According to the characteristics and requirements of natural flavor raw materials, after proper preparation and pretreatment, several processing methods are often used.
Essential oils are different from various vegetable oils or fixed oils such as rapeseed oil and olive oil because they contain many volatile aroma components. And because most essential oils are insoluble or slightly soluble in water, if the quality permits, it will be simpler and more reasonable to extract essential oils from various tissue cells or secretions of natural fragrance raw materials by steam distillation.
In actual production, it was found that although the boiling points of many components in the essential oil are close to 150-300 °C under normal pressure, when distilled with water, as the azeotropic boiling point of the two-phase mixed liquid, the temperature can be slightly lower than the boiling point of water. The gas-liquid phase balance is maintained, thereby preventing decomposition and deterioration caused by overheating.
Fragrance plant materials suitable for this method of oil extraction are:
- √ Flowers (roses, orange blossoms, etc.)
- √ Bark (cinnamon etc.)
- √ Branches (sandalwood, cypress, etc.)
- √ Branches and leaves (lina camphor, patchouli, star anise, eucalyptus, etc.)
- √ Stems and leaves (mint, spearmint, white orchid leaves, lemongrass, etc.)
- √ Inflorescence (Lavender, Fragrance, etc.)
- √ Peel (citrus peel, nutmeg coat, etc.)
- √ Seeds (Cangzi, star anise, coriander seeds, etc.)
- √ Whole grass (valerian, citronella, etc.)
- √ Roots or rhizomes (vetiver, calamus, iris, etc.)
Although some varieties will not decompose during distillation, but the content of volatile oil is small, especially the raw materials that are easily soluble in water in the aroma components, this method should not be used.
Steam distillation will still be one of the important processing methods for producing essential oils for a long time in the future.
5 Steam distillation process
According to the different characteristics of plant materials, steam distillation is divided into:
- Batch distillation on water
- Batch distillation in water
- Steam batch steaming method:
- Vacuum steam distillation
- Pressurized steam distillation
- Atmospheric pressure steam distillation (in addition to batch distillation, continuous distillation can also be used)
- Water infiltration (Hydrodiffusion) batch distillation method
- Dry distillation or destructive batch distillation (Destructive distillation)
Leaching or extraction
Volatile solvent extraction
Extracting essential oils from plants by distillation is not suitable for extracting the aroma components of some flowers due to high temperatures. This is because many unstable aromatic substances will be damaged or even damaged under the action of higher temperatures and longer time. decomposition, deterioration;
Some aromatic substances are difficult to be completely extracted by steam distillation and volatile solvent extraction due to their low volatility index. The volatile solvent extraction method can just make up for these defects.
The raw materials that can be extracted by volatile solvents can be roughly divided into three categories:
- Fresh plant raw materials, such as freshly picked jasmine flowers, white orchids, lavender inflorescences, etc., are extracted with solvents to make extracts, or pure oil is extracted from the extracts.
- The dried raw materials, as well as animal secretions, are extracted by solvent to produce balsamic resin, oleoresin, cold method (or hot method) tincture, and other products.
- Fruit juices and distillates can also be solvent-extracted for aroma components.
The volatile solvent extraction method is a physical separation method, which can use the different selectivity of different solvents to various fragrance components, from liquid-liquid or liquid-solid leaching, to completely extract the effective fragrance components in the raw materials, especially It is suitable for the extraction of top incense parts, raw materials with low content of fragrant components, varieties with small volatile index and non-volatile fragrance components.
Grease warm dip
Although this method belongs to an ancient leaching process, it still has specific meanings, mainly to meet the requirements of a certain fragrance. Most of the oils used are purified tallow, lard, sesame oil, etc., and mineral oil is rarely used. Fresh flowers are immersed in 40～80 ℃ of warm greases, after a certain period of time, fresh flowers are replaced, until after the aromatic substance in the grease is saturated, the grease that removes the residual flowers is called balsam, and ethanol washing can be used thereafter, and recovery obtains incense dipping. The liquid can also be further removed from the ethanol to make balsam absolute oil.
CO2 extraction method
Supercritical or subcritical CO2 extraction uses a supercritical fluid as the separation medium (extractant) and uses the fluid to have a highly enhanced dissolving ability in a supercritical state to achieve effective extraction of certain components (solutes) in the raw material, and then pass the temperature and the continuous adjustment of the pressure can reduce the density of the extractant, that is, reduce its solubility to the solute, so as to achieve high-efficiency separation of specific components in the raw material.
Liquid butane leaching
Butane extraction refers to the process of using butane as the primary solvent to extract compounds from the cannabis plant to create concentrated cannabis extracts. Butane, a colorless gas with a faint odor, is a non-polar solvent, meaning it only binds with fat-soluble compounds. Cannabis concentrate products made through butane extraction are often considered more flavorful and potent than other solvent-based extractions like ethanol.
How butane extraction is conducted
When butane passes through a cannabis plant, it pulls with it various compounds, including phytocannabinoids, terpenes, lipids, waxes, and chlorophyll. To refine the resulting extracted mixture into the concentrated products found on dispensary shelves, manufacturers subject it to a process called winterization, which increases the overall purity of the final product by removing lipids, waxes, and chlorophyll.
Once winterized, extractors must remove the butane. This is an extremely important step considering butane can be hazardous when consumed in high amounts. Butane is a short hydrocarbon and therefore has a low boiling point of -1°C (31℉). As a result of its low boiling point, using butane can help extractors preserve more phytocannabinoids and terpenes, which degrade when exposed to heat.
Pressing or cold pressing and cold grinding
There are not many raw materials processed by this method, mainly the “special” method of extracting essential oils from citrus fruits or peels by grinding or pressing. The whole citrus fruit peeler is used for cold grinding, and the crushed peel screw press is also used for pressing.
No matter which method is used, the raw materials must be washed, selected and classified before processing to ensure the quality of essential oils.
During the processing, circulating spray water must be continuously sprayed on the raw materials to be ground and squeezed to wash out the essential oil remaining on the oil sac. After the circulating spray water is used for a certain period of time (generally 8 to 24 hours), a small amount of essential oil contained therein can be recovered by distillation. If it is believed that the circulating spray water has deteriorated, it should be discarded.
The circulating spray water used in the screw press can adjust the pH value with baking soda or acetic acid according to the actual needs, so as to keep the slightly alkaline to inhibit the enzymatic change, while the slightly acidic can protect the active ingredients in the citrus essential oil. Sometimes a small amount of electrolyte water-soluble salts is added to the circulating spray water so that the residual pectin in the water becomes pectinate and precipitated and separated.
The oil-water mixture washed by the circulating spray water often contains peel debris, which requires coarse filtration and fine filtration. Most of the coarse filtration uses a continuous rotary round sieve filter. After filtration, it is sometimes necessary to pass through a multi-stage clapboard-type idium tank to precipitate pectinate.
The oil-water mixture after filtration and precipitation must be separated by a high-speed centrifuge to obtain essential oils. In order to allow the trace moisture and impurities in the essential oil to fully precipitate, it is often placed at a low temperature of 5 to 10 ° C, and after a period of standing, the suspended impurities in the essential oil are filtered out with reduced pressure filtration and filter aid , you can get “cold method essential oil”.
Adsorption and Absorption
Fat cold suction
Generally, a mixture of tallow and lard with moderate hardness and softness, which has been purified, does not contain any impurities, and is not prone to rancidity, is used as the fat base.
The picked mature flower buds are placed on the frame of the fat-coated glass plate and then stacked on top of each other, keeping the distance between the frame plates that the glass plates do not touch. Both sides of the glass plate are coated with an aliphatic base, which acts as a solvent for absorbing fragrance components. The fat base under the glass plate is not in contact with the flowers, so as to absorb the fragrance components emitted by the flowers.
Replace the remaining flowers on the glass plate once a day. At the same time, turn the glass plate over and put flowers on it. Repeat this up to 36 times. When the aromatic substances in the aliphatic base are basically saturated, the aliphatic base can be scraped off, which is called cold suction. Balsam (Pomade).
After washing with refined high-concentration ethanol, and after freezing to remove a small amount of fat and miscellaneous substances, the ethanol fragrance liquid is obtained. The ethanol can also be distilled off under reduced pressure to prepare the cold absorption method absolute oil (or balsam absolute oil).
The residual flowers removed from the flower frame still have some aromatic components that have high boiling points or are not easily absorbed by fat. It can be extracted with petroleum ether to prepare the extract. Because the extract contains fat, it needs to be frozen and filtered with ethanol at a low temperatures. , to remove fat and wax, the resulting product is called residual flower oil, also known as “frame oil” (Absolute from Chassis).