Compounds · Other compounds · Microbial origin
Trimethylamine
Also known as TMA · N,N-Dimethylmethanamine — an analysis may use any of these names
Fishy, a light ammonia. In good fish sauce it is just one note; in spoiled fish sauce it is everything.
- CAS
- 75-50-3
- Formula
- C3H9N
- Molar mass
- 59.11
- Odour threshold
- 0.500 ppbin air
- Boiling point
- ≈ 3 °C at atmospheric pressure
This compound boils at 3 °C, so it is lighter than any ordinary essential-oil component. It lies outside the 150–290 °C band, so the marker stops at the left edge — not because that is where it sits, but because the axis does not reach that far.
The two axes are 44 points apart. Volatility tells you whether the compound leaves a surface early or late; the threshold tells you how much of it the nose needs before it notices. When the two sit this far apart, they explain things the percentages on an analysis cannot explain on their own.
Where it comes from
Biosynthetic pathway: Microbial origin — made by bacteria and yeasts, not by plants.
About the threshold figure
Low, and since this compound boils at 3 degrees it exists as a gas under ordinary conditions — the combination of the two makes the smell carry very far.
Published thresholds differ by several orders of magnitude, because of differences in measuring method, sample purity and panel. The figure here is an order of magnitude for relative comparison, not a measurement. We give it only for compounds where the literature broadly agrees — 52 of the 106 compounds in the library. The rest are left blank rather than guessed.
Why it sits where it does
A three-carbon amine, an extremely small molecule boiling at 3 degrees, so under ordinary conditions it exists as a gas. It spreads further and faster than any other compound on this list.
Where else you meet it
Fish sauce, fermented shrimp paste, old sea fish, and some cheeses.