Comparative study of four physical approaches about allergenicity of soybean protein isolate for infant formula

The objective of this study was to investigate the influences of microwaving, high-intensity ultrasound (HIU), high-pressure homogenization (HPH) and high hydrostatic pressure (HHP) on the allergenicity and structural properties of soy protein isolate (SPI) for infant formula. Microwaving, HIU, HPH and HHP reduced allergenicity by 24.7%, 18.9%, 29.8% and 46.6%, respectively. Western blotting (WB) results indicated the allergens for Chinese soy-allergic childrens encompass 130 kD, 115 kD, lipoxidase, and subunit of -conglycinin, Chain A of glycinin, P34, 30 kD, 28 kD, Chain B of glycinin. SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) (with 2-ME) and WB patterns did not show significant differences among the native and modified SPIs. These four approaches influenced molecular interactions such as free sulfhydryl, hydrophobicity and zeta potential, compositions of secondary structures containing helices, strands, turns and unordered, and structural parameters including helices and strands (per 100 residues), average length of helices and strands. The epitopes of SPI allergens could be closely related to -helix and -sheet. In case of magnitude of secondary structure composition and parameter changes, HHP ranked top compared with other three methods. Therefore, the allergenicity reducing efficiency of HHP is much higher than those of other three treatments.