Common Methods of Scent
Extraction in Brief
Steam Distillation: Distillation is one of the older methods used for extracting the essence of a plant or flower. Basically, the process applies heat to water with the herb present in a confined area. The herb leeches its essence which becomes steam, the steam condenses, and the condensed droplets are then collected. There are other processes that are now applied to the collected material to further refine it so that only the essence itself remains.
Solvent Extraction: Solvent extraction is used for more delicate essences that would lose their quality with the application of heat as done in steam distillation. This is a more chemical process using hydrocarbons which are then removed from the resultant essence via distillation. There is alot of controversy over solvent extracted essences. The reason is that in using a toxic chemical to begin with, how can one be assured that the resultant essence does not contain some of the residue of the solvent? I feel that it is logical to say that solvent extractions (although serving of the purpose of extraction) probably cannot guarantee an organic result. Further, alot of solvents used in this process are harmful to the environment. It is up to each person to determine the quality of oil they want to use. Unfortunately, many oils you likely use now are solvent extracted. All absolutes, attars, and concretes are in fact attained via a solvent based process. Further on in my article, I address oil quality in brief and give links to some companies I feel are reputable in offering quality essentials for your use.
Enfleurage: Enfleurage, also a classic method, extracts the essences via fat. Typically, the plant material is left embedded in solid fat and left for a time to impart its essence into it. Once the plant is spent, fresh material is then added to the fat to continue increasing the intensity of the scent until eventually the fat is completely permeated with the aroma and essence of the plant. After this, further refinements are then made.
Maceration: Maceration is similar to enfleurage except that the plant material is immersed in liquid fat (oil) and heat is applied to expedite the process. Again, fresh plant material is continually added until the desired aromatic intensity is achieved. The resltant product is then refined.
Expression: Expression is a method of pressing out the valuable oil from its pliable non floral parts. Typically, expression is used for mainly citrus oils like orange, lemon and the like which contain their volatile oils in the rind part of their fruits.
Please know the above explanations are very brief to give you the general idea about oil processing.