| The extraction process of Euryale ferox starch was optimized by single factor and orthogonal experiments, and the results showed that the optimal extraction condition was sodium hydroxide concentration 0.17%; solid-liquid ratio 1:5, the soaking time of sodium sulfite 5 hours; and the sodium sulfite concentration 0.20%, the best yeild was 67.60%.Starch was the highest content of Euryale ferox, its structure and characteristics was critical in the processing. Some characteristics of Euryale ferox starch were compared with potato starch and corn starch in this study, including physical and chemical properties, molecular structure and rheological properties of starch.Euryale ferox starch contained of 11.79% of water,0.04% of fat,0.02% of fat and 0.07% of ashes. Observed with Scanning electron micrographs, the most of granules of Euryale ferox starch were polygons. X-diffraction spectrum showed that the crystal structure of Euryale ferox starch was A type.The value of solubility and swelling power increased with the increase of the temperature. The value of solubility and swelling power of Euryale ferox starch was 11.49% and 12.29%, respectively at 95℃.The value of solubility, swelling power, transparency and peak viscosity was lower than that of potato or corn starch, but the pasting temperature value and the amylase content were higher, the value of absorption rate was close to corn starch.The Gel texture characteristics of Euryale ferox starch, potato starch and corn starch were explained by hardness, thickness, poly-stickness nature, stickness and britle. Comparing with corn and potato starches, the value of poly-stickness nature of Euryale ferox starch gel is the highest. The result indicated that internal bonding force of Euryale ferox starch gel was largest. The value of britle was lower than that of corn starch, but Euryale ferox starch gel was not easy to break and its hardness was moderate.Rheological properties of Euryale ferox starch suspension at various concentrations (2%,5%,8%,10%, 20%) and at various temperatures (5℃,15℃,25℃,45℃,60℃) were observed respectively in this study. The results indicated that Euryale ferox starch suspension was a non-Newtonian, shear thickening and Anti rheological fluid. The Herschel-Bulkley models could explain the rheological behavior of Euryale ferox starch suspension accurately. Dynamic rheological tests showed that the the storage modulus (G′) and loss modulus (G″) of Euryale ferox starch paste were dependent on temperature, starch variety and frequency.According to the physicochemical and structural property of amylase and amylopectin, the component of Euryale ferox starch was separated by butanol recrystallization method. The purity of amylase and amylopectin was confirmed by gel permeation chromatograhhy. Being 0.18 and 0.96 respectively, the blue values were in the corresponding range, which confirmed that separating amylase and amylopectin had a high purity.
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