Functional Properties of Improved Glycinin and β-nglycinin Fractions

Abstract

ABSTRACT: Glycinin and β-conglycinin have unique functionality characteristics that contribute important properties in soy foods and soy ingredients. Limited functionality data have been published for glycinin and β-conglycinin fractions produced in pilot-scale quantities. Protein extraction conditions were previously optimized for our pilotscale fractionation process to maximize protein solubilization and subsequent product recovery. Glycinin, β-conglycinin, and intermediate (mixture of glycinin and β-conglycinin) fractions were prepared using optimized-process (OP) extraction conditions (10:1 water-to-flake ratio, 45°C) and previous conditions termed Wu process (WP) (15:1, 20°C). Viscosity, solubility, gelling, foaming, emulsification capacity, and emulsification activity and stability of the fractionated proteins, and soy protein isolate (SPI) produced from the same defatted soy white flakes were compared to evaluate functional properties of these different protein fractions. Differential scanning calorimetry, sodium dodecylsulfate-polyacrylamide gel electrophoresis, and surface hydrophobicity data were used to interpret functionality differences. OP β-conglycinin had more glycinin contamination than did the WP β-conglycinin. OP and WP solubility profiles were each similar for respective glycinin and β-conglycinin fractions. Emulsification activities and stabilities were higher for OP β-conglycinin and OP intermediate fractions compared with respective WP fractions. β-Conglycinin and SPI emulsification capacities (ECs) mirrored solubility profile, whereas glycinin ECs did not. OP glycinin had a higher foaming capacity than WP glycinin. OP and WP intermediate fraction apparent viscosities trended higher than those of other protein fractions. β-Conglycinin dispersions at pH 3 and 7 produced firm gels at 80°C, whereas glycinin dispersions formed weaker gels at 99°C and did not gel at 80°C.