Whether for businesses or at home, the making of steamed buns follows these steps: mixing dough → fermentation → shaping → proofing → steaming. The flour undergoes different chemical changes at each stage.
Mixing stage. An appropriate amount of water and yeast are added to the flour and kneaded into a dough. In this process, the gluten protein fragments in the flour connect with each other, forming a gluten network along with other substances, and the starch granules are evenly distributed within this network.
Fermentation process. Yeast rapidly multiplies, producing CO2 gas, causing the dough to increase in volume and become soft in texture, while also developing a unique fermented flavor.
Shaping process. The fermented dough is kneaded again and shaped into steamed buns. This process expels large air bubbles from the dough, making the internal structure more uniform.
Proofing process. The shaped dough pieces are left to rest for a period of time. This allows for more uniform air cells to form inside through further fermentation, making the dough even softer.
Steaming process. As the dough's temperature continuously rises, the gluten network, which was previously disordered, begins to set. The starch begins to gelatinize, increasing in viscosity and volume. If the gluten network is the frame of a house, then the starch granules are the bricks that fill the spaces between the frame. The interior of the "house" is filled with CO2 gas produced during fermentation, creating numerous small air cells that make the steamed bun soft and springy.