Novel Insights into the Regulatory Mechanism of the Sweet-Fruity Aroma Quality of Flavored Black Tea Based on Metabolomics and Molecular Docking

To address the pronounced bitterness, astringency, and lack of sweet-mellow taste and floral-fruity aroma in summer–autumn black tea, yellow peach, Wonhwang pear, and Yinhongli plum juices were added during fermentation. Sensory evaluation, physicochemical analyses, volatile profiling, and molecular docking were used to investigate the sweetness-modulating mechanisms of these Rosaceae fruits. Yellow peach and Wonhwang pear markedly improved the sweet-mellow mouthfeel and fruity aroma, lowering the polyphenol-to-amino acid ratio from 3.79 (water-added control) to 3.46 and 3.10, respectively, increasing free amino acids (up to 3.41%), and moderately reducing tea polyphenols. Yinhongli plum introduced an undesirable sourness. The odor activity values of sweet-fruity compounds such as linalool (up to 65.06) and phenylacetaldehyde were significantly elevated and correlated positively with sensory scores. Molecular docking showed that linalool, phenylacetaldehyde, and methyl salicylate bind strongly to the T1R2/T1R3 sweet taste receptor (binding energies −6.0 to −4.7 kcal/mol) via hydrogen bonds and hydrophobic interactions with residues including GLN237, LEU223, and LEU242. These findings preliminarily elucidate the molecular basis by which Rosaceae fruits enhance the sweet-mellow flavor of summer–autumn black tea, providing a theoretical foundation for quality control and product development.