In this study, the difference in the chemical composition among the representative types of Yunnan white tea, Yun Baihao, Yueguangbai grade Ⅰ and Ⅱ of Baimudan and Yun Shou were investigated by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Orbitrap-MS). A total of 120 compounds were identified, including catechins, dimeric catechins, amino acids, alkaloids, phenolic acids, organic acids, aroma glycosides, flavonoid glycosides, N-ethyl-2-pyrrolidinone-substituted flavan-3-ols, and lipids. Partial least squares-discriminant analysis (PLS-DA) and heatmap analysis showed that there were distinct differences in the chemical components among the different types of Yunnan white tea. A total of 76 significantly differential compounds were among these types (P < 0.05). The contents of catechins, dimeric catechins, alkaloids, phenolic acids, and theanine were higher in white tea from younger tea leaves; some amino acids and myricetin glycosides were richer in Baimudan, while the contents of apigenin glycoside, kaempferol glycoside, quercetin glycoside and lipid compounds were relatively high in Yunshou. This study can provide a theoretical basis for the studies of sensory quality, nutritional value and grade discrimination of Yunnan white 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 wereselected, 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.