Biochemical characterisation and dominance of different hydrolases in different types of Daqu – a Chinese industrial fermentation starter

BACKGROUND: Daqu is a fermentative saccharification agent that is used to initiate fermentation in the production of Chinese liquor and vinegar. This study investigated the differences of amylase, protease and esterase in dominance of different types of Daqu, which can be useful for quality control and flavor improvement of Daqu production by enzyme technology. RESULTS: H NMR spectroscopy, the protein patterns and metabolites in Daqu were further analysed. The results indicated that the highest amylase activities and diversities were found in low/medium-temperature of Daqu which had light-flavour and strong-flavour. Proteases play a significant role in determining the quality of high-temperature Daqu samples which had a sauce-flavour. Furthermore, the contributions of esterase to both strong and sauce flavour development in high-temperature Daqu are similar. CONCLUSION: Results from the present work showed that differences in amylase, protease and esterase play a leading role in different types of Daqu, which can be useful for quality control and technology development of Daqu.