Fig. 3.

PLS-DA score plot and cross-validation of metabolites of congou black tea by different rolling pressures in ESI positive (a, c) and negative mode (b, d), respectively. S-plot of PLS-DA model for all identified metabolites (e). Black triangles represent ions included in PLS-DA model, and ions highlighted with red square represent most significantly altered ions. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)