Essential Oils and Steam Distillation

Plant Distillation Techniques Essential Oils and Steam distillation

By Jill Mulvaney

When I think about this, I sigh – and stare out the window at the birds on the tree, essential oils, such an enigma. Wikipedia describes them as “a concentrated hydrophobic liquid containing volatile aroma compounds from plants”, a pragmatic answer – a concentrated substance that is repelled from a mass of water (hydrophobic) that has smell or odour (aroma compounds). Apparently they are “essential” as well!

When I’m out walking, I see and feel a plant, reach out and pick a leaf or flower, crush it in my palms, cup my hands, cover my mouth and nose and deeply inhale. The plant and I begin our conversation. We use the silent language of aroma and sensation. How I wish I could translate all that into academic words that make sense, but I have learnt to trust that the plant shares information with each aromatic conversation conducted with mindful body awareness and sensitivity. So maybe it is the soul part of the nature of plants that can speak. Aroma is certainly a powerful conduit of subtle change, 1. I have my Column Still response and reaction. Essential oils are aroma. set up in a sheltered spot in the To be able to steam distil plants I have found or grown myself has garden. I have already cleaned it been a profound experience. Even though the process is quite simple, by distilling rye flour slurry. To do you become part of a magical alchemy of transformation. The energy this I mix 450g of Rye Flour in 4 L of steam changes the chemistry of a plant so that its constituents are of water and pour into the pot. I released into liquefied steam. That in itself is enough, however then, assemble the whole still and heat that liquid releases millions of tiny bubbles of aromatic essential oil. the rye flour mix until it boils. It is lighter than water so floats to the surface and here gathers the It becomes frothy and seeps volatile aromatics – the essential soul of the plant. out the joins. Once it comes The Process of Steam Distillation out of the condenser bucket as distillate, I turn the heat off. Steam distillation is mostly used to produce essential oils. The plant When the Still is cool enough to material is subjected to steam under pressure. It does not come into handle, I dismantle it and scour contact with the boiling water. Water boils at 100°C, steam has a it with Eco Cream Cleanser (it higher temperature than boiling water; a steam scald is worse than a scald from boiling water. contains a citrus oil that cleans the copper). I rinse and dry it Distilling for Essential Oil by Steam Distillation thoroughly, leaving it in the sun to finish the drying process. I’m going to use Rosemary again as I’m taking up where I left off Before I start a new distillation in my last article in the Winter Avena issue Hydrosols and Hydro- distillation. I hope I can illustrate the difference between the two I always distil hot water to check the distillate is tasteless, distillation methods and the difference in the hydrosols produced. odourless and clear. I know I have I use a Copper Alembic Column Still for steam distillation, the only a clean still. difference between this and the one I used for hydro-distillation – the Traditional Alembic Pot Still, is that it has a Column that sits on the pot with a sieve plate at the bottom. The herb is placed in the column; the column is placed on top of the pot of boiling water. The sieve plate keeps the herb material above the water so only steam comes into contact with it.

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2. The pot is 2/3 filled with water and placed on a gas ring to bring the water to the boil. It’s important to have everything at hand for a distillation. I have my water pump on keeping a steady flow of cold water running through the condenser bucket, my sterile beakers and oil separators are ready to collect the distillate. I have a bowl of rye flour paste to seal the joins in my still so I don’t lose precious steam.

3. And of course I have harvested and prepared my herb. The leaves and flowers have been stripped from the stems of the Rosemary and sit fragrantly waiting. It is the same harvest I used for the hydro-distillation

4. I place five good handfuls of rosemary into the column. When the water in the pot is boiling, I carefully remove the onion dome and sit the column on the pot making sure it is square. I place the onion dome on the column, checking its level. Because the Rosemary is cold I have a little time before the steam works its way through.

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5. I work quickly now. If I lose any steam, I will lose precious essential oil. I quickly but carefully seal the join between the column and the pot and the column and the onion dome with the rye flour paste. As the copper heats it bakes it dry and seals the joins. By the time I have done this, the onion dome is hot which means the steam has spiralled up the column, the heat burst open the cells of the plant and the volatile oils released and carried in the steam. The steam spirals in the onion dome, any particles of dust of physical matter falls back. The steam flows down the bird’s beak, through the connecting pipe and into the condenser coil.

6. Just as in the hydro distillation, it is vital to have a steady stream of cool water runing around the condenser coil throughout the whole distillation. Actually it is even more important when distilling with steam, it’s a hotter faster distillation. The water needs to be boiling vigorously to create a good body of steam under pressure to burst the cellulose of the plants to release the essentail oil. The distillate will flow faster than a hydro distillation. The essential oil will be released in the first 200ml of distillate.

7. On a 10 L still I collect 500ml of Hydrosol. The oil has been expelled from the mass of water and floats to the top. The hydrosol is not as milky as in a hydro distillation and of course there is significantly more oil released. The aroma is stronger, sharper and more intense. I check the pH. Depending on my purpose I may continue distilling for hydrosol. There will be very little oil in the next 500ml but often the hydrosol is still of a good aroma, flavour and pH. As soon as the pH increases I stop the distillation.

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8. This is the best part! These are my oil separators. One is 500ml and other 60ml. They both sit in rings and are clamped onto a retort stand. I use the larger separator when distilling botanicals that will yield between 3-10ml of oil on 500ml - Rosemary, Eucalyptus, Lavender, Clary sage, Manuka, Thyme, Peppermint……. The smaller one is to collect precious drops – Rose Geranium, Melissa, Rose, Lemon Verbena, Chamomiles, Yarrow…..

9. I pour the hydrosol into my large oil separator. As I do this, the oil is mixed with the hydrosol again. I watch in awe as it settles. Millions of miniscule bubbles stream to the surface. They are tiny drops of essential oil that the water has released like a sponge being squeezed. The oil collects at the top, often a golden colour. The hydrosol settles and clears. At this stage I’m aware of the energetic lively nature of this process and feel a deep sense of respect and awe.

10. A clean beaker is placed at the bottom of the oil separator. I carefully turn on the tap to release the hydrosol watching carefully to turn off as the oil collects at the bottom once the hydrosol has been released! There, now I have my reward, 3ml of precious essential oil! I will need to distil another 3 times to get my 10mls! However I will also have 2 litres of fragrant Rosemary hydrosol.

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11. There is moisture still in the mix. I don’t want to leave it in as it may cause a bacterial growth and degrade my oil. I put my test tube with the oil in the freezer. This dries the oil out and freezes any moisture. I pour the oil off into an amber dripulator bottle. It goes into my precious collection of my own distilled essential oils. By this time next year I hope to have 25 of my own distilled oils. I already have 50ml Eucalyptus, 50 ml Peppermint Eucalyptus, 10 ml Rosemary, 3 ml Lemon Verbena, 10 ml Lime, 10 ml Manuka 10ml Ginger and 10ml Thyme In spring I will be harvesting German Chamomile, Rosemary before flowering, Orange, Grapefruit & Lime flowers, spring Manuka and Kanuka, Tarata, Rose Geranium, Bay leaves, Melissa. In summer it will be Lavender, Clary sage, Lemon Verbena, Basil, Peppermint, Helioscrysum, Yarrow, Angelica and some trimming of the citrus as the fruits form tiny balls – for Petitgrain. That’s enough!

Table 1 Hydro-Distillation Steam-Distillation Plant is subjected to boiling water Plant is subjected to pressure and steam Distillation is slower and cooler Distillation is fast and hot Hydrosol is often milky Hydrosol is mostly clear The distillate shows little essential oil floating on the surface, Essential oil is evident on top of the hydrosol and is removed. most remains in suspension Aroma is complex as are the flavours When the oil has been removed, the aroma of the hydrosol is light and delicate, the flavour less intense

Nothing has been separated from the distillate – it remains Has a dual result – Essential oil and the Hydrosol, however the complete hydrosol has lost an element – the essential oil

Every distillation is different depending on season, soil, and climate. This table is an approximate guide to volume’s and quantities. An idea of plant volume – 3 mature Lavender augustifolia harvested – flowering tops weighs 1kg approx. Lavender is a high yielding plant. 1kg of flowers yields approx 25-30ml of oil. Most other plants I distil yield a quarter to half that amount.

Table 2 Size Plant Lavandula Approx. ess. Hydrosol ABOUT THE Quantity angustifolia oil yield yield AUTHOR: Jill currently resides 5 L column 250g or 2-3 1 mature plant 1-2ml 250-400ml on Waiheke Island handfuls – flowering with her partner tops Charlie. Together 10 L column 500g or 5-6 1.5-2 mature 3-5ml 500-1.5 L they run distillation handfuls plants workshops and demonstrations 20 L column 1.5 – 2 KG 4-6 mature 5-15ml 3-5 L throughout New Zealand and sell plants alembic stills worldwide. Go to their website for more 40 L column 5 KG 8-10 mature 20-50ml 5-10 L information, to purchase an alembic plants still or see if there's a workshop 150 L 20-30KG 60-90 mature 200-500ml 20-50 L coming to your town soon! column plants

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