Ingredient

Lime

A lime is not a substitute lemon. It is more acidic, more bitter, and its aromatic profile is entirely different — floral, resinous and slightly medicinal where a lemon is clean and bright. Swapping one for the other changes a dish rather than adjusting it.

Where the difference actually lies

Both fruits are dominated by citric acid, and lime is usually slightly more acidic. But acidity is the least interesting difference: what separates them is the oil in the peel.

Lemon peel oil is dominated by limonene and gives that clean, sweet-sharp citrus smell. Lime peel carries limonene too but alongside a group of terpenes that read as resinous, piney and faintly bitter. That is why lime tastes "greener" and why it suits chilli, coriander and fish sauce in a way lemon does not.

Lime juice also loses its character faster than lemon juice once squeezed, going flat and faintly stale within hours. Squeeze it as you need it.

The limes you will meet

Persian lime

The common seedless supermarket lime. Larger, thicker-skinned, juicy, moderately aromatic.

Key lime

Small, round, thin-skinned, seedy, much more aromatic and more acidic. What key lime pie is properly made from.

Makrut lime

Knobbly, almost juiceless, grown for its leaves and zest. The leaves are a foundational Thai ingredient and there is no substitute for them.

Calamansi

A small orange-fleshed Philippine citrus, sharper and more fragrant. Worth seeking out.

Finger lime

Australian, cylindrical, filled with tiny juice vesicles that burst like caviar. A garnish rather than a workhorse.

Getting more juice out

A lime is meaner than it looks.

1. Choose fruit that is heavy for its size with thin, smooth, slightly glossy skin. Thick knobbly skin means less juice.
2. Bring it to room temperature. A fridge-cold lime yields noticeably less.
3. Roll it firmly under your palm on the worktop for a few seconds to rupture the juice sacs.
4. Zest it before you cut it. This is the step most often forgotten and the zest is the more valuable half.
5. Cut lengthways rather than across the equator, then squeeze — the segments release more readily this way.
6. Squeeze cut side up in your hand so the pips stay behind, or use a hand press.

Where lime rather than lemon

• With chilli, coriander and fish sauce, where lemon tastes wrong and lime tastes inevitable.
• On grilled or fried fish and seafood, particularly with anything spiced.
• In a marinade for pork or chicken, with garlic and cumin.
• Over sweet tropical fruit — mango, papaya, melon, pineapple — where it supplies the missing acidity.
• In anything set with acid rather than heat, where the flavour has to carry a whole dish.
• Zested into a rich, sweet pudding, where it cuts more sharply than lemon.
• In drinks, where the aromatic bitterness of the peel is doing most of the work.

Common questions