Reference point
Open a bag of freshly popped popcorn and smell the steam rising.
Do this before you read on. An entry only works when you have just smelled the thing.
Sweet, roasted, with a buttery note and a thin papery layer. It rises very fast and then fades within a few minutes.
That feeling of a burst that dies away is real, but it does not come from volatility. The dominant compound of popcorn is 2-acetyl-1-pyrroline, the very molecule behind freshly cooked sticky rice, and it boils at 181 degrees — the middle stage.
What makes popcorn seem fast is the way it is released: hundreds of kernels pop almost at once and let everything out within seconds, and then there is nothing to top it up. A pot of sticky rice keeps steaming for dozens of minutes. The same molecule, two ways of release, two impressions of time.
It is also one of the few smells almost everyone recognises at once, without having to learn it.
How to smell it
Smell as soon as the popping stops, a hand’s span from the mouth of the bag. Smell again five minutes later — the roasted part has dropped sharply, and only the papery and buttery layers remain.
Why this one is hard
Because it is so familiar that people do not analyse it. Ask what popcorn smells of and most people answer “popcorn” — a loop that shows there is not yet the vocabulary to separate its parts.
Don’t confuse with
This entry
Popcorn
Gourmand family
The same dominant molecule, 2-acetyl-1-pyrroline. Popcorn has an extra roasted layer from the fire; sticky rice only reaches 100 degrees, so it has no such layer.
Scientific note
Corn kernels pop at around 180 degrees, hot enough for both the Maillard reaction and caramelisation. The main product is 2-acetyl-1-pyrroline — the same compound behind the smell of sticky rice — plus pyrazines for the roasted note. Popcorn and sticky rice share their dominant molecule although one comes from fire and the other from steam.
In Vietnamese life
Popcorn came to Vietnam through cinemas and is now a street snack. Before that, the puffed rice and puffed sticky rice made in hand-cranked popping machines were what Vietnamese children knew — and they share the same dominant molecule.