Extraction of Essential Oils from Lemon Peels By Supercritical Carbon Dioxide

Lemon flavor additives are widely used in foods, drinks, cosmetics and detergents. Currently, there are many methods to extract essential oils from lemon peels. However, these methods are mostly time consuming and of low extraction efficiency. Even more, some extraction methods involve the use of organic solvents which could cause safety and health concerns as well as environmental pollution. Therefore, the purpose of this study is to apply the Supercritical Fluid Extraction using Carbon Dioxide (SFE-CO₂) to extract lemon essential oils. As supercritical carbon dioxide is non-polar, ethanol and nonionic surfactants were used as cosolvents to increase its polarity and the extraction efficiency.

About 90 % of the lemon essential oils are monoterpenes, in which the main ingredients are d-limonene, β-pinene and γ-terpinene. Our results showed that the wet and dry yields increased with a lower extraction temperature and a higher CO₂ pressure, probably owing to the increasing density of supercritical fluid. Besides, β-pinene has a higher polarity. Therefore, its extractability by SFE-CO₂ is relatively poorer. The extraction yield increased with more β-pinene extracted out with addition of ethanol to SFE-CO₂. However, the effect of added nonionic surfactants as cosolvents to the SFE-CO₂ seems insignificant.