A new technique for glycosylation modification of soy protein isolates using magnetically induced electric field: focus on structure and gel properties

Abstract

In this study, soy protein isolate (SPI) glycosylated conjugates were successfully prepared by incorporating three sugars with different molecular weights (maltose, maltodextrin with dextrose equivalent of 16, and maltodextrin with dextrose equivalent of 11) into SPI using the magnetically induced electric field (MIEF) technique. The structural and gel properties of the conjugates were subsequently evaluated. The degree of grafting and SDS-PAGE results confirmed the formation of these covalent conjugates. Maltose, due to its smaller molecular weight, was more readily incorporated into SPI. Fluorescence and UV spectroscopy analyses demonstrated that MIEF-induced covalent cross-linking caused significant conformational changes in the SPI, leading to fluorescence quenching of SPI and the formation of a more hydrophilic microenvironment around the amino acid residues. FTIR revealed that MIEF triggered substantial alteration in the secondary structure of SPI, manifested by a pronounced reduction in α-helix content accompanied by a concomitant rise in random coil structures. MIEF-induced glycosylation modification of SPI enhanced its solubility, surface hydrophobicity, and free sulfhydryl content, resulting in a looser and more flexible protein structure that positively influenced the improvement of gel properties. Further investigation of the gel properties of the glycosylated conjugates demonstrated that the gel network structure became more ordered, with hardness increasing by 62.12 % and water-holding capacity improving by 23.39 %. Rheological analysis revealed that the glycosylated conjugates formed a viscoelastic gel network structure, with a significant increase in hydrogen bonding, thereby enhancing the stability of the protein gels.