Preparation-Route-Associated Differences in Color and Non-Volatile Metabolite Profiles of Eurotium...

Area of Science:

• Food Science
• Fermentation Technology
• Analytical Chemistry

Background:

• Fu tea fermentation using *Eurotium cristatum* is achieved through both liquid-state and solid-state methods.
• Direct comparison of soluble products from these two fermentation routes is limited.
• Understanding the chemical differences is crucial for optimizing Fu tea production and quality.

Purpose of the Study:

• To directly compare the soluble chemical profiles of Fu tea produced via liquid-state fermentation (LFt-D7) and solid-state fermentation (SFt-D7).
• To identify key metabolites and chemical characteristics that differentiate the two fermentation processes.
• To correlate chemical profiles with physical properties like color and metabolite content.

Main Methods:

• Comparison of liquid-state fermented tea infusion (LFt-D7) and solid-state fermented Fu tea extract (SFt-D7) against an unfermented control (SHt-D0).
• Color analysis using Commission Internationale de l'Éclairage L*a*b* (CIELAB) parameters.
• Metabolomic profiling using liquid chromatography-tandem mass spectrometry (LC-MS/MS).
• Targeted analysis of free amino acids, flavonoids, alkaloids, and phenolic acids.

Main Results:

• Liquid-state fermentation resulted in a darker reddish-brown color with higher theaflavin and theabrownin content, and lower thearubigin content compared to solid-state fermentation.
• Metabolomic analysis revealed significant differences in metabolite profiles between the two methods, with more annotated compounds differentiating LFt-D7 from SFt-D7.
• Liquid-state fermentation (LFt-D7) retained higher levels of free amino acids and total quantified flavonoids, particularly flavanols, compared to solid-state fermentation (SFt-D7).
• Covariation was observed between metabolite modules and pigment indices, color parameters, free amino acid content, and flavonoid content.

Conclusions:

• Liquid-state and solid-state fermentation of Fu tea by *Eurotium cristatum* yield distinct soluble chemical profiles.
• Liquid-state fermentation appears to preserve a broader range of beneficial soluble compounds, including amino acids and flavonoids.
• The observed differences in chemical composition correlate with distinct physical characteristics, highlighting the impact of the fermentation route on final product quality.