Solvent extraction for absolutes is technically not considered essential oils. Extracted via a multi-step process that utilizes more delicate plant materials (such as jasmine flowers) that wouldn’t survive the heat of steam distillation.
Like absolutes, CO2 extracts aren’t considered true essential oils, such as those obtained by steam distillation and cold-pressing. Carbon dioxide (chemical abbreviation= “CO2”) is a gas familiar to most people: it’s what we exhale during breathing. We breathe oxygen into the lungs during inhalation and exhale carbon dioxide. Carbon dioxide is a waste product of the body’s metabolism. But how does carbon dioxide help produce oil?
Under pressure, CO2 gas transforms into an “almost” liquid state called the supercritical state. Plant material goes through an airtight receptacle, and carbon dioxide gas is pumped under pressure; low heat is also applied to aid extraction. As the pressure inside the container rises, the CO2 gas nearly liquifies, bathing the plant material in supercritical CO2. The combination of high pressure and low temperatures encourages the plant material to releases its aromatic components. After a period of time, the pressure reduces and the supercritical CO2 then changes back to its gaseous state, completely dissipating from the extracted material.
Because lower temperatures occur during the process, heat-sensitive plant components may destroy or inactivated during steam distillation are preserved in the CO2 extract. The combination of lower temperatures and (generally) lower pressure means that CO2 extracts contain more of a plant’s original constituents than steam distilled oils. According to Dutch aromatherapist Madeleine Kerkhof-Knapp Hayes, the scent of CO2 extracted oils is [generally] “richer and more intense because more aromatic components are present.