Divergent effects of Na+ and Ca2+ on tiger nut oil-based whey protein-flaxseed gum oleogels: intermolecular interactions and structural stability.

Salt ions play a key role in regulating the network structure of whey protein isolate-flaxseed gum (WPI-FG) composite tiger nut oil-based oleogels. This study preliminarily selected the system by adjusting Na⁺/Ca²⁺ type and concentration. CLSM showed Ca²⁺ formed denser, more stable networks than Na⁺ or ion-free controls. At 37.5 mmol/L, the oleogel exhibited 85.85% oil-binding capacity and spreadable texture. FTIR spectra suggested potential weak interactions between Ca²⁺ and -OH/-COO^– groups, which may be related to coordination-like binding. XRD suggested the amorphous structure with improved short-range order. Zeta potential supported the stronger electrostatic neutralization effect of Ca²⁺. Accelerated storage at 60 °C showed Ca²⁺-modified oleogels had lower PV and TBARS, enhancing oxidative stability. These findings clarify the structure-function relationship of ion-regulated WPI-FG oleogels, providing preliminary material-level support for the development of sustainable solid fat replacers.