Effects of soaking conditions on total phenolic and antioxidant activity of black tea and black tea combined (50:50) with bush tea

Abstract

Black tea (Camellia sinensis) and black tea combined with bush tea (Athrixia phylicoides) were analyzed for their polyphenol content, antioxidant activity and tannin contents. These teas were brewed at several combinations of temperature and soaking duration [30°C for 3 and 10 min., 60°C for 3 and 10 min. and 90°C]. Solvent extraction methods were used for extracting polyphenols, antioxidant activity and tannin contents. A completely randomized design (CRD) with three replications for each treatment was employed. Results showed that total polyphenols, antioxidant activity and tannin content of black tea decreased with decrease in temperature. At 90°C for 3 min., 7.68 mg/100 g of total polyphenols, 3.85 μmol/g of antioxidants and 2.81 mg/ 100 g of tannins were achieved and these amounts decreased to 5.50 mg/100 g for total polyphenols, 1.31 μmol/g of antioxidant activity and 0.72 mg/100 g of tannins at 30°C for 10 min. Combining two teas (50:50) resulted in significant (p<0.005) decrease in total polyphenols, antioxidant and tannin content. At high temperature of 90 °C for 3 min, 2.64 mg/100 g of total polyphenol, 2.48 μmol/g of antioxidants and 1.8 mg/ 100 g of tannins were achieved and these amounts decreased to 1.39 mg/100 g for total polyphenols, 0.35 μmol/g of antioxidant activity and 0.64 mg/100 g of tannins at 30 °C for 10 min. Hence, it is recommended to brew tea at 90°C for 3 min. which gives optimum polyphenols and antioxidant activity in the brewed liquor.