In Situ Dynamic Tracking and Discrimination of Aroma Quality Evolution during Black Tea Drying: Real-Time Profiling of Tea Volatiles via High-Pressure Photoionization Time-of-Flight Mass Spectrometry

Black tea volatile profiles change rapidly during drying, posing a challenge for real-time aroma-quality monitoring. In this study, high-pressure photoionization time-of-flight mass spectrometry (HPPI-TOFMS) was employed for continuous, in situ tracking of tea-headspace ion fingerprints at 1 min resolution throughout drying. A total of 209 volatile ion features were detected, with 26 compounds assigned at different confidence levels. Five drying stages were defined by integrating water-related signal kinetics with sensory transitions observed during drying. Temporal profiling by HPPI-TOFMS revealed distinct volatile-evolution patterns broadly consistent with these stages, capturing the shifts in aroma characteristics. Cross-platform comparison with headspace solid-phase microextraction gas chromatography–mass spectrometry showed compound-dependent agreement in temporal trends. Similar stage-specific volatile patterns were observed across three independent drying runs, and a random-forest classifier achieved accuracy of 0.927 on an independently held-out run. These findings highlight the potential of HPPI-TOFMS for high-temporal-resolution characterization and aroma-quality monitoring during black tea drying.