Pickering emulsions stabilized by chitosan nanoparticles and loaded with clove essential oil as a green biopesticide: A case study on controlling fungal growth in oranges

The purpose of this research was to optimize the production of Pickering emulsions (PEs) stabilized by chitosan nanoparticles (CS-NPs) and containing clove essential oil (CEO) as a biopesticide against the fungal growth (Penicillium digitatum) in oranges. First, CS-NPs were synthesized and characterized to prepare PEs. The produced CS-NPs had an average size < 100 nm, contact angle < 90° and a positive zeta potential; CS-NPs were hydrophilic, which showed their ability to stabilize oil-in-water PEs. Second, PEs of CEO in water stabilized by CS-NPs were prepared at different levels of nanoparticles, CEO content, and homogenizer speeds; FTIR spectrum, morphology, size and stability of these PEs during storage were studied. The optimal conditions for the production of PEs included 0.055 % CS-NPs, 1 % CEO and 25,000 rpm homogenization. This PE had an encapsulation efficiency of 98 % and a gradual and appropriate release during the storage time. In the third phase, the antifungal activity of different concentrations of PEs compared with Xedamix (a commercial fungicide) was investigated with the aim of increasing the shelf life of oranges after harvesting. According to in vitro antifungal activity, minimum fungicidal concentration of the produced PEs against P. digitatum was equal to 2 %. Moreover, there was no significant difference between in situ inhibitory effects of PEs and Xedamix on the target fungus in spiked oranges.