Dynamic evolution of flavor profiles and antioxidant capacities in black rice tea during continuous roasting

In this study, the dynamic evolution of functional components and volatile flavor profiles in black rice tea across different roasting times (90 °C, 0, 5, 10, 20, and 30 min) was investigated. Physicochemical assays, electronic nose, and gas chromatography-ion mobility spectrometry (GC-IMS) were employed to characterize the quality transformation mechanisms. The results indicated that while total flavonoids decreased continuously during heating, total anthocyanins reached a maximum at 20 min. The overall antioxidant capacity remained stable and was likely maintained by the compensatory generation of Maillard reaction products. E-nose analysis revealed an expansion of volatile aromas accompanied by a continuous depletion of water-soluble taste substrates. GC-IMS identified 46 volatile organic compounds and revealed a distinct sequential transition: initial raw-odor alcohols dissipated rapidly within the first 5 min; aliphatic aldehydes and ketones accumulated from 10 to 20 min via lipid oxidation; and roast-associated heterocyclic compounds, particularly 2-pentylfuran, peaked at 20 min through advanced Maillard reactions. Principal component analysis (PCA) confirmed the clear differentiation of these roasting stages. Overall, roasting for 20 min was recommended to achieve optimal quality of black rice tea. These results may provide certain references for quality control of black rice tea during roasting in the future.