Compounds · Other compounds · Heat (Maillard reaction and pyrolysis)
2-Acetyl-1-pyrroline
Also known as 2AP — an analysis may use any of these names
Freshly cooked sticky rice, pandan leaf, popcorn. A single molecule behind a whole region of food memory.
- CAS
- 85213-22-5
- Formula
- C6H9NO
- Molar mass
- 111.14
- Odour threshold
- 0.100 ppbin water
- Boiling point
- ≈ 181 °C estimated
For this compound the two axes sit close together. Volatility tells you whether it leaves a surface early or late; the threshold tells you how much of it the nose needs before it notices.
Where it comes from
Biosynthetic pathway: Heat (Maillard reaction and pyrolysis) — fire breaks large molecules into ones you can smell.
2-Acetyl-1-pyrroline is a case that takes two routes. In a pot of sticky rice it forms through heat. But pandan leaf makes it with enzymes at ordinary temperature, without fire — which is why fresh pandan leaf already smells of sticky rice.
About the threshold figure
At the level of parts per trillion to parts per billion. A tiny amount defines the whole smell of a pot of sticky rice.
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 small molecule with nitrogen in a five-membered ring. Very light and quick to evaporate, but the human nose detects it at below one part per billion, so it still stands out among everything else.
Where else you meet it
Sticky rice, pandan leaf, popcorn, bread crust, and some fragrant rice varieties.
Dictionary entries that mention this compound
About the boiling-point figure
Not yet cross-checked against a primary source. The value is provisional, used to place the compound on the volatility axis. Why this detail matters