Daqu- A Traditional Chinese Liquor Fermentation Starter

Chinese liquor is one of the world's oldest distilled alcoholic beverages, and it is typically obtained with the use of Daqu fermentation starters. Daqu is a saccharifying and fermenting agent, having a significant impact on the flavour of the product. Daqu can be categorized according to maximum incubation temperatures (high, medium and low) and flavour (sauce, strong, light and miscellaneous). Most Daqu are prepared by solid-state fermentation from wheat, barley and/or peas with ingredient formulation, grinding and mixing, shaping, incubation and maturation. Although there is a wealth of artisanal experience in the production of a range of different types of Daqu, the scientific knowledge base—including the microbiota, their enzymes and their metabolic activities—needs further development. Daqu as a specific alcoholic starter is compared with other Asian amylolytic fermentation starters in terms of microbial diversity and function. Filamentous fungi (Rhizopus, Rhizomucor, Aspergillus and other genera), yeasts (Saccharomyces, Candida, Hansenula and other genera) and bacteria (acetic acid bacteria, lactic acid bacteria and Bacillus spp.), are considered to be the functional microbiota, responsible for the formation of a range of lytic enzymes, formation of substrates for alcoholic fermentation and formation of flavour compounds. However, the knowledge about the microbiota composition and their function is still fragmentary information, so further research is required to establish the functionality and growth kinetics of the microbiota in diverse types of Daqu.