The Study On Polymerization Of Dextrin By Microwave Assisted Reaction And Its Characteristic

Poly-dextrin which was widely used in food for enriching the content of dietary fiber isnot only a good resource of dietary fiber. In this paper, poly-dextrin which as a dietary fiberwere synthesized from dextrin, which are obtained after acid hydrolysis of corn starch, withsorbitol, citric acid by microwave irradiation. The investigations of influence of the reactionconditions of the dextrose equivalent (DE) values of10dextrin on the content of poly-dextrinand the changes of structure and properties of poly-dextrin which were synthesized afterdifferent DE value of dextrin were synthesized from the DE value of5,10,15dextrin havebeen presented.The study found that the condition of the hydrolysis of starch under microwaveconditions for dextrin with the DE value of5,10,15: microwave power600W, microwavetemperature of110°C, microwave reaction time was5min,8min,12min. Through the singlefactor experiment and the orthogonal experiment, The study found that the reaction conditionsof the microwave temperature, microwave power, the amount of sorbitol and citric acid havea greater impact on the content of poly-dextrin content. The content of poly-dextrin changeslittle when Microwave reaction time was in10min-14min, the reaction time was selected12min; the polymerization conditions of dextrin were optimized by the response surface analysisexperiments. The optimal parameters were as follows: microwave power612W, microwavetemperature of127°C, sorbitol amount of4.6%citric acid amount of1.9%, and the contentof poly-dextrin is69%.The transparency, hygroscopicity, freeze-thaw stability and rheological properties ofpoly-dextrin were investigated. By comparing the native starch, dextrin and poly-dextrin, itwas found that the transparency, freeze-thaw stability and hygroscopicity of dextrin couldimproved by increasing the DE value, the hygroscopicity of dextrin slightly decreased afterpolymerization; The poly-dextrin apparent viscosity is relatively small, and with the increaseof DE value increased, but decreased with the increase of temperature, Rheological propertiesof dextrin and poly-dextrin showed shear thinning (pseudoplastic) behaviour. Observed by polarizing microscope, the starch granules of the crystallization regionwhich in poly-dextrin largely disappear, but there are still a small amount of crystalline region,when the temperature rose to60℃, the crystallization region disappear completely, when thetemperature rose to90℃, particle morphology completely disappear. By using scanningelectron microscopy (SEM) to observe the microscopic structure of the dextrin andpoly-dextrin product, it was found that dextrins formed a lot fragment losed the granularstructure of native starch, the surface of starches granular were very coarse, and had apparenthollow, The X-ray diffraction indicated that most crystal reign was destroyed during thepolymerization, Infrared spectroscopy analysis confirmed that the polymerization of dextrinreaction.