Optimization of Reaction Conditions for Carboxymethylated Sago Starch

This study involved the optimization of determining parameters in reaction conditions of carboxymethylation process of sago starch (metroxylum sagu) against degree of substitution (DS) and reaction efficiency (RE%). Characterizations were carried out by analyzing the spectrum of Fourier transform infrared (FTIR), the thermograms of differential scanning calorimetry (DSC), the X-ray diffraction (XRD) patterns, the scanning electron microscopy (SEM) photomicrographs and viscosity analysis. The optimized reaction conditions were determined by the amount of sodium hydroxide in the system, the time taken for a complete reaction, the temperature used for the reaction to occur and the ratio of the anhydroglucose unit to sodium monochloroacetate produced in the final yield of the product. The optimized reaction conditions of 20% concentration of NaOH, reaction time of 1 h, reaction temperature of 55°C and NaMCA:AGU molar ratio of 1.5:1.0 produced a DS value of 1.05 and RE of 85.9% carboxymethylated sago starch. The FTIR spectrum clearly displayed the new peaks at 1587 cm^-1 and 1416 cm^-1, which indicated the presence of carboxymethyl group. SEM Photomicrographs showed starch granules being distorted, the surfaces were rough and grooved compared to the native starch granules indicating an acid or enzyme-treated reaction took place. The DSC thermograms exhibited an endothermic peak for sago starch but none for the treated sago suggesting the absence of gelatinization, which was later confirmed by the changes of the XRD patterns. These optimization factors allowed higher yields of carboxymethyl sago starch providing plenty of opportunities for its multi-applications.