide residues in fruits

Abstract Background During storage, fruits and vegetables are susceptible to the pathogens responsible for postharvest decay. Various tools are available to manage these issues, but not all are environmentally sustainable. Low-temperature plasma (LTP) has garnered significant attention among the most promising and eco-friendly solutions. LTP can be applied directly or indirectly, offering versatile applications. One notable indirect application is the utilization of plasma-activated water (PAW). In this study, we investigated the efficacy of an aerosol made by droplets of water nebulized by the effluent gases of a plasma discharge as a delivery method of PAW to substrates. We named this novel application, reported for the first time, plasma-activated fog (PAF). In this work, it was tested as a new alternative technology for fruit decontamination against postharvest fungal pathogens and pesticide residues. Results PAF was generated via volume dielectric barrier discharge (VDBD) in a jet-like configuration and was applied to evaluate the in vitro effects on the conidial germination of major fungal postharvest pathogens, such as Alternaria alternata , Aspergillus carbonarius , Botrytis cinerea , Cladosporium sp., Monilinia fructicola , Penicillium italicum , Penicillium expansum and Rhizopus sp. Differences in fungal sensitivity to PAF were recorded, with A. alternata showing the lowest sensitivity to treatments. For most species, complete spore inhibition was obtained after 3–5 min of exposure. The efficacy of PAF against fungal rot was assessed on table grapes and strawberries, revealing a reduction in the percentage of rotted fruits exposed to 10 min of treatment, ranging from 45 to 80% on table grapes and from 52 to 74% on strawberries. PAF treatments also reduced pesticide residues on grape bunches and strawberry fruits, with various results depending on the active ingredient, with reductions of up to 96% for abamectin among insecticides and acaricides, and up to 38% for the fungicide fenhexamid. Conclusions The results obtained in the present work have the potential to refine and optimize PAF treatment conditions for the antimicrobial decontamination of plant products. Graphical abstract