The fermentation time of steamed bread has a great relationship with temperature. Yeast has strong activity at high temperature and high fermentation efficiency. If steamed bread is fermented in summer, 2-3 hours is enough. If the steamed bread is fermented in winter, it takes a long time and takes 5-6 hours. When the dough rises to about twice its original size, it is inelastic and sour when pressed by hand, indicating that the dough has been fermented.

There are three kinds of leavening agents used for fermentation:

Baking soda, flour fertilizer (old noodles), dry yeast powder. They all work on the same principle. Under suitable conditions, the starter produces carbon dioxide gas in the dough, and then the dough becomes soft and delicious by heating and expanding.

However, the gas released by baking soda is not rich, so the softness of the finished product with baking soda is not very good. Moreover, it is a weakly alkaline substance, which will destroy the vitamins in flour and reduce the nutritional value of pasta.