Incorporation of carminic acid in gelatin/chitosan nanoparticles for stabilizing high internal phase Pickering emulsions and its functional 3D/4D printing.

Gelatin/chitosan nanoparticles loaded with carminic acid were adopted to construct and stabilize high internal phase Pickering emulsions for 3D/4D printing. Carminic acid was incorporated into gelatin/chitosan nanoparticles with excellent compatibility via interactions like hydrogen bonding and bridging flocculation. These gelatin/chitosan/carminic acid complex nanoparticles exhibited outstanding emulsifying ability, due to the fact that nanoparticle's amphiphilicity (hydrophilic-lipophilic balance) and interfacial wettability (contact angle) promoted its adsorption at the oil-water interface. The optimal high internal phase Pickering emulsion with proper-content carminic acid illustrated uniform droplets, excellent emulsion appearance, high viscosity, great thixotropy, high yield stress, high mechanical strength and outstanding thermal stability. The optimal emulsions also presented excellent 3D/4D printability with high shape maintainability, as well as potential usage in dysphagia diets. This study provides important implications for stabilizing emulsions with carminic acid-loaded nanoparticles and constructing creative, high-quality and functional food products via 3D/4D printing.