| Essential Oils - Extraction and quality |
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Extraction
Any part of a plant - the stems, leaves, fowers, fruits, seeds, roots or bark - may produce essential oils or essences but often only in minute quantities. Thus the method of extraction varies considerably, and in order to harvest the oils in appreciable amounts, it is usually necessary to collect a large quantity of the part of the plant needed and to subject the material to a process that causes the oil glands to burst. One of the most common methods is 'distillation'. The plant material is packed tightly into a press or still and steamed at a high temperature. This causes the oil glands to burst and the essential oil vaporises into the steam. This is then cooled to separate the oil from the water. Other methods include 'solvent extraction' which involves dissolving the plant material in a solvent or alcohol; 'maceration' in which the plant is soaked in hot oil and the essential oils released are extracted by separation and purification from the hot oil; and 'pressing' which is literally squeezing out essential oils from rinds and peel of ripe fruit such as oranges.
Quality
The quality of an essential oil can vary from year to year, just like the vintage of a fine wine. Altitude and soil affect quality, as much as climate and the exact moment of harvest. Picking the raw ingredient is only the first consideration, for if they are left too long or not extracted using the best possible method, the essential oils might end up being inferior. Certified organic essential oils indicate that they have been grown without the use of synthetic pesticides, and extracted along strict guidelines.
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