Fractionation and quantitative differences of glutenin from wheat varieties varying in baking quality

Properties of glutenin and other wheat proteins that may be responsible for varietal differences in wheat flour performance were investigated. The proteins from several wheat flours differing in mixing time and dough strengths were extracted with a solution of 0.1 N acetic acid, 3 M urea and 0.01 N hexadecyltrimethylammonium bromide buffer. After dialysis and lyophilization, the extract was dissolved in 5.5 M guanidine hydrochloride and passed through an agarose gel filtration column. The glutenin protein was separated into 2 fractions: a very high MW fraction eluting at the void volume and some lower MW proteins eluting as a broad peak. The gliadins and water-soluble proteins were eluted in close sequence. Glutenin I and II differed only slightly in amino acid analysis and gel electrophoresis patterns of their subunits. The elution profiles (from the 4% agarose columns) of the extracts from the various wheats differed significantly, especially in the glutenin region. The ratio of glutenin I to glutenin II was generally higher in bread wheat flours exhibiting long mixing times and strong doughs. In accordance with observations by Orth and Bushuk, these flours also contained the highest amount of unextracted protein. Flours of weak dough wheats generally had lesser contents of both glutenin I and unextracted protein. A sufficient total amount of protein, and suitable proportions of the two glutenin fractions and the insoluble fraction are necessary for a good baking flour.