Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/1996
Publication Date: N/A
Interpretive Summary: How starches behave when they are cooked in water or dispersed in other fluids to form concentrated liquids is of major interest to food processors and companies that use starch in industrial applications. This work describes some newly discovered properties of how different starches behave in fluids when they are gently processed. This information will encourage starch users to consider new ways to use and process starch.
Technical Abstract: The phenomenon of shear-thickening was observed with eight unmodified starches which had been gently dissolved at 3.0% concentrations in 0.2N NaOH. Phase microscopy and circular dichroism measurements confirmed the development of shear-induced structure implied by this shear-thickening behavior in starch fluids. These structures were rather stable in 90%DMSO-H2O. In this solvent the intrinsic viscosity was shown to be not tightly coupled with flow behavior. Shear-thickening is influenced by solvent type. The relative abilities of solvent to enhance shear-thickening are: 0.2N NaOH > 90%DMSO-H2O >> H2O or 0.5N KCl at neutral pH. Waxy starches-maize, rice, and barley-and potato starch showed this phenomenon to a greater extent than did wheat, normal rice, or normal maize starches. The amylopectin component was shown to be responsible for shear-thickening and shear-induced structure formation/alteration. The property of shear-thickening was extremely sensitive to sample treatment; severe treatment of the sample destroyed the ability of the starch to form shear-thickening fluids.