Abstract: In this study,the carboxymethylation of inulin was investigated.The modified parameters including alkalization time,etherification time,NaOH dosage and isopropyl alcohol volume fraction were studied using orthogonal test with substitution degree as index.The optimized conditions were as follows:alkalization time 40 min,etherification time 70 min,m(Inulin):m(NaOH):m(chloracetic acid)=27:4:13.8,isopropyl alcohol volume fraction 95%.Under these conditions,a maximum substitution degree of carboxymethyl inulin of 0.628 was obtained.Compared with unmodified inulin,the scavenging activities of carboxymethyl inulin at 1 mg/mL concentration level on DPPH free radicals,hydroxyl radicals and superoxide anion increased 12.6%,24.0%,13.9% respectively.

Key words: inulin, carboxymethylation, antioxidant activity