Metabolomics investigation of biochemical variations in two representative aged Fujian teas

The biochemical variations occurring in different types of tea during extended storage periods are fascinating. In this study, quantitative measurement and targeted metabolomics analysis were employed to investigate the changes of the main compounds in Fujian ‘Da Hong Pao’ oolong tea (OT) and ‘Lapsang Souchong’ black tea (BT) across one to ten years storage durations. A total of major 19 bioactive compounds were quantified, including catechins, phenolic acids, as well as theanine (Thea) and caffeine (CAF). Univariate analysis was used to identify compounds with significantly different abundances between the two tea types, with higher catechins levels in oolong tea. By integrating variable importance in projection (VIP) scores from partial least squares regression (PLSR) with correlation analysis, we prioritized aging-associated key compounds; notably, vanillic acid and gallocatechin (GC) were both strongly associated with aging and showed significant inter-type differences. Furthermore, network analysis revealed tea-type-specific compound co-variance patterns induced by aging. Differential network analysis further compared these patterns between ‘Da Hong Pao’ oolong tea and ‘Lapsang Souchong’ black tea, ultimately identifying 19 compound pairs with significantly different associations. This study offers a comprehensive understanding of the dynamic compositional changes during the storage of teas with differing fermentation degrees, providing a theoretical basis for the analysis and utilization of aged tea.