Effects of endogenous walnut pellicle polyphenols on the structure and functional properties of walnut meal isolate proteins

This study aims to investigate how endogenous walnut pellicle polyphenols (WPP) alter the structural and functional properties of walnut protein isolate (WalPI). WPP influence was assessed by adjusting polyphenol content in walnut meal (WM) through treatments that peeled and dephenolized the pellicle. Results showed that WPP decreased the β-sheet content of unpeeled walnut protein isolate (UWalPI), increased random coil structures, and structural unfolding was induced. These structural changes raised the water-holding capacity of UWalPI from 1.72 to 2.48 g/g and boosted foaming capacity and foam stability by 31.12% and 46.44%, respectively. Conversely, surface hydrophobicity declined by 62.9%, oil-holding capacity reduced to 2.44 g/g, and emulsifying capacity, solubility, and thermal stability were compromised. Scanning electron microscopy indicated WPP-induced rearrangement and aggregation, Molecular docking simulations predicted interactions between WPP and WalPI. The results clarify the mechanisms of WPP-WalPI interactions and provide strategies for the application of WM and WalPI in food processing. • Walnut pericarp polyphenols (WPP) influenced walnut protein isolate (WalPI). • WPP influences the structure and functional properties of WalPI. • WPP enhances WalPI's water-holding, foaming capacity, and foam stability. • WPP reduces WalPI's surface hydrophobicity, solubility, and thermal stability.