First, the yeast is not selected correctly or used in the wrong way, which makes the yeast lose its activity. If you are a novice or unfamiliar with bread making, you should buy high-activity dry yeast when making bread.

Second, open the bread cover at will during the fermentation process, so that the yeast temperature can not meet the requirements. Do not open the bread cover at will during dough fermentation, so as to avoid lowering the fermentation temperature and affecting dough fermentation due to frequent opening of the cover.

Thirdly, the water temperature of dough is not enough, which leads to insufficient yeast activity. You can use warm water of about 40 degrees for dough mixing. When the temperature is low, the fermentation of yeast is slow. Using warm water and flour can improve yeast activity.

Fourth, the fermentation time is insufficient, and the fermentation time should be appropriately extended. Sometimes it is affected by fermentation temperature and humidity. Under normal circumstances, the fermentation scale of 2 to 2.5 times is the most ideal.