Antigenicity in soybean hypocotyls and its reduction by twin-screw extrusion

The purpose of the present study was to develop a simple method to make a low-antigenicity food and/or feed rich in isoflavones from soybean hypocotyls. The antigenicity of soybean hypocotyls for bovine antisoybean sera was assessed by enzyme-linked immunosorbent assay. Immunoblotting demonstrated that the antigenicity was derived from storage proteins, which were present in hypocotyls as glycinin and β-conglycinin, and from unknown proteins. Ground soybean hypocotyls (32-mesh sieve size) were passed through a twin-screw extruder to reduce the antigenicity to 1% of the original activity. The degradation of antigen proteins in soybean products was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Trypsin inhibitor and urease activity were also greatly reduced. The concentrations of isoflavones were unaffected.