The International Organization for Standardization (ISO) defines an essential oil as a product made by distillation with either water or steam or by mechanical processing of citrus rings or by dry distillation of natural materials. Following the distillation, the essential oil is physically separated from the water phase.
Therapeutic-grade essential oils are both complete in their chemical constituents and kinetically "alive," able to affect the human body, restoring balance and normal function to weak body systems.
A truly high-quality, therapeutic-grade essential oil has three key properties: 1. its chemistry, 2. its fragrance and 3. its frequency which contribute to its unique healing benefits. If any of these properties is missing or inferior, an essential oil cannot be called therapeutic-grade.
Few people appreciate how chemically complex essential oils really are. Essential oils are a complex mosaics of molecules containing anywhere from 80 to 200 distinct chemical constituents. Some highly complex essential oil like lavender can contain considerably more.
One key to producing of therapeutic-grade essential oils is to preserve as many of these aromatic compounds within the essential oil as possible.
The problem is that these aromatic compounds are quite fragile, and not easily extracted from the plant material. It takes a lot of understanding of the essential oil, and the willingness to invest the necessary time and expense. To make a great, therapeutic-grade essential oil, you must:
Use proper cultivation methods
Plants should be grown on virgin land, uncontaminated by chemical fertilizers, pesticides, fungicides, or herbicides. The plant materials must be kept free of agrochemicals, since these can react with the essential oil during distillation and produce toxic compounds. And, because many pesticides are oil-soluble, they can also mix into the essential oil. If these oils are diffused or topically applied, the toxic chemicals in the oils are carried into the body with potentially devastating results.
Plant materials should also be grown away from pollution sources such as nuclear plants, factories, interstates, highways or heavily populated cities, if possible. And the soil should be conditioned with an advanced mix of enzymes, trace minerals, and organic bio-solids, since plants lacking in certain minerals and nutrients yield oils low in therapeutic value.
Land and crops should be watered with reservoir or watershed water. Mountain stream water is best because of its purity and high mineral content. Municipality treated water, or secondary runoff water from residential and commercial areas, can introduce undesirable chemicals and residues into the plant and its essential oil.
Harvest with knowledge and care
The timing of the harvest is one of the most important factors in the production of therapeutic-grade essential oils. If the plant is harvested at the wrong time of the season, or even at the incorrect time of day, a substandard essential oil can be produced. In some cases, changing harvest time by even a few hours can make a huge difference. For example, German chamomile harvested in the morning will produce oil with far more azulene than chamomile harvested in the late afternoon.
Other factors that should be taken into consideration during the harvest include the amount of dew on the leaves, the percentage of plant in bloom, and the weather conditions during the two weeks prior to the harvest.
Also, because of the volatility of the essential oils, to prevent herbs from drying out prior to being distilled (and so, losing many of the precious, aromatic molecules to evaporation), distillers should be located as close to the field as possible. Transporting herbs to distillers hundreds, or even thousands, of miles away also heightens the risk exposure to pollutants, dust, mold, and petrochemical residues.
Extract the oils in the proper way
Essential oils can be extracted from the plant by a variety of methods, including solvent extraction, carbon dioxide extraction, and steam distillation. Steam distillation is one of the most common, and has several advantages over the other methods.
However, distillation is as much a science as it is an art, and subtle differences in distillation equipment and processing conditions can translate into huge differences in essential oil quality.
Factors to consider include:
The fragile aromatic molecules of an essential oil are easily destroyed or altered by high temperatures; and so, the distillation process must use low-temperature methods. High temperatures seem to cause a harshness in the oil. Even the oil's pH and the electropositive and electronegative balance are greatly affected by such high temperatures.
For example, the distilling process for lavender should not exceed 245 degrees Fahrenheit, cypress should be distilled at 245 degrees Fahrenheit.
The fragile aromatic molecules of an essential oil are also easily destroyed or altered by high pressure during distillation, causing a harshness in the oil, as well as affecting the essential oil's pH, and electropositive and electronegative balance.
Marcel Espieu (the President of the Lavender Growers Association in southern France for 21 years) stated that the best oil quality would be produced when the pressure was zero pounds during distillation.
In the distilling process for lavender, pressure should not exceed three pounds. For cypress, it should be about five pounds of pressure.
The length of time taken for distillation is important. For lavender, the time required for distillation is about an hour and a half. On the other hand, cypress requires 24 hours of distillation to extract all of its active ingredients. If distillation is shortened by only two hours, 18 to 20 of the essential oil's chemical constituents will be missing.
The chemical composition of the cooking pots is also important. Essential oils should be kept from contact with chemically reactive metals, such as copper or aluminum. A therapeutic-grade essential oil should be distilled in a food-grade stainless-steel cooking chamber.
And finally, the size of each batch is important. Essential oils should be distilled in small batches.
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