Soy Protein Isolate/ <i>Tremella Fuciformis</i> Polysaccharide Complex-Stabilized High Internal Phase Pickering Emulsions: Andrographolide Delivery, Digestive Behavior, and 3D Printability

The development of advanced bioactive delivery systems is critical for enhancing nutraceutical stability, controlled release, and functional food design. This study presented the fabrication of high internal phase Pickering emulsions (HIPPEs) stabilized by soy protein isolate (SPI) and <i>Tremella fuciformis</i> polysaccharide (TFP) complexes. The SPI/TFP complex was comprehensively characterized, revealing pH-responsive electrostatic and hydrophobic interactions that regulated complex coacervation and colloidal stability. Optimized SPI/TFP HIPPEs formed at neutral pH with 0.5% TFP exhibited superior physicochemical properties, including reduced droplet size, increased zeta potential, enhanced viscoelastic moduli, pronounced shear-thinning behavior, rapid thixotropic recovery, and stable microstructures. Incorporation of andrographolide (Andr) into the SPI/TFP HIPPEs significantly enhanced their protection against ultraviolet irradiation, thermal stress, and prolonged storage. In vitro digestion studies demonstrated controlled lipid hydrolysis kinetics and facilitated micellarization, resulting in the superior bioaccessibility of Andr compared to conventional formulations. Furthermore, the SPI/TFP HIPPEs exhibited excellent 3D printability with high shape fidelity and mechanical resilience and were unaffected by Andr loading. These findings elucidated the structure-function relationships in SPI/TFP-stabilized HIPPEs and established their potential as multifunctional platforms for nutraceutical delivery and customizable 3D-printed functional foods.