An Improved Isolation Method of Soy β-Conglycinin Subunits and Their Characterization

This study aimed at establishing an effective preparative isolation method of soy β-conglycinin constituent subunits and characterizing some of their physicochemical properties and their heat-induced aggregation. These subunits were isolated in relatively large amounts and in high purity by dissociating β-conglycinin in 6 M urea and using a combination of DEAE-Sepharose fast flow column chromatography and immobilized metal ion affinity chromatography (IMAC). At a pH deviating from isoelectric point (pI), zeta potentials of α′ and α subunits were much larger than that of β subunit, while in the latter case, the hydrophobic groups were more buried within the proteins. Dynamic light scattering analysis indicated that the extent of heat-induced aggregation of β subunit was much higher than that of α′ and α subunits, and the aggregation was also more affected by the increase in ionic strength. Atomic force microscopy analysis indicated that more ordered and stranded aggregates were formed for α′ and α subunits. These results confirm a close relationship between physicochemical properties and heat-induced aggregation of β-conglycinin subunits.