Updated: Feb 9, 2021
There are several extraction methods used to acquire essential oils. Although, steam distillation is the most common extraction to produce essential oils, there is also cold pressing for the citrus fruit, CO2 extraction, and absolutes. Of the later, there are many amazing varieties now available.
Absolutes offer a wonderful way to capture floral fragrances more accurately. They differ from essential oils in that they contain not only essential oil, but also a higher density of coloring, waxes, and other constituents from the plant.
The efficiency and low temperature of this particular extraction process helps to prevent damage of the fragrant compounds. Most absolutes carry the aromas closer to the original plant than it is possible with essential oils produced through steam distillation.
Absolutes are used extensively in the cosmetic and perfume industries due to their strong aromas.
Absolutes require the use of solvent extraction techniques or more traditionally, through enfleurage.
Solvent extraction is used on plant material that is more delicate and not easily steam distilled. One example is Tuberose (Polianthes tuberosa), if it was steam distilled, very little oil would be produced and the oil does not have as nice of an aroma as solvent extracted Tuberose.
Solvent extraction is used for jasmine (Jasminum sambac), tuberose (Polianthes tuberosa), carnation (Dianthus caryophyllus), gardenia (Gardenia jasminoides), mimosa (Albizia julibrissin), violet leaf (Viola odorata) and other delicate flowers. Others like neroli (Citrus aurantium var. amara) and rose (Rosa damascena) can be either distilled or solvent-extracted.
Also, some raw materials are either too delicate or too inert to be steam-distilled and can only yield their aroma through other methods, such as solvent extraction or lipid absorption.
There is a multi-step process to acquire an absolute:
First step: Extracting the aromatic oil from the plant material with a chemical solvent such as hexane or toluene. After the solvent is removed what is left behind is a waxy substance called a concrete or resinoid, depending if the extract is waxy or resinous. Concretes and resinoids are used in a wide range of industries, but specialist knowledge is required to use them because they are very difficult to work with due to their thick, heavy consistency. This is one of the main reasons that concretes and resinoids (with the exception of benzoin-Styrax benzoin) are rarely used in aromatherapy.
Second step: The aromatic oils are then extracted from the concrete with ethyl alcohol to separate the aromatic compounds from pigments and waxes. Many of these waxes have little aromatic value and make the oil challenging to use due to their insolubility, although these waxes are useful in skin care products.
After the ethyl alcohol is removed, the remaining substance is an absolute – an oil with an aroma close to the plant from which it came. An absolute is the most concentrated form of fragrance and highly regarded in natural perfumery.
Once the solvent extraction process has been completed, the resulting absolute will have an extremely low concentration of solvent residue, approximately 5 to 10ppm (parts per million). In the past, there were concerns related to the solvent and alcohol residues left in absolutes which are claimed to be unacceptably high for use in aromatherapy. Howeve