Abstract:

Cassava starch was mechanically activated for 60 min using a stirring type ball mill in order to provide activated cassava starch for preparing carboxymethylated starch using NaOH as a catalyst and ClCH2COOH as an etherification agent. The structure of carboxymethylated cassava starch was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). After mechanical activation, the structure of cassava starch had no obvious changes. Carboxymethylation reaction could be observed on the surface and interior of activated cassava starch. Its carboxymethylated counterpart showed an irregular adhesive form and an aggregative state and maintained both the precarboxymethylation crystal structure and morphological features of starch granules. In contrast, carboxymethylation controlled on the surface area was mainly completed in the amorphous zone and partly in the crystalline area of inactivated cassava starch.

Key words: mechanical activation, carboxymethylated cassava starch, structural characterization