Characterization Of Three Modified Maize Porous Starches Based On Enzymatic Method And Their Application Of Encapsulated Curcumin

Porous starch（PS）,also known as microporous starch,is used as a carrier for unstable substances,an adsorbent for volatile substances and a protective agent for sensitive substances due to its high porosity,large specific surface area,strong adsorption and high loading capacity.However,the pores of porous starch lead to poor structural strength and stability,and the strong hydrophilicity of starch also severely restricts the stable loading and controlled release of guest small molecules.In this paper,corn porous starch was prepared from corn starch granules by usingα-amylase（AM）,glucose amylase（GAM）and mixed enzymes（ME）,and the properties and functions of the porous starch obtained from the preparation were investigated.On this basis,different modifications such as chitosan,sodium trimetaphosphate and sodium hypochlorite were used to modify,cross-link and oxidize the porous starch to strengthen the structure of porous starch,and to load curcumin with it,and then to achieve the slow release of curcumin.The main research contents and results are as follows.（1）Firstly,different corn porous starches were prepared from corn starch using AM,GAM and ME under different enzyme activities to investigate the effects of different enzymes on the pore size,microstructure,particle morphology,adsorption properties and pasting characteristics of porous starches in the preparation of porous starches.Scanning electron microscopy（SEM）showed that the pore structures of porous starches had different pore size distributions and pore areas depending on the type of enzyme and enzyme activity;AM produced the largest pores,GAM produced the deepest pores,and ME produced large and deep pores.The enzyme modification had a significant effect on the adsorption capacity,and GAM had a greater effect.X-ray diffraction and Fourier transform infrared spectroscopy（FT-IR）analysis showed that the porous starch had a high relative crystallinity.the ME-treated starch had a high solubility,but the swelling capacity,peak viscosity,final viscosity,disintegration value and regenerative viscosity were all reduced compared to the original starch.The results show that different enzymes can prepare porous starches with different pore sizes according to the enzymes’action sites.In production,different kinds of enzymes and their enzymatic activities can be used to prepare ideal cavities and pore sizes according to practical needs,which provides a theoretical basis for the practical application of porous starch.（2）The generation of porous starch pores leads to poor structural strength and thermal stability of the starch.In order to strengthen the structure of PS and increase its utilization range,chitosan modified porous starch（CMPS）,cross-linked porous starch（CPS）and oxidized porous starch（OPS）were prepared and characterized by using chitosan,sodium trimetaphosphate and sodium hypochlorite for modification,cross-linking and oxidation of porous starch,respectively.The effects of the increase or decrease of molecular weight of porous starch and complexation with hydrosol on the structure,pasting properties,thermal stability and adsorption properties of PS were investigated.The results showed that the modified porous starch had a higher thermal decomposition temperature than PS,indicating that the modified porous starch had a higher thermal stability.The particle size and apparent viscosity of the modified porous starch suspension particles were increased.X-ray diffraction and FT-IR analysis showed that the chemical modification did not change the crystal type of porous starch,but caused a decrease in its orderliness and double helicity.In addition,the solubility and swelling power of CMPS and CPS were decreased,while those of OPS were increased.Adsorption experiments showed that the adsorption amounts of CMPS,CPS and OPS were higher than those of PS,indicating that chemical modification could improve the thermal stability and adsorption properties of porous starch,providing theoretical significance and data basis for increasing the use of porous starch.（3）Porous starch-curcumin microspheres（PS-C,CMPS-C,CPS-C and OPS-C）were prepared by encapsulating curcumin（Curcumin,Cur）in the modified porous starch,respectively.The effects of cross-linking and oxidation on the properties of porous starch encapsulated and protected curcumin were investigated.The morphology and physicochemical properties of porous starch-curcumin microspheres were analyzed by SEM,specific surface area Brunauer Emmett Teller（BET）,FT-IR,and X-ray diffraction;the release of curcumin was evaluated by simulated gastric-small intestine model.XRD results showed that curcumin was amorphously encapsulated in the composites,and FT-IR analysis indicated that formation of hydrogen bonds between porous starch and curcumin is one of the main driving forces for encapsulation.The modified porous starch-curcumin microspheres increased the initial decomposition temperature of curcumin and had a protective effect on curcumin,while CPS and OPS improved the encapsulation efficiency of porous starch and the ability to scavenge ABTS and DPPH radicals.The release mechanisms of curcumin microspheres in the stomach and intestine were consistent with the primary and Higuchi models,respectively,suggesting that controlled release of curcumin can be achieved by encapsulation of curcumin in different porous starches.Modified porous starch has great potential as a wall material for the encapsulation and delivery of curcumin.（4）To overcome the instability and poor water solubility of curcumin,a novel alginate microsphere oral drug delivery system was designed.The four factors of curcumin concentration,starch concentration ratio,sodium alginate,and calcium chloride concentration were selected as the main raw materials,and the optimal formulation conditions for the microspheres were A₂B₃C₁D₂ through single-factor as well as orthogonal experiments,and the most influential effect on the microsphere formation was the starch concentration（B）,followed by curcumin concentration（A）sodium alginate concentration（C）,and calcium chloride concentration（D）in that order.The protection of curcumin by alginate microspheres was greater than that of curcumin by microcapsules.