Characterization Of Starch Isolated From Dioscoreae Zingiberensis

Dioscoreae Zingiberensis, a Chinese yam, which is also called as HuoTougen. It belongs to the family of monocotyledon Liliales, Dioscoreaceae, Dioscorea L. As a particular plant in China, Dioscoreae contains rich dioscorea saponins, so as to be one of the most important resources of medicinal plant of Steroid Hormon Drugs. Dioscoreae starch isolated from Ankang in ShanXi province was chooesed as the experiment material. Scanning electron microscopy, Polarizing microscope, Laser particle size analyzer, X-diffraction, Differential scanning calorimetry, Brabender viscosity and regular physico-chemical analysis were used to research the characterization of Dioscoreae starch, and then comparing with the control sample of potato starch and maize starch. The following conclusions are drawn:(1) Proximate composition analysis indicated that Dioscoreae starch contains 12.80% moisture, 73.40% starch, 8.23% protein, and 23.60% amylase.(2) Scanning electron micrograph of Dioscoreae starch revealed the presence of oval or obtate shaped granuales, with major lenth ranging from 6.32～56.37μm, the surface was smooth without observed dents and angles. X-ray diffraction profile showed the starch had A- type crystallinity, the polarized mode shows "X". Hilum was hardly being observed because of lying on the edge of starch particle.(3) Dioscoreae starch has a good solubility and swelling ability, pasting temperature 78. 53℃, the eigenvalue of Differential scanning calorimetry were T₀ (Start temperature) 70.49℃,T_P(Peak temperature) 78.53℃,T_C(End temperature) 85.96℃,AH(enthalpy of gelationization)12.73(J/g).(4) The clarity of Dioscoreae starch is better than maize starch but worse than potato starch. Adding citric acid and glucose promote the clarity of Dioscoreae starch while adding NaCl and NaHCO₃ reduce its clarity. The freeze thaw stability of Dioscoreae starch is not well compared to potato and maize starch. Elevating of rotation speed and adding NaCl and NaHCO₃ reduced the viscosity of Dioscoreae starch while adding sucrose promoting it. Dioscoreae starch has highest viscosity under neutral pH, acid and alkali both reduce the viscosity of Dioscoreae starch, the reducing effect by acid is more notable.(5) The process of boiling, high pressure, microwave, baking promote the digestibility of Dioscoreae starch. Among these processes, boiling promote the digestibility most, next is microwave, the lowest promotion of digestibility of starch is high press and baking.