Protein modification, IgE binding capacity, and functional properties of soybean protein upon conjugation with polyphenols

The modification, structure, functionality and IgE binding capacity of soybean protein (SPI) upon covalent conjugation with gallic acid (GA), caffeic acid (CA), and tannic acid (TA) under alkali treatment were assessed. SDS-PAGE showed the formation of SPI-polyphenol conjugates and the cross-linking of SPI. Protein unfolding in the conjugates was observed, characterized by a reduction in α-helix and an increase in UV ultraviolet absorption, surface hydrophobicity and free sulfhydryl groups. LC/MS-MS demonstrated that the modification of protein and major allergens varied with the types of polyphenols. Western-blot and ELISA demonstrated that SPI-polyphenol conjugates exhibited a significant reduced IgE binding capacity due to the masking or destruction of epitopes among Gly m 4, Gly m 5, Gly m 6 and P28, resulting from structural changes. Additionally, antioxidant capacity and emulsifying properties were increased in SPI-polyphenol conjugates. Therefore, polyphenol treatment may be a promising method to prepare hypoallergenic soybean products with desired functionality.