초록
Maillard reaction products (MRPs) produced during thermal processing of tea are intimately related to its flavor. Our recent work revealed that both levels of l-theanine and d-galacturonic acid in tea leaves decreased dramatically during drying, whereas the specific MRPs from l-theanine and d-galacturonic acid remain elusive. Here, the MRPs formed from l-theanine and d-galacturonic acid were investigated and their taste characteristics and the involved mechanisms were explored. Two novel MRPs from l-theanine and d-galacturonic acid were identified as 1-(1-carboxy-4-(ethylamino)-4-oxobutyl)-3-hydroxypyridin-1-ium (MRP 1) and 2-(2-formyl-1H-pyrrole-1-yl) theanine (MRP 2). MRP 1 and MRP 2 accumulated in dark tea and black tea and were associated with sour (threshold, 0.25 mg/mL) and astringent tastes and an umami taste (threshold, 0.18 mg/mL), respectively. Molecular docking revealed that the taste characteristics of MRPs may be due to strong binding to umami taste receptor proteins (CASR, T1R1/T1R3) and the sour taste protein OTOP1 via hydrogen bonds and hydrophobic interactions.