Effect of heat-treated Nuruk on the quality characteristics of aged Yakju

• Published in: Food science and biotechnology 2018, Vol.27 (3), p.715-724
• Main Authors: Kang, Ji-Eun, Kim, Chan-Woo, Yeo, Soo-Hwan, Jeong, Seok-Tae, Kim, Yong-Suk, Choi, Han-Seok
• Format: Article
• Language: Korean
• ISSN: 1226-7708; 2092-6456

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 ($50-80^{\circ}C$, 30 min) on Yakju quality. The saccharogenic powers and glucoamylase, ${\alpha}$-amylase, and carboxypeptidase activities were similar in non-heat-treated Nuruk and that treated at $50^{\circ}C$. However, acidic protease and alcohol dehydrogenase decreased above $50^{\circ}C$. The content of nitrogen-containing compounds was inversely proportional to the heat-treatment temperature. Compounds that cause off-flavors decreased at $50-60^{\circ}C$, but increased at $70-80^{\circ}C$, whereas compounds that provide fragrance increased at $50-60^{\circ}C$. Sensory evaluation indicated that bad taste attributes were higher in Yakju produced using non-heat-treated Nuruk. Therefore, heat treatment of Nuruk at $50^{\circ}C$ can be adopted as a method for improving Yakju quality, as enzymatic activities that affect color, aroma, and taste are regulated.