Relationship of the extrusion temperature and the solubility and disulfide bond distribution of wheat proteins

Wheat flour was extruded at die temperatures of 60, 90, 120, and 160 degrees C. The soluble protein content in the extrudates decreased by 66.7% in the extracting buffer (1% sodium dodecyl sulfate in 50 mM sodium phosphate buffer, pH 6.9) as the extrusion die temperature was increased to 160 degrees C. The most insoluble proteins in the extrudates extruded at die temperatures of up to 120 degrees C could be resolubilized by using sonication. The changes in the disulfide/protein ratio corresponded with the changes in protein solubility in the extrudates. SDS-PAGEs showed that the content of large molecular weight proteins in the extrudates increased as the extrusion die temperature was increased. However, these proteins completely disappeared after being reduced by B-mercaptoethanol. This study showed the relationship between the extrusion temperature and the solubility and disulfide distribution of wheat proteins.