Esterification Of Gum Arabic And Its Application In Powder Oil Microcapsules

In this paper,gum arabic(species of Acacia seyal)as raw material,octenyl succinic anhydride was applied to the esterification of gum arabic,and synthesized the product of octenyl succinic acid gum arabic ester.Synthesis technology,characterization of structure,physical and chemical properties and application in oil microcapsules as wall material of gum arabic were studied.In one-factor-at-a-time experiment,the effects of the factors on esterification reaction were investigated,including octenyl succinic anhydride content,initial concentration of gum arabic,the pH in the reaction system,reaction temperature and reaction time.Based on those,by the response surface methodology,the primary and secondary order of the factors effecting on the grafting rate of octenyl succinic anhydride is as follows: reaction time > reaction temperature > the p H in the reaction system.The optimal synthesis conditions for octenyl succinic acid gum arabic ester were determined as follows: octenyl succinic anhydride,3.0%(based on the dry weight of gum arabic);initial concentration of gum arabic,40%;pH,8.85;reaction temperature,33 ?;and reaction time,130 min.Under these conditions,the grafting rate of octenyl succinic anhydride in octenyl succinic acid gum arabic ester was 1.99%.The structure characterization of gum arabic was researched with modern instrumental analysis methods.FT-IR and 1H NMR revealed that octenyl succinic anhydride groups were introduced into gum arabic molecular structure and possibly substituted the rhamnopyranosyl of gum arabic.SLS showed that the molecular weight of octenyl succinic acid gum arabic ester significantly increased,and increased with increasing grafting rate of octenyl succinic anhydride.Meanwhile,the crystallinity of gum arabic and octenyl succinic acid gum arabic ester by XRD demonstrated no significant difference.Compared with original gum arabic,the solubility and transparency of octenyl succinic acid gum arabic ester were reduced.The apparent viscosity of octenyl succinic acid gum arabic ester was higher than that of original gum arabic,and the rheological behavior which was shear thinning at low shear rate and Newtonian fluid at high shear rate was similar with original gum arabic.In addition,the emulsion activity and emulsion stability were also significantly improved,and increased with increasing grafting rate of octenyl succinic anhydride.Microencapsules of evening primrose oil with gum arabic,octenyl succinic acid gum arabic ester,octenyl succinic acid starch ester and octenyl succinic acid gum arabic ester-octenyl succinic acid starch ester as wall material,respectively,were prepared by spray drying.The physical and chemical properties and microscopic morphology were studied.Results showed that octenyl succinic acid gum arabic ester was suitable for wall material of oil microencapsules,and the effect of oil microencapsules with octenyl succinic acid gum arabic-octenyl succinic acid starch ester(1:3)as wall material is best.