Partial characterization of starches from Dioscorea opposita Thunb. cultivars

The physicochemical, morphological, thermal and crystal properties of the starches separated from four different Dioscorea opposita Thunb. cultivars (Yongji, Anguo, Jinpingyao and Shandongniutuimi) were studied. Amylose content of D. opposita Thunb. starches from different cultivars were in the range of 19.38-22.02%. Moisture content, swelling power, solubility and water-binding capacity of starches differed significantly. Scanning electron micrographs revealed the presence of smooth or rough surface, oval to spherical shaped granules, with mean particle size in the range of 29.2-36.96 mu m. The gelatinization transition temperatures (T-o, T-p and T-c) and enthalpy of gelatinization (Delta H-gel), peak height index (PHI) and gelatinization temperature range (R) were determined. T-o, T-p, T-c of D. opposita Thunb. starches ranged from 70.2 to 75.8, 77.5 to 81.1, and 82.8 to 86.9 degrees C, respectively. D. opposita cv. Anguo starch showed the highest Delta H-gel values (12.47 J/g) while D. opposita cv. Shandongniutuimi starch showed the lowest values (10.54 J/g). The crystal type of starches separated from different D. opposita Thunb. cultivars was a typical C-type X-ray diffraction pattern. The relative crystallinity of the starches ranged from 34.3% to 43.1%. (C) 2006 Elsevier Ltd. All rights reserved.