| The supercritical fluid extraction of bitter orange essential oil was studied using dehydrated or fresh bitter orange peel as raw material and CO2 as solvent. The influence of sample preparing (dried or fresh sample) on the Limonene extraction yield was studied.
Essential oils produced from fruit peels are widely used as flavours and fragrances in the food, perfume and cosmetic industries. Peel oils are mainly composed of a volatile fraction consisting of terpene hydrocarbons and their oxygenated derivatives, and of a non-volatile fraction including waxes and pigments. Hydrocarbons have to be removed in order to stabilize the product since they can oxidize, developing unpleasant odours. Distillation techniques are commonly used to remove these components but these techniques employ high temperature, which could degrade aroma components. Therefore, supercritical fluid extraction (SFE) seems to
be an attractive alternative to traditional extraction techniques, in order to avoid the use of organic solvents and thermal processes.
In the last two decades, numerous researchers have investigated the fundamentals and process applications of supercritical fluids. SFE has been used for the extraction of organic compounds such as flavour and fragrances from natural products. Supercritical fluids as solvents have advantages such as excellent mass transfer and control of solubility by temperature and pressure. Liquid CO2 seems to be the most interesting solvent for flavour extraction because of its high selectivity towards aroma representative constituents and the low temperature of its critical point. Attempts to extract aroma products from fruits and plant materials with supercritical CO2 have been reported for apples, pears, different aromatic plants, and also different citrus peel oil such as orange, lemon, lime, bergamot, mandarin, but there is no reported study on bitter orange peel oil extraction.
Limonene, the principal component of the citrus peel oil, is an unsaturated terpene hydrocarbon, which is unstable to heat, light and oxygen. Then, it is possible to represent the effect of sample dehydration on the quality of extraction by its principal component, Limonene.
Figure 64- The quality of extraction process based on the amount of extracted limonene.
To conclude, during supercritical fluid extraction of limonene from bitter orange peel oil (both fresh and dried sample), the solubility of limonene increases when operating pressure increases. The use of co-solvent in this extraction has a beneficent effect on the extraction quality. Regarding the sensitivity of aroma compounds to the high temperature, it is shown that drying samples can decrease aroma content of extract.
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