Effects of Heat and Ionic Strength Upon Dissociation-Association of Soybean Protein Fractions

The effects of heat and ionic strength upon dissociation or association of soybean proteins were characterized by an immunoelectrophoresis. Among thermal products of both glycinin and β-conglycinin, the dissociated subunits of β-conglycinin retained their antigenic reactivities, while the thermal products of glycinin lost their antigenic reactivities. Appearance of immunoprecipitin arcs was dependent on the ionic strength of the solutions. This is based on the conformational changes at the ionic strengths below 0.1 where the thermal denaturation of β-conglycinin transforms from association to dissociation. The immunoelectrophoretic results can be used to determine the ionic strength of the solution in complex systems including whole soybean extracts and soybean milk. Relationship between the differences in textural properties of tofu and conformational changes of soybean protein is discussed.