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Effect of Varying Protein Content and Glutenin-to-Gliadin Ratio on the Functional Properties of Wheat Dough

¹Quality Wheat CRC Limited, Locked Bag No 1345, P.O. North Ryde, NSW 1670 Australia. ²CSIRO Plant Industry, GQRL, P.O. Box 7, North Ryde, NSW 1670 Australia. ³Plant Breeding Institute, Woolley Bldg A0, The University of Sydney, NSW 2006 Australia. ⁴Corresponding author. E-mail: p.gras@pi.csiro.au

Gluten, starch, lipids, and water-soluble material were separated from seven wheat samples with a range of protein contents and breadmaking quality. The isolated glutens were further partitioned into gliadin- and gluteninrich fractions using pH precipitation. Protein content and glutenin-togliadin ratio were systematically altered by blending these fractions into the original flours in calculated amounts. Mixing properties, extension-tester parameters, and baking performance of composite flours were determined using small-scale techniques. Results of dough testing with blends of constant glutenin-to-gliadin ratio showed increases in the mixing time, mixograph peak resistance, maximum resistance to extension, extensibility, and loaf volume as the protein content increased. At constant protein content, increases in glutenin-to-gliadin ratio were associated with increases in mixing time, mixograph peak resistance, maximum resistance to extension, and loaf volume, and with decreases in extensibility. Thus, total protein content and glutenin-to-gliadin ratio independently affected dough and baking properties. The results have allowed the separation of the effects of flour protein quantity and composition on breadmaking properties.