Pre-Harvest Factors Drive Metabolic and Flavor Variations in Hainan Dayezhong Black Tea

This study investigated the influences of geographical origin, harvest season, and plucking position on the chemical composition and flavor characteristics of Hainan Dayezhong black tea. Systematic analysis of basic components, volatile profiles and metabolomes of tea samples collected under different pre-harvest conditions revealed significant variations in polyphenols, flavonoids and catechins, as well as distinct differences in volatile composition. Key aroma-active compounds identified were nerolidol, linalool, benzaldehyde, benzeneacetaldehyde and methyl salicylate, which were determined to be decisive for the characteristic aroma profile of Dayezhong black tea. Untargeted metabolomics further demonstrated that these factors do not merely alter individual metabolite levels, but also reprogram energy metabolism, carbon–nitrogen allocation, and secondary metabolic pathways, resulting in distinct metabolic signatures among samples. From a systematic chemical perspective, this study elucidates the metabolic basis of Hainan Dayezhong black tea quality formation and establishes a scientific foundation for targeted quality optimization through regulation of key components.