Formation and molecular taste perception mechanism of novel L-theanine Amadori products formed during tea drying

Amadori rearrangement products (ARPs) are key Maillard reaction intermediates influencing tea flavor, yet systematic studies on L-theanine-derived ARPs (Thea-ARPs) are limited. This work investigates the formation, identification, and taste perception mechanisms of Thea-ARPs formed during tea drying. Results showed temperature-dependent depletion of L-theanine and four monosaccharides, confirming their precursor roles. Four novel Thea-ARPs ( N -deoxy-1- L -theanine- D -glucose, N -deoxy-1- L -theanine- L -arabinose, N -deoxy-1- L -theanine- L -rhamnose, and N -deoxy-1- L -theanine- D -galacturonic acid) were structurally characterized. Density functional theory calculations revealed formation energetics with reactivity order: uronic acid (UA) > pentose > hexose. Thea-ARPs were naturally present in various teas, with abundance reflecting both precursor availability and processing conditions. Sensory evaluation identified umami as the dominant taste attribute of Thea-ARPs (thresholds: 0.125−0.5 mg·mL⁻¹). Molecular docking and cellular calcium signaling assays demonstrated that Thea-ARPs activate the umami receptor T1R1/T1R3 through hydrogen bonding and hydrophobic interactions. This work establishes Thea-ARPs as potentially important umami contributors, providing a molecular basis for understanding and regulating tea taste.