Combined metabolomics and electronic tongue technology elucidated the mechanisms of regulation of color–taste characteristics of Huangqin (Scutellaria baicalensis Georgi) herbal tea after various roasting processes

Roasting is essential for optimizing Huangqin herbal tea (HHT; Scutellaria baicalensis Georgi) quality. This study integrated metabolomics, electronic tongue analysis, and computer vision to compare microwave roasting (MR), electric roasting (ER), charcoal roasting (CR), steam roasting (SR), and natural drying (ND). All roasting methods significantly reduced bitterness and sweet-bitter aftertaste. CR produced infusions with intense yellow-brown coloration while enhancing umami, saltiness, and baicalin retention. SR uniquely increased brightness, reduced chroma, and imparted richness while suppressing bitterness. Metabolomic analysis demonstrated that roasting universally elevated caffeine and catechin derivatives but reduced free amino acids and reducing sugars. Specifically, SR preserved bitter-salty ornithine while degrading gallic acid derivatives and uronic acids. Weighted compound coexpression network analysis revealed that flavonoid glycosides coregulate color with phospholipid derivatives, whereas nitrogenous compounds and iridoid glycosides govern flavor profiles. These findings establish a framework for precision optimization of HHT processing.