Metabolomics Analysis of Chemical Constituents in Compressed Shoumei White Tea with Different Storage Periods

To ascertain the influence of storage time on the chemical composition of compressed Shoumei white tea, metabolomics based on ultra-high performance liquid chromatography-quadrupole-orbitrap mass spectroscopy (UPLC-QExactive-MS) was applied to investigate the chemical composition of compressed white tea with different storage periods (3-14 years). A total of 148 chemical compounds were identified including 12 catechins, 12 dimeric catechins, 16 N-ethyl-2-pyrrolidinol-substituted flavanol (EPSF), 17 alkaloids, 11 amino acids, 4 flavonoid aglycones, 30 flavonoid glycosides, 4 aroma glycosides, 11 phenolic acids, 7 organic acids, 14 lipids, and 10 others. Using partial least squares-discriminant analysis (PLS-DA) and heatmap analysis, we selected 145 significantly differential compounds among white tea with different storage periods, which indicated that the chemical composition greatly changed with storage time. The contents of catechins, dimeric catechins, amino acids, phenolic acids, and organic acids decreased, whereas the contents of EPSFs, alkaloids, lipids and flavanol aglycones increased. EPSF content in white tea produced in 2020-2013 was strongly correlated with storage time with a correlation coefficient of 0.882. This study provides a theoretical basis for scientific storage of white tea.