Study On The Enzymatic Processing Technology And Its Foaming

At present, starch foam products have biodegradability, but the starch foam composites exsist most of the common problems of poor water resistance, low foaming ratio and cell distribution etc. Through modified corn starch by a-amylase to change the molecular weight of starch, the flow properties of starch To improve the foaming properties of modified starch and cell uniformity, the plasticizers, foaming agent were supplemented.Then in this article baking foaming, extrusion foaming and molding foaming were used for the preparation of all starch foamed material.Hydrolysis degree of starch was measured by UV spectrophotometric.and using. The molecular weight of modified starch was characterized by ubbelohde viscometer in different hydrolysis time.The processing liquid, heat resistance and mechanical properties in different hydrolysis time of modified starch by α-amylase were studied by melt flow rate (MFR), infrared spectroscopy (FTIR), thermogravimetric analysis (TG) and scanning electron microscope (SEM).The optimal hydrolysis time was identified.The reaction activity of a-amylase was the maximum when hydrolysis temperature (T) was 55℃, pH=5.5 and enzyme dosage was 0.6%.And the absorption was gradually increased as the creasing system temperature(T), pH and α-amylase content. The performance of modified system comprehensive was the best when the hydrolysis time was for 30 minutes.The modified starch was respectively plasticized by glycerol, formamide, and a mixture of formamide and urea. Compared with the raw starch, the fluidity and mechanical properties of modified starch has been improved. The melt flow rate was increased as the increasing of plasticizer contents of glycerol and formamide, but a mixture of formamide was decreased as a plasticizer. The shear viscosity and the tensile strength was decrease as the increasing of plasticizer contents. The elongation at break was increased. Compared with plasticizers, the materials of mixed plasticizer of formamide and was suitable for preparation of foam.Use baking foam, extrusion foaming and moulding foaming were carried out on the foam.The suitable foaming agent of sodium bicarbonate (NaHCO3) was 20 phr.The conditions of baking foaming process was as follows:T= 100 ℃, t= 60 min,extrusion foaming process conditions was as follows:T=140 ℃,the screw rotation speed was 30 r/min.At last,moulding foaming process conditions was:T=170 ℃,t=7 s.The foaming ratio of modified starch was the maximum by baking foaming composite and the foaming performance was the best among them.