Reference point
Squeeze a piece of Nam Roi pomelo peel hard, so the oil sprays out.
Do this before you read on. An entry only works when you have just smelled the thing.
Bright and cold for the first three seconds, as if someone had just opened a window. After that beat comes a fine bitter layer along the edges, then a thick sweet base that lime peel lacks entirely. The three layers arrive in order and leave in order, so if you smell a little slowly you will catch the whole structure rather than just an impression.
This is not the smell of the pomelo segments. The flesh is sour and watery, with almost no oil; everything you smell sits in the outermost layer of the peel, in tiny pockets that burst when squeezed. Nor is it the dried pomelo peel people boil for washing hair — that has lost all its brightness and kept only the bitterness.
Peel left overnight is almost useless. Limonene, which makes up most of it, oxidises very quickly in air, and what it turns into smells of damp paper. That is why market sellers always squeeze the peel in front of the customer rather than in advance.
How to smell it
Choose a pomelo with its stalk and tight skin. Break off a piece of peel the size of a fingertip, fold it with the outer side facing out, and squeeze hard about two hand-spans from your nose. You will see a mist of oil spray out. Smell within the first three seconds and write down three words. Wait thirty seconds and smell the same piece again — the brightness has gone, and what remains is the bitterness and the sweetness. Two sniffs half a minute apart are enough to understand why people say a smell has layers.
Why this one is hard
Beginners often smell the whole fruit instead of squeezing the peel, and conclude that pomelo has little smell. The mistake is that the oil sits in sealed pockets and does not come out on its own; you have to break them to have anything to smell. This is a lesson for the whole citrus family.
Don’t confuse with
This entry
Crushed pomelo peel
Citrus family
Pomelo has a sweet lining behind and a bitter note at the edges; king orange is evenly bright, without that lining. Squeeze both at once, one in each hand, and you will hear it immediately.
Scientific note
Pomelo peel oil sits in secretory pockets just under the surface, so a squeeze is enough to release it, with no distillation needed. The main component is limonene, but the character comes from nootkatone — a fifteen-carbon sesquiterpene ketone boiling at around 290 degrees, against 176 for limonene. Its molecular weight is only about sixty percent higher, but the ketone group and larger skeleton are enough to push the boiling point up by more than a hundred degrees. It is present in very small proportions and stays long after the bright part has gone.
In Vietnamese life
Pomelo peel is one of the few aromatic materials Vietnamese people have used continuously for generations without calling it an aromatic material: hair-washing water, steam baths for colds, Tet sweets. One object, three settings, and in each of them people recognise it at once without ever having been taught its name.