Multi-omics network analysis of flavour formation in golden-flowered Tibetan dark tea processed by "flowering" using raw materials with different fermentation degrees

Abstract

Dark tea, a traditional post-fermented tea, develops distinct flavour and health benefits through microbial fermentation. The "flowering" process, marked by golden fungal growth, is well-studied in Fu-brick tea but underexplored in Tibetan dark tea. This study investigated how "flowering" affects flavour, chemistry, and microbiota in Tibetan dark teas of varying fermentation degrees. Four samples were assessed using sensory evaluation, widely-targeted metabolomics, 16S/ITS sequencing, and WGCNA. Results showed that "flowering" modulated key microbial taxa (e.g., Aspergillus heterocaryoticus, Pullulanibacillus), altered polyphenol degradation and amino acid profiles, and shaped sensory traits including returning sweetness, sourness, and aged aroma. In lightly fermented tea, "flowering" enriched Streptomyces and Delftia, aiding Aspergillus dominance and reducing bitterness. In deeply fermented tea, prolonged humid conditions favored thermotolerant fungi and organic acid accumulation. A substrate-microbiota-metabolite-sensory network was established, offering insights for targeted modulation of flavour in golden-flowered Tibetan dark tea.

Keywords: Tibetan dark tea; metabolomics; microbiota; pile fermentation; taste quality; “flowering” fermentation.