COMPARISON OF SMALL AND LARGE DEFORMATION MEASUREMENTS TO CHARACTERIZE THE RHEOLOGY OF WHEAT-FLOUR DOUGHS

The rheological properties of wheat flour doughs are largely governed by the contribution of starch, protein and water. Starch, the most abundant component in dough (50-55% wt), is in high enough concentration to form a continuous network of particles which gives rise to viscoelastic behavior. Gluten, the protein phase of flour, also has the ability to form a continuous macromolecular network, provided enough water for hydration exists, and sufficient mechanical energy is supplied during mixing. These two independent sources of viscoelastic behavior and their possible interaction make rheological properties of wheat flour doughs difficult to interpret. An attempt is made to uncouple these sources of viscoelastic behavior by careful evaluation of small and large deformation rheological measurements. Two different types of flours and different mixing times were utilized in order to alter the protein phase of the doughs. The results of this study indicate that small deformation, dynamic oscillatory measurements are sensitive to starch-starch, starch-protein, and protein-protein interactions; however, the relative contributions of each of these interactions are difficult to resolve. In contrast, large deformation shear measurements seem to resolve the relative contributions of long-range interactions (protein-protein) and shorter range interactions (starch-starch, starch-protein), to the viscoelastic behavior of wheat flour doughs.