Time-dependent changes of aroma and volatile compounds during drying of Keemun black tea

Keemun black tea (KBT) is a globally renowned black tea, celebrated for its distinctive and complex aroma. While previous studies have focused on identifying the aroma profile of finished KBT, the dynamic changes of volatile compounds during drying stage remains poorly understood. Here, volatile profiles of KBT samples at different drying time points were analysed using HS-SPME-GC/MS. A total of 104 volatile compounds were identified, with alcohols and aldehydes predominating. PLS-DA revealed 20 compounds significantly contributing to aroma discrimination across drying stages. Based on odor activity value (OAV) analysis, six key odorants-trans-β-ionone, linalool, geraniol, benzeneacetaldehyde, nonanal, and theaspirane-were identified as primary contributors to characteristic KBT aroma. Their concentration dynamics closely linked to the development of floral, fruity, and caramel notes during drying. This study provides the time-dependent characterization of volatile evolution during KBT drying, offering practical insights for optimizing drying protocols to enhance aroma quality and standardize production.