Abstract: Changshan yam starch (CYS) was successfully isolated from the rhizomes of Dioscorea opposita Thumb. cv. Changshan by sodium hydroxide solution immersion and its granular characteristics, physicochemical properties, pasting kinetics and crystalline properties were determined and analyzed. The scanning electron microscope (SEM) examination indicated that the shape of the starch granules was approximately oval or round with a smooth surface. The size distribution of starch granules showed a single peak curve at 48.57 μm, with a median diameter of 22.72 μm. Examination with a polarizing microscope revealed that the starch granules had significant cross-polarization. At 95 ℃, the solubility and swelling power of the starch were 16.78% and 33.55%, respectively. The transparency of the starch paste was 23.2% and the retrogradation stability was 6 h. The syneresis rate was 48.20%. Differential scanning calorimetric (DSC) analysis showed that the gelatinization onset and conclusion temperatures were 72.50 and 85.40 ℃, respectively. The gelatinization kinetics of Chinese yam starch belonged to a first-order reaction. Rapid viscosity analysis indicated that the peak viscosity, holdthrough, final viscosity, breakdown and setback were 6 220, 3 902, 5 702, 2 318 and 1 800 cP, respectively. X-ray diffraction revealed the starch was typical C-type crystalline starch.

Key words: starch, granule characteristics, pasting kinetics, crystallinity