The starting  tea plant leaf and the processing method are two key factors that affect the chemical composition of various tea types, thus determine their flavor and aroma. In the present study, we plucked the fresh leaf from a given tea plant cultivar, followed by six typical processing methods to make green, white, yellow, oolong, black, and dark teas. The chemical profiling of the non- volatile component of the tea samples as well as the fresh leaf were analyzed by untargeted metabolomics approaches employing LC-Orbitrap-MS. Generally, the six tea types made from relative methods can be clearly seperated and clustered into four chemical phenotype groups by PCA and HCA, which were green and yellow tea, oolong tea, black and white tea, as well as dark tea, indicating the degree of endogenous enzymatic reaction played a crucial role of the chemical profiling of the given tea types. 112 features were annotated by either authentic standards or database matching of MS/MS fragmentations. Heat- map analysis demonstrated that the processing methods of green tea and yellow tea preserved major chemicals from the fresh leaf, the catechins and some organic acids were sharply decreased by black tea processing, amino acids and gamma aminobutyric acid were significantly increased by white tea processing, in particular, dark tea processing produced more dopa, valine, betaine, theophylline and some phenolic acids due to the post fermentation by enviromental microbials. Further, the VIPs to two processing factors of post fermentation and enzymatic reaction  rate were calculated through orthogonal partial least squares analysis on green tea and dark tea, black tea and white tea, respectively. Overall, this study provided a wide range of chemicals that affected by the processing methods of six tea types.

From leaf to tea: The impact of six typical processing methods on the tea chemical profiling

256th National Meeting (2018)

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