Structural basis for the effects of thermal treatment on soybean seed β-conglycinin.

The production of soy protein in the food industry is inextricably linked to the thermal sterilization process. To gain a deeper understanding of the changes in protein structure during this process, we compared the structural effects of typical thermal sterilization methods (pasteurization and ultra-high temperature sterilization) on β-conglycinin. Chemical characterization of the solutions showed that two thermal sterilization methods did not affect the primary structure and overall morphology of β-conglycinin. However, the α-helix and β-sheet content were reduced. Additionally, the crystal structure of β-conglycinin after different heat treatments was successfully determined by X-ray crystallography. Notably, we precisely observed the sites where the secondary structure was altered at the atomic level. This allowed us to propose a hypothesis that the highly variable continuous antiparallel β-sheet within the C-terminal core β-barrel structural domains may represent an intermediate state influenced by temperature, acting as the initiation site for protein structure dissociation.