Effects of moderate electric field on the structural properties and aggregation characteristics of soybean protein isolate

The effects of moderate electric field (MEF) at different intensities (4–10 V/cm) on the structural properties and aggregation characteristics of soybean protein isolate (SPI) during ohmic heating (OH) were investigated. Fourier-transform infrared spectroscopy, fluorescence spectroscopy, and analysis of surface hydrophobicity and total free sulfhydryl groups showed that MEF treatments at 4 and 6 V/cm facilitated the unfolding of the protein structure, thus exposing more hydrophobic residues and enhancing surface hydrophobicity. Protein aggregation increased with the increase in electric field intensity, as demonstrated by the turbidity and particle size measurements, size exclusion chromatography, and atomic force microscopy. MEF treatments at 8 and 10 V/cm induced the formation of large, soluble aggregates dominated by disulfide bonds and hydrophobic interactions. Rheological analysis showed that the MEF treatments at 4 and 6 V/cm improved the gelation capacity. These results contribute to improving the understanding of the changes in structure and aggregation properties of SPI during MEF treatment and create opportunities to modify protein structure by MEF technology.