Synergistic strengthening of gelatin by Chinese yam polysaccharide: Multi-scale structural characterization and gelation mechanism.

Improving the structural stability and water-retention capacity of gelatin hydrogels is important for expanding their application in high-moisture food systems. In this study, composite hydrogels (CYPG) were prepared by combining gelatin with Chinese yam polysaccharide (CYP), and the effects of CYP concentration (0-0.8%) on gel properties, water distribution, structure, and molecular organization were systematically investigated. CYP produced concentration-dependent changes in hydrogel performance, with 0.6% CYP showing the optimal overall performance. At this concentration, the water-holding capacity increased from 52.37% to 89.79%, accompanied by improvements in hardness, gumminess, chewiness, and viscoelastic moduli. Low-field nuclear magnetic resonance (LF-NMR) analysis showed increased proportions of bound and immobilized water and restricted water mobility, while scanning electron microscopy (SEM) revealed a finer and more uniform porous structure. Changes in ζ-potential and Fourier-transform infrared (FT-IR) bands suggested alterations in electrostatic association and the hydrogen-bonding environment. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) further indicated changes in thermal stability and structural ordering after CYP incorporation. However, increasing the CYP concentration to 0.8% partially reversed these improvements. These results suggest that the enhancement of gelatin hydrogels at an appropriate CYP concentration is associated with coordinated changes in molecular association, pore structure, and water immobilization, providing a basis for the design of food-grade protein-polysaccharide gel systems.