Preparation of octenyl succinic anhydride-modified cassava starch by the ultrasonic-assisted method and its influence mechanism

As an effective physical method for starch modification, ultrasonic treatment can significantly improve the chemical activity and quality of starch, but its mechanism needs to be further investigated. In this paper, ultrasonic-modified cassava starch and octenyl succinic anhydride (OSA)-modified cassava starch with low degree of substitution were prepared under ultrasonic conditions. The effects of ultrasound on the structure and properties of native cassava starch and the quality of OSA-modified cassava starch were studied. The results showed that the crystallinity decreased from 30.7% to 26.4%, the reaction efficiency increased from 62.28% to 66.20%, and other characteristics also changed after 1 min of ultrasonic treatment. While the structure and properties of cassava starch changed differently after ultrasonic treatments for 8 min and 32-60 min. Consequently, these changes showed that ultrasonic treatment had a significant mechanochemical effect on starch granules. The quality of OSA-modified cassava starch was improved significantly and its influence mechanism was analyzed by the mechanochemistry theory. Practical applications During the esterification of starch, the dense arrangement of crystalline regions limits the reaction of esterifying agents with starch granules. This study showed that ultrasound exerted strong mechanical forces on starch granules, which promoted the production of free radicals and increased the free energy of starch molecules. Besides, the increase of mechanochemical active sites in starch granules was conducive to the homogeneous reaction of octenyl succinic anhydride (OSA) and starch molecules. Therefore, the quality of OSA-modified cassava starch prepared by ultrasonic-assisted treatment was significantly improved. This study provides a reference for the application of ultrasonic technology in other fields and also lays a theoretical basis for the industrial development of high performance-modified starch.