Caused by cooking for too long or removing the lid immediately after cooking. Bean buns are made from fermented flour. If they are cooked for too long, the gluten inside will be destroyed and collapse. And when you cook them, the first time you open the lid, you don't dry out the moisture when you fry the beans, they are too wet.

The noodles of the sticky bean buns should not be too thin. If the noodles are thin, it will be easy to be crooked. Steamed sticky bean buns will love to lie down and collapse. Sticky beanbag face to be slightly dry, steaming time can not be too long, load the pot when the beanbag to be compact, so that when doing sticky wet skin tofu is prone to collapse problems, in doing the year wet skin tofu, soaked in advance of the beans must be boiled in the pot dry fried through, mainly to sticky dry fried so that the skin tofu can wet skin, not only will not collapse; but also viscous and tasty. When the temperature is relatively high, the bean bag is full of hot air, so the bean bag will bulge a lot, then suddenly lift the lid, the cold air outside the pot will quickly enter, so that the bean bag suddenly cooled, due to thermal expansion and contraction, the bean bag will become flat.

If the lid is left on for a few minutes while the temperature inside the pot slowly drops, the dough will collapse as the gluten in the dough is destroyed. Close the lid of the pot after steaming and don't lift the lid immediately because the air pressure inside and outside the pot differs greatly, which can easily cause collapse. The dough is rolled out too thin, the skin is too thin, and the bean paste filling is too big. During the steaming process, the dough cannot rise, so the bean paste looks dead and the water temperature is not hot enough when steaming. There are many reasons for collapsing bean paste. Frozen fillings can also cause steamed buns to collapse and shrink back. They can also collapse if they are steamed for too long.

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