Calcium-Independent Gelation of Abelia macrotera Pectin Induced by Sodium Ions and Its Synergistic Interaction with Pea Protein Isolate

The effects of Na+ and pea protein isolate (PPI) concentrations on the gelation behavior of Abelia macrotera pectin (AMP) were systematically investigated using texture analysis, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). AMP formed stable gels in the presence of Na+ without requiring Ca2+, and gel properties strongly depended on Na+ concentration and a transition from dense to loose microstructures with increasing Na+ concentrations. Optimal gel performance was achieved at Na+ concentrations of 0.15–0.20 mol/L. The AMP–PPI composite gel exhibited the optimal performance at an AMP:PPI ratio of 0.3:7.5 and Na+ concentrations of 0.10–0.15 mol/L, showing enhanced textural properties, water-holding capacity, and network compactness. FTIR results revealed that Na+ induced non-covalent electrostatic and ion–dipole interactions without forming new covalent bonds. These findings provide a theoretical basis for developing sodium-regulated, calcium-free pectin–protein gels.