A nontargeted and targeted metabolomics study on the dynamic changes in metabolite levels during the anaerobic treatment of γ-aminobutyric acid (GABA) tea

γ-Aminobutyric acid (GABA) tea is a popular tea with high GABA content (>1.5 mg/g). In this study, the influence of anaerobic treatment, which is a key manufacturing process for GABA tea, was investigated by a nontargeted metabolomics method combining with targeted compounds quantifications. The results showed that the anaerobic treatment not only led to a ~16-fold increase in GABA content but also caused significant changes in the levels of TCA cycle metabolites, dimeric flavanols, lipids, bases/nucleosides, and most of amino acids (p