Altitude and picking period affect the quality of Lushan Yunwu tea: Insights from sensory and metabolomic analysis.

Lushan Yunwu tea (LYT) is recognized as one of China's top ten famous teas, with a long-standing reputation. However, the relationship between LYT quality at different altitudes and picking periods remains unclear. Hence, this study systematically explored the synergistic effects of these two factors on LYT quality. The results revealed significant differences in the taste and aroma profiles of LYT across different altitudes and picking periods. This study demonstrated that the first-picked LYT from medium-to-high altitudes exhibited superior quality with distinct characteristics at different elevations. In the first pick, teas from medium to high altitudes contained more umami and sweet amino acids, whereas those from higher altitudes exhibited higher levels of aromatic compounds, contributing to intense floral, woody, and fruity flavors. Furthermore, the caffeine, theobromine, catechin, and gallic acid contents declined with increasing altitude in the first-picked LYT. In contrast, the contents of these four components were significantly higher in the second-picked LYT from medium-to-high altitudes than in the first-picked LYT. Finally, a multi-parameter flavor wheel was developed for LYT quality, incorporating nine key taste-active and 13 key aroma-active compounds. The findings demonstrated that altitude and picking period act as interdependent drivers of tea quality, which jointly shape its characteristics through their combined effects on temperature and light exposure. These results provide a theoretical basis for understanding the mechanism of LYT quality formation and offer practical guidance for the cultivation and processing of high-quality LYT.