Kaffir lime leaves and lemongrass in beer

Two citrus aromas from very different plants

Kaffir lime leaves (also called makrut lime leaves) smell sharp, green and intensely lime-like. Much of that comes from citronellal, the same compound that gives citronella its smell. Lemongrass is softer and sweeter, with a lemon sherbet note from citral, a mix of geranial and neral.

Neither adds sugar or acid. They add aroma, plus a little bitterness or grassiness if you push them. Think of them as a dry hop from the spice shelf: powerful, quick to extract and easy to take too far.

Finding good leaves and stalks in India

Lemongrass grows easily across Kerala, the north east and in many home gardens. It is sold fresh in most city vegetable markets. Kaffir lime leaves are harder to find but turn up in Thai and north eastern grocers and online. A small potted kaffir lime tree will keep a homebrewer supplied for years.

Fresh beats dried for both. Dried lemongrass loses its brightness and can taste of hay. Dried lime leaves keep their aroma better, but use about half again as many. Frozen lime leaves are almost as good as fresh, so freeze a bag when you find them.

When to add them

Lemongrass holds up to some heat. Bruise the lower, pale part of the stalk with the back of a knife, chop into short lengths and add it in the last five minutes of the boil or to a whirlpool at around 80 °C. Discard the tough green tops; they taste of grass.

Kaffir lime leaf is best added cold, after fermentation, like a dry hop. Tear the leaves along the central vein to release oil but leave them in pieces large enough to remove easily. Three to five days of contact is plenty. Longer contact pulls out a green, bitter edge.

The one floor detail to remember: remove the central vein of the lime leaf if you can. It is tough and carries much of the harsh, woody bitterness.

How much for a 20 litre batch

These are starting points, not rules. Plant material varies a lot by season and freshness:

• Lemongrass: 2 to 4 fresh stalks (roughly 30 to 60 grams of trimmed pale stalk) at flameout for 20 litres.
• Kaffir lime leaves: 4 to 8 fresh leaves in the fermenter for 20 litres.

If you are unsure, make a tincture. Soak a few torn leaves or a chopped stalk in 100 millilitres of vodka for two days, strain, then add measured drops to a glass of the beer until it tastes right. Scale up to the batch. It takes the guessing out of dosing.

A worked lime leaf witbier for 20 litres

Here is a simple starting recipe to try the method, aiming for about 1.048 original gravity and 12 IBU:

• 2.2 kg Pilsner malt (54%)
• 1.7 kg flaked wheat (41%)
• 0.2 kg flaked oats (5%)
• A low alpha noble-type hop at 60 minutes to about 12 IBU
• 10 grams freshly crushed coriander seed and 3 bruised lemongrass stalks at flameout
• 6 torn kaffir lime leaves in the fermenter for three days after fermentation
• A Belgian witbier yeast, fermented at 18 to 20 °C

Mash at around 66 °C. The flaked grains carry no enzymes, so the Pilsner malt does all the conversion; at 54% of the grist it has plenty of power to spare. Add rice hulls if your system is prone to a stuck runoff.

Taste the beer before the lime leaves go in. If the coriander and lemongrass already give enough citrus, use four leaves rather than six.

Styles and pairings that work

Both plants suit light, crisp beers with low bitterness:

• A witbier, swapping some or all of the orange peel for lime leaf.
• A saison, where the yeast's peppery character meets lemongrass well.
• A pale lager or rice lager for the Thai and Kerala food table.
• A hop water or low alcohol pale, where the herbs carry the aroma alone.

Hops can help. Sorachi Ace is famous for a lemon and lemongrass note. Many citrus-forward varieties pair naturally too. Our guide to citrus peel and gondhoraj in beer covers another Indian route to a citrus aroma.

Common mistakes and the fix

• A soapy, perfumed beer: too many lime leaves. Halve the dose next time.
• A grassy, vegetal beer: green lemongrass tops or long contact. Use only the pale stalk.
• No aroma at all: lemongrass boiled for too long. Move it to flameout.

Designing a herb or spice beer means deciding what the base beer, yeast, hops and herb each contribute, then dosing so none of them shouts. That balancing act is the heart of speciality styles.

Your first step: make two small tinctures, one lemongrass and one lime leaf. Dose a glass of a plain lager with each until you find the level you like.

Common questions

When should I add lemongrass to beer?

Add bruised, chopped pale stalks in the last five minutes of the boil or in a whirlpool at around 80 °C. Long boiling drives off the aroma.

How many kaffir lime leaves go into 20 litres of beer?

Start with 4 to 8 fresh leaves added after fermentation for three to five days. Tear them along the vein and remove the tough centre if possible.

Can I use dried lemongrass?

You can, but it loses brightness and can taste of hay. Fresh lemongrass gives a far cleaner lemon aroma.