Optimization of microwave assisted process for extraction of nutmeg seed essential oil

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 nutmeg seed essential oil. The developed extraction system consists of a microwave cavity, extraction unit, supporting stand and energy meter. In order to evaluate the developed system towards extraction of nutmeg seed essential oil, the process parameters like solid: water ratios of 2:1, 4:3 and 1:1, power densities of 7.2, 8.4 and 9.6 W/g and soaking times of 2, 3 and 4 h which would influence the essential oil yield, extraction time and energy consumption were chosen as independent variables. The physical quality characteristics like refractive index, specific gravity, solubility and colour of essential oil were selected as dependent variables. The optimized conditions of solid: water ratio, power density and soaking time for extracting nutmeg seed essential oil in microwave assisted process was found to be 2:1, 8.4 W/g and 4 h respectively. The extraction time, yield of nutmeg seed oil and energy consumption at this optimum process parameter levels were found to be 4h, 3.5 ml/100g and 1.1 KWh respectively whereas the same were found to be 7h, 3.5 ml/100g and 2.5 KWH respectively for conventional hydrodistillation process. It was also revealed that active component myristicin was found to be higher in MAE nutmeg seed oil extracted under optimized condition compared to hydrodistilled nutmeg seed oil. Therefore, microwave assisted extractioncould 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.