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Influence of Gliadin-Rich Subfractions of Glenlea Wheat on the Mixing Characteristics of Wheat Flour^1,2

¹Presented in part at the AACC 81st Annual Meeting, Baltimore, MD, Sept. 1996. ²Publication 1690 of the Agriculture and Agri-Food Canada, Cereal Research Centre, Winnipeg, Canada. ³Agriculture and Agri-Food Canada, Cereal Research Centre, 195 Dafoe Road, Winnipeg, MB Canada R3T 2M9. E-mail: ahussain@em.agr.ca

The effect of gliadin-rich subfractions of extra-strong wheat on the mixing properties of Canada Prairie Spring (CPS) wheats and Canada Western Extra Strong Red Spring wheat (CWES) cv. Glenlea was determined by the 2-g mixograph. Thirteen subfractions isolated from the single ethanol extract of Glenlea showed differences in their SDS-PAGE patterns of total proteins, low molecular weight glutenin subunits, the ω-gliadin component, and acid-PAGE electrophoregrams. High molecular weight glutenin subunits were found only in one subfraction isolated by increasing the concentration of ethanol. Subfractions that remained solubilized in the water phase after removal of ethanol from the extract were deficient in ω-gliadins and contained a number of fast-moving protein bands. These fractions caused a significant delay (from 2.64 to 5.41 min and from 5.75 to 8.16 min) in the mixograph peak development of CPS and Glenlea flours, respectively. On the contrary, the water-insoluble subfractions reduced the mixing time requirement (from 2.6 to 1.08 min and from 5.8 to 1.7 min for CPS and Glenlea flours, respectively) and caused a rapid decline in the dough stability as the mixing continued. Both base flours showed an increase in peak height with the addition of ethanol-extractable protein subfractions. Mixograph development time and energy to peak increased with the addition of water-soluble subfractions but decreased with water-insoluble subfractions of the 70% ethanol extract. The band width at peak increased when water-soluble subfraction 6.5 was added to CPS flour but decreased when it was added to Glenlea flour. Removal of ethanol-extractable components from flours resulted in loss of viscoelasticity. Adding subfraction 1.5 back to the flour residue caused a return of this physicochemical attribute. Addition of a nonwater- dispersible subfraction (1.5) to CPS flour or CPS flour residue caused a significant increase in the formation of gluten. Approximately 35–42% of the added gliadins were incorporated into the gluten network of CPS flour and 34–52% into the flour residue.