| With corn starch as raw material,the effect of annealing and debranching treatments,below gelatinization temperature,on amylose leaching and formation of slowly digestion starch was studied in this thesis.The factors of amylose leaching,including starch concentration,time,temperature,and enzyme concentration during annealing and enzyme debranching treatments were analyzed.The factors were optimized with RSM(response surface methodology)for annealing and debranching treatments,respectively.A correlation was established between the factors and amylose leaching,and regression equations were obtained for both treatments.Based on Guraya method,the slowly digestion starch(SDS)content of various conditions was determined for annealing and debranching treatments.A correlation between amylose leaching and SDS content was established.The study on granule morphology,crystallization properties,and thermal properties of starches was carried out through scanning electron microscope(SEM),X-ray diffraction(XRD)and differential scanning calorimetry(DSC).The results were as follows:Based on single factor experiments,the effect of starch concentration,temperature,and time on amylose leaching was optimized with RSM.A correlation was established between the three factors and the amylose leaching,and the regression equation was obtained.Confirmation experiment showed that the model can be used to predict the process of amylose leaching during the corn starch annealing treatment.Based on single factor experiments,the effect of starch concentration,temperature,time,and pullulanase concentratin on amylose leaching was optimized with RSM.A correlation was established between the four factors and the amylose leaching,and the regression equation was acquired.Confirmation experiment showed that the model can be used to predict the process of amylose leaching during the com starch debranching treatment.To determine the content of slowly digestion starch after annealing and debranching treatments,the Guraya method was employed.The results revealed that compared with native starch,more SDS was formed during annealing and pullulanase debranching treatments below gelatinization temperature;the content of SDS and amylose leaching has close correlation,and the polynomial fitting result was good.The results of SEM indicated that,the granules of corm starch present round and polygon shapes with smooth surface;particle surface showed no corrosion and damage.Compared with that of native starch,the surface of starch granule,after annealing and debranching treatments,became rough,with varying degrees of depression and broken;the greater the amylose leaching,the more obvious the particle surface change was.It suggested that the looseness of the starch surface was improved after annealing and debranching treatments below the gelatinization temperature.The results of XRD indicated that the corm starch show the A-type of diffraction pattern characterized by characteristic peaks around 15.274° 17.203°,18.108°,and 23.186°,respectively.After annealing and debranching treatments,X-ray diffraction patterns of the starch showed no obvious change;this revealed that the crystalline structure had no obvious change,at the same time 2 theta degree shifted a little,half peak width and crystallinity also decreased,which indicated that the effect of annealing and debranching treatments below gelatinization temperature on digestion rate was due to the adjustment of crystalline structure.Compared with quantity,the crystal quality has greater influence on the formation of SDS.The results of DSC illustrated that the corn starch onset temperature was 62:52? and compared with those of native starch,the onset temperature,peak temperature,and conclusion temperature of the corn starch after annealing and debranching treatments increased,gelatinization temperature range decreased,enthalpy had no change.The result indicated that the crystalline structure became compact which lowered the digestion rate of corn starch. |
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