Composition dependencies of the rheological properties of rice starch blends
2004
Chen, J.J. | Lai, V.M.F. | Lii, C.Y.
The gelatinization, pasting, and dynamic rheological parameters of rice starch dispersions from Kaoshiung Sen 7 (KSS7), Taichung Waxy 70 (TCW70), and their blends were examined in relation to total starch concentration (C(t)) and the property of starch components. Mixing the rice starches, especially at equivalent ratios, resulted in decreasing onset temperature for gelatinization or developing viscosity and in cold-paste viscosity, accompanied by a synergistically increased peak viscosity. The logarithmic of storage moduli, G', for all starch dispersions except the retrograded systems of C(t) = 20-30 wt%, showed two linear dependencies on the weight-average amylose content (AC) of the blends separating at a critical AC of 20 wt% (i.e., TCW70 = 25 wt%). Interestingly, the temperatures at which G' started to increase drastically maximized on heating, and the exponent n of G' infinity C(n)t also maximized at the same TCW70 starch concentration. Generally, the elasticity of the systems after complete gelatinization and retrogradation followed the isostress models of Takayanagi's blending laws at C(t) = 10 wt%, but changed to the intermediates of isostress and isostrain at C(t) = 20-30 wt%. The changes in these parameters can be explained by competitive swelling behavior, the strengthening effect of swollen granules, and shear disintegration.
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