Metabolomic Analysis of the Chemical Composition of ‘Tieguanyin’ and ‘Shuixian’ Tea

In order to investigate the effect of cultivar and processing technique on the chemical composition of tea, this study analyzed green tea, fresh-scent oolong tea, strong-scent oolong tea and black tea made from the fresh leaves of the ‘Tieguanyin’ and ‘Shuixian’ cultivars from the same graphical origin using metabolomics based on ultra-high performance liquid chromatography-time-of-flight mass spectrometry (UPLC-TOF-MS). The results showed that the chemical compositions of tea samples made from different tea cultivars differed considerably. The contents of most lipids, alkaloids and methylated catechins were higher and the contents of theanine, most catechins, flavone (flavonol) glycosides, phenolic acids and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols were lower in ‘Tieguanyin’ tea than in ‘Shuixian’ tea. Processing techniques also significantly impacted the chemical composition of tea. A total of 127 differential compounds were selected, among which the contents of most catechins, dimeric catechins, alkaloids and some amino acid compounds were significantly higher in green tea than in other kinds of tea. The contents of some amino acids and flavone (flavonol) glycosides (quercetin-3-galactoside, and kaempferol-3-glucosylrutanoside) were higher in fresh-scent oolong tea. The contents of N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), some flavone (flavonol) glycosides (quercetin-3-glucoside, and kaempferol-3-6”-acetylgalactoside), and lipid compounds in strong-scent oolong tea were higher, while black tea was richer in theaflavins and several flavone (flavonol) glycosides.