Ultrasound-assisted egg yolk granule-EGCG conjugation via multiple mechanisms for improved functionality and...

This study explores ultrasound-assisted egg yolk granules (EYG)-EGCG conjugation via non-covalent (NC), acidic (C3), alkaline (C9), and free-radical (FR) mechanisms. All methods achieved high-binding efficiency (62-68 %). C9 exhibited the smallest particle size (112 nm), most uniform distribution (PDI 0.25), highest ζ-potential (-40 mV), and lowest surface hydrophobicity (78.4 %), resulting in outstanding protein solubility (95 %) and exceptional emulsifying performance (EAI: 24.0 m²/g; ESI: 770 min) through structural unfolding and electrostatic stabilization. While FR and NC exhibited the highest antioxidant inhibition ratios (DPPH: 77-80 %; ABTS: 71-87 %; FRAP: 80-83 %), C9 uniquely balanced functionality, with creaming stability (100 % for 5 h) and tiny, uniform emulsion droplets (0.5-2 μm). Spectroscopic and thermal analyses confirmed that alkaline conditions best modulate protein structure and stability. In contrast, NC, C3, and FR induced aggregation or oxidative crosslinking, compromising functionality. C9 conjugation is recommended for functional food and nutraceutical applications requiring stability and emulsification.