How Temperatures Affect Essential Oils
As winter storms recently buried the North, I thought of some of our friends in Alaska, Washington, Oregon, Idaho, Illinois and so on. Don't worry if your essential oils are delivered in cold weather, even if they have to sit outside for a good while. Dr. David Stewart writes, "even in the extreme, cold never hurt any oil - regardless of whether it is essential, expressed, absolute or a carrier blend. If your oils are ever chilled to the freezing point, don't apply any heat to thaw them out. Keep the lids on and just let them warm up gradually to room temperature, and they will be fine."
While I'm covering the temperature topic, we have friends in the deep south who want to know about the effects of heat on the essential oils. I try to protect my essential oils from excessive heat, yet I do realize that true essential oils are the product of distillation at temperatures well above the boiling point of water (212F or 100C). They prove themselves to be stable at these high temperatures or else they would not be worth much to us once the high temperatures separated them from the plant. The flash point of some essential oils is between 100-140F (38-60C), which means that the lightest oil components may temporarily separate, vaporizing in the sealed bottle. The good news is that, once the bottle has cooled back down, these components condense and become liquid again, leaving their chemical makeup unaltered. If your essential oils do get too warm, keep the lids on until they have cooled back down. If you must open a bottle that is too warm, the lightest compounds may escape and alter the balance of the oil. In that case, your oil will likely not be as effective as before the incident.
Expressed oils such as Bergamot, Grapefruit, Lemon, Lime (although our Lime is distilled) Mandarin, Orange and Tangerine, can be damaged by temperatures in excess of 100F (38C), and they need to be kept in moderate temperatures. Blends with these oils in them are included. We try to keep our citrus oils and blends that contain them in temperatures we feel comfortable in. If they have been subject to temperatures over 90F, allow them to cool down before removing the lids. If damaged, they will smell different than when they were fresh, and the damage will reduce their therapeutic value and may cause skin irritation.
Absolutes fragrances, such as Jasmine, are destroyed by excessive heat (90F or 32C). They are slightly more sensitive to heat than expressed oils. Normal room temperatures help them maintain their delicate chemistry.
Carrier oils are typically cold pressed because heat makes them susceptible to undesirable alteration. When fatty oil molecules break down, we say they have become "rancid." Blends that contain carrier oils, should be kept reasonably cool and will last longer if refrigerated.
Stewart, David Ph.D, D.N.M., The Chemistry of Essential Oils Made Simple, 2005, pages 431-436.