Rheological properties and phase transition of starch under shear stress

A Haake rheometer with a twin-roll mixer was used to investigate the gelatinization processing and rheological properties of starch under shear stress conditions. Torque variation with time and temperature was used to describe starch gelatinization under shear stress. Microscopy and differential scanning calorimeter (DSC) were used to study the phase transition of samples collected from the mixer at different times and temperatures during processing. The relationship between torque variation and phase transition was used to study the mechanisms of starch gelatinization under shear stress, and to design the optimum extrusion conditions. The results showed that DSC was able to detect a certain degree of gelatinization enthalpy, even after birefringence had disappeared. Crown Copyright (C) 2007 Published by Elsevier Ltd. All rights reserved