Synergistic modulation of pH and dextran on high internal phase Pickering emulsions stabilized by soy protein isolate...

This study developed novel high internal phase Pickering emulsions (HIPPEs) based on soy protein isolate microgel particles (SPIMP) and dextran (DEX) and systematically investigated the effects of pH and SPIMP/DEX ratios on their stabilization mechanisms and 3D printing performance. Multispectral and interfacial properties revealed that pH-induced conformational unfolding of SPIMP exposed more binding sites, and DEX displayed pH-dependent distribution within the system. Under acidic conditions (pH 3), the high aggregation and low adsorption efficiency (45.7 %) of SPIMP led to a predominantly "free" state of DEX. Under neutral and alkaline conditions (pH 7 and 9), SPIMP and DEX formed stable "core-shell" complexes, achieving optimal binding efficiency at pH 9. These complexes exhibited better interfacial wettability (Contact angle = 90° ± 5°). CLSM and rheological properties indicated that the acidic HIPPEs stabilized by solely SPIMP exhibited bridging flocculation structures. The depletion effect driven by "free" DEX optimized the viscoelastic balance of the system (G' > 1000 Pa, G" > 100 Pa). The neutral and alkaline HIPPEs leveraged the steric hindrance effect of SPIMP/DEX complex to form uniform small-sized droplets, enhancing their mechanical properties and shear recovery (Yield stress >170 Pa, Recovery rate > 80 %). Ultimately, high-precision 3D printing was achieved at SPIMP/DEX ratios of 1:1, 1:3, and 1:2 in acidic, neutral, and alkaline HIPPEs, respectively. The pH and DEX co-modulation strategy offered novel insights and technical pathways for designing advanced emulsifiers and expanding 3D printing applications.