Non-targeted metabolomics reveals distinct chemical compositions among different grades of Bai Mudan white tea

So far, the chemical quality of different grades of white tea has largely remained unexplored. The objective of this study was to establish a model for quality evaluation of different grades of Bai Mudan white tea. We applied non-targeted ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry in combination with multivariate analysis and analyzed four different grades of Bai Mudan white tea. We found that the metabolite composition from the super-grade and the first-grade shared higher similarity compared to the second-grade or the third-grade white tea, and the Partial Least Square-Discriminant Analysis model showed high capability to explain the sample variation (R2Y = 0.998, Q2 = 0.95 in negative ionization modes). In total, 93 metabolites were structurally identified, wherein 21 low abundant metabolites showed distinct changes in abundance that were closely correlated with tea grade variation. These findings suggested their potential as markers to discriminate different grades of Bai Mudan white tea.