Mechanisms of heat-activated soy protein isolate-chitosan oligosaccharide complexation: Synergistic interactions for enhanced gelation.

The strategic utilization of natural polysaccharides presents a critical approach for enhancing the gelation properties of soy protein isolate (SPI), which is a key factor in developing superior plant-based food textures. This study demonstrates a strategic technique to enhance SPI gel properties via preheating treatment and electrostatic complexation with chitosan oligosaccharide (COS). Structural analyses revealed that preheating and electrostatic complexation induced SPI unfolding, facilitating conformational transitions toward β-sheet (increased from 53.00 % to 65.35 %) and β-turn (increased from 5.10 % to 7.60 %) configurations while exposing buried tryptophan residues. Fourier-transform infrared spectroscopy, surface hydrophobicity, measurement of interaction force, and molecular docking confirmed that SPI-COS complexation was driven by synergistic electrostatic attractions, hydrogen bonds, van der Waals forces, and hydrophobic interactions. Increasing COS concentration (0-0.16 %, w/v) progressively enlarged complex particle size (100-350 nm) but reduced colloidal stability, as evidenced by turbidity, ζ-potential, and cryo-scanning electron microscopy. Critically, COS incorporation at 0.08-0.16 % (w/v) significantly elevated storage modulus (increased by 275 %) and viscosity while optimizing the regulation of bound and immobilized water in a concentration-dependent manner. These findings establish that COS-mediated electrostatic complexation restructures SPI networks into mechanically robust gels, providing a green strategy for next-generation plant-based foods.