Study On Extrusion Preparation And Physicochemical Properties Of Corn Starch

The corn wet milling process is the most common and practical processing method for preparing corn starch,the soaking time is 36-60h,0.2%-0.3%SO₂ needs to be added to thesoaking solution to destroy the connection between protein and starch,long immersion time and high energy consumption,the addition of SO₂ will cause pollution,corrode instruments andequipment,and cause residues of harmful substances in the product.The mechanical forcegenerated by the extrusion process destroys the protein matrix surrounding the starch particles by breaking the intermolecular and intramolecular disulfide bonds,thereby making the physicalseparation of starch and protein easier,shorten the action time of corn in the sulfurous acidsolution,the extrusion process is instantaneous and efficient,the length of the production cycle is reduced,and the damage of sulfurous acid to equipment and environment is reduced.The main research of this topic is as follows:Corn starch was prepared through extrusion pretreatment combined with wet milling process,the starch extraction rate was used as an index to study the six factors of moisture,temperature,rotation speed,soaking time,temperature,and sulfurous acid concentration ofsoaking solution,the response surface optimization experiments based on a single factor showed that the optimal parameters were:extrusion moisture,temperature,and screw speed were 45%,40°C,and 180 r/min,respectively,soaking time,temperature,and sulfuric acid concentration in the soaking solution were 14 h,50℃,0.2%,under these conditions,the starch extraction rate was 93.25%,and the purity was 96.82%,the traditional wet milling process has a starchextraction rate of 89.46%,a purity of 91.37%,and a soaking time of 48 h.The comparison shows that the starch extraction rate and purity of the research process increased by 3.79%and 5.45%respectively compared with the wet milling process,and the soaking time was shortened by 34h.This process can effectively reduce starch preparation time,reduce pollution,and increaseoverall process benefits.The structural characteristics of starch produced by two processes were analyzed.FT-IR analysis of the characteristic peaks of corn starch showed that the functional groups of the two process starches were the same,indicating that the extrusion pretreatment as a physical wall breaking process in this study did not undergo chemical changes.SEM showed that the surface of starch granules prepared by extrusion pretreatment was slightly damaged,but the shape of the granules was not significantly different from ordinary starch;the amylose content of the extruded pre-treated starch increased from 24.86%to 26.57%,the change in the amylose content willaffect the other physical and chemical properties of the starch to a certain extent;If the starch sedimentation volume increases from 74%to 79%,the change is not obvious;the lighttransmittance of starch decreased from 3.76%to 3.52%,but there was no significant difference;The results of RVA analysis showed that the viscosity of corn starch prepared by extrusionpretreatment was lower than that of starch prepared by traditional wet milling process,which indicated that the proportion of amylose and amylopectin of starch obtained after extrusion treatment changed.DSC analysis results showed that there was no significant change in the thermal properties of the two starches,indicating that the research process did not change the thermal stability of the starch;Compared with the starch prepared by the traditional wet milling process,the physical and chemical properties and structural characteristics of the extrusionpretreatment are slightly changed,but the difference is not significant,and it can replace ordinary starch.