Abstract: SDE was used to analyze the essential oils content of fresh and fixation materials of Huangdan cultivar, and aroma composition and its alcoholic precursors distribution compared between Huangdan raw material and fixation materials, in order to find out the effects of fixation procedure on free aroma compositions and its alcoholic precursors distribution and content, so as to find the major pathway to transform aroma compositions of oolong tea. The results showed that the contents of free essential oil of raw material in stems are the highest (20.95 mg/kg), and that in leaves was the lowest (8.15 mg/kg). But the content and distribution of bound alcoholic essential oil were reverse with those of free essential oil. The content of free essential oil of fixation material in shoots is the highest (48.22 mg/kg), and that in leaves the lowest (43.75 mg/kg). After fixation procedure, the content of free essential oil in stems and leaves increases significantly, while the difference between stems and leaves is reduced. Besidse, total content of bound essential oils is reduced about 13.2%～27.4% in stems and leaves. The changes of bound nerolidol and geraniol involved are that terpene aroma is majorly transformed from isopentenylpyrophosphate (IPP) via multilevel enzyme- catalyzed reactions, while the approach of hydrolysis release of glycosidase is only the subordinate pathway.

Key words: Huangdan, raw material, fixation leaves, free state aroma, bound state aroma, distribution