The main function of distiller's yeast is to inoculate grains with microorganisms and enzymes for brewing, and it is also one of the sources of bringing in miscellaneous bacteria. We have seen many poorly packaged and poorly sealed distillers' yeast. On the one hand, it is easy to enter the air and bring in miscellaneous bacteria, on the other hand, it is easy to get wet. There is also a harsh environment for making koji, especially for making koji. This kind of koji is at greater risk of being contaminated by bacteria.
If the fermentation level is still relatively calm after several days of fermentation, then most of the fermentation has not yet started. There are several reasons for this:
Insufficient particle size of raw materials
What is the appropriate degree of grain crushing? Here is an empirical value, one grain is crushed into 8 to 12 petals.
Especially in the liquid fermentation of raw materials, raw materials must be crushed relatively evenly. We can observe the broken grains. There shouldn't be too many whole grains in them. It would be better if the clinker is liquid, because there is an extra process of steaming grain.
The water temperature of ingredients is too low.
This happens easily in winter. If cold water is used directly, it will lead to slow fermentation and no bubbling. The water temperature is generally controlled at about 30 degrees, so do some heat preservation measures.
There is no stirring.
In the early stage of liquid fermentation, particles are easy to sink to the bottom. If the grain is not stirred 3-4 days before fermentation, the contact area between koji and grain is not enough, which will lead to slow fermentation.