Citral
Also written geranial, neral, citral (geranial and neral)
Quick answer
The compound that smells of lemon without being from a lemon — the reason lemongrass, some basils and fresh ginger share a citrus note that none of them gets from citrus.
What it does
Citral is intensely lemony, and it is a mixture of two closely related forms — geranial, which is sharper and more assertively lemon, and neral, which is softer and slightly sweeter. It is the dominant aromatic of lemongrass and gives lemon balm, lemon verbena and lemon myrtle their names. It is the clearest case in this catalogue of a smell being a molecule rather than an ingredient: a dish flavoured with lemongrass and one flavoured with lemon zest share a compound and share almost nothing else, because the zest brings limonene and acid along with it and the grass does not.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- high
- Fat solubility
- high
- Water solubility
- low
- Heat stability
- low
Citral is volatile, heat-sensitive and prone to oxidation, and it is also unstable in acid — which is a genuinely unusual combination and explains several things at once. Lemongrass is bruised and added to a curry rather than simmered for hours, because a long open cook takes it; dried lemongrass is a poor shadow of fresh for the same reason. It is fat-soluble, so it carries well into coconut milk and into an infused oil, which is how Southeast Asian cooking mostly deploys it. And its instability in acid is why a lemongrass infusion made with lime juice in it tastes flatter than the same infusion soured afterwards — the order of operations matters in a way it does not for a stable aromatic.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- LemongrassPrincipal component
The dominant aromatic and the entire reason the grass is used.
- BasilContributing component
Prominent in lemon basil and slight in sweet basil. Basil cultivars differ mostly in the balance of citral, estragole, linalool and eugenol.
- GingerContributing component
The bright lemony edge of fresh ginger, and one of the things lost on drying — which is part of why dried ginger reads as hot where fresh reads as fresh.
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Limonene
The other compound people call citrusy, and a different smell: limonene is orange peel and citral is lemon. Both are in citrus fruit and only limonene is in black pepper, which is why cracked pepper smells bright and never lemony.
Questions this page answers
- what is citral
- what does citral do
- which spices contain citral