Unraveling the structural heterogeneity and lenthionine-binding behavior of pea protein fractions under critical pH-shifting

Understanding the structural heterogeneity of pea protein fractions is key to designing plant-based matrices with enhanced flavor retention. In this study, we investigated how critical pH-shifting (pH 10.4/10.6) alters the conformation and lenthionine (LEN)-binding behavior of pea protein isolate (PPI) and its major globulin fractions, 7S vicilin and 11S legumin. Critical pH-shifting significantly enhanced LEN retention, with binding performance ranked as PPI > 7S > 11S; notably, PPI retention increased from 38.89% to 53.69% after treatment. Structural analyses showed that pH-shifting induced controlled conformational loosening, marked by increased free sulfhydryl exposure, reduced crystallinity and thermal stability, and formation of an amorphous network that favored LEN incorporation. Among the fractions, 7S exhibited the highest surface hydrophobicity, whereas 11S remained more compact and less accessible. Molecular docking confirmed a higher theoretical affinity of 7S for LEN than 11S, with binding energies of -31.21 and -17.89 kcal/mol, respectively. Consistently, molecular dynamics simulations showed that 7S formed more accessible hydrophobic binding regions under pH-shifting. Notably, despite the stronger molecular-level affinity of 7S, PPI achieved the highest practical retention, suggesting a composite-matrix advantage that balances binding-site accessibility and structural stability. These findings establish a fraction-dependent structure–function framework for understanding flavor retention in pea proteins and provide a basis for developing protein-based hydrocolloids with improved flavor delivery properties.