Phase separation behavior of ovalbumin-chitosan: Application for the development of Janus-type fruit preservation coatings

To mitigate post-harvest losses in field-grown fruits and thus contribute to global efforts against malnutrition and hunger, this study presents an edible coating inspired by the phase separation of ovalbumin (OVA) and chitosan (CS) complexes, resulting in distinct inner and outer functional layers. We demonstrate that the phase behavior of the OVA-CS complexes is modulated by resveratrol (RES). Specifically, RES modifies protein conformation and intermolecular interactions by enhancing hydrophobic forces and reorganizing hydrogen bonds, driving the self-assembly of a Janus-type coating during drying. Optimized at pH 5.6, the OVA-CS-RES (OCR) coating exhibits superior barrier properties, achieving the lowest water vapor permeability and oxygen permeability. Anisotropic wettability was confirmed by contact angle measurements and atomic force microscopy, with the maximum contact angle difference between the inner and outer surfaces reaching 57.2°. Scanning electron microscopy and confocal laser scanning microscopy further verified uniform coverage and effective sealing of epidermal pores on fruit surfaces. Application experiments showed that the OCR coating significantly delayed fruit oxidation, reduced weight loss, preserved texture and ascorbic acid content, and maintained aroma integrity throughout 40 days of storage. Overall, this study introduces a scalable, single-step coating strategy leveraging self-assembled functional Janus coatings to significantly extend fruit shelf life.