Heat-induced changes in epitopes and IgE binding capacity of soybean protein isolate

The effects of heating temperature on epitopes, IgE-binding capacity, and conformation of soybean protein isolate (SPI) were investigated in this study. Indirect ELISA demonstrated that the IgE binding capacity of SPI was increased by 13.1 %-31.6 % after being heated at 60-100 °C for 20 min. SDS-PAGE demonstrated no changes in protein profiles, and native PAGE revealed the formation of aggregates. Structural analyses demonstrated the protein unfolding, appearing temperature-dependent, thus exposing conformational epitopes. Peptide mapping analysis revealed the changes in peptide profiles of major allergens (Gly m 4, Gly m 5, Gly m 6, P28, and Kunitz trypsin inhibitor). LC/MS-MS demonstrated that heating caused the masking or exposure of linear epitopes in Gly m 4 - Gly m 6 and P28. Therefore, heating caused structural changes to expose epitopes to increase IgE binding capacity in SPI. Patients with soybean allergy should avoid the heated SPI until the results of clinical trials are confirmed.