Physicochemical characterization of sweet potato starches popularly used in Chinese starch industry

• Starches of 11 sweet potato cultivars used in Chinese starch industry were studied.
• Amylose content varied between 13.33 and 26.83%.
• Starches with higher amylose content showed higher retrogradation tendency.
• Significant correlations were observed in their thermal and pasting parameters.
• The study projected the useful potentials of these starches in the starch industry.

Physicochemical properties of starches isolated from 11 sweet potato cultivars popularly used in Chinese starch industry were studied. Moisture, protein, ash, lipid and phosphorus content of the starches varied from 3.86 to 6.52%, 0.28 to 0.75%, 0.10 to 0.47% and 0.00 to 0.02%, respectively. Amylose content varied between 13.33 and 26.83%. The starches differed in their mean granule sizes, particle size distribution, and susceptibility to pancreatin hydrolysis. Swelling power and solubility ranged from 13.46 to 26.13 g/g and 8.56 to 18.77%, respectively. Higher retrogradation tendency was observed in pastes of starches of high amylose content. Gelatinization temperature and enthalpy ranged from 55.54 to 69.11 °C and 6.40 to 11.89 J/g, respectively. Pasting properties including peak viscosity (134–255 BU), breakdown viscosity (91–162 BU), setback viscosity (26–112 BU), peak time (5.97–7.03 min) and pasting temperature (67.20–73.00 °C) varied significantly among the sweet potato starches. Pearson's correlation analysis showed that phosphorus content of the starches had substantial effect on their swelling power (r = 0.70, p ≤ 0.05) showing positive correlations. There was significant positive correlation between swelling power and solubility of the starches (r = 0.64, p ≤ 0.05). Thermal and pasting parameters also showed significant correlations.

Scanning electron micrographs of various sweet potato starch granules showing diversity in shapes and sizes. Figures in parentheses denote the degree of magnification. A, Shi 5 (×3500); B, Xushu 28 (×600) C, Xushu 27 (×1000).Figure optionsDownload as PowerPoint slide