Because the bread fermented once is shaped before fermentation, this kind of bread is generally hard and difficult to fluffy because of the uneven distribution of carbon dioxide gas in the dough and the uneven distribution of large holes in the bread structure. This method is simple and quick, but sometimes fermented bread will encounter many problems, such as uneven internal structure and poor expansion effect. Therefore, after the first fermentation, the dough is beaten to exhaust air, and then re-kneaded to make it ferment again, which is called "secondary fermentation".