"My frankincense smells like sage" — your theory is right, and it is not what happened here

Someone posted on r/DIYfragrance with a theory, an observation and a specific question:

"A few years ago i bought a black pepper EO and it really just smelled like lemon, only lasting as much as lemon does. I've read that this is because a low effort distillation will only extract the highly volatile molecules (terpenes, pinenes, harsh and citrusy stuff)."

"I have got two new essential oils: patchouli (light) and frankincense. The patchouli EO has zero of that harsh freshness… The frankincense oil on the other hand smells like sage. Green, harsh, dirty citrusy, even minty."

"Does this mean that my patchouli oil is high quality? Does this mean that my frankincense oil is low quality?"

His theory can be checked, and the answer is: the mechanism is real, and it is almost certainly not what happened here.

The short version

• The mechanism he describes is real. A 2019 study measured lemon thyme essential oil at different hydrodistillation times: longer distillation lowered the monoterpene percentage and raised the sesquiterpene percentage. A short run does favour the light molecules.
• That same paper also says the effect saturates: hydrodistilling lemon thyme "longer than 60 min is useless".
• What actually goes wrong with commercial frankincense has been measured, and it is uglier. A 2022 study used GC-MS and chiral GC-MS on 21 commercial and 2 lab-distilled frankincense (Boswellia carteri) oils.
• Among the 21: 6 adulterated with synthetic limonene, 3 with synthetic octyl acetate, 3 with castor oil, 2 contaminated with frankincense resin, 2 with Boswellia occulta, 1 with Boswellia serrata, and 1 with phthalates.
• And octyl acetate's odour field reads: green, earthy, mushroom, herbal, waxy, fruity, apple. Which is what he described.
• The database holds 14 frankincense records across 4 different CAS numbers. The main record's first odour descriptor is terpenic.
• So terpenic is not a defect. It is how this material is recorded. And his green note is likelier to come from species or adulteration than from a lazy distillation.

About 9 minutes.

His theory is right

Credit where it is due: that mechanism has been measured.

Jurevičiūtė and colleagues studied lemon thyme (Thymus × citriodorus) essential oil at different hydrodistillation times in Natural Product Research in 2019.

What they found:

Elongation of hydrodistillation time decreased percentages of monoterpenes but increased percentages of sesquiterpenes in essential oil.

Monoterpenes are the light ones (lower boiling, out first) and sesquiterpenes the heavy ones (out later). So a short distillation does bias what you collect toward the light end.

Which is exactly what he read.

And the same paper has a sentence he did not read:

Results showed that the hydrodistillation of essential oil from lemon thyme longer than 60 min is useless.

The effect saturates. It is not a dial you can keep turning to buy depth.

(To be clear: that study is lemon thyme, not frankincense and not black pepper. Oil gland structure and the boiling-point spread of the constituents differ between plants, so that 60 minutes does not transfer. I cite it to establish that the mechanism — distillation time shifting the monoterpene-to-sesquiterpene ratio — exists.)

But that is not commercial frankincense's problem

This section is the substance of the piece.

Ojha and colleagues did something direct in Plants in 2022: they compared 21 commercial frankincense (Boswellia carteri) essential oils against 2 they distilled themselves, using GC-MS and chiral GC-MS.

The purpose was authentication. The results:

Found among the 21 commercial samples	Count
Adulterated with synthetic limonene	6
Contaminated with synthetic octyl acetate	3
Adulterated with castor oil	3
Contaminated with frankincense resin	2
Contaminated with Boswellia occulta species	2
Contaminated with Boswellia serrata species	1
Phthalates, plus a cheap essential oil of similar composition	1
Copaiba resin + frankincense resin + synthetic octyl acetate	1
B. serrata, further adulterated with castor oil and frankincense resin	1

(These categories overlap — the last two rows are compound cases already counted above — so I cannot derive "how many of the 21 were clean" from the abstract. I list the items as the paper states them.)

Note three of those entries: synthetic limonene, synthetic octyl acetate, Boswellia occulta.

All three make a bottle of frankincense smell greener, sharper and less like what you expected.

Octyl acetate is that "sage" note

This is the piece's most direct correspondence.

He described his frankincense as "green, harsh, dirty citrusy, even minty" and "smells like sage".

And the database's odour field for octyl acetate reads:

green, earthy, mushroom, herbal, waxy, fruity, apple

Green, earthy, herbal.

And octyl acetate has two routes into a bottle of frankincense:

1. Synthetic, added deliberately — the paper found it in 3 samples, plus one more as part of a compound adulteration.
2. Natural, because it is not B. carteri — Boswellia occulta is naturally rich in octyl acetate, and the paper found that species contaminating 2 samples.

Somebody in the thread was already pointing at this:

"The extraction methods often make a difference too. For example, take Boswellia Occulta - A rarer type of frankincense (olibanum). The essential oil has much sharper top notes, but a CO2 extract has a much rounder profile with a fuller bodied, deeper scent. Same tree, same resin but different scent profile."

They had the species right and the extraction point right.

The paper adds the half they did not mention: those sharp top notes can also have been put there as synthetic octyl acetate.

The database holds 14 "frankincenses"

One more thing complicates the question: the name does not denote one thing.

Querying records whose name contains frankincense, olibanum or boswellia returns 14, spanning four different CAS numbers:

CAS	Records
8016-36-2	frankincense oil (93 suppliers), frankincense absolute
8050-07-5	frankincense resinoid (63), frankincense gum, frankincense resin
97952-72-2	Boswellia serrata oil, gum and CO₂ extract
89957-98-2	Boswellia carteri resin extract

Four CAS numbers, one common name. The same class of problem as the jasmine piece, and the same rule as check the CAS, not the name.

And the main record's odour field is worth reading:

frankincense oil (93 suppliers): terpenic, incense, peppery, spicy, woody old wood…

Terpenic is the first descriptor.

So to his question — are higher-quality oils less terpenic — the database's answer is that frankincense oil is recorded as terpenic-first. Terpenic is not a signal of a defect.

(Incidentally, the frankincense gum record's odour field includes fresh. Under one common name, one of the records is "fresh".)

What he should actually do

The thread's four replies together give a decent answer; here it is as something executable.

1. Establish which species you bought.

If the seller writes only "frankincense oil" with no botanical name, you do not know which of those four CAS numbers you have. The odour differences between B. carteri, B. serrata, B. papyrifera, B. frereana and B. occulta are far larger than "quality differences" within one species.

2. Do not use terpenic-ness as a quality indicator.

The thread's first reply put it plainly:

"scent profile isn't tied firmly to quality."

And the database agrees: the main record's first descriptor is terpenic.

3. Change the extraction, not the "grade".

What he wants is a deep, rich frankincense without green freshness. That is not a quality question but an extraction question. The commenter was right that a CO₂ extract from the same tree is rounder than the steam-distilled oil. And the resin forms — resinoid, resin, gum — are separate records in the database.

4. Smell it at different dilutions.

The second reply asked a good question: "Did you smell your oils in different dilutions?"

We worked through dilution arithmetic last round: a material shows different facets at 1% and at 10%, and a sharp top note will bury everything at high concentration.

5. If you suspect adulteration, that is a different problem, and you cannot smell it.

That paper used GC-MS and chiral GC-MS, the chiral analysis being there to look at enantiomeric distribution — one of the strongest tools for separating natural from synthetic.

Your nose cannot do that. We've written about what GC cannot protect you from; this is the other side of it: some things only GC can do.

What you can do is buy from reputable sellers and ask for the botanical name.

Collecting it up

• "A lazy distillation extracts only the light molecules" is a real mechanism, and it has been measured.
• But the effect saturates, and that study was a different plant.
• What has actually been measured in commercial frankincense is adulteration and species confusion: across 21 samples, synthetic limonene, synthetic octyl acetate, castor oil, phthalates and three different Boswellia species.
• His "green, sage-like" description matches octyl acetate's odour field, and octyl acetate reaches a bottle by two routes, one natural and one not.
• "Frankincense" is 14 records and 4 CAS numbers. Ask for the botanical name before buying.
• Terpenic is not a low-quality signal. It is the material's first descriptor.

What this doesn't establish

I have not smelled his bottle, or any frankincense. All of this is written against his text, database fields and two papers.

"His bottle might be B. occulta or contain octyl acetate" is a hypothesis, not a diagnosis. I list possibilities, and the only way to know is to analyse that bottle.

Ojha's study covered 21 commercial Boswellia carteri oils. That is a particular sample, not a random draw from the market, and the paper does not say how those 21 were chosen. "Commercial frankincense is often adulterated" is a stronger claim than that paper supports, so I have not written it.

Those categories overlap and I cannot produce a clean total. The abstract does not state how many samples were free of findings.

Jurevičiūtė's study is lemon thyme. The 60-minute conclusion belongs to that plant and that apparatus. The direction of the monoterpene-to-sesquiterpene shift is general; the numbers are not.

"Terpenic is not a defect" refers to how the database describes it. It does not mean any terpenic-smelling oil is good — it means you cannot judge by that alone.

The octyl acetate correspondence comes from setting his description beside the database's odour field. He did not say "octyl acetate", and sage's own main constituents (thujone, cineole and others) are a different class of molecule. Both can give a green herbal impression, which does not mean what he smelled was octyl acetate.

The thread's account of B. occulta CO₂ versus essential oil is a commenter's experience, and I did not verify it.

References

P. K. Ojha, D. K. Poudel, A. Rokaya, R. Satyal, W. N. Setzer, P. Satyal, Comparison of Volatile Constituents Present in Commercial and Lab-Distilled Frankincense (Boswellia carteri) Essential Oils for Authentication, Plants, 11(16), 2134 (2022). PMID 36015437. doi:10.3390/plants11162134

R. Jurevičiūtė, K. Ložienė, M. Bruno, A. Maggio, S. Rosselli, Composition of essential oil of lemon thyme (Thymus × citriodorus) at different hydrodistillation times, Natural Product Research, 33(1), 80-84 (2019). PMID 29394873. doi:10.1080/14786419.2018.1434642

Related: octyl acetate, frankincense, batch variation, what GC cannot protect you from.