Abstract: In this study, coix seed starch nanoparticles were prepared by nano-precipitation method using three different systems (alkali solution, water-ethanol system and dimethyl sulfoxide (DMSO)-ethanol system). The structures and physicochemical properties of the three nanoparticles were investigated by analysis of their particle characteristics, molecular characteristics, crystallization characteristics and thermal characteristics. The results showed that the nanoparticles prepared using alkaline solution had the highest proportion of nanoparticles (85.65%). Both the nanoparticles prepared using alkaline solution and water-ethanol system had an A-type crystalline structure, while the crystalline structure of the nanoparticles prepared using DMSO-ethanol system changed from A-type to amorphous. The nanoparticles prepared using alkali solution at 45 ℃ had the smallest particle size (348 nm), the highest polydispersity, higher degree of order, relative crystallinity and thermal stability, indicating that alkali solution was the most suitable to prepare coix seed starch nanoparticles. This study may provide a theoretical basis for the preparation of starch nanoparticles and the study of their structural properties as well as the expansion of the application of coix seed starch.

Key words: coix seed; starch nanoparticle; alkali solution; water-ethanol system; dimethyl sulfoxide-ethanol system; structural properties