Lipid extraction process on texturized soy flour and wheat gluten protein-protein interactions in a dough matrix

ABSTRACT Protein‐protein interactions between wheat flour and solvent‐extracted (SE) or nonsolvent extracted (NSE) texturized soy flours were compared. Doughs were prepared to contain varying ratios of texturized soy flour in combination with wheat flour. Sucrose esters (2.5%) were included in several formulations. Doughs were fractionated into soluble and insoluble fractions at pH 4.7 and pH 6.1. Fractions were dried, powdered, and analyzed using SDS‐PAGE and spectrophotometric techniques. Electrophoretic evaluation indicated interactions between wheat gluten proteins and texturized soy proteins in the absence of sucrose esters. Electrophoretic gels of the wheat‐soy flour mixtures maintained a characteristic soy protein band after acidification to the soy protein isoelectric point. Inclusion of sucrose esters increased the interaction. Texturization conferred effects similar to that of sucrose ester on both forms of lipid‐extracted soy. Sulfhydryl analyses using 7‐chloro‐4‐nitrobenzo‐2‐oxa‐4, 3‐diazole (NBD‐Cl) revealed no change in the relative amount of sulfhydryl groups present in doughs prepared from either the texturized soy flours or the doughs containing equal amounts of wheat starch. These data indicate that interactions between soy protein from texturized soy flours and wheat proteins are not covalent.