Structural and Thermal Aggregation Behaviors of Soybean Protein in View of Subunits: A Mini-Review

The characteristics of soybean protein-based products are primarily influenced by protein aggregation, there is always a considerable discrepancy in the formation of protein aggregates when the subunit compositions differ. αα'-subunits, β-subunits, and A polypeptides each become more stable after forming aggregates with an increase in the α-helix content. B polypeptides and β-subunits contain more hydrophobic amino acids that undergo hydrophobic thermal aggregation. This strong hydrophobic thermal aggregation also leads to larger particle size and poor solubility. The charged amino acids of the αα'-subunit and the hydrophilic amino acids of the A polypeptides resulted in aggregates with smaller particle sizes. The surface hydrophobicity of the subunits/polypeptides was reduced after aggregation except for the αα'-subunits. The extension region of the αα'-subunit did not contain hydrophobic amino acids, resulting in the surface hydrophobicity not being affected by the heating temperature, resulting in increased stability of its dispersed system. This review provides an in-depth examination of the structures and thermal aggregation behaviors of α-, α'-, and β-subunits and A and B polypeptides, to provide insights that may inform the efficient use of the processing properties of soybean proteins in the food industry.