Set up a still and a batch of jasmine flowers. Heat it. You will get a scented liquid, and that scent is not jasmine.
It is the clearest example in the whole trade of choosing the wrong method.
What is lost
The smell of jasmine is built from three main groups of compounds. Benzyl acetate gives the waxy sweet part. Linalool gives the soft floral part. And indole gives the indolic layer that newcomers describe as slightly dirty.
It is that third layer that sets jasmine apart from every other white flower. Take it away and an anonymous sweetness remains.
Saying that indole is destroyed by heat is not accurate — it boils at around 254 degrees and still appears in some crude distillates. The problem lies elsewhere.
Benzyl acetate and the light esters are hydrolysed in hot steam, so the balance between the three groups shifts badly. At the same time, the yield is so low that an enormous mass of flowers must be processed, and flowers waiting their turn are already breaking down on their own. What comes out of the condenser is not a version lacking indole but a version with the wrong proportions — and with white flowers, proportion is everything.
Why this is a general problem for white flowers
Jasmine is not an isolated case. Tuberose, orange blossom, night-blooming jessamine and ylang-ylang all face a similar problem to varying degrees.
What they share: white flowers tend to rely on large, polar, easily altered molecules. That is exactly the group of compounds that tolerates heat least.
One simple observation explains it all: the flowers that give off their scent most strongly at night, when temperatures are low, are often the ones that tolerate heat worst in processing.
The commercially viable method
Solvent extraction at low temperature. The flowers are soaked in a volatile solvent to obtain a concrete, which is then washed with alcohol to separate the absolute.
The product is expensive, thick, dark, and clearly indolic. It is also not called an essential oil in the narrow sense, because it retains solvent traces at the parts-per-million level.
Enfleurage gives a result even closer to the living flower, because the whole process takes place at room temperature. But it is so labour-intensive that it has almost disappeared from commercial production, so on the market you will only find absolutes.
What this tells you when buying
If you see a bottle labelled jasmine essential oil that is clear, thin and cheap, it is almost certainly not jasmine. It may be a synthetic fragrance, another essential oil with fragrance added, or a distillate of something else.
The quickest check is not the price but smelling for the indolic layer. If the sample is only sweet and clean, with nothing that makes you slightly uncomfortable, the most characteristic part of jasmine is missing.
An honest seller will write the word absolute on the label and explain why.