THERMAL AGGREGATION OF SOY PROTEIN ISOLATES

摘要

Thermal behavior of soy protein isolates under different conditions of temperature, time, pH, protein concentration, and presence of reducing agents was studied. Thermal treatments above 85 degrees C showed a decrease in concentration of the AB-11S subunit and of the two protein species of 20 and 29 kDa, and a gradual increase in the concentration of the A and B polypeptides of glycinin. None of the thermal treatments tested led to modifications of the relative proportions either of the high molecular weight aggregates (100-200 kDa) observed in the electrophoretic profiles or of the alpha' and alpha subunits of beta-conglycinin. Increasing the pH to 9 or 10 and increasing the protein isolate concentration enhanced AB-11S aggregation during the thermal treatment. Either the presence of Na2SO3 or the pH 9-10 favored the beta-beta-conglycinin/B-glycinin aggregation. This interaction requires an increase of SH groups. Initially the beta-beta-conglycinin/B-glycinin aggregates were stabilized by hydrophobic interactions and later by SS bonds.