Response surface method applied to supercritical carbon dioxide extraction of Vetiveria zizanioides essential oil

Three operating parameters of supercritical carbon dioxide extraction (SCE) have been optimized by a response surface method using central composite design to obtain high yields of essential oil from roots of Vetiveria zizanioides. Analyses by multiple regression indicated that pressure has a major linear effect on oil yield, whilst temperature and time have a lesser impact. However, the effect of temperature in combination with pressure is significant. Overall, extraction yields increase with both pressure and temperature. The optimal SCE yield (1.38%) obtained at the operating conditions of 190 bar, 50 °C and 100 min was about four times higher than that achieved by hydro-distillation. In general, the quality of vetiver oil extracted by SCE is suitable for the food industry. In order for the SCE extracts to be acceptable in the perfumery industry, however, a high yield of vetiver oil would be required in association with high khusimol and low zizanoic acid contents.