Terroir-Regulated Aroma Chemistry of 200–300-Year-Old Mengku Large-Leaf Tea: Mechanisms and GI Applications

Ancient Mengku large-leaf teas from 200–300-year-old Camellia sinensis var. assamica trees in the Bingdao region of Yunnan, China, are highly valued, yet the ecological and biochemical basis of their characteristic floral aroma remains unclear. This limits the understanding of terroir and the development of reliable tools for geographic authentication. Here, we used unmanaged, agrochemical-free ancient tea stands as a field model to examine how soil conditions shape key aroma-active volatiles and sensory properties. Across five core villages (150 trees in total), we combined headspace GC–MS, detailed soil nutrient profiling, and sensory evaluation according to GB/T 23776–2018. Soil total nitrogen was positively correlated with floral terpenes such as linalool and geraniol, while higher available potassium coincided with reduced levels of LOX-derived aldehydes including hexanal. In comparatively nitrogen-poor, organic-matter-poor, but potassium-rich soils, β-ionone reached the highest odor-activity values and drove strong floral perception despite lower linalool; this pattern was most evident in Nuowu village. Based on these compound-specific relationships, we defined a five-compound marker set (β-ionone, linalool, nonanal, geraniol, and hexanal) that enabled accurate geographic origin discrimination within the ancient-tree data set (AUC = 0.93) and performed similarly on an extended archival data set (n = 1,170; AUC ≈ 0.92). These results link measurable soil properties to volatile pathways and sensory outcomes, supporting a mechanism-informed toolset for the authentication and protection of high-value teas.