SOY PROTEIN ISOLATE SOLUBILITY AND SURFACE HYDROPHOBICITY AS AFFECTED BY ANTIOXIDANTS

Addition of tert-butylhydroquinone or a mixture of butylated hydroxyanisole and tert-butylhydroquinone (200 ppm on a lipid basis) during SPI processing gave increased protein solubility over that of the control (55%, 56% and 34%, respectively). These increased solubilities correspond to 32% and 18% decrease in oxidation of free sulfhydryls and 20% and 12% reduction in protein oxidation, as determined by protein carbonyl content. Increased protein solubilities, due to added antioxidants, were accompanied by higher total protein surface hydrophobicity, as determined by the sodium dodecyl sulfate (SDS) binding method, and soluble protein hydrophobicity, as determined by the fluorescence probe 8-anilino-1-naphthalene sulfonate (ANS).