The interaction between tea polyphenols and wheat gluten in dough formation and bread making

The effect of tea polyphenols (TPL) on the gluten network structure in TPL-fortified bread and dough systems was investigated. In the bread system, the addition of tea polyphenols (TPL) dose-dependently (0, 0.5, 1.0, 1.5, and 2%) deteriorated the bread quality in terms of the loaf volume, hardness and sensory properties. In the gluten dough system (2% TPL), farinograph results showed that the stability and development time of the bread dough were decreased, resulting in a weak dough with a significantly increased elastic modulus (G'). The disulfide bonds, key to the dough network formation, were decreased by 9.9 μmol g^-1 (24.2%), and their stability was also reduced due to the reduction (15.0%) of the relative content of the gauche-gauche-gauche structure. The addition of tea polyphenols also increased the internal hydrogen bonds and hydrophobic forces along with the increased random coil and decreased α-helix secondary structure of gluten. The water distribution experiment showed that the bound water peak in the nuclear magnetic resonance (NMR) spectrum disappeared, but the adsorbed water and free water were increased by 17.3% and 0.4%, respectively. Collectively, the interaction between wheat gluten and tea polyphenols affects the water-gluten relationship and the protein structure, which leads to a disrupted network structure of the wheat dough and deteriorated bread quality. Strategies to prevent gluten-phenolic interaction in functional bread preparation warrant further investigation.