SHEAR-THICKENING AND FLOW-INDUCED STRUCTURE IN A SYSTEM OF DMSO CONTAINING WAXY MAIZE STARCH

Waxy maize starch in the solvent 90%DMSO-H2O exhibited the phenomena of shear-thickening, quasihysteresis loops of shear stress versus strain rate that were anticlockwise and flow-induced structure that was observed with phase contrast microscopy. These phenomena were not seen with normal maize starch and an enriched fraction of normal maize amylopectin. The ability of a waxy maize starch sample to have these properties could be destroyed by severe treatment. We consider the flow properties of shear-thickening and anticlockwise shear stress/strain rate loops to be indicative of a flow-induced structure that occurs with waxy maize starch amylopectin. Because these effects do not occur with normal maize starch we infer that there is a significant structural difference between the amylopectins of waxy maize starch versus normal maize starch.