Five cassava genotypes were investigated to identify the fine amylopectin structures and granule chemical compositions, which differentiated the starches into high (T(o) = 63.7 degrees C on average) and low (57.3 degrees C on average) gelatinization temperatures. The amylose contents (15.9-22.4%) and granular dimensions (12.9-17.2 microm) significantly differed among the starches. Diverse amylopectin structural elements resulted in significant swelling power, viscoelastic properties, and gel firmness. Debranched starches revealed a trimodal amylopectin distribution of three fractions: FIII (DP 12), FII (DP 24.31), and FI (DP 63) and FIII (DP 12), FII (DP 24.69), and FI (DP 67) for the low and high gelatinization starch groups, respectively. The higher proportion of FI long chain entanglement with amylose chain lengths to form longer helical structures was confirmed in the high gelatinization starch group, which developed "true" gels with better shear resistance, frequency independence, and higher gel firmness. Significant amounts of resistant starch fractions revealed the potential for application of these genotype starches in diverse foods.

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SynopsisThe viscoelastic properties of amylose triacetate films plasticized with diisobutyl phthalate were studied. The modulus-temperature curves of diisobutyl-phthalate-plasticized amylose triacetate are typical for amorphous polymers with the decrease of amylose triacetate content. The glassy modulus is not affected by the incorporation of diiiobutyl phthalate, but the rubbery modulus and glass transition temperature are depressed with increased diisobutyl phthalate.The rubbery modulus appears at f i s t to maintain for a wide temperature range, then disappears with increased diisobutyl phthalate. From the results of modulus-time measurements and x-ray diffraction patterns: in a system of amylose triacetatediisobutyl phthalate, amylose triacetate exists as an amorphous polymer at all concentrations of amylose triacetate and it acts intermediately between semicrystalline and amorphous polymers at lower concentrations below about 90%.

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