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.