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

Abstract

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.

Keywords: (+)-gallocatechin (GC, PubChem CID65084); (–)-Epigallocatechin gallate (EGCG, PubChem CID65064); (–)-epicatechin (EC, PubChem CID72276); (–)-epicatechin gallate (ECG, PubChem CID107905); (–)-epigallocatechin (EGC, PubChem CID72277); Cordyceps militaris; D, L-4-chlorophenylalnine (PubChem CID4652); Ethyl decanoate (PubChem CID8048); GC–MS; Gallic acid (GA, PubChem CID370); LC–MS; Sensory; Solid-state fermentation; Summer-autumn tea.