Finding the Bio in Biobased Products: Electrophoretic Identification of Wheat Proteins in Processed Products

Authors: Robertson, George; Hurkman Ii, William; Cao, Trung; Tanaka, Charlene; Orts, William

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2010
Publication Date: 3/12/2010
Citation: Robertson, G.H., Hurkman Ii, W.J., Cao, T., Tanaka, C.K., Orts, W.J. 2010. Finding the Bio in Biobased Products: Electrophoretic Identification of Wheat Proteins in Processed Products. Journal of Agricultural Food & Chemistry. 2010 April 14;58(7):4169-79.

Interpretive Summary: Verification of the bio-content in biobased or green products is needed to identify counterfeit copies, support or refute content claims and ensure consumer confidence. In the case of cereal protein containing products we applied methods of ethanolic leaching and capillary electrophoresis of the extract to the detection of these proteins and succeeded in identifying wheat gluten protein in an automobile ignition coil that was reputed to be encased in a gluten containing material. This methodology should have general use for assessing biobased products that contain cereal protein provided that the processing conditions have not pyrolyzed the protein.

Technical Abstract: Verification of the bio-content in bio-based or green products identifies genuine products, exposes counterfeit copies, supports or refutes content claims and ensures consumer confidence. When the bio-content includes protein, elemental nitrogen analysis is insufficient for verification since non-protein, but nitrogen-rich, content also may be present. However, the proteins can be extracted, separated by electrophoretic methods and detected by UV absorption, protein stain, or immuno-blotting. We utilized capillary zone electrophoresis (CZE) to separate proteins in a gliadin fraction that had been dissolved in aqueous ethanol (70%) and polyacrylamide gel electrophoresis (PAGE) to separate proteins in a gliadin-plus-glutenin fraction that had been dissolved in water containing both sodium dodecylsulfate (SDS) and a reducing agent dithiothreitol (DTT). We sought to verify the presence of these wheat grain proteins in wheat bread, a wheat flake cereal, wheat beer, and an enclosure for an antique automobile ignition coil reputed to contain wheat gluten. Proteins extracted from commercial wheat, corn, and soy flours served as standards and proteins from heat-altered wheat served as process condition references. This approach successfully identified wheat proteins in these products especially if the process temperature did not exceed 120°C. Above this temperature attenuation was nearly complete for proteins analyzed by CZE, but wheat like patterns could still be recognized by one- and two-dimensional PAGE. Immunoblots reacted with grain specific antibodies confirmed the identities of the cereal component especially when the protein pattern was greatly altered by thermal modification, specific protein adsorption, or protein digestion. In addition to verifying that wheat proteins are present, the complementary use of these methods can reveal whether whole wheat gluten or merely an alcohol soluble fraction had been used in the specific product and indicate the level of thermal damage.