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 (10-10(4) 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 s(n), and a coefficient of determination R(2) = 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 R(2) = 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. (C) 2010 Elsevier Ltd. All rights reserved.