Is old steamed bread really unhealthy?

Not necessarily. Earlier steamed bread was fermented with old noodles. This method is actually to put the old noodles for a period of time and ferment them with wild strains in nature, which will carry a lot of miscellaneous bacteria. If it is not tightly stored, it may be patronized by flies and mosquitoes. Mold will grow. There are many lactic acid bacteria in the air, and the old noodles are easy to sour, so it needs to be neutralized with alkali, which will also destroy its nutritional value. In addition, the fermentation of old noodles is not easy to develop well, which is easy to cause dead noodles and rancidity. "Dead noodles" means that there is not enough yeast in the dough as a strain, which leads to the unsuccessful fermentation of some noodles. Generally speaking, steamed bread made of old flour should be eaten as soon as possible after it is made. Like the weather now, it will be sour in about half an hour. However, old steamed bread also has its own "advantages": adding an appropriate amount of alkaline water may produce another taste, which some people just like.