Carboxymethylation of (1 → 6)-α-dextran from Leuconostoc spp.: Effects on microstructural, thermal and antioxidant properties.

The carboxymethylated (1 → 6)-α-dextran (CM-dex) was synthesized by introducing carboxymethyl groups at different degrees of substitution (DS). The resulting dex1-1, dex2-1, dex3-1, and dex4-1 products had degrees of substitution of 0.57, 0.78, 1.13, and 1.25, respectively. The dex3-1 showed the highest glass transition temperature (T g) of 215.96 °C, whereas T g of pure dextran was 149.83 °C. TGA results indicated that the residual loss was reduced along with the increase of DS in the high-temperature region (450–600 °C). Besides, the CM-dex had stronger scavenging capacity against OH radicals but lower scavenging capacity for DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals compared to that of pure dextran. The carboxymethylation of (1 → 6)-α-dextran will extend the applications for modified dextran. • The (1 → 6)-α-dextran is carboxymethylated with chloroacetic acid. • Carboxymethylation improved the thermal stability of dextran. • Dex3–1 had the highest T g of 215.96 °C. • The OH radical scavenging ability of dextran increased with degree of substitution. [ABSTRACT FROM AUTHOR]