Application of new techniques for extraction of the volatile components and essential oils

The conventional methods for the essential oil extraction (hydro-distillation and steam distillation) have some disadvantages. Losses of some volatile constitute, low extraction efficiency, degradation of unsaturated or ester compounds through thermal or hydrolytic effects and toxic solvent residue in the extract may be encountered using these extraction methods. The development of new extraction techniques for the food and herbal drugs industries has received a lot of attention lately due to the environmental restrictions and the need for minimizing the energy costs. In order to reduce the extraction time, and the operation costs and possibly improve the oil yield and the quality of the essential oil, new approaches such as microwave-assisted extraction, supercritical fluid extraction, and ultrasound-assisted extraction have also been sought. Results of our study indicated that the changes in yield of the volatile oil during extraction depended on extraction method and temperature, type constituent and the biological characteristics of the plants. Extraction methods had significant effects on aroma quality of the dried samples in Iranian herbs. In conclusion, extraction of the essential oil from some Iranian medicinal and aromatic plants with microwave-assisted steam hydro-diffusion was better in terms of extraction time, phenolic and aroma fractions, and product quality.