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Physicochemical properties of native and hydroxypropylation cassava (Manihot sculenta Crantz) starch varieties were studied. Starches from three cassava varieties were analyzed, codified as CM 7138-7, CUMBRE 3 and SM 707-17. The objective was to identify the changes in the physicochemical properties due to hydroxypropylation process. It was also obtained the pasting curves, thermal properties by differential scanning calorimetry (DSC) and thermogravimetry (TGA) and Fourier transform infrared spectroscopy (FT-IR). The native starches exhibited differences in the pasting curves, glass transition temperatures (Tg) and fusion temperatures (Tm). The modified starches showed differences in the molar substitution degree, pasting curves, Tg, Tm and the FT-IR spectrum. The hidroxypropylation process did generate significant changes in the properties of native starches. In both cases, this differences could be attributed to starch amylose and amylopectin content. Respect to native and modified starches differences, hidroxypropylation process generated changes over studied properties. Due to amylose content and modified starch less viscosity and Tg values, was concluded that variety CM 7138-7 was selected as the one with probably major package making potential. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of different oxidation conditions by hypochlorite, on the content of carboxyl and carbonyl groups of cassava starch, finding that the concentration of oxidant had the highest effect on the formation of both groups functional. The pH had a highest effect on the content of carbonyl groups than on the content of carboxyl groups. Likewise, oxidized starch was obtained at three degrees of oxidation which exhibited lower viscosity, higher gel stability and lower retrogradation tendency when compared with native starch. Films were obtained and their mechanical and thermal properties were evaluated, finding that higher modification degree incremented stress while the strain exhibited no significant differences. Conversely, the greater modification degree, the films showed lower strain and the stress showed no significant differences. The thermal analysis showed a Tg, which is not present in native starch films, a higher Tm and a gradual decrease of ΔHm with oxidation degree increasing, which might suggest a greater miscibility and interaction between film components as well as greater stability. [ABSTRACT FROM AUTHOR]