Effects of thermal sterilization on the allergenicity of soybeans

The study assessed the effects of industrialized sterilization (boiling and autoclaving) on proteins immunoreactivity, composition and conformation of soybeans (R251, R252 and R253). The results of indirect ELISA demonstrated that boiling and autoclaving reduced the allergenicity of soybeans by 43%–59% and 82%–83%, respectively. SDS-PAGE revealed that there was more dramatic degradation of proteins in autoclaved soybeans, compared to boiled soybeans, resulting in the destruction of epitopes. LC/MS-MS and SEM showed the changes in amounts of peptides and unique peptides (proteins screening scores ≥ 20) and micro-structure, respectively, suggesting the structural changes. Circular dichroism furtherly illustrated a greater reduction of α-helix in autoclaved soybeans, resulting in the masking of epitopes. Conformational analyses demonstrated that the effects of boiling and autoclaving on conformation also varied among treatments and soybean cultivars. Interestingly, the surface hydrophobicity was increased and decreased after boiling and autoclaving, both resulting in the masking of epitopes. In conclusion, autoclaving was an effective method to reduce the allergenicity of soybeans, resulting from dramatic proteins-degradation and reduction of α-helix. Of note, the allergenicity of raw soybeans was positively correlated with their intensity of surface hydrophobicity and total amounts of peptides and unique peptides.