| Abstract: | Increased public awareness of health benefits of green tea is generally based on the high polyphenol content of tea leaves and the resulting beverage. A number of factors, such as species, season, agronomic condition and age of the leaves, are known to affect the composition of commercial teas. In the present study the effects of factors associated with domestic preparation and analytical methods, such as brewing time, concentration, solvent and type of tea product, on levels of catechins and caffeine, antioxidant activity and estimated daily intakes were investigated. There were large variations in the levels of total catechins: 43 and 117 mg g?1 dry matter (DM) (brewed for 30 s and 5 min respectively); 72 and 161 mg g?1 DM (extracted in boiling water and 50% acetonitrile respectively); 72 and 117 mg g?1 DM (a tea bag and tea leaves respectively). The effects on caffeine content were comparatively smaller. These variations consequently led to considerable variations in estimated daily intakes based on three cups (600 ml), ranging between 538 and 2014 mg g?1 DM of total catechins and between 103 and 466 mg g?1 DM of caffeine. The antioxidant activity was highest (26 680 µmol g?1 DM) for tea leaves brewed for 5 min and lowest (10 110 µmol g?1 DM) for a tea bag product brewed for 1 min. Copyright © 2005 Society of Chemical Industry |
