Document Type : Original Article
Department of Chemical Engineering, Faculty of Engineering, Diponegoro University, Jl. Prof. Jacub Rais, Semarang, Central Java, Indonesia
Department of Food Technology, Faculty of Animal and Agricultural Sciences, Diponegoro University, Jl. Prof. Soedarto, SH, Semarang, Central Java, Indonesia
Glucomannan carboxymethylation is conducted to increase its hydrophobic properties and expand its interaction with hydrophobic compounds. However, glucomannan has high molecular weight and long polysaccharide chain which prevented the modification of its amphiphilic properties. This study aimed to examine the effect of molecular weight, deacetylation, and carboxymethylation on glucomannan properties. Performance of the modified glucomannan to stabilize oil in water (o/w) emulsion was also studied. Ultrasonication was applied to glucomannan at 40 kHz for 15-45 min to obtain various molecular weights. Sodium carbonate (Na2CO3) and sodium monochloroacetate were used as deacetylation and carboxymethylation agents, respectively. The results show that decrease molecular weight supported the deacetylation and the carboxymethylation process on attaching the hydrophobic groups to the glucomannan chain, hence, lowering the hydrophilic properties and swelling degree of glucomannan. Structural and morphological changes of glucomannan after modifications were confirmed from the IR spectra and SEM images. Excellent performance of the amphiphilic glucomannan on stabilizing o/w emulsion was observed as only ~5% phase separation occurred after 300 h of storage in ambient conditions. Hence, ultrasonication is proposed as a suitable preliminary treatment for amphiphilic glucomannan production.