Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/5/2005
Publication Date: 5/1/2005
Citation: Dupont, F.M., Chan, R., Lopez, R., Vensel, W.H. 2005. Sequential extraction and quantitative recovery of gliadins, glutenins and other proteins from small samples of wheat flour. Journal of Agricultural and Food Chemistry. 53(5):1575-1584. Interpretive Summary: Thousands of tons of wheat flour are used every year by the baking and food industries. Mixing, baking and final quality of the resulting food products depend heavily on the protein composition of the flour. However, wheat flour is composed of a complex mixture of proteins that are not easily identified and quantified. This paper presents a reliable method to separate wheat proteins into the categories of gliadins, glutenins, and albumins/globulins in order to facilitate analysis of protein composition. Identities of many of the proteins were determined by HPLC, SDS-PAGE and mass spectrometry.
Technical Abstract: Simple, reliable methods for quantitative analysis of wheat flour proteins are essential for determining flour composition and evaluating relationships between proteins and end-use functionality. However, it is difficult to completely recover and separate the major flour protein types from a single sample. Methods for sequential extraction and fractionation of protein were evaluated, in order to develop a reliable procedure to recover and determine the total amounts of gliadins, glutenins and albumins/globulins in small flour samples. Proteins were extracted with 1-propanol, KCl, NaI and SDS solutions and were recovered by freeze-drying or by precipitation with ammonium acetate/methanol or acetone. The resulting protein fractions were analyzed by a combination of RP-HPLC and SDS PAGE. The best separation and recovery of flour protein types was achieved by sequential extraction with 0.3 M NaI in 7.5% 1-propanol followed by 2% SDS, 25 mM DTT in 25 mM Tris, pH 8.0 and sequential precipitation of the solubilized proteins with ammonium acetate/methanol followed by acetone. This method for evaluating total protein content and composition should be useful for comparing flour from different wheat varieties, evaluating unknown flour samples, determining effects of environment on total protein composition, and for preparing proteins for proteomic analysis.