Large-Deformation Properties of Wheat Flour and Gluten Dough

Keywords: Wheat, gluten protein, bread, puff pastry, flour dough, gluten dough,rheology,uniaxialextension, biaxial extension, fracture.Rheologicaland fracture properties of flour and glutendoughsfrom eight wheat cultivars were studied and related to gluten protein composition and baking performance in bread and puff pastry. For bothuniaxialand biaxial extension flour dough showed a more than proportional increase of stress with increasing strain, a phenomenon called strain hardening. Inuniaxialextension (i) stresses at a certain strain were higher and (ii) stress was less dependent on strain rate than in biaxial extension. Stress at a certain strain and strain hardening depended much stronger on the type of deformation for gluten than for flour dough. These findings are consistent with published data on birefringence of gluten and show that orientation of structure elements inelongationalflow plays an important role in flour and gluten dough.For flour dough fracture stress and strain increased with increasing strain rate. At higher strain rates and lower temperatures fracture strains hardly differed between different flourdoughsno matter the protein content or composition. At lower strain rates and higher temperatures the smallest fracture strains were found for flourdoughswith the lowestglutenincontents and/or the lowest protein contents. We concluded that the strain rate and temperature-dependency of the fracture strain is a very important factor to relate to protein composition. Fracture stresses were much higher for gluten than for flour dough, while fracture strains were in the same range or higher. Contrary to flour dough, the smallest fracture strains were found for glutens with the largestglutenincontents.Puff pastry volume was positively correlated with strain hardening and negatively with thestrainrate-dependency of the stress and the strain rate and temperature-dependency of the fracture stress and strain. For bread it were thedoughswith intermediate dough strength that gave the highest loaf volume, while loaf volumes of flours with high dough strength (i.e. high stress-level and high strain hardening coefficient) gave intermediate loaf volumes. We concluded that a high internal stress limits the deformability of dough films between gas cells and with that of the loaf volume that can be obtained.