Effects of red-light withering on the taste of black tea as revealed by non-targeted metabolomics and transcriptomics analysis

This study investigated the influence mechanism of red-light withering on the taste quality of black tea. Compared with natural withering (control), red-light withering (RLW) can significantly improve the taste quality of the summer-autumn black tea by reducing its bitterness and astringency. Specifically, RLW was shown to have a greater impact on the amino acids and theaflavins of tea, with an increase of 10.6% and 25.6% in their content after RLW, respectively. The increase in amino acid content is mainly attributed to the content increase of the protein-amino acids induced by the up-regulated expression of phenylalanine and tryptophan synthesis genes as well as the activity of peptidases. Additionally, RLW can inhibit the down-regulation of key genes in catechin synthesis to increase the content of partial catechins (EGC and GCG). Meanwhile, RLW can also significantly increase the enzyme activity of polyphenol oxidase and peroxidase and promote the formation of theaflavins in the fermentation stage. This study provides a theoretical basis for improving black tea withering technology and withering equipment.