Shear and extensional viscosities of hard wheat flour dough using a capillary rheometer

The rheological behaviour of hard wheat flour dough was investigated for a high shear rate range (10-10⁴ s⁻¹) using a capillary rheometer. The shear viscosity obtained from capillary measurements demonstrated a shear thinning behaviour of dough and described by a power law model with a power law index n = 0.38, a consistency coefficient K = 1387 Pa sⁿ, and a coefficient of determination R² = 0.997. The extensional viscosity obtained from capillary measurements for a high extensional rate range (0.16-154 s⁻¹) showed a tension thinning behaviour and described by a power law model with a power law index m = 0.38, a consistency coefficient K_E = 353,000 Pa s^m, and a coefficient of determination R² = 0.977. Torsional measurements using a parallel plates rheometer for a shear rate range (10⁻³-20 s⁻¹) demonstrated the time or strain dependence of wheat flour dough, no steady state shear viscosity of dough, and the shear viscosity increased with time or strain to a maximum value and then decreased, suggesting a breakdown or rupture of the dough structure.