Abstract:The effects of different exogenous additives on the activity of oxidases and the change of components during fermentation of Yunnan pu-erh tea were studied.The results suggested that the significant change of ascorbic acid oxidase activity of fermented pu-erh tea was detected with different additives during fermentation process: The activity of ascorbic acid oxidase of pu-erh tea ranked in the order of pyrogallic>gallic acid>water>glycine>glucose when tea samples fermented after 10 days,that after 20 days the order changed to water>gallic acid>glucose>pyrogallic>glycine,that after 30 days in the order of pyrogallic>glucose>water>glycine>gallic acid.The activity of polyphenol oxidase of tea samples appeared a downward trend with different exogenous additives addition during fermentation,and the polyphenol oxidase activity in the first pile-up(ferment for 10 days) sample was the highest.The contents of theaflavins have no significant changes and the content of polyphenols and thearubigins reduced significantly,and the content of theabrownins increased significantly of fermented pu-erh tea samples with different additives.The study indicated that the different exogenous additives such as glucose,gallic acid,pyrogallic and glycine exhibited remarkable effects on the oxidases activity and the components of pu-erh tea during fermentation,and they could accelerate the formation of theabrownins in pu-erh tea.
