Preparation And Application Of Dual-modified Starch By Oxidation And Octenyl Succinate Esterification

Octenyl succinate anhydride starch was prepared in the aqueous phase and ethanol solvent respectively.The physicochemical properties and the structure of the octenyl succinate anhydride starch were characterized as well.Next the dual-modified starch by oxidation and octenyl succinate esterification was synthesized by one-step technology in water and the application of the dual-modified starch in microcapsule wall material was carried out.The contents were as follows:The optimal parameters of preparing octenyl succinate anhydride starch from cassava starch in the aqueous phase was studied through single factor experiments and orthogonal optimization.The results showed that the starch concentration was 35%,p H was 8.0,reaction temperature was 35℃,the dosage of octenyl succinate anhydride was 10%（based on dry starch solids）,the dilution ratio of the anhydride was 5 times and the reaction time was 4 h.Under this condition,the degree of substitution of the product was 0.0464 and the reaction efficiency was 60.26%.The absorption peaks near 1728 cm^-1 and 1572 cm^-1 in the FT-IR spectrum indicated that the ester carbonyl group was successfully introduced into the starch molecule.The esterification did not change the crystalline structure of the starch,but the relative crystallinity of the starch decreased as the degree of substitution increased.SEM showed the surface of the starch granule became rough as the degree of esterification increased.Rheological property showed that the viscosity of paste declined while shearing and octenyl succinate anhydride starch had pseudoplastic fluid characteristics.The anti-retrogradation properties and emulsifying ability of starch improved after esterification.The process of esterification in ethanol solvent was also studied.Pretreated starch was prepared from native cassava starch in the ethanolic solution while heating and then the pretreated starch reacted with octenyl succinate anhydride in ethanol solvent.In this way octenyl succinic anhydride pretreated cassava starch was synthesized and the preparation process was optimized.The results showed that the dosage of octenyl succinate anhydride had a primary influence on the degree of substitution.The optimal condition was reaction time of4 h,30%octenyl succinate anhydride,35℃,p H 8.5,starch concentration of 35%.The degree of substitution of the product under this condition was 0.0889.Compared with native cassava starch,the pretreatment significantly improved the reaction degree.FT-IR spectrum showed that pretreated starch successfully reacted with octenyl succinate anhydride and was introduced with ester carbonyl group.XRD showed that the native cassava starch was partly transformed from type-A crystal structure to type-V crystal structure after pretreatment,and the relative crystallinity decreased from 21.48%to 8.61%.Esterification led to the decrease of crystallinity of starch to 3.89%.SEM showed that compared with the native starch,the pretreated starch granules swelled.The surface of octenyl succinic anhydride pretreated cassava starch was rough and wrinkled and the particle morphology collapsed as the degree of substitution increased.The starch had a thickening effect after esterification and the viscosity of cold paste increased up to 14 times compared with native starch.Transparency results indicated that pretreatment reduced starch transparency from 32.3%to 10.1%and esterification resulted in an increase of transparency of the paste to 39.5%.In sodium chloride solutions with a mass fraction from 0.5%to 2.0%,octenyl succinic anhydride pretreated cassava starch had better salt resistance.Emulsifying ability were positively related to the degree of substitution of the product.Compared with native starch,octenyl succinic anhydride pretreated cassava starch had lower water holding capacity and worse thermal stability.The technology and method of this study also carried out scale-up experiments on an industrial scale.The preparation of dual-modified starch by one-step technology was studied.Dual-modified starch by oxidation and octenyl succinate esterification from waxy corn starch was prepared in water,with the modification sequence of oxidation by sodium hypochlorite and then esterification with octenyl succinate anhydride.FT-IR spectrum showed that the starch had been oxidized to introduce the carboxyl group and esterified to introduce the ester carbonyl group successfully,which indicated the dual-modified starch derivatives were synthesized.Oxidation of starch introduced carboxyl groups and caused steric hindrance,which was not conducive to the subsequent esterification and the increase of the degree of oxidation led to a decrease in the degree of esterification.As the degree of oxidation increased,the viscosity of dual-modified starch by oxidation and octenyl succinate esterification declined and it helped to obtain low-viscosity products.SEM showed that modification formed more pores on the surface of starch granules.The preparation of low-viscosity dual-modified starch was studied and the application in microcapsule was carried out.Dual-modified starch by oxidation and octenyl succinate esterification was combined with pyrolysis in acidic condition later.Low-viscosity dual-modified starch was used as the microcapsule wall material to study the embedding performance of microcapsule of soybean oil made by spray drying.Compared with low-viscosity octenyl succinate anhydride starch which was esterified without oxidation,the whiteness of the low-viscosity dual-modified starch increased to 96.5.Oxidation to a certain extent was beneficial to improve the ability of film-forming and embedding effect of microcapsules,the surface oil content reduced by a maximum of 37.5%.Low-viscosity dual-modified starch of whiteness up to 95 and embedding rate of 91.5%was prepared.