Sunny Flavour Unveiled: Decoding the signature taste of yellow tea through chemical quantification and metabolomics

Abstracts: Yellow tea, distinguished by its bright hue and characteristic flavour, has seen recent growth in production. However, sun-drying techniques remain underutilized in its processing, and the chemical basis of its flavour profile remains poorly understood. In this study, tea samples from two cultivars (‘Fuan Dabai Tea’ and ‘Zhongcha 111’) were prepared using different drying technologies, followed by quality evaluations and nonvolatile compound analyses. The results showed that sun drying considerably enhanced the aroma intensity and umami taste of yellow tea. Notably, cultivars and drying methods had differential effects on the compositional characteristics of major taste components. Using ultrahigh-performance liquid chromatography-quadrupole electrostatic orbital mass spectrometry (UPLC-Q Exactive/MS), the nonvolatile metabolites of yellow tea were identified as comprising 10 alkaloids, 17 amino acids, 4 primeveroside compounds, 2 carbohydrates, 12 dimeric catechins, 7 N-ethyl-2-pyrrolidinone-substituted flavanols (EPSFs), 12 flavanols, 1 flavone, 24 flavonol O-glycosides, 5 flavone C-glycosides, 7 lipids, 4 organic acids, 13 phenolic acids, and 7 other compounds. Phenolic acid, flavanol, and flavanol O-glycoside contents were affected by drying methods, whereas tea cultivars differed in amino acid, flavanol and polyphenols contents. Additionally, specific alkaloids and flavonol glycosides were identified as potential markers for differentiating processing techniques. In conclusion, this study provides theoretical reference for the quality design and targeted production of yellow tea.