LAUSR

BACKGROUND JIUYAO is a critical fermenting agent in traditional Huangjiu brewing and affects the quality of Huangjiu. To assess and monitor the quality of JIUYAO effectively, we determined the differences between two common types of defective JIUYAO and normal JIUYAO, with emphasis on the comparison of the main components, enzymatic activity, volatile substances, and microbial community structure. RESULTS Water and starch contents, acid protease activity, and the esterification capability of type I defective JIUYAO were significantly lower than those of the normal JIUYAO, and the protein contents, liquefaction capability, glycation capability, and neutral protease activity were substantially higher than those of the normal JIUYAO. Type II defective JIUYAO had significantly lower indices than the normal group except for starch and free amino acid contents, which were significantly higher than those of the normal JIUYAO. Significant differences were observed for the content of 21 volatile compounds between defective and normal JIUYAO, 2-pentylfuran could be used as markers of defective JIUYAO. Type I defective JIUYAO contained a higher abundance of aerobic Pediococcus and Marivita compared to the normal JIUYAO. Type II defective JIUYAO consisted of a higher abundance of anaerobic Mucor and Staphylococcus. CONCLUSION The quality of JIUYAO was significantly affected by the water content. Due to the different abundances of aerobic and anaerobic bacteria in JIUYAO, oxygen may also be an important parameter affecting the quality of JIUYAO. We believe that the present study offers a theoretical basis for the quality evaluation and control of JIUYAO. This article is protected by copyright. All rights reserved.