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.