Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 2008
Publication Date: August 27, 2008
Citation: Dupont, F.M., Chan, R., Samoil, V. 2008. Extraction of up to 95% of unreduced wheat flour protein using warm SDS. Journal of Agricultural and Food Chemistry. 56:7431-7438. Interpretive Summary: Bakers use thousands of tons of wheat flour every year, and variability in flour quality is of major concern. Mixing and baking properties and final quality of the baked goods are strongly influenced by the protein composition of the flour. However, wheat flour is composed of a complex mixture of proteins that are not easily studied. These include glutenin subunits linked into large polymers as well as unlinked gliadins. A major obstacle to study of the flour proteins is inability to solubilized large glutenin polymers without disrupting them. This paper presents a method to solubilize up to 92% of the intact glutenin polymer that will be useful for measuring the size and composition of the polymers. It also demonstrates differences between strong and weak flours in the way that gliadins interact with the glutenin polymer.
Technical Abstract: Extraction of intact glutenin polymer without sonication is an essential prerequisite for accurate determination of the molecular size distribution of the polymers. Sequential fractionation of wheat flour extracted up to 95% of total protein and up to 92% of polymeric protein without sonication or reduction. Flours were from the hard red spring wheat Butte 86 and the hard red winter wheat Jagger, which have good baking quality, and the red spring wheat Chinese Spring with poor baking quality. Extracts were analyzed by size-exclusion HPLC, reverse-phase HPLC, and SDS-PAGE. The albumin and globulin fraction extracted with 0.1 M KCl was proportionally smaller for Chinese Spring compared to Jagger and Butte 86. The proportion of alpha- and gamma-gliadins and polymer extracted with 0.25% SDS was greatest for Chinese Spring. The fraction extracted with warm 2% SDS consisted of glutenin polymer, omega-gliadins and the remaining alpha- and gamma-gliadins and was greatest for Butte 86 and least for Chinese Spring. Unextractable glutenin polymer was solubilized with 2% SDS/DTT and was greatest for Jagger and least for Chinese Spring. We propose that 2% SDS at 60oC disrupts H-bonds in glutenin and glutenin-gliadin aggregates and facilitates solubilization of the aggregated protein.