Dough viscosity measurement

Figure H3.1.9 The characterization of the baking of a cookie dough by the measurement of the complex viscosity (r, solid line) as a function of temperature (°C, dashed line).

These results highlight the genuine need for carrying out steady state experiments for accurate measurement of dough extensional viscosity. At the present time, there is no other instrument available that can provide stress-growth profiles for doughs. 

One technique for measurement of extensional flow that has been used to study various doughs is that of Cogswell (1972, 1978) for entrance flows. The analysis is based on several assumptions (Padmanabhan and Bhattacharya, 1993) (1) The flow is isothermal and creeping (negligible inertial effects), (2) the fluid is incompressible and has a pressure-independent viscosity, (3) the shear viscosity follows the power law model, t]a = Ky" (4) there is no slip at the edge of the converging profile, and (5) that the entrance pressure drop (Ape) in converging flow from a circular barrel in to a circular die can be considered to be made up of that due to shear (Ape,s) and extensional flow (Ape,E) ... 

Bagley (1992a) measured the apparent biaxial elongational viscosity of wheat flour dough. The upper convected Maxwell model was considered to be adequate in explaining both the effect of crosshead speed and sample... 

Huang, H., and Kokini, J. L. (1993). Measurement of biaxial extensional viscosity of wheat flour doughs. J. Rheol. 37, 879-891. 

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