Metabolomics and sensory evaluation analyses for determining the effect of grades on taste quality of Liupao tea

In order to investigate characteristic marker metabolites and their grade-dependent variations in Liupao tea, non-volatile compounds from four grades of Liupao tea were analysed by combining sensory evaluation with UPLC-Q-TOF-MS based untargeted metabolomics. Sensory evaluation revealed that decreasing Liupao tea grade was accompanied by reduced stale flavour, gradual increases in bitterness and astringency, and an overall deterioration of sensory quality. In total, 4 099 non-volatile compounds were detected, of which 181 metabolites were common across all four grades. 14 significantly differential metabolites, including EC, EGC and L-theanine, displayed regular grade-related changes with Pearson correlation coefficients of |r| ≥ 0.7. Multivariate statistical analysis confirmed strong correlations between these 14 key compounds and both tea grade and sensory attributes. A PLS regression model built upon the 14 markers achieved an internal fitting R²of 0.9929. It should be noted that this model was trained solely on samples originating from a single tea garden, multi-sample external validation is required to verify its generalisability. This study provides theoretical references for unravelling flavour differences among differently graded Liupao tea.