| In order to deeply study the properties and applications of the high temperature pullulanse,we use gene recombination of the plasmid to obtain it.In this paper,the high temperature pullulanse is obtained by affinity chromatography and anion exchange column and we applied it to amylopectin.We measure the digestibility and the content of amylose and amylopectin of modified starch.Differential scanning calorimetry(DSC)is used to measure the molecular weight of the modified starch.HPSEC-MALLS-RI is used to measure the molecular weight,HPAEC is used to mesure the length of chain distribution of modified starch and Fourier transform-infrared spectroscopy(FT-IR)is used to analysis the functional group of the modified starch.The results show that the optimum temperature of the high temperature pullulanse which we obtained in our laboratory can reach 100℃.After the enzyme treatment,the rapid digestion of starch(RDS)is increased,the content of slow digestion starch(SDS)and resistant starch(RS)are decreased;the content of amylose increases from 1.6% to 12.4%,the content of amylopectin decreases from 98.4% to 87.6%;the initial gelatinization temperature(To)is almost unchanged,the peak temperature(Tp),the final gelatinization temperature(Tc)are significantly increased.The number average molecular weight(Mn),weight average molecular weight(Mw),density(ρ)and the Rz of the modified starch are significantly decreased,polydispersity index(PDI)is significantly increased.Dp6-12 is significantly decreased,Dp13-24 is significantly increased,Dp25-36 and Dp>37 increase at first and then they decrease.The functional group of FT-IR spectrum is not change,and the intensity of absorption peak has a slight change.In order to investigate the properties of processing and nutrition of canna starch,instrumental analysis by DSC,Brabender Micro Visco-Amylo-Graph(BV)and Brookfield R/S Plus rheometer,and pullulanase hydrolysis are performed in this study.The results show that the gelatinization temperature of 5%(w/v)canna starch milk which dissolves 5 g of canna starch in 100 mL of distilled water is 65℃-67℃.The viscosity increases greatly at 75℃.The max/mum viscosity of starch slurry is 429.3 BU.After the starch is hydrolyzed by pullulanase at 100U/g starch,the content of RDS decreases from 88.2% to 59.0%,the content of SDS increases from 8.5 % to 16.9%.The enzymatic modified canna starch with low digestibility might be resulted from the changes of the content of amylose from 12.8 % to 18.1 % and amylopectin from 86.8 % to 79.9 %.In order to futher study the molecular structure and physicochemical properties of modified starch which is applied to use commercial pullulanse to treat cyperus starch.In this paper,we measure the digestibility of modified starch and the content of amylose and amylopectin of modified starch,HPSEC-MALLS-RI is used to measure the molecular weight,HPAEC is used to measure the length of chain distribution of modified starch and FTIR is used to analysis the functional group of the modified starch.The results show that RDS decreased,the content of SDS and RS increased;the content of amylose increased from 9.71% to 47.94%,the content of amylopectin decreased from 90.29% to 52.06%;Mn,Mw,ρ and Rz of the modified starch are significantly decreased,PDI is significantly increased;Dp6-12,Dp25-36 and Dp>37 are significantly decreased,Dp13-24 is significantly increased;The results of steady shear rheological properties show that the modified starch milk is typical yield pseudoplastic fluid.The results of dynamic shear rheological properties show that storage modulus(G′)and loss energy(G")significantly decrease and the loss tangent(tanδ)increases significantly;In the FTIR spectrum,the addition of enzyme compare 0 with 60 U,the position and shape of the absorption peak are almost unchanged. |
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