Effect of Anaerobic Treatment on Bioactive Properties of Yellow Tea and Metabolomic Analysis of Its Promoting Effect on γ-Aminobutyric Acid Enrichment

In this study, we aimed to explore the effect of anaerobic treatment on the contents and functions of bioactive components such as γ-aminobutyric acid (GABA) in yellow tea and to analyze the mechanism by which anaerobic treatment promotes GABA enrichment using metabolomics. We also analyzed the changes in related metabolism pathways. The results showed that the content of GABA in yellow tea was increased to 3.3 mg/g after anaerobic treatment, and the contents of the upstream and downstream amino acids related to GABA were changed correspondingly. Moreover, anaerobic treatment significantly increased the contents of total phenolics and total flavonoids in yellow tea. In vitro bioactivity evaluation showed that anaerobic treatment improved the free radical scavenging capacity, total antioxidant activity and inhibitory effect on the formation of glycosylation products of yellow tea, but had little effect on the ability of yellow tea to inhibit starch digestion enzymes. A total of 218 differential metabolites between fresh and GABA-rich tea, including amino acids, organic acids, flavonoids, nucleotides, and sugars. Pathway enrichment analysis demonstrated that the amino acid biosynthesis, tryptophan metabolism, flavonoid biosynthesis, and butyrate metabolism pathways were significantly regulated. Anaerobic treatment could regulate the GABA content in yellow tea by affecting the L-glutamate and succinic semialdehyde pathways. This study can provide a reference for the research and development of GABA-rich tea.