Improving the tensile strength of yuba films via disulphide bond breaking-mediated aggregation of soy proteins

Abstract Yuba films, a traditional unfermented soybean product, primarily consist of protein and lipid. These films are formed on the air-contact surface of soymilk by heating. However, their industrial production is currently challenged by poor mechanical properties. In this study, we proposed a simple yet effective strategy to enhance the tensile strength of yuba films by introducing sodium metabisulphite (SM) to participate in the formation of protein aggregates in the emulsions. SM accelerated the dissociation of subunits of soybean protein by disrupting the disulphide bonds, resulting in the development of larger protein aggregates. The rheological properties and interfacial adsorption behaviour suggested that these large protein aggregates exhibited greater diffusion and rearrangement rates, and were more readily to unfolding at the interface and re-crosslinking to form a denser protein network. The circular dichroism (CD) and fluorescence spectrum indicated that the protein aggregates formed from SM-treated emulsions had a stronger trapping of hydrophobic residues compared to those from the control group. These findings have the capacity to contribute to the development and industrial production of yuba films and other plant protein-based film products with specific qualities.