Discrimination of Tanzanian Black Tea by Geographical Origin and Seasonal Variations of Chemical constituents using HPTLC and NIR Spectroscopy

We present the results of a study that differentiated black tea by geographical origin using high-performance thin-layer chromatography (HPTLC) and near-infrared spectroscopy (NIRS). Quantitative measurements of important components (caffeine, chlorogenic acid, and L-theanine) are also reported. Classification and identification of black tea were performed using a combination of PCA and NIRS used for tea clustering. The findings have shown that the differences in tea quality between the southern highlands (Katumba, Kibena, and Lugoda estates) and north-eastern zones (Herkulu, Kwamkoro, and Dindira estates) were related to caffeine, L-theanine, and Chlorogenic acid contents. HPTLC findings revealed higher content of caffeine (13.17 ± 0.47–21.30 ± 0.58 mg/g), chlorogenic acid (13.20 ± 0.46–19.7 ± 0.47 mg/g), and L-theanine (14.50 ± 0.47–19.20 ± 0.46 mg/g) in Southern highlands of Tanzania (Katumba, Kibena, and Lugoda estates) than caffeine (9.65 ± 0.15–13.57 ± 0.21 mg/g), Chlorogenic acid (0.25 ± 0.11–9.84 ± 0.14 mg/g), and L-theanine (5.88 ± 0.22–15.88 ± 0.51 mg/g) of the tea samples collected from the north-east of Tanzania (Herkulu, Kwamkoro, and Dindira estates). NIRS combined with principal component analysis (PCA) grouped tea samples into two-sided clusters those from southern highlands and those from the north-eastern zone with a total of 99% variations among origins. This method successfully discriminates black tea according to its geographical origin.