Stir-frying treatment improves the color, flavor, and polyphenol composition of Flos Sophorae Immaturus tea

Low-temperature drying is the mainstream method of Flos Sophorae Immaturus (FSI) tea processing, while the advantages of stir-frying treatment were illustrated in this study. Herein, the reasons for stir-frying treatment improving the main quality indicators of FSI were clarified by measuring the changes in color difference, flavor, and polyphenol composition during the stir-frying process, as well as the xanthine oxidase inhibitory activity. The results showed that the color of FSI became more attractive after stir-frying at appropriate conditions (160–200 °C for 20–40 min). A total of 75 volatile compounds were identified by GC-MS, and the main volatiles were aldehydes (42.8%) and heterocyclic (16.7%) after stir-frying treatment at 200 ℃ for 20 min, which played a considerable role in the flavor of stir-fried FSI. Meanwhile, the main volatiles of stir-fried FSI tea screened out by the Flash GC E-nose were furaneol, 2-pentylfuran, 3-methylheptane, 3-furaldehyde, 2,5-dimethylfuran, etc. Additionally, the quercetin, kaempferol, and isorhamnetin content gradually increased after stir-frying treatment, which improved the xanthine oxidase inhibitory activity of FSI.