Physicochemical and Structural Properties of Starch from Cassava Roots Differing in Growing Duration and Ploidy Level

Wide variability exists in starch properties even among the same botanical source depending on climatic factors, genotypic differences, harvesting period, etc. The present study is an attempt to understand changes in structure, composition and physicochemical properties of cassava starch with root development. Starch is isolated from five cultivars of cassava at different root harvesting periods starting from root initiation stage, that is, 2-12 months after planting. The cultivars are selected in such a way that they represent different growing duration (short and normal), ploidy level (diploid and triploid), and end use (industrial and edible). Amylose/amylopectin ratio varies in a narrow range (0.24-0.28) for the starch from different varieties. Starch granule morphology does not show any significant variation with root growth and cultivar, but the average granule size varies significantly. All the starches show A-type X-ray diffraction pattern and the percentage crystallinity ranges from 37% to 48%. Average chain length and molecular weight of the starch show varietal differences. Even though the swelling power, solubility, water binding capacity and paste clarity are not significantly affected by the root harvesting period, the cultivar differences are evident for these parameters. Significant differences in the physicochemical and functional properties of starch with ploidy of the plant are not observed.