Study On Microwave Synthesis, Structure And Properties Of Debranched Starch Citrate

Corn starch is a very important product in corn processing industry,which has a wide range of sources and low price.Modification of corn starch can effectively improve some properties of corn starch and broaden its application in industry.Therefore,starch modification is a research hotspot in recent years.In this paper,corn starch was taken as the research object,the optimal technological conditions of corn starch debranching by pullulanase were studied,And then the optimal industrial conditions of microwave-assisted preparation of starch free citrate were studied.At last,the differences of structure and properties between the naative starch and the debranched starch,the native starch and the citric acid esterified starch,the debranched starch and the debranched citric acid esterified starch were compared.The results are as follows:Pullulanase debranching corn starch was related to debranching time,debranching temperature,debranching pH,and the amount of enzyme added.The results show that the degree of influence of each factor is as follows:debranching temperature>debranching pH>debranching time>enzyme dosage.The optimal technological conditions of corn starch debranching by pullulanase was:debranching temperature was 55℃,debranching time was 2 h,debranching pH=5,and enzyme dosage was 75 U/g.Experimental verification showed that the DE value is 22.6%under the optimal conditions.Microwave-assisted preparation of the debranched citric acid esterified starch was related to microwave time,microwave power,reaction pH,reaction time,reaction temperature,and the esterifying agent dosage.The results showed that the microwave time,reaction time,reaction temperature and pH had a significant effect on the degree of substitution of starch,and the degree of influence of each factor is as follows:microwave time>reaction time>pH>reaction temperature.The optimal technological conditions of the preparation of esterified starch was:reaction temperature was 113 ℃,reaction time was 6.33 h,pH=3.70,microwave time was 8 min.Experimental verification shows that the degree of substitution is 0.068 under the optimal conditions.After the starch was debranched by pullulanase,its amylose content,blue value,transparency,surface hydroxyl number,and retrogradation rate were increased,but the digestibility,swelling power,freeze thaw stability,emulsifying capacity and emulsion stability and crystallinity were reduced.After debranching,the starch surface changed from smooth to rough,and the uniform and complete particles became starch fragments of different sizes and shapes.Debranching did not change the crystalline form and characteristic peaks on the infrared spectrum of starch.Debranching did not change the crystalline form and characteristic peaks on the infrared spectrum of the starch.After the native starch and debranched starch were esterified,their amylose content,blue value,digestibility,transparency,surface hydroxyl number,retrogradation rate,gelatinization temperature(To,Tp,Tc),enthalpy(ΔH)and the degree of crystallinity were reduced,but the swelling power,freeze thaw stability,emulsifying capacity and emulsion stability and gelatinization temperature change range(Tc-To)were increased.After the original starch was esterified,slight adhesion occurred between the starch granules,and tiny holes appeared on the surface,while large adhesion occurred between the debranched starch after the esterification,and there are countless tiny holes on the rough surface of the starch.After the esterification,the crystalline form of the starch changed to B type.The infrared spectrum analysis showed that the characteristic peak corresponding to the ester bond C=O appeared at a wave number of 1735 cm-1.