Cereal Chem. 70:506-511   |  VIEW ARTICLE

Improved Chromatographic Separation and Characterization of Ethanol-Soluble Wheat Proteins.

F. R. Huebner and J. A. Bietz. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

A fraction of oligomeric wheat proteins, ethanol-soluble glutenin (ESG), formerly referred to as high molecular weight (HMW) gliadin, is coextracted with low molecular weight (LMW) monomeric gliadins using 70% ethanol. ESG has several subunits that are apparently identical to LMW-glutenin subunits (40-55 kDa). The cysteine residues of these subunits may be in different locations from those of LMW-monomeric gliadins, and these locations may favor intramolecular cross-linking. This distribution of cysteine residues enables these subunits to form oligomers of two to six subunits, with molecular masses of 80-250 +/- 50 kDa. Variation of these polypeptides between wheat cultivars could significantly affect mixing and baking quality. To examine such quantitative and qualitative variation, we extracted defatted flours with 70% ethanol. Solubilized proteins were separated by size-exclusion liquid chromatography into ESG and LMW monomeric gliadins. Amounts of each fraction were determined gravimetrically after lyophilization. Fractions were then analyzed by reversed-phase high-performance liquid chromatography, before and after reduction of disulfide bonds, to compare cultivars and seek relationships to flour-quality parameters or wheat class. Carbohydrate and amino acid analyses of fractions were also done. ESG consisted of up to 37% of the total ethanol-soluble protein extracted, but results varied significantly among cultivars, possibly because of structural differences among proteins.