Interfacial engineering of quinoa protein-guar gum complexes for 3D printable Pickering emulsions: Rheological modulation, structural fidelity, and lipophilic bioactive delivery.

The development of food-grade bio-inks combining 3D printability with bioactive protection is important for personalized nutrition applications. This work presents a quinoa protein isolate-guar gum (QPI-GG) Pickering emulsion system for encapsulating lipophilic bioactives and enabling 3D printing. Particle size, ζ-potential and wettability analyses showed the formation of stable complexes with a unimodal distribution near 200 μm, a ζ-potential of -37.9 mV and intermediate wettability. FTIR, XRD, SEM and CD analyses, together with dynamic interfacial tension, AFM, molecular docking and molecular dynamics simulations, showed that GG associated with surface-accessible regions of 11S globulin through persistent hydrogen bonding, electrostatic interactions and van der Waals forces. This association altered QPI secondary structure, redirected heat-induced aggregation toward interconnected and conformationally adaptable assemblies, and enhanced interfacial adsorption and steric stabilization. The resulting emulsions formed elastic, shear-thinning networks with enhanced deformation recovery, enabling support-free printing with a collapse rate of 1.11% and water-holding capacity of 99.78%. The optimized formulation encapsulated CoQ10 with 96.81% efficiency, restricted gastric release to 20.9%, and achieved 51.7% cumulative release after intestinal digestion. This study demonstrates QPI-GG Pickering emulsions as a clean-label bioink platform integrating interfacial engineering and additive manufacturing for nutraceutical delivery.