Theaflavins which are formed when flavanols are oxidized make up approximately 2 percent of the weight of dried black tea. Alone,they are very astringent,and the amount of caffeine in tea should make it very bitter.

• 黄烷醇氧化时形成的茶黄素约占干红茶重量的2%25。茶黄素在单独存在时很涩，同时茶中那样数量的咖啡因理应使茶变得很苦。