Dynamic Chemical and Flavor Changes in Black Tea During Fermentation

Fermentation is one of the key steps to produce high-quality black tea, during which the chemical compositions change dramatically. However, the dynamic changes of this sophisticated process are far from clear, and are often characterized through identifying a few compounds. A nontargeted metabolomics approach using Agilent ultrahigh performance liquid chromatography coupled with quadrupole time-of-fl ight mass spectrometry and Agilent Mass Profi ler Professional software was applied to map the variations of metabolites in tea samples during fermentation, which was partially based on the work published by Tan et al. recently1. Principal component analysis indicated obvious stepwise changes to the tea metabolome during the fermentation. Sixty-two compounds including catechins, dimeric catechins, fl avonol glycosides, amino acids, phenolic acids, alkaloids, and nucleosides were identifi ed or tentatively identifi ed. Some of the compounds identifi ed correlated excellently with the varying bitterness and astringency of the black tea. This study provides a comprehensive picture of the metabolite changes during the tea fermentation process. This enhanced understanding will be benefi cial for improvement of tea quality in both taste and nutrition during black tea manufacturing.