Solubility and aggregation of soy protein isolate induced by different ionic liquids with the assistance of ultrasound

The aim of this study was to evaluate the effects of ionic liquids (ILs) and ultrasound on the solubility and aggregation behavior of soy protein isolate (SPI). A variety of ILs were tested. Results showed that changes in cation or anion altered the physicochemical properties of ionic liquids, which in turn influenced the solubility of SPI. High concentration of ILs resulted in the formation of insoluble aggregates, which lead to the decrease of solubility. In most of the cases, ultrasound pretreatment had a considerable impact on the solubility and aggregation of SPI. The solubility of SPI processed by combination of 1 mg/mL 1-butyl-2,3-dimethyl imidazolium chloride ([BDMIM]Cl) and ultrasound changed remarkably compared with single ultrasound and single [BDMIM]Cl processing, which was increased by 71.8% compared with that of control ( P <  .05). Changes in particle size, intrinsic fluorescence spectra and free sulfhydryl (SH) groups indicated that the structure of SPI refolded and reaggregated after the ultrasound and ILs pretreatments. Combined ultrasound and 1 mg/mL [BDMIM]Cl pretreatment showed a synergistic effect on changing the SPI microstructure. In conclusion, ultrasound-assisted ILs could be an effective modification method for the globular proteins .