Fibrillation mechanism of soybean protein isolate and pea protein isolate composites: Focused on structure and rheological properties

Plant protein fibrils have significant potential for development in the food industry and have garnered considerable attention in recent years. However, the interactions between heterologous plant proteins during fibril formation remain largely unexplored. In this study, novel composite fibrils (PSF) were fabricated under acidic heating (pH 2.0, 85 °C, 0–24 h) using hybrid proteins prepared through pH-shifting treatment of soy protein isolate and pea protein isolate at varying ratios (1:2, 1:1, 2:1). SPI and PPI exhibited competitive growth mechanism within PSF, with the dominant protein component dictating the fibrillation process. When heated for 12 h, PSF with a SPI to PPI ratio of 1:1 demonstrated the strongest fibrillation capability and optimal rheological properties, achieving a fibril conversion rate exceeding 60 % and a β-sheet content of 45.21 %. Microstructural analysis revealed that increasing the PPI proportion resulted in smoother fibril surfaces (Rq = 1.33 nm), effectively suppressing the surface gelation tendency of soy protein fibrils. FTIR analysis confirmed hydrogen bonding and hydrophobic interactions as the primary driving forces for fibril formation, and the incorporation of PPI enhanced the structural stability of the fibrillar network. Molecular docking validated the binding potential between PPI and SPI, laying the theoretical groundwork for subsequent fibrillation. This study innovatively engineered structurally and functionally tunable plant protein fibrils to broaden their applications in the food industry.