Fig. 1

Process diagram for the production of high-temperature Daqu. Wheat is mixed with 10% (w/w) water and squeezed, and then broken into three or four pieces to adequately release the starch. Then, 40% (w/w) water is added to the wheat, and the mixture is shaped by hand or machine. After the mixture are shaped to bricks weighing 4 to 5 kg each, the bricks are placed in a Daqu room, namely a fermentation chamber, stacked into 4 to 5 layers and fermented for 40 days. Microorganisms, mostly bacteria, are provided by the wheat, water, and air. During the fermentation, workers cover the bricks with rice straw to maintain heat for microbial growth and flavor compound formation. Daqu is turned over to lower the temperature, involving the first turning of Daqu bricks (the 7th day of fermentation) and second turning of Daqu bricks (the 14th day of fermentation). Daqu needs to mature during storage for about 6 months before use