Abstract: After ascertaining the results of improying the tea quality by using exogenous polysaccharide hydrolase (EPSH) for the processing of broken black tea,the mechanism of improving tea quality was made clear from the several respects of hydrolysis,biochemical disruption and formation of colorant by the tests of electronmicroscope and HPLC.The hydrolysis of the insoluble polysaccharides in the cell wall by using EPSH resulted in the biochemical disruption of cell wall,the decrease of the pH value and the increase of the polyphenol oxidase (PPO) activity in the tea extract and the enhencement of the extraction rate of effective tea components in the extractad tea so that the product quality was overall improved.The biochemical discrupting effect resulting from the hydrolytic action of EPSH was the pssence of the multiple effects on improving the qunlity of broken black tea.

Key words: Broken black tea Exogenous polysaccharide hydrolase (EPSH) Soluble solid (SS) Teaflavin (TF) Electron microscope High performance liquid chromatography (HPLC)