Effects of theacrine on the astringency of EGCG by affecting salivary protein − EGCG interactions through different molecular mechanisms

(−)-Epigallocatechin gallate (EGCG) and theacrine are involved in imparting tea with its astringent and bitter tastes. This study investigated the effect of theacrine on the astringency of EGCG and its molecular mechanism. Sensory evaluation was used to study the astringent intensities of EGCG solutions in the presence and absence of various concentrations of theacrine. The results indicated a considerable increase in the astringency values of EGCG–theacrine solutions compared with those of EGCG solutions alone. Furthermore, dynamic light scattering (DLS) and molecular dynamics simulations (MD) were to explore the interaction mechanisms. The results revealed that theacrine increased the particle size of EGCG-proline-rich proteins (PRPs) aggregates with that of EGCG and PRPs alone. MD revealed that theacrine potentially acted as a bridge between EGCG and PRPs, promoting their interaction and intensifying the EGCG's astringency. However, theacrine could not bridge two or more mucins owing to the substantial spatial structure of mucin. •Theacrine contributed to the astringency of (−)-Epigallocatechin gallate (EGCG).•Theacrine promoted the combinations of the EGCG and saliva proteins.•Theacrine acted as a bridge between the combinations of EGCG and proline-rich proteins.•Theacrine could not contribute to the combinations of mucins and EGCG owing.