The relationship between the chemical composition and the quality of the soybean film during peeling process.

Soybean film is a traditional nonfermented soy product in China. It is a film formed on the surface of the soymilk during heating process. The nutrient components of soymilk will affect the quality of the soybean film. The results of this study showed that during the peeling process, the proportion of protein and carbohydrate in soymilk decreased, and the proportion of lipid increased. The mechanical properties (fracture extension and tensile strength) of the soybean film decreased during the peeling process. During the heating treatment, the Maillard reaction occurred and its intermediate products accumulated, which caused the change in soybean film color. White globular protein granules (<100 nm) existed on the surface of the soybean film. The lipid that was not wrapped by the protein network structure was exposed, and the evaporation of water led to the formation of black and gray holes on the skin (<500 nm). In addition, the results of correlation analysis showed that the changes in color, taste, and odor, as well as the mechanical properties of the skin, were all related to the changes in nutrients in the soybean film during peeling. This research provided a deeper understanding of the quality change in the soybean milk and the soybean film during the heating process.