This situation has the following reasons:

(1) The amount of water added. When the amount of water added is within the appropriate range, the whiteness value of steamed buns will be relatively high. This is because when the amount of water added to the dough is too low, the dough will become dry and hard, and it is difficult to achieve fine and even pores in the steamed buns made. Especially when the hard dough is overly proofed, the hole structure will collapse and cause dark spots to appear; when the amount of water added is too high, , the light reflection is weakened, causing the whiteness of the product to decrease.

(2) Dough mixing time. If the dough mixing time is too long, it will destroy the gluten network structure of the dough, water will leak out of the dough, and even the steamed buns will not hold up or shrink, resulting in white degree dropped. Insufficient mixing time makes it difficult for the materials to mix evenly, or the gluten has not reached an expanded state, and high whiteness cannot appear.

(3) During the proofing time, the inside of the steamed buns will have uniform and small holes, and the whiteness will be the best. If there is insufficient proofing, the holes will be too few or too small, or even no holes, and the buns will not be white. If the buns are overproofed, the holes will be large and uneven, and good whiteness will not be produced.

(4) The number of times of pressing (kneading) the dough. Pressing the dough makes the bubbles disappear and a tight layered structure appears, which is conducive to the subsequent proofing to produce uniform small pores. If the dough is not kneaded enough, the air in the dough cannot be completely eliminated, and the holes are not fine. If the dough is rolled too much, the dough will be watery and sticky, and the internal structure will be uneven, which will also reduce the whiteness of the product. When the dough is pressed to its optimal state, the internal structure of the product will be fine and the holes will be even.

(5) Dough pH value Dough, when the pH value is 6.5, the whiteness value of steamed buns is the highest. When the pH value of the dough is lower than 6.5, as the amount of alkali added increases, the pH value gradually increases, and the whiteness also increases; but as the amount of alkali added continues to increase, the dough gradually becomes alkaline, and the alkali content increases. The sexual environment affects the fermentation of the yeast in the dough, and the color of the steamed buns begins to darken. Even the alkali combines with the isoflavone pigments in the flour to turn the buns yellow, and the whiteness of the steamed buns gradually decreases.

(6) Add shortening, emulsifier, etc. Shortening, emulsifier, sugar, etc. can be added to the ingredients for making steamed buns. This is mainly used in southern steamed buns. Adding shortening, emulsifier, sugar, etc. not only makes the skin of the steamed buns bright, delicate in structure, soft and slightly sweet in taste, and larger in volume, but also increases the whiteness of the steamed buns. The principle of whitening is that the emulsifier promotes the combination of fat and other ingredients in the dough to form fine fat particles that are evenly dispersed. Shortening, cake oil, etc. are also emulsified fats and play an important role here.

(7) Steaming process, steamed buns that cannot be cooked thoroughly, or steamed buns that are over-steamed will not reach the optimal whiteness. If the steam pressure is too high, it may cause hot spots on the surface of the buns, thereby reducing the whiteness of the buns; if the steam pressure is too low, the tops of the buns cannot lift up, which may lead to dead buns or shrunken buns, which also affects the whiteness of the buns.