Effects of Spontaneous Fermentation and Hot-Water Extraction Conditions on Antioxidant Properties and Color Characteristics of Yongan-Bullobang Tea

This study investigated the effects of spontaneous fermentation and hot-water extraction conditions on the antioxidant-related properties, soluble solids, and color characteristics of Yongan-Bullobang tea prepared from ginger, jujube, fennel, licorice, clove, and agarwood.The mixed ingredients were supplemented with 1% raw sugar, treated at 45°C for 24 h, and subsequently heated at 70°C for six days.Untreated and processed samples were extracted at 90, 95, or 100°C for 5, 10, or 15 min.The DPPH radical scavenging activity, total phenolic content (TPC), total flavonoid content (TFC), total soluble solids, color values, and browning index (BI) were evaluated.The processed samples showed higher DPPH radical scavenging activity, TPC, and TFC than the untreated samples.TPC was highest after extraction at 95°C for 15 min (76.05±0.85mg GAE/mL), whereas the DPPH radical scavenging activity and TFC were highest at 100°C for 15 min, reaching 30.44±0.84% and 120.50±2.04mg QE/mL, respectively.The total soluble solids increased slightly after processing.These changes may reflect the increased extraction of water-soluble reducing substances and phenolic-and flavonoid-equivalent compounds.The processed samples also showed lower L * values and higher a * , b * , ΔE, and BI values, indicating enhanced color development and browning.Overall, spontaneous fermentation followed by thermal treatment was associated with improved antioxidant-related properties and marked color changes in Yongan-Bullobang tea.Extraction at 95-100°C for 15 min was favorable for enhancing the antioxidant-related properties, but accompanying browning should be considered in product applications.