Abstract
Long-term aging of Yakju, a traditional Korean liquor made of rice and Nuruk (a fermentation agent), causes browning and odor and flavor development. This study investigated the effects of heat-treated Nuruk (50-80°C, 30min) on Yakju quality. The saccharogenic powers and glucoamylase, α-amylase, and carboxypeptidase activities were similar in non-heat-treated Nuruk and that treated at 50°C. However, acidic protease and alcohol dehydrogenase decreased above 50°C. The content of nitrogen-containing compounds was inversely proportional to the heat-treatment temperature. Compounds that cause off-flavors decreased at 50-60°C, but increased at 70-80°C, whereas compounds that provide fragrance increased at 50-60°C. Sensory evaluation indicated that bad taste attributes were higher in Yakju produced using non-heat-treated Nuruk. Therefore, heat treatment of Nuruk at 50°C can be adopted as a method for improving Yakju quality, as enzymatic activities that affect color, aroma, and taste are regulated.
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