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Title: EXPERIMENTAL AND CONCEPTUAL PROBLEMS IN THE RHEOLOGICAL CHARACTERIZATION OF WHEAT FLOUR DOUGHS

Author
item Bagley, Edward
item Dintzis, Frederick
item CHAKRABARTI, SUMANA - KRAFT GENERAL FOODS, INC

Submitted to: International Conference on Wheat Structure, Biochemistry and Functionality
Publication Type: Proceedings
Publication Acceptance Date: 8/15/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The rheological characterization of viscoelastic doughs is not simple and there are both experimental and theoretical difficulties. For example, in attempting to determine the viscosity of such systems by cone-and-plate viscometry, it is found that the samples often "roll out" of the gap before a steady-state viscosity can be determined. Gleissle's "mirror relations" can be used to extract steady-state viscosity estimates from transient data, but how are the values so obtained to be confirmed? One approach is to determine viscosities independently through capillary extrusion, but in such experiments it becomes evident that capillary geometry effects need to be investigated to determine true viscosity values. Also, it is found that normal mixing procedures yield doughs that are heterogeneous. This heterogeneity causes unacceptable fluctuations in data obtained with dies of the usual dimensions used in capillary viscometry. The quantitative determination and interpretation of extensional flow properties of doughs by either uniaxial or biaxial extension also present major difficulties. For instance, the very broad distribution of relaxation times found with doughs has significance and consequences not well understood. Processing of doughs and characterization of both wheat flour and wheat flour dough properties are of continuing concern and importance, and it is evident that basic studies of dough rheology are still desperately needed.