  2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center  |
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Rheological changes of rice starch composites with blending conditions. J. J. CHEN (1), V. M. F. Lai (2), and C. Y. Lii (1). (1) Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan; (2) Department of Food and Nutrition, Providence University, Taichung 43301, Taiwan.
Dynamic rheological property of starch blends was investigated in relation to the blending ratio and total concentration of starches. Mixtures of Kaohsiung Sen 7 (KSS7, indica variety) and Taichung Waxy 70 (TCW70, waxy variety) starches at KSS7:TCW70 ratios from 85:15 to 15:85 (w/w) were used as samples. All starches blends at whatever total concentrations used (10, 20 or 30 wt%) showed that both tand and temperature relating to G' maximum (G'(max)) (tandG'(max) and T(G'max), respectively) maximized at the KSS7:TCW70 ratio = 50:50. The tand values on cooled to 25°C (tand25), aged at 25°C for 1 hr (tand1h) and swelling power were increased successively with decreasing the KSS7:TCW70 ratio (P<0.05). However, the storage modulus (G') and loss modulus (G") of pure KSS7 at 30% (w/w) decreased more significantly than the other starch blends during aging period. According to the polymer blending laws, only G'(max) and G'95 of starch blends were close to the theoretical values derived by isostress model. Hence, it can be concluded that the polymer blending law can be applied to describe the elasticity of the starch systems on heating, rather than on cooling, i.e. the systems composed of swollen granules (stronger fillers) and leaching materials (weaker continuous phases) without remarkable molecular interactions involving retrogradation.
Copyright 2001
The American Association of Cereal Chemists