Abstract:Ultrasound-assisted enzymatic hydrolysis method was employed to extract polysaccharide from millet bran. The extraction process was optimized and carboxymethylation modification was carried out to investigate the processing characteristics and antioxidant properties of millet bran polysaccharides before and after carboxymethylation modification. The results were as follows：The optimum extraction conditions were an extraction temperature of 96 ℃，extraction time of 186 min，material-liquid ratio of 1∶22（g/mL），and ultrasonic time of 32 min. The polysaccharide yield was 8.21%. The results of infrared spectroscopic analysis showed that COO—was successfully introduced into millet bran polysaccharide.It was also shown that the waterholding capacity of millet bran polysaccharide and carboxymethylated millet bran polysaccharide were 1.78 g/g and 3.13 g/g，respectively.The oil-holding capacity was 3.43 g/g and 5.64 g/g，respectively.Emulsifying properties were 10.58% and 22.33% respectively.Emulsion stability 56.49%，57.38%；foaming property 53.75%，50.87%；foam stability 39.32%，41.93%. After carboxymethylation，the scavenging ability of polysaccharide on free radicals was enhanced，and the highest scavenging rates against DPPH·，·OH，and O2-· were 78.21%，64.27%，and 70.27%，increased by 12.32%，17.09%，and 9.35%，respectively. Therefore，both millet bran polysaccharide and carboxymethylated millet bran polysaccharide had good processing characteristics and strong antioxidant properties，and carboxymethylation could significantly improve their antioxidant properties.