Nano/submicrometer red rice particles were obtained through processing a type of red rice using media-milling. The diameters of red rice were gradually reduced as processing time increased. After 4 h of processing, the particle size of milled red rice was reduced to around 692 nm. Microscopic observation and SEM analysis confirmed the presence of nano/submicrometer particles. The phytochemical contents of milled red rice were analyzed. The total anthocyanin content of red rice increased after milling process. Its phenolic and flavonoid contents were slightly decreased after the milling process. All milled red rice exhibited good ferric reducing antioxidant property (FRAP) and DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The emulsifying ability of milled red rice particles with different milling time was characterized. Milled red rice starch particles with a concentration of 0.8-3.5% were able to form stable Pickering emulsions, and milled red rice particles retarded the oil oxidation process when being used as Pickering emulsions stabilizers. This pioneer study directly modifies whole grain materials to submicrometer particles that can form stable food grade Pickering emulsions with intrinsic antioxidant properties.
Keywords: antioxidative; media-milling; phytochemicals; red rice.