The facts about essential oils Part 4 of 5
The freshness factor
How do you know if essential oils are fresh? It's difficult to know when we buy essential oils whether they are fresh or past their date without specific experience with those materials. Unfortunately many oils don't usually come in sealed packages with "use by" dates. We can of course read up on them but that is not quite the same.
Rules of thumb
There are a few rules of thumb that can help you gauge an oil's freshness:
- First Check your source. Are you buying from the manufacturer or a dealer. If a dealer does he appear to have a regular turnover? Are essential oils his main business?
- Essential Oils and absolutes should have representative smells of the original plant material. Generally the more like the original leaves, herbs or flowers, the more likely it is to be fresh.
- Citrus Oils - citrus oils when they are first pressed have a definite light color of the fruit they came from. i.e.. Lemon oil is yellow, orange oil is orange, Tangerine oil is tangerine, Bergamot is green etc. The colors in the citrus oils are generally not very stable. If the oils have been exposed to light or kept in poor storage conditions their color fades. So most Citrus Oils after a year or so tend to become almost colorless. Note Distilled Lime oil is always colorless even when fresh because the color does not volatilize with the oil during the process of distillation.
- Terpenes (chemicals that occur in all essential oils) tend to polymerize in the presence of oxygen and produce sticky resinous masses so look for any signs of gooey masses, they will be translucent brown and will tend to collect around caps or may present themselves as sticky precipitates.
- If an oil is very freshly distilled it will have a gassy green "still" note on top. This is particularly characteristic on Geranium Oil which should have a sweet corn note (from dimethyl sulphide). These notes generally dissipate after a month or so.
- Woody type oils with high concentrations of sesquiterpenes are more viscous than their mono terpenoid cousins and become increasingly viscous with age. This frequently improves the odor of the oil. Such as in Patchouli, Vetiver, Sandalwood etc so for the woods, you may like to have an older oil.
- Some oils kept in steel drums (even lacquered ones have scratches and allow some contact with bare metal) will pick up iron from the steel material and this slowly darkens the oil over time. The most susceptible oils are the spicy oils Clove and Cinnamon which will eventually turn black, but all oils and materials will be somewhat affected.
- Most oils will tend to soften in odor as they age as the functional groups (aldehydes, alcohols, esters etc.) on the constituent chemicals break down. Strong aldehydes turn into their weaker smelling alcohols. If esters break down they may produce the acids and a sourness may develop.
Of course these tips will have many exceptions but these generalities should help you to pick out most common changes in oils that could indicate they are past their best. They are a good starting point to add your own experience with specific oils.
We know a whole lot more about essential oils than most companies that sell them because we use them a lot in perfume artistry. However, and I can never say this enough, we don’t ever recommend them for your face.