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Basic Rheology of Bread Dough with Modified Protein Content and Glutenin-to-Gliadin Ratios

¹Quality Wheat Cooperative Research Centre Ltd., Locked Bag 1345, North Ryde, NSW 1670, Australia. ²Corresponding author. Phone: 61 2 9351-7141. Fax: 61 2 93517060. E-mail: suthay@mech.eng.usyd.edu.au ³Department of Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia. ⁴Plant Breeding Institute, The University of Sydney, NSW 2006, Australia. ⁵CSIRO Plant Industry, Grain Quality Research Laboratory, P.O. Box 7, North Ryde, NSW, 1670, Australia.

The uniaxial elongational and shear rheology of doughs varying in either the protein content or glutenin-to-gliadin ratio were investigated. Increasing the protein content at constant glutenin-to-gliadin ratio increased the strain-hardening properties of the dough, as shown by increasing elongational rupture viscosity and rupture stress. Glutenin and gliadin had a more complex effect on the elongational properties of the dough. Increased levels of glutenin increased the rupture viscosity but lowered the rupture strain, while elevated gliadin levels lowered the rupture viscosity but increased the rupture strain. These observations provide rheological support for the widely inferred role of gliadin and glutenin in shaping bread dough rheology, namely that gliadin contributes the flow properties, and glutenin contributes the elastic or strength properties. The shear and elongational properties of the doughs were quite different, reflecting the dissimilar natures of these two types of flow. Increasing protein content lowered the maximum shear viscosity, while increasing the glutenin-to-gliadin ratio increased maximum shear viscosity. Strong correlations between the results of basic and empirical rheology were found. These basic, or fundamental, rheological measurements confirmed prior empirical studies and supported baking industry experience, highlighting the potential of basic rheology for bread and wheat research.