Physicochemical characteristics and antioxidant activities of grape Yakju

The physicochemical characteristics and antioxidant activities of grape yakju, a traditional Korean alcoholic beverage, were investigated during the fermentation process. Reducing sugars decreased while total acid content increased throughout fermentation. Alcohol content increased up to 16–20% after the 10^th day of fermentation. The content of total phenolic compounds and flavonoid in yakju increased with fermentation time. Anthocyanin was found only in yakju made from grapes. ‘Muscat Baily A (MBA)’ yakju was the most preferred regarding color, flavor, taste, and overall acceptance. Antioxidant activities of grape yakju, except for the 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, increased with fermentation time, with the following in the order of increasing antioxidant activity after fermentation: ‘MBA’, ‘Campbell’, ‘Kyoho’, and control yakju. Antioxidant activities of grape yakju depended on total flavonoid content rather than total phenolic compounds.