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Nonlinear viscoelastic behaviors of wheat flour dough under exponential and interrupted shears |
C. H. HWANG and S. Gunasekaran. Biological Systems Engineering Department, University of Wisconsin-Madison, 460 Henry Mall, Madison, WI 53706 Nonlinear viscoelasticity of materials can be evaluated under exponential and interrupted shear experiments using a sliding plate rheometer (SPR). Large deformations generated by the SPR are normally encountered in many food processes such as dough mixing. Our objective was to determine the exponential and interrupted shear behavior of wheat flour dough using the SPR. The effects of moisture content and temperature on the rheological properties of dough were studied. Soft winter wheat flour dough with 42, 44, and 46 % water were prepared and used at 30, 40, and 50oC. Exponential shear tests were performed at a=0.35 and A=0.001 in order to observe both linear and nonlinear viscoelastic ranges. Interrupted shear tests were performed at strain rates of 2 and 10 and time intervals between two-step shears up to 45 min. For the exponential shear test, exponential viscosity was determined to be between 50 and 250 kPa.s depending on the dough moisture content. Due to dough structural failure and slippage, the viscosity was only measured when shear levels were less than 0.06. The exponential viscosities in the linear viscoelastic region were fairly independent of moisture content but decreased with temperature. Interrupted shear tests results showed that dough with 42 % moisture content at 30oC recovered completely after 5 min of rest time. Higher moisture contents and temperatures led to weaker stress responses and caused unstable results. Compared to the interrupted shear test, the exponential shear test is a better choice to determine the linear and nonlinear viscoelasticity of wheat flour dough. It can be used to overcome the material slippage and simulate the actual dough processing.
Session 42, Food Engineering: Rheology and texture
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