JiaKun PENG1,2,WeiDong DAI1(
Tea Research Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Hangzhou 310008
Graduate School of Chinese Academy of Agricultural Sciences, Beijing 100081
Yongchun Agricultural and Rural Bureau, Quanzhou 362600, Fujian
Agilent Technologies (China) Co., Ltd., Beijing 100102
Abstract
Oolong teas made with different tea cultivars have a great difference in flavor and chemical components. In this study, non-targeted metabolomics, absolute quantitative analysis, and multivariate statistics analysis were used to investigate the chemical differences among Yongchun Foshou (YCFS), Tieguanyin (TGY) and Shuixian (SX) oolong tea and to screen characteristic chemical components of YCFS oolong tea, as well as to study the influence of tea cultivars on chemical components and sensory quality of oolong tea.
Camellia sinensis cv. Foshou was used as the main research sample and Camellia sinensis cv. Tieguanyin and Camellia sinensis cv. Shuixian were used as the controls. Three tea cultivars were manufactured into fresh-scent, strong-scent and aged-scent oolong teas. Ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) was used for non-targeted metabolomics analysis to screen differential compounds in the oolong teas made from different cultivars. In addition, ultra-high performance liquid chromatograph, amino acid analyzer and ultra-high performance liquid chromatography-quadrupole-orbitrap-mass spectrometry (UHPLC-Q-Orbitrap-MS) was applied for absolute quantifications of main chemical constituents and differential compounds in oolong teas made from different tea cultivars.
Compared with the control oolong teas of same scent type, YCFS oolong tea had relatively higher contents in total amino acid and theanine. The contents of total catechins and caffeine were not significantly different among the 3 cultivars in fresh-scent and strong-scent oolong teas, which were the highest in YCFS in aged-scent oolong teas. The content of gallic acid was SX>YCFS>TGY in 3 scent types oolong teas. Metabolomics analysis combined with multivariate statistics analysis showed that the compound patterns in oolong teas made from different tea cultivars were significantly different. In fresh-scent, strong-scent and aged-scent oolong teas, there were 50, 59 and 47 differential compounds between YCFS and control cultivar, respectively. Among them, 23 differential compounds were common, including 14 flavone (flavonol) glycosides, 5 catechins and their derivatives, 1 lipid, 1 alkaloid, 1 organic acid and 1 amino acid. Further quantitative analysis of 20 main flavone (flavonol) glycosides showed that the contents of 14 flavone (flavonol) glycosides were the highest in YCFS oolong teas, whose contents were 1.4 to 14.6-fold of that in TGY oolong teas and were 1.3 to 18.0-fold of that in SX oolong teas. Among four kinds of flavone (flavonol) glycosides, quercetin glycosides were the main flavone (flavonol) glycosides with higher contents than glycosides of kaempferol, myricetin and apigenin. Sensory evaluation combined with chemical composition results showed that the higher contents of flavone (flavonol) glycosides did not significantly enhance the astringency of YCFS oolong tea infusions.
The metabolomics method effectively characterized the component differences in oolong teas made from different tea cultivars in this study. There were obvious differences in compound patterns among YCFS, TGY and SX oolong teas. Flavone (flavonol) glycosides were the most significantly differential compounds. The higher content of flavone (flavonol) glycosides was a major chemical feature of YCFS oolong tea and was expected to be used as a discriminant index for the identification of oolong tea cultivar in the future.
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