Immunochemical and Electrophoretic Analysis of the Modification of Wheat Proteins in Extruded Flour Products.

Antibodies specific for wheat proteins were used to identify protein fractions modified during extrusion of Hard Red Spring wheat flour (14% protein) under four different combinations of extrusion conditions (18 and 24% feed moisture and 145 and 175°C die temperature). Antibody binding was assessed on immunoblots of proteins extracted from flour and extrudates separated by SDS-PAGE. Antibodies to high molecular weight glutenin subunits (HMW-GS) and to B-group low molecular weight glutenin subunits (LMW-GS) recognized intact subunits from both flour and extrudates. Antibodies to C-group LMW-GS had diminished binding to extruded proteins. Glutenin-specific antibodies also recognized protein in the extrudates migrating as a smear at molecular weights higher than intact subunits, indicating cross-linked proteins. Antibodies recognized albumins or globulins in flour but not in extrudates, evidence that these fractions undergo significant modification during extrusion. Acid-PAGE and antibody reaction of gliadins extracted in 1M urea and in 70% ethanol revealed total loss of cysteine-containing (alpha), (beta), (gamma)-gliadins but no obvious effects on sulfurpoor (omega)-gliadins, suggesting gliadin modification involves replacing intramolecular disulfides with intermolecular disulfide cross-links. Identifying protein fractions modified during different extrusion conditions may provide new options for tailoring extrusion to achieve specific textural characteristics.