The effects of exogenous GABA on the quality of processed mulberry leaf tea were investigated based on metabolomics

Morus alba 'Seedless Dashi' is an excellent variety with large leaves, which is very suitable for making tea. GABA is an important functional component in mulberry leaf tea, but its role and influence on flavor components and metabolism of mulberry leaf tea are still unclear. In this study, metabolomics methods were used to comprehensively analyze the differences between externally added GABA mulberry leaf tea and non-added GABA mulberry leaf tea. The results showed that GABA treatment significantly increased the total amount and diversity of volatile components of mulberry leaf tea (+38.95%), especially the addition of 6 new pyrazine compounds, which gave mulberry leaf tea nutty and caramel characteristics. Compared with ordinary mulberry tea, 73 different metabolites were screened (65 up-regulated and 8 down-regulated). It was found that GABA tea promotes the accumulation of functional components by regulating amino acid and lipid metabolism pathways. This study provided a theoretical basis for the quality optimization of GABA mulberry leaf tea and confirmed that GABA has the dual role of flavor-enhancing and functional components in mulberry leaf tea. • The flavor quality of mulberry leaf tea was improved after GABA was added. • New 6 kinds of pyrazines and a variety of other aroma substances. • Phosphoric acid, phosphatidic acid decreased,Amino acids, polypeptides rise. • GABA can lead the transformation and formation of some non-volatile compounds.