Study On Preparation Of Porous Starch By Extrusion-Enzyme Synergistic Method

Porous starch, due to its large specific surface area, good adsorption capacity and efficient,non-toxic, safety features have been widely used in the food, pharmaceutical and other industries.Based on the corn starch to prepare for porous starch and optimize the extrusion and enzymatichydrolysis process parameters. At last property, mechanism of porous starch were in-depthresearched and discussed by the modern analysis techniques in order to further optimize thepreparation of porous starch process, improve the quality of porous starch.Porous starch was produced with corn starch using extrusion pretreatment before enzymolysis,and the effect of system parameters on oil absorption rate of porous starch were investigated.Barrel temperature, moisture content of material, rotation speed of screw and aperture diameter ofextruding machine were considered as factors, the oil absorption rate of porous corn starch wasemployed as evaluation index. Through the experiment of single factor and response surfaceexperiment, with the aid of Design-Expert, the mathematical model of response factors on theindex was established. The effect of interaction between factors of models on index was analyzed.The results indicated that the optimal extrusion conditions were barrel temperature68℃, moisturecontent of material42%, screw speed150r/min and the aperture diameter of12mm. Under theoptimal conditions, the oil absorption rate is62.13%.The preparation of porous starch was based on optimal extrusion conditions for thepreparation of porous starch, ultimately determine the optimal extrusion composite enzymaticpreparation of porous starch process line by enzymatic single factor and orthogonal set ofexperiments. The research results indicated that the optimal conditions of porous starch enzymatichydrolysis process: alpha-amylase: glucoamylase is1:4, substrate concentration is20%, complexenzyme content is2.0%, the enzymolysis temperature is50℃,enzymolysis time is8h, reactionsystem pH is6.0. Oil absorption rate of porous starch is66.38%.The nature and microstructure of preparation of porous corn starch were observed by themodern analysis method, and determined the crystal structure, specific surface area and pore sizedistribution and thermal properties and viscosity properties of starch granule. Preparation ofporous starch by extrusion compound enzymatic and its water absorption, oil absorption,transmittance and other physical properties is higher than that of native corn starch and enzymaticpreparation of porous starch. The surface is full of a lot of holes, small aperture, small hole from surface to center, particle shape is similar to the honeycomb, surface area is bigger than corn starchgranules and surface is roughness by scanning electron microscopy. The result show that theporous starch obtained by extrusion composite enzymatic hydrolysis and enzyme, retains a typecrystal structure of original starch, crystallization peak did not reduce or become wider, butCrystallinity increase by X-ray diffraction.The specific surface area analyzer found specificsurface area, pore size of pore volume of porous starch by the process for preparation increased, soit can accurately explain the enhanced adsorption ability of porous starch. Thermal properties ofporous starch have changed, gelatinization temperature range become narrow, crystallinityuniformity is better than the original corn starch by means of differential scanning calorimetry(DSC). Starch structure becomes loose by enzymatic hydrolysis, water molecules easily enter thestarch molecules, after that the gelatinization occurs inside the starch,shearing and agitation powerdecline and decreased the stability of paste by rapid visco analysis method (RVA).The extrusion method is better than the other two methods compared to ultrasonicenzymolysis method and heat composite enzymolysis between method process control test,properties and microstructure.