Effects of epigallocatechin-3-gallate on the structural hierarchy of the gluten network in dough

This study examined the effects of epigallocatechin-3-gallate (EGCG) concentration on the structural hierarchy of the gluten network in dough. At micro scale, 1.0% or higher EGCG destroyed the continuity of the gluten network, which was proved by the increase of lacunarity and almost doubling at 2.0% EGCG. At nano-scale, the increase of EGCG concentration significantly (p < 0.05) raised the proportion of the bulk water and lowered the bound water, and significantly reduced the amount of glutenin macromolecule in the dough. At atomic scale, EGCG (≥0.8%) reduced covalent bonds (mainly disulfide bonds in gluten) to dis-aggregate gluten network, but significantly increased the hydrogen bonds, ionic bonds, and hydrophobic interactions to aggregate. In non-covalent bonds, the hydrophobic interaction has positively linearly correlation with the amount of EGCG, indicating that it is the main driving force for EGCG binding gluten, thereby the burial of tryptophan in the tertiary structure of gluten happened. However, at the molecular level, EGCG increased the ratio of aggregate and β-turns, and decreased α-helix in the secondary structure as well as disulfide bridge g-g-g conformation, but not significantly raised in general β-sheet. These unstable secondary structure and disulfide bridge conformation suggested gluten disaggregation caused by EGCG disruption of disulfide bonds outweighed gluten aggregation it promoted through non-covalent bonds, resulting in a loose aggregation morphology of gluten and a discontinuous gluten network.