Effect of acidic pH-shifting combined with sonication on the structural and functional properties of peanut protein

In order to further improve the functional properties of peanut proteins, this paper investigated the effects of pH-shifting at pH 1.5 and pH 2.5 individually or combined with ultrasonic treatment on the structural and functional properties of peanut proteins extracted by aqueous method. The results showed that compared with untreated proteins, the subunits of peanut proteins were degraded to a certain extent after treatment in different ways, and the particle size, absolute potential were decreased, while the surface hydrophobicity was increased significantly. The complex modification resulted in a more stretched structure of the protein compared to the pH-shifting treatment alone. The ability of peanut proteins to reduce the interfacial tension between oil and water was enhanced by different treatments, and both emulsifying activity and stability were increased. The pH-shifting at pH 1.5 combined with sonication increased the emulsifying stability of peanut proteins by a factor of 2. The proteins of pH-shifting at pH 1.5 possessed the highest modulus of elasticity (G'), which may be related to their structural properties of exposing the highest free sulfhydryl content and the lowest absolute potential. The pH-shifting at pH 1.5 or combined with sonication significantly improved the functional properties of peanut proteins.