Rheological properties of acid converted waxy maize starches in water and 90% DMSO/10% water

Rheological properties of acid-converted Amioca starches in 90% dimethyl su lfoxide (DMSO)/10% water and 100% water were examined. Rheological flow dat a was described using Cross and Carreau models while zero-shear viscosities were found for starches that had been acid modified at least 25 min, appar ent yield stresses were exhibited by unconverted Amioca dispersions. Dynami c rheological tests showed that the acid modified starch dispersions behave d like Newtonian liquid-like solutions, while unconverted Amioca dispersion s behaved like weak gels. The Cox-Merz rule was followed by starches that h ad been acid modified for at least 45 min. The reduction in molecule size o f acid converted starches (+45 min) allowed the Cox-Merz rule to hold as op posed to the highly branched Amioca and 25 min acid converted starches whic h showed apparent viscosity higher than complex viscosity. (C) 1999 Elsevie r Science Ltd. All rights reserved.