Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 22, 1999
Publication Date: N/A
Technical Abstract: When the starches were solubilized in most commonly used solvents (i.e., NaOH solution or Dimethylsulfoxide (DMSO)/H2O mixture), it is found that the solubilization procedure seriously affects the final state of the solutions. When the solution of the starches were stirred, the incompletely solubilized patches formed during solubilization causes shear- -induced aggregation yielding high viscosity and shows shear-thickening behavior (state I). On the other hand, when the solution was prepared by shaking, a clear solution with low viscosity was obtained (state II). Although both of these states are stable, only the transition from state I to II was allowed by shaking while the inverse transition was not induced by stirring. Only the state I solution showed shear-induced pattern, but the formed patterns disappeared after shaking the solution. These observations were explained by shear-induced aggregation of starches in solution. Optical micrographs and SEM images of these solutions support our interpretation.