3.2. Synthesis of Carboxymethyl Rice Starch (CMSr)

The synthesis of CMSr was conducted by following the method detailed in Rachtanapun et al. [31]. Briefly, 400 mL of isopropyl alcohol was dissolved in 30 g of monochloroacetic acid. Then, it was added to 100 g of native rice starch and stirred well. Different concentrations of NaOH (10%, 20%, 30%, 40%, 50%, and 60% w/v of water) were studied, then heated for 20 min at 50 °C. Glacial acetic acid was added to neutralize the solution. Finally, the solution was filtered and rinsed 4 times with 95% methanol in the CMSr purification. The modified CMSr was evaporated at 50 °C for 17 h and left through an 80-mesh sieve (Scheme 1).

Synthesis of carboxymethyl starch (CMS) from rice starch.