Cereal Chem. 73 (4):478-482 |
Extensional Properties of Dough Sheets.
M. P. Morgenstern (1), M. P. Newberry (1), and S. E. Holst (1). (1) Grain Foods Research Unit, New Zealand Institute for Crop and Food Research Ltd., Private Bag 4704, Christchurch, New Zealand. Accepted March 12, 1996. Copyright 1996 by the American Association of Cereal Chemists, Inc.
A device is described for measuring rheological properties of a dough sheet with an Instron universal testing machine. A mathematical analysis of the setup is presented, allowing the stresses, deformation (elongation), deformation rate, and elongational viscosity to be calculated. Measurements on sheeted wheat flour dough at a water level suitable for pastry showed that stress increases with elongation rate. This behavior was linear on a double logarithmic scale, with a slope of 0.2-0.25. Elongational viscosity was of the order 10(^5)-10(^6) Pa·sec when the elongation rate varied from 10(^3) to 10(^1) sec(^1). Water addition affected the slope and the intercept of the straight lines. With more water added, the slope increased and the intercept decreased. The relaxation of dough sheets took place in about 50 min. The experimental data showed qualitative agreement with data obtained by other researchers using other (compression) methods.