Fermentation characteristics and aroma compounds of sweet potato soju using enzymes

The production of sweet potato soju using enzymes was evaluated and compared with the traditional method involving white koji. The cumulative weight reduction of the fermentation mash using enzymes was over 30% higher than that of the white koji method, and alcohol productivity improved by 17% to 23%. A variety of aromatic compounds were detected in sweet potato soju, including 14 alcohols, 16 esters, eight fatty acids, six terpenes, three aldehydes, two alkanes, two sulfides, three ketones, and one pyrazine. The total alcohol content was 380.60 mg/L for white koji steamed sweet potato and 585.19 mg/L for non-steamed sweet potato. Enzyme-steamed and non-steamed sweet potatoes contained 316.37 mg/L and 422.20 mg/L alcohol. The total esters ranged from 162.89 to 212.31 mg/L for white koji sweet potato soju and 99.05 to 125.53 mg/L for enzyme sweet potato soju. The total terpenes were 0.17 to 0.38 mg/L for white koji sweet potato soju and 0.45 to 0.82 mg/L for enzyme sweet potato soju. Principal component analysis indicated that non-steamed sweet potato soju made with white koji strongly correlated with aromatic compounds such as alcohols, aldehydes, alkanes, and sulfides, while enzyme-treated non-steamed sweet potato soju exhibited a strong correlation with terpenes and ketones. These results suggest that enzyme production increases the alcohol content of sweet potato soju, with β-glucosidase positively enhancing terpene content.