Contribution of catechin monomers in tea polyphenols to the structure and physicochemical properties of wheat gluten and its sub-fractions

Abstract Wheat gluten with unique viscoelasticity is a key component that affects the quality of wheat products. In this study, the four typical catechin monomers (EGCG, EGC, ECG, EC) on the physicochemical and structural properties of both wheat gluten and its sub-fractions were systematically studied to clarify the dough/gluten enhancing ability of tea polyphenols. It was found that the two ester-type catechin monomers, EGCG and ECG, played a major role in improving gluten strength, which dramatically extended dough stability from 2.9 min to 18.4 and 7.6 min, respectively. Tea polyphenols, EGCG, and ECG monomers induced a more compact network structure for gluten and glutenin-rich fraction, and resulted in a well-organized and ordered network for gliadin-rich fraction. EGC and EC monomers presented no significant effect on the strength and structure of gluten. Tea polyphenols and the monomers can break the -S-S- bonds in glutenin aggregates, and promote their repolymerization during gluten formation. Unlike most gluten-enhancing agents, tea polyphenols improve gluten strength by enhancing hydrogen bonding and hydrophobic interactions, water-solid interaction, and the strong binding between ester-type monomers and proteins, instead of promoting -S-S- bonds formation.