Osa Rice Starch Prepared By Ultrasound-assist Method And Its Application Exploration

The esterification of octenyl succinic anhydride(OSA)and rice starch is one of the most widely used methods,which could expand the application range of rice starch.However,OSA starch prepared by traditional aqueous method has low degree of substitution and non-uniform distribution of OSA group,restricting its use.In order to develop the reaction efficiency and physiochemical properties of OSA starch products,it is of great significance to introduce other technologies to reform the traditional aqueous method.Studies have shown that ultrasonic treatments could promote OSA to enter starch granules and thus elevating reaction efficiency.Based on this conclusion,the present research first applied ultrasonic radiation to rice starch.Changes of hierarchical structures(e.g.chain length distribution,long/short-range ordered structure,particle morphology)were analyzed,and the ultrasonic effects on hierarchical structures and physiochemical properties of rice starch were clarified.Then,the esterification of OSA and rice starch were carried out with the assist of ultrasound.Differences between traditional aqueous method and ultrasound-assisted method were analyzed in esterification efficiency,reaction site and emulsification propertites of products,and the underline mechanism of ultrasonic assist were evaluated from the perspective of ultrasonic power-molecular structure-emulsification performance.Finally,the mechanism of regulating the bioaccessibility of curcumin in the OSA starch emulsion delivery system was revealed by constructing a simulated in vitro digestion model,which explored promising application of OSA starch prepared by ultrasonic assist.Main results of research are listed as follows:(1)Ultrasonic treatments could significantly change the morphology of rice starch granules,producing cracks and pores on the starch surface.And the reduction of starch particle size is mainly caused by the desintegration of large starch agglomerates and the enhancement of homogeneity,rather than destruction of individual starch particle.In addition,low-power ultrasound would preferentially destroy the amorphous region of starch,causing a tighter crystalline structure.With the increase of ultrasonic power,ultrasound could damage the crystalline region,decreasing the degree of crystallinity.However,ultrasound has no significant effects on the crystalline pettern and chain-length distribution of amylopectin.(2)Ultrasound-assisted method could promote OSA esterification.Compared with the traditional aqueous method,the reaction efficiency of OSA was increased by almost 23% under the assist of 600 W ultrasound.In addition,ultrasonic assist had no significant effects on the longrange ordered structure of starch,but decreased its short-range ordered structure,indicating that OSA esterification mainly occurs in the amorphous region rather than the crystalline region of rice starch.(3)Compared with the traditional aqueous method,ultrasound-assisted method could significantly improve emulsifying performance of OSA starch,which was reflected in higher emulsion storage stability after 15 days,more stable emulsion network structure and greated resistance to external shearing.The results could be attributed to the combinition of electrostatic force and steric hindrance.On one hand,ultrasound-assisted method increased absolute value of Zeta potential,which enhanced electrostatic repulsion between droplets;On the other hand,low-power ultrasound might advance emulsifying ability by decreasing hydration radius of starch,while high-power ultrasound mainly elevated DS of starch to advance its emulsifying ability.(4)Emulsions formed by OSA rice starch prepared by ultrasound-assisted method could carry curcumin more efficiently,and the bioaccessibility of curcumin was higher than that of traditional aqueous method.This could be attributed to higher DS,which increased hydrophobic groups on starch surface and resulted in higher encapsulation of curcumin.In addition,OSA starch prepared by ultrasonic assist had higher resistance to attacks of biofactors in digestive fluid,producing less oil droplet coalescence and flocculation.The maintenance of small droplet size and uniform size distribution accelerated the digestion rate of oil,promoting the release of curcumin from oil phase and increasing its dissolution in the micellar.