Enhancing the functional properties of egg yolk through post-treatments following short-term fermentation for...

Egg yolk proteins (EYP) are natural emulsifiers with wide applications in food systems; however, their poor solubility and limited processing stability hinder industrial utilization. This study developed a composite modification strategy combining short-term lactic acid bacteria fermentation with post-treatments, including pH shifting, enzymatic hydrolysis, or their combination, to improve the structural and functional properties of EYP. Fermentation for 3 h significantly enhanced emulsifying activity and stability, although solubility remained low. Subsequent enzymatic hydrolysis and pH shifting further increased solubility (up to 70.47 %), elevated surface hydrophobicity, and reduced particle size, thereby promoting interfacial adsorption and emulsion stability. FTIR and XRD analyses confirmed conformational rearrangements and reduced crystallinity, while UV derivative spectroscopy revealed greater exposure of aromatic residues, supporting enhanced protein-solvent interactions. Modified EYP exhibited superior emulsifying activity and emulsion stability compared with untreated samples. When applied to powdered oils preparation, EYP-based powders showed higher encapsulation efficiency (63.6 %), bulk density (0.39 g/mL), and rehydration stability than whey protein and pea protein isolates. Overall, unlike conventional single-step modification techniques, this synergistic "fermentation and post-treatment" approach enables multilevel structural reorganization, resulting in markedly improved solubility, interfacial adsorption, and emulsion stability. These findings demonstrate that the synergistic use of fermentation and post-treatments provides a safe, green, and effective approach to enhance EYP functionality, offering valuable insights for developing high-performance powdered fat products and expanding the industrial applications of yolk-derived proteins.