Effect of NaCl on the structural and foaming properties of egg yolk granules

Egg yolk granules (EYGs), as natural supramolecular assemblies, play crucial roles in food functionality. However, the precise mechanisms underlying their dissociation and functional modulation by salt (NaCl), a ubiquitous food ingredient, remain incompletely understood. This study aimed to elucidate the molecular mechanism of NaCl-induced dissociation of EYGs and systematically evaluate its impact on their functional properties, specifically foaming performance. This study systematically investigated the molecular mechanism of NaCl-induced dissociation of yolk granules and its impact on their functional properties. Multiscale characterization techniques, including laser particle size analysis, zeta potential measurement, SDS-PAGE, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), were employed to analyze the effects of different NaCl concentrations (0-0.5 mol/L) on the physicochemical properties, structural characteristics, and foaming performance of yolk granules. The results demonstrated that 0.3 mol/L NaCl treatment significantly altered the assembly structure of yolk granules, reducing the particle size to (551.02 ± 23.92) nm, increasing the absolute zeta potential to (24.62 ± 1.50) mV, enhancing water-holding capacity and improving solubility to 46.39 % (p<0.05). Structural analyses confirmed that NaCl dissociated the granules by disrupting the phosphoprotein-high-density lipoprotein complexes, as evidenced by increased calcium and phosphorus release, altered surface hydrophobicity, and secondary structure rearrangement. Notably, the 0.3 mol/L NaCl-treated samples exhibited optimal foam stability, which was closely associated with their specific structural features, including moderately dissociated assembly morphology and optimized surface properties. These findings provide mechanistic insights into yolk granule dissociation and establishing clear correlations between their physicochemical properties, microstructure, and foaming functionality and offer a theoretical foundation for developing yolk granule-based stabilizers in food foaming applications.