In this study, a number of 40 dried tea products, including green, oolong, black, and Pu’erh teas were collected from specific tea-tree plantation regions in the Suoi Giang (Yen Bai Province, the North of Vietnam), Lam Ha and Da Lat (Lam Dong Province, the South of Vietnam). The total flavonoid contents (TFCs) and trolox equivalent antioxidant capacities (TEACs) of those samples were determined and evaluated. The determination of TEACs were carried out based on different chemical reaction mechanisms, i.e., the DPPH/ABTS free radical scavenging activities, ferric reducing antioxidant power (FRAP), and cupric ion reducing antioxidant capacity (CUPRAC). The results indicates the variabilities of TFCs and TEACs among various tea products regarding their differences in origins, species, and processing methods, typically the oxidation levels, in which green tea generally exhibited the highest values. For the oolong tea derived from Lam Dong Province in the present study, the oolong tea products in Lam Ha performed their dominant DPPH radical scavenging activity values compared to those from Da Lat. Additionally, the obtained TFCs and TEACs data were used as the variables for the principal component analysis (PCA) to discriminate these dried tea products based on their processing methods.
Author: MSc. Nguyen Cong Hau
Dr. Tran Thi Nhu Trang
Dr. Do Minh Huy
BSc. Le Thi Anh Dao
