Preparation of nano-sized flake carboxymethyl cassava starch under ultrasonic irradiation

An efficient method was described for the synthesis of nano-sized flake carboxymethyl cassava starch (CMCS) with high-degree substitution under ultrasonic irradiation. The scanning electron micrographs (SEM) revealed that nano-sized CMCS flakes with the substitution degree of 1.15 were in shape of hexagon with smooth surface and with the size of 100-400 nm. The substitution degree of carboxymethylation had a great influence on the morphology and the size of these CMCS. In addition, the effect of reaction parameters on DS value of CMCS was also studied, including the influence of the molar ratio of NaOH/starch, the molar ratio of monochloroacetic acid (MCA)/starch, reaction temperature, ultrasonic power and sonication time.