Incorporation of co-stabilizer cellulose nanofibers/chitosan nanoparticles into cajuput oil-emulsified chitosan coating film for fruit application

The development of edible coating to maintain the quality of fruit are rising. The aims of this work are to develop a novel chitosan nanoparticle (Chi-NP) in chitosan (Chi) Pickering emulsion coating co-stabilized cellulose nanofibers (CNF) and to characterize the antifungal and hydrophobicity features of the coating film. As an application, tangerine and tomato were coated and stored at ∼18 °C and ∼48% RH. The coating formulation consisted of 0.8% Chi and 0.5% Caj. Chi-NPs at 0.06% or 0.12% dosage were used as an emulsion co-stabilizer of CNFs (0.24%). The pH was adjusted below the isoelectric point to obtain beneficial properties of Chi-NP (both stabilizer and antifungal co-agent), partially by the amino group protonation. The incorporation of Chi-NP may improve the performance of Chi and Chi/CNF antifungal activities additively, against Penicillium digitatum and Rhizopus stolonifera, as confirmed with a series of assays (in vitro, in vivo, and membrane integrity changes). The incorporation of CNF- or CNF/Chi-NP-stabilized Pickering emulsion contributed to enhance one of functional properties of pure Chi coating, hydrophobicity, as confirmed using water contact angle and fruit weight loss. This novel coating film may have potential applications for maintaining the quality of fruit, particularly from fungal decay.