1. The fermentation time of the steamed buns is too long. After steaming, the steamed buns lose their support and collapse.

2. The proofing humidity and temperature are too high, and the skin is blistered. The appropriate proofing humidity is 70-75 and the temperature is 35-38°C.

3. The steaming time is too long. Steamed buns are generally steamed for 15 minutes and then simmered for 3 minutes.

4. When steaming the steamed buns, use a high fire (steaming cabinet, too much pressure), which causes the steamed buns to rise too fast. The gas raises a layer of skin on the surface of the steamed buns. After cooling, there is no support and collapses.

5. The flour quality is not good.