Comparative study about some physical properties, in vitro digestibility and immunoreactivity of soybean protein isolate for infant formula.

The objective of this study was to determine molecular weight subunit distributions of soy protein isolate (SPI) by SDS-PAGE and gel size exclusion chromatography, and further to investigate the differences of thixotropy, viscosity, in vitro digestibility and immunoreactivity of SPI for infant formula produced in Chinese domestic companies and world famous SPI manufacturers such as Dupont and Fuji. The molecular subunit distributions were analyzed by SDS-PAGE and gel size exclusion chromatography, indicating that Solae and Fuji were hydrolyzed by proteolytic enzymes. The thixotropy of Fuji and Solae significantly reduced around by 95 %, compared with those of Mantianxue and Dupont Zhengzhou. The allergen contents of Fuji and Solae strikingly decreased by 60 and 84 % respectively, in contrast to that of Mantianxue. The in vitro protein digestibility of Solae at the end of pepsin and trypsin digestion markedly increased by 11.7 and 11.3 %, respectively, in comparison to those of Mantianxue. Suitable enzymatic hydrolyzed SPIs showed lower thixotropy, viscosity, immunoreactivity and higher in vitro protein digestibility than those from the other SPIs. The lower thixotropy indicates low difficulty or shear stress in swallowing for infants. The lower immunoreactivity will improve the safety of SPI for cow milk allergic babies.