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 sulfoxide (DMSO)/10% water and 100% water were examined. Rheological flow data was described using Cross and Carreau models while zero-shear viscosities were found for starches that had been acid modified at least 25 min, apparent yield stresses were exhibited by unconverted Amioca dispersions. Dynamic rheological tests showed that the acid modified starch dispersions behaved like Newtonian liquid-like solutions, while unconverted Amioca dispersions behaved like weak gels. The Cox–Merz rule was followed by starches that had been acid modified for at least 45 min. The reduction in molecule size of acid converted starches (+45 min) allowed the Cox–Merz rule to hold as opposed to the highly branched Amioca and 25 min acid converted starches which showed apparent viscosity higher than complex viscosity.