Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 2004
Publication Date: September 2, 2004
Citation: Robertson, G.H., Cao, T. 2004. Proteins extracted by water or aqueous ethanol during refining of developed wheat dough to vital wheat gluten and crude starch as determined by capillary-zone electrophoresis (cze). Cereal Chemistry. 81(5):673-680. Interpretive Summary: Advanced separation technology will facilitate the participation of wheat as a biorefined substrate to meet national needs for biofuels and biobased products. This manuscript is one of a series evaluating separation strategies based on use of cold ethanol as a primary processing fluid. Here we applied a new analytical method, capillary electrophoresis, to identify and characterize proteins solublized by the process fluids. We found that very little of the valuable gliadin protein is solubilized by the cold ethanol and that albumin protein is removed in an insoluble form at the same time as the starch. Conventional water processing removes the albumins in a soluble form. The fate of the wheat proteins is important to know because deletion of proteins from gluten will affect the gluten properties and value. It is also important to know because these proteins may also alter the properties of the crude starch and, if soluble, may become a waste treatment problem.
Technical Abstract: The bulk, fluid-based separation of wheat starch and protein leads to extraction of wheat components and alteration of the composition and properties of the resulting protein and starch fractions. The degree of extraction and the specific components extracted depend on the physical form of the flour (dry flour or dough), the fluid composition (water or aqueous alcohol), the temperature, and the mechanical processing method. This study was conducted to identify protein compositional changes by high-performance capillary electrophoresis applied to fluids and solids obtained in and during the separation. Dough-ball and batter-like methods of separation were applied using water at 22°C or 70% ethanol in water at -13°C. Data were referenced to extraction of wet, developed dough using 70% ethanol in water at 22°C. The dough structure created as a separable state was found to allow rapid extraction of both starch and water-soluble or albumin proteins, but to retard the extraction of 70% ethanol-soluble gliadin proteins. Albumins not appearing as soluble in 70% ethanol were found associated with the insoluble crude starch. Capillary electrophoresis patterns for the albumin proteins have distinctive and characteristic shape and position that depend on the composition of the displacing fluid. The slowly appearing gliadin proteins were released to the ethanol by random processes based on comparing the peak area for a,b gliadins to the peak area for g gliadins. These results (a) confirm the benign character of cold-ethanol processing to produce crude protein and starch provided the mechanical working of the dough is limited and (b) characterize the nature and fate of albumin protein removed from separable dough during processing.