Qualitative and quantitative evaluation for caffeine, phenolic compounds and nutrient elements in six marketed brands of Kazi and Kazi tea produced in Bangladesh

Six marketed brands of Kazi and Kazi tea produced in Bangladesh viz; Black tea, Ginger tea, Tulsi tea, Green tea, Orthodox black tea and Orthodox green tea were studied before expiry dates for qualitative and quantitative evaluation to screen out their status of caffeine, phenolic compounds [Total Polyphenol (TP), Theaflavin (TF), Thearubigin (TR), Highly Polymerized Substances (HPS), Total Liquor Colour (TLC), Briskness Index (BI) and Colour Index (CI)] and nutrient elements (N, P, K, Ca and Na). All the studied parameters were found to have been varied with brands. The values of caffeine and TP were found to be varied from 2.24% (Orthodox green tea) to 2.65% (Black tea) and 18.84% (Black tea) to 21.88% (Orthodox green tea) respectively. Likewise, the estimated amounts of TF, TR, TLC, CI and BI were determined to be the highest in Black tea but maximum HPS was in Orthodox green tea whereas the lowest TF, TLC and CI were determined in Orthodox green tea. On the other hand TR, and BI were detected to be minimum in Ginger tea and HPS was detected to be minimum in Black tea. On the contrary, the total amount of studied nutrient contents (N, P, K, Ca and Na) was estimated to be the highest in Orthodox black tea (9.99%) and the lowest in Ginger tea (7.55%). The present study concludes that the Orthodox green tea is superior over the other brands in relation to total qualitative status and consequently, all the studied brands of Kazi and Kazi tea may be ranked as Orthodox green tea>Green tea>Orthodox black tea>Ginger tea>Black tea>Tulsi tea.