Supercritical fluid extraction proposed in recent years, appears to be a promising technique since it requires low energy for separation. It is a relatively new technique for extracting fragrant compounds from a raw material, which often employs Supercritical CO2. Due to the low heat of process and the relatively nonreactive solvent used in the extraction, the fragrant compounds derived often closely resemble the original odor of the raw material.
Essential oils have traditionally been derived using either steam or hydro distillation, or extracted using chemical solvents such as hexane, heptane or ethanol. The supercritical CO2 extract and its process have many benefits over the traditional distillation processes, which should be taken into consideration when choosing a natural aromatic oil for use in body care products, aromatherapeutic blends, natural perfumes or similar products.
The CO2 extraction process consists of pumping pressurized carbon dioxide into a chamber filled with plant matter. When carbon dioxide is subjected to pressure it becomes “supercritical” and has liquid properties while remaining in a gaseous state. Because of the liquid properties of the gas, the CO2 functions as a solvent, pulling the oils and other substances such as pigment and resin from the plant matter. Thus, the difference between CO2, or supercritical, extraction and traditional distillation is that CO2 is used as a solvent instead of heated water or steam. The temperature involved in the supercritical extraction process is around 35C to 38C -as opposed to 60C to 100C in steam distillation. An important difference between CO2 extracts and distilled essential oils is that CO2 extracts typically contain more constituents found in the plant than just the essential oil portion. In this way they more closely resemble the original plants chemical make up, and could be considered to contain a fuller spectrum of constituents from the plant than essential oils do. There are a few more positive aspects of the supercritical CO2 extraction process and the resultant supercritical CO2 extract over some aromatic extracts such as absolutes.
The CO2 supercritical extraction process eliminates the need for potentially harmful solvents like hexane that is often used in the manufacture of absolute oils, avoiding unnecessary environmental pollution and potential human bodily harm. Another positive aspect to the CO2 distillation process is the aroma of the extract. A CO2 supercritical extract often will exhibit a more genuine aroma of the actual herb, spice or plant than a distilled essential oil. The aroma of the CO2 extracts of ginger, cardamom and other spices, for instance, are more alive, active, spirited than the aroma of the same plants that have been steam distilled.
Besides being the method of choice for applications designed to extract flavors and aromas, Supercritical CO2 extraction is also gaining momentum in the high-growth sector of plant substances (nutraceuticals, botanicals, food supplements). Here, requirements for naturalness and purity are very high and conventional methods simply aren’t up to the challenge.
The video above is a promotional video from Evonik Industries and shows us how this extraction technique is used to produce decaffeinated tea. In this spesific process, the activated carbon absorbs 90 % of the tea’s caffeine,which originally makes up 3 % of the entire content. This absorbed substance is regenerated and recycled into the production process while the bulk that is left over is the decaffeinated tea.
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