Improving flavor of summer Keemun black tea by solid-state fermentation using Cordyceps militaris revealed by LC/MS-based metabolomics and GC/MS analysis

Cordyceps militaris ( C. militaris ) has been approved and widely used in healthy food. The present study aimed to improve the flavor of summer Keemun black tea (KBT) using C. militaris solid-state fermentation. Combined with sensory evaluation, the volatile and non-volatile components of solid-state fermentation of KBT (SSF-KBT) and KBT were analyzed. The results showed that after the solid-state fermentation, the contents of total polyphenol, total flavonoid, and total free amino acids were significantly reduced. Further non-targeted metabolomics analysis revealed that the contents of non-galloylated catechins and d -mannitol increased, while the galloylated catechins and flavonoid glycosides decreased as did the bitterness and astringency of KBT. Dihydro- β -ionone and β -ionone (OAV = 59321.97 and 8154.17) were the aroma-active compounds imparting woody and floral odors in SSF-KBT, respectively. Current study provides a new avenue to develop summer-autumn KBT.