What a lab report can’t smell

In short

• A terpene table is most of what a lab measures for aroma. It isn’t everything you smell.
• Research has traced skunk and gas notes to sulfur compounds, and some savory and sweet notes to other compounds that aren’t terpenes either. The reports NOSE reads don’t list them.
• NOSE compares only what a report measured. So we expect matching to hold best for jars whose smell terpenes lead, and to miss most often on gas, savory and sweet jars. That’s an expectation your votes are testing, not a finding.
• There’s no Gas family, because the reports NOSE reads don’t measure it. Showing one would be a guess.
• A vote can carry up to three smell words. “Didn’t match” beside “Gas or fuel” tells NOSE which smell the report missed.

What the report measures

A terpene panel is a list of named compounds the lab looked for, each with an amount. For aroma, it’s most of what a report gives you, and for good reason: terpenes are the most plentiful aroma compounds in cannabis. But the compounds you notice most aren’t always the most plentiful ones, and a panel only covers the names on its list.

Smells that come from somewhere else

In 2021, a research group traced the classic skunky note to a family of sulfur compounds. Terpenes were the most plentiful aroma compounds in the samples, but the researchers found little sign that they make that smell, and the samples a panel of smellers judged most pungent carried the most of one sulfur compound in particular (Oswald et al., 2021; summary).

In 2023, the same group looked at a wider range of aromas (Oswald et al., 2023). It linked:

• tropical and citrus notes in some cultivars to a different set of sulfur compounds;
• savory and chemical notes to skatole;
• sweet notes to esters;
• and the gassy note mainly to the sulfur family found in 2021.

It also found terpene profiles very similar across cultivars that smelled very different. If that holds for flower, two reports can look alike while the jars don’t smell alike.

Two things are worth knowing about that study. It looked at rosin, a pressed extract, not at flower, so its results may not carry straight over to flower. And most of its authors, nine of fourteen, work for a company that sells flavor blends, which also paid for the work. That doesn’t make it wrong, but it’s part of reading it fairly.

None of these compounds is on the terpene tables NOSE reads. They aren’t terpenes, and terpene panels don’t look for them.

What it means for a match

NOSE compares only what the report measured. Where terpenes lead a jar’s smell, as limonene can for citrus, α-pinene for pine and terpinolene for herbal, the comparison has the right things in hand. Where the smell comes from somewhere else, as gas, savory and sweet notes can, and as citrus sometimes does, the score can be wrong in either direction:

• Two jars can share a terpene mix and still smell different, if one carries a gassy note the report can’t see. NOSE would call them close.
• Two jars can smell alike for that same unseen reason while their terpene mixes differ. NOSE would call them different.

Made-up values, in % of sample. Jar D: myrcene 0.50, limonene 0.30, β-caryophyllene 0.25, linalool 0.10, α-humulene 0.08. Jar E: myrcene 0.48, limonene 0.32, β-caryophyllene 0.24, linalool 0.11, α-humulene 0.08. Jar F: β-caryophyllene 0.40, limonene 0.30, myrcene 0.15, α-humulene 0.12, linalool 0.05. Jar G: myrcene 0.50, α-pinene 0.25, terpinolene 0.15, limonene 0.12, β-caryophyllene 0.10. Scores computed with NOSE’s matcher.

Now suppose Jar E also smells of gas and Jar D doesn’t. They’d smell different, and the score would still be 99. Suppose Jars F and G both smell strongly of gas. They’d smell more alike than 46 suggests. Neither report can show it.

This is an expectation, not a finding. NOSE doesn’t yet know how often it happens, or for which smells. That’s what the votes are for.

Why there’s no Gas family

NOSE sorts terpenes into six aroma families, citrus, earthy, spice, pine, floral and herbal, and every one of them is built from compounds a lab measured. A Gas family would need a number too, and the reports NOSE reads print none for the compounds behind gas. NOSE could estimate one from the terpenes, but an estimate drawn on the fingerprint bar would look like a measurement, and it wouldn’t be one. So the bar shows only what was measured, and gas stays off it.

How your votes help

Under every result, NOSE asks: did the smell and taste match the score? You can answer Matched or Didn’t match, and add up to three words from a fixed list: Gas or fuel, Skunk, Savory or garlic, Chemical, Sweet, Fruity or tropical, Hay, Citrus, Earthy, Spice, Pine, Floral, Herbal. The words are buttons, so there’s nothing to type.

A “Didn’t match” beside “Gas or fuel” says which smell the report missed. Enough of those, and NOSE can see whether matching really does fail most for gas, savory and sweet jars, rather than expecting it. What a vote keeps is on the privacy page.

Sources

The studies this guide draws on.

1. Oswald IWH, Ojeda MA, Pobanz RJ, et al. (2021). Identification of a new family of prenylated volatile sulfur compounds in cannabis revealed by comprehensive two-dimensional gas chromatography. ACS Omega. doi.org/10.1021/acsomega.1c04196
2. ScienceDaily (December 1, 2021). A plain-language summary of the 2021 study above, from the American Chemical Society. sciencedaily.com/releases/2021/12/211201085147.htm
3. Oswald IWH, Paryani TR, Sosa ME, et al. (2023). Minor, nonterpenoid volatile compounds drive the aroma differences of exotic cannabis. ACS Omega 8(42):39203–39216. A study of 31 rosin extracts; its funding and its authors’ interests are stated in the paper. pmc.ncbi.nlm.nih.gov/articles/PMC10601067