Analysis of Daqu produced in different seasons

This investigation undertook a systematic analysis of two kinds Daqu (Tao-hua qu and Fu-qu) made by same method, but in different seasons (spring and summer). The analysis determined the content of microorganisms, enzyme activity and flavour component of the Daqu. From the results, it was noted that the prokaryotic microbial species present in Daqu were much more complex than the eukaryotic microorganisms; from the results of Operational Taxonomic Units, prokaryotic microorganisms were about 6–8 times greater than eukaryotic microorganisms. With regards to eukaryotic microorganisms, Fu-qu contained a more complex consortium than Tao-hua qu, but Tao-hua qu contained a more complex prokaryotic population than Fu-qu. The saccharification and liquefaction of Daqu were achieved by the mould and a saccharifying enzyme, which was secreted by the mould. The growth temperature of the mould was 20–30 °C and from the analysis results it can be seen that the saccharification and liquefaction of Tao-hua qu produced in the spring was higher than that of Fu-qu produced in the summer. A qualitative analysis of the volatile flavour substances in Daqu was performed using the methods of the NIST data-base and relative retention indices. Approximately 26 kinds of volatile flavour substances were detected in the Tao-hua qu compared with approximately 22 kinds of volatile flavour substances in the Fu-qu. A specific observation of the volatile flavour substances of the two was that Tao-hua qu and Fu-qu had about 13 volatile flavour compounds that were common to both. Copyright © 2016 The Institute of Brewing & Distilling