Effect of ultrasound-assisted ionic liquid pretreatment on the structure and interfacial properties of soy protein isolate

The application of dual-frequency ultrasound-assisted ionic liquids (UA-IL) pretreatment on the development of compound modification and produce soy protein isolate (SPI) with excellent functional properties is limited. In this research, the effect of UA-IL on the structure and interfacial properties of SPI were evaluated. The results of UV spectrum and intrinsic fluorescence showed that combined ultrasound and ionic liquids pretreatment could loosen the protein structure and expose more hydrophobic groups that were initially hidden inside the molecules. The SDS-PAGE showed there was no significant change in the primary structure of SPI. Besides, the data from FTIR and DSC suggested that the UA-IL could destroy the hydrogen bond between protein molecules and promote its distribution more uniformly. Moreover, UA-IL (1-butyl-3-methyl imidazolium hexafluorate phosphate, [BMIM][PF 6 ]) pretreatment significantly increased the protein’s solubility, reaching 38.33% at the IL/protein ratio of 0.1. There was also an increasing trend for the emulsion activity, foaming capacity and foaming stability of SPI after the UA-IL pretreatment. The current findings indicated that combining ultrasound and ionic liquids pretreatment might be a promising method to change the SPI structure and interfacial properties.