Citronella Oil Microencapsulated in Carboxymethylated Tamarind Gum and its Controlled Release

Citronella oil is one of possible natural insect's repellents extracted from leaves of Cymbopogon winterianus. It is used extensively as a source of perfumery chemicals such as 25% citronellal, 18% citronellol and 20% geraniol. To prolong the citronella oil release, carboxymethylated tamarind gum (CTG) was used as coating material for citronella oil encapsulation and compared to crude tamarind gum (TG), using spray drying technique. Three formulas of microcapsule were prepared at different gum to oil ratios (1.25, 1.14, and 0.87). The appearance feature of CTG microcapsule from SEM images showed a smooth surface while TG microcapsule showed many holes and crack on particle surface. It was observed that increasing the gum to oil ratio increases the retention of citronella oil in microcapsules. At 1.14 gum to oil ratio, CTG microcapsules were shown longer oil retention more than one month. The citronella oil release mechanism was analyzed by different kinetic models such as Korsmeyer-Peppas, Higuchi, and Avrami's models. The microcapsules were found to release the citronella oil by Fickian-diffusion mechanism and following Avrami model release kinetics.