Rheological behavior of cross-linked waxy maize starch dispersions during and after heating

A model was developed to describe the complex viscosity versus temperature (eta*-T) data on 5% (w/w) cross-linked waxy maize (CWM) starch dispersions (STDs) obtained over the frequency range (omega) 1.26-31.38 rad s(-1) and temperature range 55-95 degrees C. The 5% CWM starch dispersions had an onset gelatinization temperature at 60 degrees C with a peak complex viscosity ( eta(peak)*) of 6.9 Pa a at 64 degrees C. The lowest post-gelatinization complex viscosity (eta*) was about 0.85 eta(peak)* at 80 degrees C. The complex viscosity was related to the apparent viscosity using a Modified Cox-Merz rule. Flow tests on gelatinized 5% CWM STDs showed that the sample exhibited a combined time-dependent shear-thickening (antithixotropic) and time-dependent shear-thinning (thixotropic) behavior. The antithixotropic behavior, that appears to have resulted from a shear-induced structure formation, predominated when the level of shear stress imposed on the sample was less than 120-150 Pa. (C) 2000 Elsevier Science Ltd. All rights reserved.