Conformation changes and interfacial behavior of pea protein isolate fibers: Role of protein concentration

The fabrication of protein nanofibers is a promising strategy to enhance the functional properties of plant proteins. In this study, the fibrillation behavior of pea protein isolate (PPI) was investigated under acid-heat-induced conditions (pH 2.0, 85 °C, 12 h), with a particular focus on the regulatory effect of protein concentration (10-40 mg/mL) on nanofiber conformation. The resulting pea protein isolate fibrils (PPIFs) were systematically characterized using ThT fluorescence, surface hydrophobicity, fluorescence, infrared and SEM, and atomic force microscopy. The findings demonstrated that protein concentration plays a key role in governing the kinetics and morphology of fibril assembly. At an optimal concentration of 20 mg/mL, the β-sheet content increased significantly to 42.12 %, surface hydrophobicity was enhanced by 4.5-fold compared to native PPI, and slenderer, flexible nanofibrils were formed. Further investigation of interfacial behavior revealed that while higher concentrations (20-40 mg/mL) promoted fiber thickening and shortening, these structures exhibited reduced interfacial activity due to slower diffusion and aggregation at the oil-water interface. In oil-in-water emulsions, PPIFs prepared at 20 mg/mL significantly enhanced emulsion stability, as evidenced by a decrease in Turbiscan stability index (TSI) from 3.40 (PPI) to 1.58 after 12 h. this study provided a theoretical basis for the controlled assembly and functionalization of plant protein nanofibers and establishes a quantitative "concentration-conformational-interfacial behavior" relationship, offering valuable guidance for their application in food-grade emulsification systems.