Synthesis and some physicochemical properties of carboxymethyl starch from maize grains

Abstract

The objective of this study was to synthesize carboxymethyl starch (CMS) from maize grains (Zea mays Linn, var. cuseoensis), and to evaluate some of its physicochemical properties. Maize starch was extracted from maize grains by wet-milling followed by filtration and drying. The starch was treated with monochloroacetic acid in the presence of sodium hydroxide (NaOH) of concentrations between 10 and 50% w/v to produce sodium carboxymethyl starch (CMS). The properties of the CMS evaluated included swelling and hydration capacities, density and porosity. Fourier transform infra-red (FTIR) analysis was also employed to confirm the attachment of carboxymethyl group to the starch molecule. Results showed that the CMS synthesized with 40 and 50% NaOH (CMS 40 and CMS 50) possessed swelling capacities of 3940 and 4405%, with hydration capacities of 627.50 and 632.40% respectively. Their bulk density was lower than that of the natural maize starch, while their porosity was higher. These suggest good tablet disintegration characteristics. The FTIR results revealed the presence of carboxymethyl group in the modified starch.

Keywords: Carboxymethyl starch, monochloroacetic acid, sodium hydroxide solution, Fourier transform infra-red analysis, swelling power, hydration capacity