Electrophoresis studies for determining wheat-soy protein interactions in dough and bread

The interactions between soy and wheat proteins after dough mixing and bread baking were studied. Protein extractions from gluten and breadcrumbs elaborated with mixtures of wheat flour and enzyme-active full-fat, heat-treated full-fat, and enzyme-active defatted soy flours, and commercial isolated soy proteins were analyzed by electrophoresis. Different buffer systems with specific chemical action on proteins were used to investigate the types of forces between soy and wheat proteins in gluten and breadcrumbs. The presence of protein bands of similar molecular weight to soy proteins in gluten fractions after intensive dough washing indicated association between these proteins. Nonreduced wheat-soy gluten proteins had higher amount of sodium dodecyl sulfate soluble protein aggregates than wheat gluten. Soy and wheat proteins interacted by means of noncovalent and covalent (disulfide) bonds and the extent of the interactions depended on the soy protein state.