Concentration-dependent interfacial co-assembly of chitosan/whey protein isolate–tannic acid complexes with rice bran wax in Pickering bigels

This study examined the concentration-dependent role of chitosan/whey protein isolate–tannic acid (CS/WTN) complexes in the formation of rice bran wax-based Pickering bigels. The incorporation of WTN induced the formation of CS/WTN complexes with enlarged particle size and modified colloidal characteristics, which further affected interfacial adsorption and assembly. Dynamic interfacial tension and interfacial rheology showed that moderate WTN incorporation enhanced CS/WTN complexes interfacial adsorption and strengthened interfacial viscoelasticity, whereas excessive addition led to aggregate overgrowth and reduced interfacial assembly efficiency. Among the tested formulations, CS/WTN4 exhibited the most favorable interfacial properties. Accordingly, its corresponding Pickering bigels (CS/WTN4), showed the highest fraction of interfacially adsorbed protein (77.28%), the smallest aqueous droplet size (19.94 ± 2.98 μm), the most homogeneous microstructure, the highest bulk viscoelasticity, and the best recovery after shear. LF-NMR further indicated stronger proton confinement and a more compact internal organization in Pickering bigels CS/WTN4, while selective solvent dissociation suggested enhanced hydrogen bonding and hydrophobic interactions. In contrast, CS/WTN8 increased microstructural heterogeneity and weakened the Pickering bigels. These findings provide mechanistic insight into interfacial co-assembly in Pickering bigels.