Evolution in the chemical composition of Liubao tea during processing

BACKGROUND: Liubao tea (LBT), a representative dark tea, undergoes extensive biochemical transformations during fermentation and aging, which shape its chemical profile and overall quality. This study conducted a comprehensive metabolomic analysis of tea materials, Mao tea and fermented tea stored for different durations using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). RESULTS: Fermented tea displayed superior aroma and taste compared with Mao tea and tea materials, with teas produced in 2010 scored higher than those from 2015. A total of 189 differential metabolites were identified among tea materials, Mao tea and fermented tea from 2015, primarily flavonoids and phenolics. As fermentation intensified, catechin derivatives and phenolic esters decreased, whereas alkaloids, terpenoids, amino acid derivatives, and phenolic acids increased, accompanied by substantial shifts in flavonoid and phenolic profiles. Comparing 2010 and 2015 samples, 27 differential metabolites were detected in Mao tea (six up-regulated, 21 down-regulated) and 99 in fermented tea (51 up-regulated, 48 down-regulated). Twelve metabolites were shared between both years, indicating potential aging-associated biomarkers. Targeted quantification corroborated these compositional trends, and pathway enrichment revealed flavonoid transformation and purine metabolism as central processes in LBT evolution. CONCLUSION: Fermentation is the primary driver of chemical conversion in LBT, while aging further modulates its metabolite composition. These results provide a metabolomic basis for quality evaluation, process optimization, and future research on the bioactive attributes of LBT. © 2026 Society of Chemical Industry.