Physicochemical properties and antioxidant activities of Korean traditional alcoholic beverage, yakju, enriched with mulberry.

UNLABELLED: Mulberry fruits (Morus alba L.), rich in health beneficial compounds such as polyphenols, flavonoids, and anthocyananis, have traditionally been used as nutritional foodstuffs and fork medicines. In this study, physicochemical properties and antioxidant activities of a traditional Korean alcoholic beverage ``yakju'' enriched with mulberry were evaluated. The beverage was enriched with smoothies prepared from Korean mulberry cultivars of Cheongilppong (CP), Suwonppong (SP), and Daesungppong (DP). In comparison to the control, an increase in alcohol content and total acidity and a decrease in sugar level in yakju enriched with mulberry were observed during 15 d of fermentation. The total polyphenol and total flavonoid content increased in the following order: DP yakju > SP yakju > CP yakju > control yakju. In contrast, the anthocyanin content decreased during the fermentation periods. The trans-resveratrol content of mulberry yakju increased during the fermentation and the resveratrol content of DP yakju (0.24 mg/L) was significantly higher than that of SP yakju (0.21 mg/L) and CP yakju (0.14 mg/L) on the 15th day of fermentation (P < 0.05). The antioxidant activities of mulberry yakju, which was assessed using the 1,1-diphenyl-2-picryl hydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenozothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and reducing power assays, decreased during the 1st day of fermentation and increased into thereafter. The increase in antioxidant activities of mulberry yakju might have been affected primarily by the total flavonoid and total polyphenol content with increasing alcohol concentration, as a good extractor, during the fermentation; however, the antioxidant activities may have also been affected by the total anthocyanin content up to the 1st day of fermentation. PRACTICAL APPLICATION: The physicochemical properties and antioxidant activities of a traditional Korean alcoholic beverage ``yakju'' enriched with mulberry were investigated. This analysis is important for the potential applications of mulberry yakju as functional alcoholic drinks.