Effect of tea polyphenol binding to soybean β-conglycinin and glycinin on structure, aggregation, allergenicity and in vitro digestion characteristics

Non-covalent interactions between soybean storage proteins β-conglycinin (7S) and glycinin (11S) and two tea polyphenols, catechin and epigallocatechin-3-gallate (EGCG), were examined to elucidate their effects on protein conformation, stability, digestibility, allergenicity, and antioxidant capacity. Due to its smaller molecular size, catechin more easily penetrated the hydrophobic cores of proteins, yielding higher binding stoichiometry and concentration-dependent aggregation. At 4 mM, extensive aggregation masked proteolytic cleavage sites, reducing gastrointestinal digestibility by 7.3 % for 7S and 15.1 % for 11S. In contrast, EGCG, with an additional galloyl moiety and a denser hydroxyl network, interacted with proteins through synergistic hydrogen bonding, π–π stacking, and hydrophobic forces. It produced more stable supramolecular complexes with much larger diameters (462.2 ± 6.8 nm for 11S-EGCG, versus 30.3 ± 1.5 nm for native 11S), and lowered IgE-binding capacity by approximately 19.5–38.7 %, probably through epitope masking and surface-charge changes. For both polyphenols, binding significantly decreased solvent accessibility of hydrophobic regions, reorganized secondary structure (α-helix loss and β-sheet gain), and markedly enhanced intrinsic antioxidant capacity. These findings demonstrate that selecting an appropriate polyphenol type and dose can simultaneously confer hypoallergenic potential, controlled digestibility, and elevated antioxidant function. These findings highlight the potential of non-covalent protein-polyphenol assemblies to develop plant-based foods and nutraceuticals with improved health benefits.