New significance of the solid-state saccharification process in xiaoqu-mijiu production

摘要

Xiaoqu-mijiu is a traditional Chinese spirits made from rice and xiaoqu. Xiaoqu is prepared by culturing mold and yeast naturally on cereals and thus used as a source of enzyme for brewing. Xiaoqu-mijiu production begins with solid-state saccharification, where steamed rice is mixed with 1% (w/w) xiaoqu and incubated for 24 hours. A saccharification in the solid-state is unique process compared with other alcoholic beverages. We aimed to investigate the significance of the solid-state saccharification process. Xiaoqu could convert 75% of starch into glucose during solid-state saccharification process. It was calculated as 2,459 U/g saccharification power in xaioqu. While, the saccharification power of crude extract from xiaoqu at 2% starch is 78 U/g in xiaoqu. These showed a great difference between the enzyme activities before and after saccharification. The saccharification power of free-and bound-form in xiaoqu were 104 and 52 U/g at 4.5% starch, respectively. The apparent Km and Vmax for total saccharification power on starch were 6.1% and 278 U/g. We investigated the changes of the microbe number and enzyme activities induced by solid-state saccharification. After saccharification, moid grew about 10 times, and a-amylase activity and saccarification power were also increased 46 and 73 times, respectively. These results indicate that the solid-state saccharification process in xiaoqu-mijiu production is not only for saccarification but also for mold growth followed by production of enzymes to accelerate the saccharification.