Structural reorganization of Maillard-induced peanut protein isolate-gallic acid-carrageenan conjugates: Interfacial behavior and emulsion stability

The study aimed to construct a microwave-modified peanut protein isolate (MPPI)–gallic acid (GA)–carrageenan (CG) (MPGC) ternary covalent conjugate, and systematically investigate the effects of glycation covalent modification on the conformation, functional properties and interfacial behavior of MPPI, with the goal of developing new emulsifiers exhibiting superior oil-water interfacial performance. Additionally, the environmental stability of emulsions formulated using the covalent conjugate was evaluated. The results showed that as the proportion of CG increased, the degree of covalent modification significantly enhanced. When the mass ratio of the MPPI-GA conjugates to CG was 1:4 (MPGC4), the grafting degree reached 28.72%. The covalent grafting of CG induced the unfolding of MPPI-GA conjugates structure (decreased β-sheet content and increased random coil content), leading to enhanced surface hydrophobicity and surface charge of the MPPI-GA conjugates. Analysis of oil-water interface characteristics revealed that the MPGC4 conjugates exhibited optimal wettability, significantly reducing the oil-water interfacial tension from 17.34 mN/m to 13.99 mN/m, and demonstrated greater rates of interfacial diffusion, penetration and rearrangement, forming a dense adsorption layer at the interface. The emulsifying activity and emulsion stability of the MPGC4 conjugates were increased to 143.98 m 2 /g and 405.60 min, respectively. When 1.5% (w/v) MPGC4 conjugate was applied to oil-in-water emulsions, the emulsion exhibited a significantly reduced particle size with a more uniform distribution, and excellent environmental stability. This study provides a theoretical basis for the development of novel high-performance plant protein-based emulsifiers.