IMPROVED CHROMATOGRAPHIC-SEPARATION AND CHARACTERIZATION OF ETHANOL-SOLUBLE WHEAT PROTEINS

A fraction of oligomeric wheat proteins, ethanol-soluble glutenin (ESG ), formerly referred to as high molecular weight (HMW) gliadin, is coe xtracted 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 subunit s may be in different locations from those of LMW-monomeric gliadins, and these locations may favor intramolecular cross-linking. This distr ibution of cysteine residues enables these subunits to form oligomers of two to six subunits, with molecular masses of 80-250 +/- 50 kDa. Va riation of these polypeptides between wheat cultivars could significan tly 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 chromato graphy into ESG and LMW monomeric gliadins, Amounts of each fraction w ere determined gravimetrically after lyophilization. Fractions were th en analyzed by reversed-phase high-performance liquid chromatography, before and after reduction of disulfide bonds, to compare cultivars an d seek relationships to flour-quality parameters or wheat class. Carbo hydrate and amino acid analyses of fractions were also done. ESG consi sted of up to 37% of the total ethanol-soluble protein extracted, but results varied significantly among cultivars, possibly because of stru ctural differences among proteins.