Chemical Patterns of Polyphenols and Free Amino Acids in Teas Affected by Processing Methods

Polyphenols and free amino acids are important components in terms of tea quality. In this study, specific fresh spring shoots harvested from bushes of 7 different tea cultivars (Camellia sinensis), including Jinguanyin, Huangguanyin and Fuyun 6, were processed into green, white, black and oolong teas.Polyphenols, catechins, and total free amino acids (FAAs) in the fresh leaves as well as the teas made from them were determined for comparison. Based on the scatter plot for the polyphenols and FAAs contents of the 4 teas, 3 distinguishable patterns emerged. They were grouped as Type I, which included the green and white teas along with the fresh 2^nd/3^rd-leaf-1 bud leaves, Type Ⅱ, which consisted of the oolong teas and the fresh 2^nd-to-4^th-leaf-1 banjhi bud leaves, and Type Ⅲ, which was the black tea. Maturity of shoots was found to bea key factor that differentiated oolong tea from others. On the other hand, aprincipal component analysis (PCA) using data on catechins or FAAs would be necessary for a satisfactory differentiation on white tea. The non-ester type catechins were more prone to oxidization than the ester type catechins during tea processing, and withering contributed to the increase of FAAs, especially threonine and leucine, in the white tea.