In situ examination of starch granule-soy protein and wheat protein interactions

The objective of this study was to evaluate the association between heat and pressure-treated soy proteins and wheat prime starch relative to the level of granule surface proteins present. Soy isolates were manufactured from defatted soy flour and from two types of textured soy flour. Conditions for binding between wheat starch and soy fractions were established by altering pH, protein and sucrose concentrations. Conformations of exogenous proteins bound to the wheat starch granule surface were evaluated using an amyloglucosidase assay. Proteins present on the granule surface were removed and soy protein binding was reevaluated. Thermal and pressure processing of soy protein significantly influenced binding kinetics. Textured soy proteins exhibited increased wheat starch granule adsorption characteristics compared to untreated soy protein. Removal of native wheat starch granule surface proteins decreased the binding of added proteins. This suggests that native granule proteins may mediate the binding of exogenous protein. (C) 2007 Elsevier Ltd. All rights reserved.