Carboxymethylation of Glucomannan from Porang Tuber (<I>Amorphophallus oncophyllus</I>) and the Physicochemical Properties of the Product

Objective: This study was conducted to describe the synthesis of carboxymethyl porang glucomannan (CPGM) and its physicochemical characteristics. Materials and Methods: The CPGM was synthesized by treating porang glucomannan (PGM) with sodium chloroacetate under basic conditions at different temperatures (50, 60 and 70°C) for different durations (20, 40 and 60 min). The CPGM products were then analyzed to determine what functional groups were present, the degree of substitution (DS), the water solubility, the zeta potential and the viscosity. Results: Carboxymethylation of the porang glucomannan was confirmed by the increase in the intensity of the carbonyl absorption peak in the fourier transform infrared (FTIR) spectra. Compared to the native porang glucomannan, the carboxymethylated porang glucomannan was more negatively charged and more water soluble but was less viscous. Both temperature and reaction time influenced the viscosity and water solubility, but the DS value was more influenced by reaction time than by temperature. Conclusion: Carboxymethylation of porang glucomannan yielded a more useful product than did native porang glucomannan. The increase in water solubility and decrease in viscosity made the product widely applicable in the food industry. The negatively charged polymer has the potential to interact with positively charged polymers to develop new products. Further research may be conducted to tune the reaction time to achieve certain properties that will suit additional needs.