Abstract
Tea is a widely consumed non-alcohol drink and its flavour has been shown to vary during manufacturing process and affected by geographical condition. Aroma is among one of the important factors to determine the characteristic and quality of tea, and it is generated from odorless precursors during the tea manufacturing process of withering, panning, rolling, and drying. More than 600 volatile flavour compounds（VFCs）were reported to relate to tea aroma. This thesis aims to use oolong tea manufacturing process to evaluate the aroma forming pathway and to improve the aroma eventually. The other aim is to accomplish geographical classification and to identify the origins of black tea. To achieve the aforementioned goal, we integrate chemical fingerprint and compound specific isotope ratio analysis to observe the variation during manufacturing and due to origins. SPME/GC/MS and SPME/GC/IRMS method were developed for quantitative and isotope ratio analysis of VFCs in tea, respectively. The content of VFCs in tea increases with withering process and reaches its maximum just before panning. Higher panning temperature was used to stop the enzymatic activity The content, composition and isotope ratio of VFCs after panning becomes more stable, justifying that panning would stable the VFCs. Base on results from compound specific carbon isotope ratio analysis and t-Test, Taiwan tea can be distinguished from India, Sri Lanka, and Vietnam tea.