Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

The antioxidant activity and the total phenolics content of various tea ext racts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Tro lox equivalent antioxidant capacity (TEAC) test and the low density lipopro tein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics incre ased from 33.8 mg/100 mi after 0.5 min up to 68.4 mg/100 mi after 10 min br ewing time. Stirring during brewing led to higher phenolic yields in the ex tract. Thus, phenolics in stirred black tea ranged from 44.5mg/100ml (0.5mi n) to 96.7mg/100ml (10min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the co rresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test.