Decoding the dynamic evolution of volatile organic compounds of dark tea during solid-state fermentation with Debaryomyces hansenii using HS-SPME-GC/MS, E-nose and transcriptomic analysis

Debaryomyce species is the core yeast during Fu brick tea (FBT) production, nevertheless, its role on the flavor characteristics formation of FBT remains unclear. In this study, the dynamic evolution and formation pathways of volatile organic compounds (VOCs) in dark tea during solid-state fermentation (SSF) with Debaryomyces hansenii were explored. Headspace solid-phase microextraction gas chromatography mass spectrometry (HS–SPME–GC–MS) and E-nose showed SSF with D. hansenii significantly affected the evaluation of VOCs in dark tea. A total of 50 VOCs in dark tea during SSF were identified, and D. hansenii greatly increased the levels of flavors with sweet floral, fruity, minty, and woody aromas. Furthermore, 20 VOCs (e.g., methyl salicylate, linalool and its oxides, β-damascenone, and acetophenone, etc.) were screened as key differential VOCs during dark tea fermentation. D. hansenii significantly degraded the flavor precursor free amino acids, and secreted various extracellular enzymes contributed to the formation of VOCs. Transcriptomic analysis revealed that genes expression of D. hansenii drastically altered during fermentation, and the key differential genes involved in the formation of key VOCs were clarified. Thus, this study demonstrated D. hansenii drastically improved the flavor characteristics of dark tea, and offered insightful information for utilizing D. hansenii as an inoculation culture to control and improve the aroma characteristics of FBT.