RHEOLOGICAL CHARACTERISTICS OF WHEAT-STARCH PASTES MEASURED UNDER STEADY SHEAR CONDITIONS

Wheat starch pastes consist basically of swollen gel particles of various sizes which are dispersed in a continuous phase containing dissolved polysaccharides. The rheological properties of such pastes have been measured in the steady shear mode. At high shear rates the pastes behave as shear thinning liquids, while at low shear rates they exhibit a yield stress. The rheological properties vary with wheat starch variety and paste preparation conditions; this variation is of considerable economic importance to the starch industry. The present investigation shows that the flow behavior of pastes depends largely on two factors, namely, the volume which the starch gel particles would occupy when close packed if excess solvent were present, and the size distribution of the particles. Starch variety and paste preparation conditions influence these two factors and hence steady shear properties.