Distilling Catnip Essential Oil from Fresh Leaves
After making catnip insect repellent using fresh leaves and alcohol, I found that although it was effective, it was not very effective. I though that adding a more concentrated essential oil could improve my bug repellent mixture.
This page describes my first efforts distilling fresh catnip leaves to get catnip essential oil.
What is Catnip
Catnip (Nepeta cataria), catmint, catnep, is a hardy perennial herb of the mint family (Labiatae).
Distribution of Catnip
Catnip originated in Europe and parts of Asia, and was planted by settlers in colonial gardens in North America. Catnip escaped to the wild and is now common across Canada and the U.S..
Catnip tea was widely used as a soothing drink.
Catnip is cultivated and sold for use by cat owners. It is grown mainly in the Pacific Northwest and parts of Canada, particularly in Alberta and British Columbia.
What is steam distillation
Steam distillation is a widely used method of extracting essential oil from plant material when the products are temperature sensitive and could be damaged by too high a processing.
In the past it was a widely used method but has been replaced mostly by vacuum distillation. It remains the most common way of extracting essential oils and perfume components from plant material.
It is also used by the petrochemical industry to separate various volatile compounds from petroleum.
The process is simple. Steam is passed through vegetable matter and this causes essential volatile oils to evaporate and mix with the steam. This mixture is then passed through a condenser and the condensed liquid collected.
This condensed liquid is mostly water mixed with a small amount of oil and other substances which evaporated from the plant material.
The oil collects at the top of the liquid and can be decanted or otherwise collected.
How much oil can be produced this way?
An average concentration of oil to fresh plant material ranges between .02 to 10% The high figure is for myrrh which is quite an oily material and is in dry form. Figures from aroma web.com
If I distill 1 kilo of catnip leaves I can hope to get .3 grams of essential oil if the catnip has a concentration of .3% oil in the leaves. (one ounce is roughly 28 grams) so yields are very small. Since the leaves are very young I expect the concentration of oil is very small, probably less than .3%. The low yields explain why essential oils are expensive.
My distillation apparatus.
To produce steam I'm using my pressure cooker. It has a convenient vent at the top on which I can attach a plastic tube. Since my steam will not be under pressure it will be at boiling temperature and the reinforced tubing will be sufficient for my experiment. I used a hose clamp to fasten the tube to the stem vent hole on the pressure cooker.
Instead of piping steam into a second container of leaves as in commercial set ups, I'm just going to separate the leaves from the steam with a little steam rack and use only one container. The leaves will just sit above the boiling water. There will not be any pressure in the system.
I have a roll of 3/8 copper tubing left over from making the SCAMP Sailboat project and will use that to carry the steam to the condenser and in fact to make the condenser.
To condense the steam I will lead the copper pipe into a water container and use the end of the pipe to drip the condensed liquid into a collecting jar.
I used an old fiberglass flower pot and blocked the hole with a piece of plywood with a hole the size of the pipe.
I glued the wooden piece on the bottom of the pot with silicone sealer to cover the existing hole, and gooped a whole lot of silicone sealer around the pipe from the inside of the pot. This sealed the pipe as it went through the hole in the wood. It turned out to be waterproof and worked very well.
If I was going to do more steam distillations, I would set up my condenser so that cold water flowed in the bottom and warm water flowed out from the top of the condenser. The water heats up very quickly with the steam flowing through and condensing.
I had to dish out hot water and replace it with cold, while the still was in use.
I put a jar under the pipe to collect the liquid that condensed.
This is what the whole set up looked like. The pot is on the left sitting on the stove. There is a plastic pipe connected to the pot on the steam valve of the pressusre cooker. The copper tube connects the pot to the water filled condenser (flower pot) and extends under the pot to drip in a glass jar. The flower pot sits on an oven rack over the sink. I'm ready to go.
I have many patches of catnip on the property. The cats like it but it is also a really good bee and butterfly plant.
I put a steam rack in the bottom of the pot and filled the rest with as much catnip as I could stuff in. Winston is acting as quality control agent here. I estimate that I got about 3 pounds of leaves in the pot.
I added 2 litres of water to the the bottom of the pot.
After closing the lid tightly I turned on the heat and the temperature gradually went up. After about 15 minutes the copper pipe started heating up. Steam was getting through. The water in the condenser also started to heat up and after about 20 minutes I had a steady drip of milky water collecting in the jar under the condenser.
I kept going for about an hour at medium heat. By that time I had over a litre of water. I did not want to run dry and risk damaging my pressure cooker, so I stopped the heat. I found that there was about a cup of liquid on in the bottom when I opened it so it was just right. I guess the rest of the water settled in the leaves and some escaped as steam.
Did I get any Essential Oil?
I let the condensed liquid settle for a day and checked it. The top of the liquid in the large jar is covered by a thin coat of oil. I guess that's my catnip essential oil!
Commercial Catnip essential oil, containing mostly Nepetalactone, but also citral, geraniol, citronellol, nerol, thymol and limonene, is extracted by steam distillation. I expect that's what I have.
It was hard to photograph the oily film. It covers the whole of the top and seems thicker in some spots. I'll let it settle for a few days to see if more collects at the top.
Because nepetalactone is volatile catnip essential oil will lose its effect over time. It should be stored in a closed container preferably in a cool place.I'm planning to scoop up the oil and put it in with my alcohol catnip insect repellent mixture
Research has shown that both mosquitoes and some biting flies as well as deer ticks are deterred from biting by catnip. Here is a link to the abstract.
More recently, research done at Iowa State Univerty, showed that catnip was 10 times more effective at repelling mosquitoes than DEET.
NOTE: Catnip has not been shown to be poisonous for humans or cats but essential oils are highly concentrated and could be toxic or irritating, they should not be eaten by humans or animals.
This article is provided for information and entertainment only. Most of the reported uses of catnip have not been researched or properly documented. This article is not intended to replace medical or veterinary help. If you or your cat are sick see a doctor or vet.