Research On The Ultrasonic-microwave Synergistic Synthesis Of Crosslinked Hydroxypropyl Dioscorea Alata Starch

Dioscorea alata lianas of Dioscorea.The Dioscorea alata has been grown in Hainan for a long time. It is one of the potential underutilized plants and will be a new energy plant with the outstanding qualities (short growth phase,drought-tolerant, heat resistance, high yield, and contains nearly 20%-40%starch on dry weight basis in fresh palm).In order to obtain the better degree of crosslinking, degree of substitution and higher viscosity of Dioscorea alata modified starchJn this paper Dioscorea alata were provided by College of Agriculture, Hainan University. Dioscorea alata strach was prepared and then was Crosslinking and hydroxypropyl ether compound modified with ultrasonic-microwave assistance. The aim to lay a foundation for the sustainable development and comprehensive utilization of Dioscorea alata procesing industry. Main research contents are as follows:1.Preparation of crosslinked Dioscorea alata starch rapidly with ultrasonic-microwave assistanceSodium trimetaphosphate,pH walue, microwave power, microwave irradiation time as the main factors of preparation of crosslinked starch were researched. The optimum conditions were obtained by analyzed the results of the experiment that sodium trimetaphosphate 1%(w/w), pH 10, microwave power 80 w, microwave irradiation time 100 s,the settling volume of the starch prepared in this condition was 0.57 mL.2. Hydroxypropyl Dioscorea alata starch rapidly prepared with ultrasonic-microwave assistanceStudied the five factors (propylene oxide, sodium hydroxide, anhydrous sodium sulfate, microwave treatment time and microwave power) that influence the preparation of hydroxypropyl Dioscorea alata starch were paticular analyzed.The ultrasonication power was fixed at 50 w, Under analyzed the single-factor optimum conditions were determined as propylene oxide 12%(w/w), sodium hydroxide 1.0% (w/w), anhydrous sodium sulfate 8%(w/w), microwave irradiation time 110 s and microwave power 80 w. The optimal condition of the product gave a MS value at 0.82.3. Ultrasonic-microwave synergistic synthesis of crosslinked hydroxypropyl Dioscorea alata StarchThrough effected on the starch peak viscosity, using sodium trimetaphosphate,, propylene oxide, sodium hydroxide, anhydrous sodium sulfate, crosslinking pH, microwave treatment time and microwave power as test factors of ultrasonic-microwave synergistic synthesis of crosslinked hydroxypropyl Dioscorea alata Starch, the starch peak viscosity as the response value. SAS 9.0 software for response surface analysis,a Box-Behnken Control-Composite experimental design was applied. The optimum conditions were determined as pH 9, propylene oxide 18% (w/w), sodium hydroxide 0.8%(w/w), anhydrous sodium sulfate 14% (w/w),microwave power 64 w, microwave irradiation time 71 s, odium trimetaphosphate4%(w/w) and. The optimal condition of the product gave a peak viscosity at 2886 mPa·s. Among the 7 factor levels we chose, the ranking order of effect on results of crosslinked hydroxyptopyl starch peak viscosity was:pH maximun,followed by propylene oxide, the minimum was sodium trimetaphosphate.4. Physicochemical properties of Dioscorea alata starch samplesAfter analyzed of the solubility, acid resistance,enzymatic hydrolysis, pasting properties, transparency, freeze-thaw stability of Dioscorea alata strach samples.The resules showed better solubility and light transmittance,stronger freeze-thaw stability and acid resistance,the highest reducing sugar content in the hydrolysis of a-amylase and peak viscosity, final viscosity.5.Granule appearance and structural characterization of Dioscorea alata starch samplesThe granule appearance and structural characterization of Dioscorea alata starch samples were observed by SEM,DSC,X-ray, FT-IR and polarized light micrograph.The chemical reaction of Dioscorea alata modified starch concentrated on the on the particle surface was observed by SEM. Through the FT-IR detected at 2000～2500cm-1 there was a strong absorption peak of Dioscorea alata cross-linked, cross-linked hydroxypropyl starch excepted the hydroxypropyl starch.By the DSC analyzed, the pasting temperature, peak gelatinization temperature of cross-linking hydroxypropyl starch lower,and gelatinization temperature is higher than the other starch samples, the enthalpy change (△H) of gelatinization just below the hydroxypropyl starch △H. Through the X-ray diffraction analyzed,the position and intensity diffraction peaks of modified starch samples were same as the Dioscorea alata original starch, and indicated that crystal type did not change after deformation.The ordered stucture was not changed obviously was observed by polarized light micrograph.6. Application of Dioscorea alata starch samplesThe melting rate and viscosity were measured of the ice cream that the fat was raplaced by modified Dioscorea alata starch samples showed the melting rate reduced and the viscosity increased.Innovation:Explained the effect of microwave radiation used in the synthesis of crosslinked hydroxypropyl Dioscorea alata starch for the first time.The condition of ultrasonic-microwave synergistic synthesis of crosslinked hydroxypropyl Dioscorea alata Starch was been optimized.Researched and discussed the granule appearances and crystal structures of Dioscorea alata original starch,cross-linked starch, hydroxypropyl starch, cross-linked hydroxypropyl starch.