Food Chemical Studies on Soybean Proteins

Part XII. Effect of pH and heating on the solubility of water extracted protein

Abstract

The effect of heating on the solubility of water extracted protein at various pH was studied; it was recognized that the minimum solubility near isoelectric point was decreased by heating and the diffrential solubility between unheating and heating was minimum at pH 6.0, but maximum between pH 6.5 and 8.5, and at pH 3.5. Also the effect of heating at various pH on the solubility against standard solvent (0.076M tris-citrate buffer, pH 8.6, containing 0.01M 2-mercaptoethanol) was studied; the solubility was decreased by heating over 70°C between pH 3 and 7, but the insolubilization by heating was not recognized below pH 3 and over 7.
The effect of heating at various pH on the gel electrophoretical behavior of the protein was studied; the main components, 7 and 11 S, were dissociated into the subunits by heating being followed polymerizing of the subunits, and the stability of the 11 S component against heating was higher over pH 9 and lower below pH 3 than the 7S component.