Genipin-induced crosslinking regulates the kinetics and conformational evolution of interfacial self-assembly of soy hull polysaccharides

Soy hull polysaccharide (SHP), an anionic pectin-like polysaccharide derived from soybean processing by-products, exhibits moderate emulsifying capacity but limited interfacial strength due to its reliance on weak physical interactions. To enhance its interfacial performance, this study systematically investigated how genipin (GP) induced covalent crosslinking regulates the adsorption kinetics, conformational evolution, and self-assembly behavior of SHP at the oil-water interface. Dynamic interfacial tension and dilatational rheology analyses revealed a non-monotonic dependence of interfacial properties on crosslinking density. At a moderate SHP:GP mass ratio of 10:5, the system formed a continuous covalent network dominated by Schiff base linkages, achieving the highest interfacial dilatational modulus (120 mN/m) and the fastest molecular rearrangement rate. Correspondingly, high internal phase emulsions (HIPEs) prepared under this condition exhibited the smallest droplet size (460 nm), the highest absolute ζ-potential (−69.69 mV), and enhanced rheological and thermal stability. In contrast, excessive crosslinking (10:8) induced structural over-constraint, interfacial embrittlement, and aggregate formation, leading to reduced adsorption efficiency and compromised emulsion uniformity. Spectroscopic analyses confirmed progressive covalent bond formation and conformational restriction with increasing GP concentration. At high GP levels, the interfacial network transitioned from a homogeneous structure to a heterogeneous phase-separated system, accompanied by GP self-aggregation and SHP conformational collapse These findings demonstrate that crosslinking density critically governs the balance between network connectivity and chain mobility during interfacial self-assembly. This work provides mechanistic insight into the controlled design of polysaccharide-based HIPEs through precise covalent modification and supports the high-value utilization of soybean by-products in advanced food hydrocolloid applications.