Unraveling the impacts of different processing methods on hawk tea's volatiles and flavor via non-targeted Volatilomics approach

To systematically explore how processing regulates the volatile metabolites and flavor of Hawk Tea (Litsea coreana), this study used non-targeted volatilomics, HS-SPME-GC-MS, and multivariate analysis (including K-means clustering) to analyze four samples with varying fermentation degrees (non-fermented green, slightly fermented white, semi-fermented oolong, deeply fermented black). A total of 379 volatile metabolites were identified, with terpenoids (28.0%) and esters (18.5%) forming the "floral-fruity" aroma foundation. K-means clustering (k = 6) grouped differential volatiles into fermentation-responsive subgroups. Fermentation reduced terpenoids/aldehydes (grassy aroma) and increased esters/heterocyclic compounds (sweet/caramel aroma); semi- and deeply fermented samples had 3.4- and 2.9-fold higher total volatiles than non-fermented ones. The rOAV ≥1 identified 90 key aroma compounds (10 core compounds). Sensory evaluation showed fermentation darkened soup color (yellow-green→orange-red), shifted aroma (camphor→fruity→sweet), and reduced astringency. KEGG analysis enriched aroma-related pathways (e.g., phenylpropanoid biosynthesis). The "processing-volatile-flavor" model provides a basis for standardizing Hawk Tea processing and improving quality.