Examining the effects of processing techniques on the quality of hawk tea through liquid chromatography–tandem mass spectrometry and two-dimensional gas chromatography–time-of-flight mass spectrometry

Processing techniques are critical factors influencing the quality of hawk tea, yet systematic studies on their effects are limited. This study investigates the impact of four key processing procedures-fixation, reddening, fermentation, and compressing-using sensory evaluation, LC-MS/MS, and GC × GC-TOF-MS. Analysis identified 6951 non-volatile metabolites, including 107 marker metabolites, primarily in flavonoid synthesis and degradation pathways. Fermentation increased sweetness and richness by enhancing sugars and amino acid content, while significantly reducing flavonoid levels. Reddening improved flavor, color, and retained more beneficial flavonoids. Volatile analysis detected over 1800 compounds, including 398 volatile marker metabolites. Fermentation increased alcohols and heterocyclic compounds, reducing hydrocarbons and ketones. Additionally, 26 camphoraceous and 12 pungent aroma compounds characteristic of hawk tea were identified, and an aroma-flavor correlation map was established. By elucidating the impact of processing methods on its chemical and sensory properties, this study lays the groundwork for targeted quality control of hawk tea.