You probably wouldn’t be reading this if you didn’t already have an interest in quality of essential oils. So it’s worth taking time to go more deeply into the factors that determine the characteristics of the end product.
Did you know that distillation is one of the critical factors that determines whether we end up with a mediocre oil or one that reverberates with energy and vitality? Do you have a feeling for this process?
Let’s talk a little about the process of distillation…
Different harvesting methods
This picture shows the large commercial harvesting of Clary Sage in Provence. A combine harvester transfers the plant material to a trailer where it is cut up ready for distillation. This process is quick and efficient, but will not be suitable for producing a therapeutic grade oil.
Distillation is an art. It takes years to learn and master, and this is a never-ending process. There are many different methods to employ; different materials of still to use; water and steam distillation; quick and slow; long and short; low and high pressure. All give different results. Which we use will depend on what outcome we have in mind. And different processes suit different plants. The process will also be different whether we are distilling in order to end up with an oil or a hydrolat.
Some distillers speak in almost mystical terms about the process, talking about the magical fusion of the elements of water, fire, earth and air, and many will refuse to leave the still even for a moment during what they see as a sacred process, keeping their careful attention on the procedure throughout. There is no doubt that for some people distillation is approached with an almost shamanic reverence.
Of course this is not true for all distillers. Remember that only a very small proportion of the global essential oil production is ultimately destined for therapeutic use, and naturally there are large commercial farms distilling, say, lavandin which will ultimately end up in soap or washing powder. For them the parameters are simply different, and their main focus will be to maximize yield. Quality will not be the main issue and the approach to distillation will be correspondingly different.
So the attitude of the distiller is a big factor in the vibrancy of the end-product, and listed below are some of the things he will bear in mind.
After the process is complete, the spent plant material is allowed to dry before being used as a ‘free’ energy source for a future distillation.
Preparation of the plant material: This is vitally important, but there is no hard and fast rule here because the optimum procedure varies from plant to plant. Rose petals must be picked early in the morning and distilled without delay before the fragrance fades. On the other hand Lavender is traditionally cut, left in the field under the hot sun to dry for three days and turned twice a day before the distillation process can begin. This allows important enzymatic changes to take place in the plant which contribute to the quality of the final oil.
If you go to Provence you can notice different harvesting procedures. Sometimes the plants are left to dry in the field, but you will also notice the presence of combine harvesters pouring plant material straight into large trailers where it is crunched up immediately ready for the still (see photo above). Such processes will be used where speed, efficiency and yield overtake the requirement of therapeutic quality. Again we see a different process for a different end-product.
Speed, pressure and temperature: If you distill under high pressure and high temperature you end up with a better yield but a lower-grade oil. The finest oil will always be produced with a lower pressure and temperature, and the cost will be correspondingly greater.
Distillation duration: I don’t hear this discussed too much and yet it is a major factor. Let’s try to understand why.
As you know, essential oils are composed of many different biochemical compounds. Some of these exist in tiny amounts, and yet it is these trace elements that add to the character of the essential oil, the depth of fragrance, and probably also contribute greatly to its therapeutic efficacy.
During distillation the lighter, more volatile compounds come through first, while the heavier, slower-moving molecules make their stately way through the process at a much more leisurely pace. Commercial pressures could lead to the ‘cutting of corners’, bringing the process to a close before those final few trace elements have made it through to the final product, perhaps in order to fit one extra distillation in the day for the same cost.
The key message here that we should note from all this is that ‘all distillations are not the same’ — they produce big variations in the end product — so again we come back to a theme that we’ve mentioned many times before: the importance of knowing the original source of the oil, and ideally sourcing the oil direct from the grower.