The reported extraction methods of Foeniculum Vulgare Oil are steam distillation (HD), microwave assisted extraction (MAE), simultaneous distillation extraction (SDE) and supercritical CO2 fluid extraction (SFE-CO2).
1. Steam distillation (HD)
HD is the most commonly used method for separating volatile oil from plant samples. There have been many reports using this method to extract cumin oil. This method is easy to operate and requires less equipment. However, it consumes a lot of energy, and because of the large amount of water, the volatile oil has different degrees of dissolution loss. In addition, due to the long heating time, the thermally unstable components in the volatile oil are prone to chemical reactions, resulting in an unsatisfactory aroma of the volatile oil obtained.
2. Microwave Assisted Extraction (MAE)
The volatile oil of cumin was extracted by MAE method using absolute ethanol as extractant. In fact, what is obtained by this method is the extract of Foeniculum Vulgare Oil, not the volatile oil in the true sense. In order to obtain volatile oil, steam distillation should be performed on the extract to separate the volatile oil from other non-volatile fat-soluble components in the extract. This method needs to deal with a large amount of organic solvent, and there is the problem of residual organic solvent, so it is rarely used at present.
3. Simultaneous Distillation Extraction (SDE)
SDE is a common method for extracting Foeniculum Vulgare Oil, which is an extraction method that simultaneously performs two steps of steam distillation and organic solvent extraction. The SDE method realizes the extraction of volatile oil at one time through the multiple and large-area contact of the water vapor phase and the organic solvent phase, and avoids the adsorption loss on the vessel wall and the operation of transferring trace amounts of volatile oil when the volatile oil is extracted by the steam distillation method. difficulty. It not only realizes high-efficiency extraction of volatile oil, but also reduces the possibility of a large amount of organic solvent remaining in the volatile oil, which is a great improvement to the extraction of volatile oil by steam distillation. This method is considered to have a high recovery rate for a variety of compounds, and it is currently the most widely used sample preparation method for the full-component analysis of plant aroma. In the research at home and abroad, this method has been widely used in the extraction of aroma substances, and there has also been extensive research on the extraction of volatile oils from plants.
4. Supercritical CO2 Fluid Extraction (SFE-CO2)
SFE-CO2 uses higher than critical temperature and critical pressure to avoid the decomposition of heat-sensitive components during steam distillation and the loss of components caused by possible hydrolysis and water solubilization. There is no solvent residue in this method, no environmental pollution is caused, and the extracted product has good aroma quality. Compared with organic solvent extraction, it has the advantages of high selectivity and tunable solubility. Specific operation: put an appropriate amount of fennel powder in the extraction tank, and then open the supply valve of the CO2 tank. After the CO2 is compressed to the ideal pressure by the compressor, the system is heated to make the system in a supercritical state, and flows through the extraction tank from bottom to top. Volatile oils are extracted along with other lipophilic components. After decompression, the obtained extract flows through two separators in sequence, and macromolecular substances such as resin and pigment are obtained in the primary separator, and cumin oil is obtained in the secondary separator. CO2 is vented as a gas or compressed and then recycled.