| Arenga pinnata(Wurmb.)Merr.,belonged to palmae,arenga,is a kind of evergreen trees.Not only abundant of starch(usually contained about 12%)in stem of Arenga pinnata(Wurmb.)Merr.,but also rich in Fe,Mg,Mn,Ca,Zn and other elements which the human body needs.Besides,dietary fiber content is as high as 5.7%.However,there are rarely reported about Arenga pinnata(Wurmb.)Merr..However,there are rarely reported about Arenga pinnata(Wurmb.)Merr..Therefore,in this paper,Arenga pinnata(Wurmb.)Merr.starch was selected as raw material,and the purification,physicochemical and structural characteristics of Arenga pinnata starch were investigated by polarized-light microscopy,scanning electron microscope,X-ray diffraction,gel permeation chromatography,differential scanning calorimetry,rheometer,etc.These results will provide important theoretical basis and the guiding principle for the development of high-value utilization of Arenga pinnata starch in the future.The main results are as follows:1.The single factor result of purification starch by cellulose enzyme degradation showed that the optimum condition of purification of starch was enzyme dosage 1500 U/g,solid-liquid ratio 1:10,the temperature of enzyme solution 45 ?,pH 9,enzyme digestion time 60 min.The degree of regression fitting from response surface analysis was well,the coefficient of correlation R2 = 0.9914.The optimum technology of purification of starch from Computer software simulation was enzyme dosage 1517.75 U/g,enzyme digestion time 60.57 min,pH 9.31,temperature of enzyme solution 43.15 ?.According to this technology,the content of cellulose of purified Arenga pinnata starch from actual experimental operation is 0.297%,which is close to predictive value 0.28%.It indicated that the validity of model.The raw starch was further treatment by organic solvents and vacuum drying,and the purity of Arenga pinnata starch was 94.96%,including amylase(59.43%),residual amount of protein(0.76%),crude fiber(0.30%),moisture content(9.22%),ash(0.19%),crude fat(0.25%).2.The physicochemical and structural characteristics of Arenga pinata starch were investigated by polarized-light microscopy,scanning electron microscope,X-ray diffraction,gel permeation chromatography,differential scanning calorimetry,rheometer,etc.The result from FT-IR displayed that the basic functional groups of Arenga pinnata starch was similar to corn starch and potato starch.The number-average molecular weight,weight-average molecular weight,polydispersity of Arenga pinnata starch were 167046 g/mol,300478 g/mol,1.80,respectively,which is lower to corn starch.The morphology of Arenga pinnata starch granule was nearly roundness with smooth surface and grain size range from 45 to 65 ?m.The Arenga pinnata starch granule had apparent at polarization cross lying at the center of the granule,displayed "X" or"?" shape.The data obtained from X-ray diffraction exhibited that the crystalline type of Arenga pinnata starch was C-type and the degree of crystallinity was 22.5%,which is lower to potato starch(32%)and corn starch(25%).The swelling power and solubility of Arenga pinnata starch is lower than potato starch but higher than corn starch,and not easy ageing.The pasting temperature from Brabender viscometer was 65.2? which was higher than the data got from DSC test.In addition,compare with corn starch and potato starch,the Arenga pinnata starch paste has low pasting temperature,indicating that Arenga pinnata starch held weak thermostability.These works will provide theoretical basis and the guiding principle for the production and development of Arenga pinnata starch. |
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