DEVELOPMENT AND OPTIMIZAION OF MICROWAVE ASSISTED PROCESS FOR EXTRACTION OF ESSENTIAL OIL FROM ALLSPICE LEAVES

Abstract

Essential oils which are the volatile components distilled from the aromatic plant materials, have gained importance in cosmetic, therapeutic, aromatic, fragrant and spiritual uses. But the conventional methods of distillation carry the disadvantages mainly concerned with the quality of final product such as loss of some volatile notes, low extraction efficiency and degradation of unsaturated ester compounds through thermal or hydrolytic effects. These processes also requires high extraction times and energy consumption. However, in order to reduce these difficulties microwave energy could be effectively used to mediate extraction of essential oil in place of steam or water heating in order to introduce its inherent advantages. As in the case of microwave heating of food materials, the internal heating of the in-situ water within the plant material by the microwaves leads to the rupture of the glands and oleferous receptacles freeing the essential oil which is then evaporated by the in-situ water of the plant material. The water then evaporated could then be passed through a condenser outside the microwave cavity where it is condensed. This study envisages evaluation of developed microwave assisted extraction system towards extraction of allspice essential oil. The developed extraction system consists of a microwave cavity, extraction unit, supporting stand. In order to evaluate the developed system towards extraction of allspice essential oil, the process parameters like solid: water ratios of 2:1, power densities of 30, 40, and 50 W and extraction times of 1, 2 and3 h which would influence the essential oil yield were chosen as independent variables. The physical quality characteristics like specific gravity, solubility and colour of essential oil were selected as dependent variables. The optimized conditions of solid: water ratio, power and extraction time 63for extracting allspice essential oil in microwave assisted process was found to be 2:1, 50W and 2h respectively. The results showed that with increase in extraction time above 2 hr, the total essential oil yield was found to decrease. Increase in power results in an increase in total essential oil yield, however too high power can lead to volatile oil loss and degradation of components in essential oil. When power exceeds more than 50W there is no significant yield. Hence the optimum microwave power as per the experiments is 50 W. Microwave assisted process resulted in a maximum oil yield of 3.6 ml, with an extraction time of 2 hr and power of 50 W. The time taken for extracting the allspice essential oil in hydro distillation process was around 5 hr for the oil yield of 0.5 ml. This indicates that the oil yield, in microwave assisted process resulted in a rapid extraction process when compared to hydro distillation process. Therefore, microwave assisted extraction of allspice oil could be considered as an extraction technique that results in the production of high quality oil in higher quantity in less time with minimum energy consumption.