Kokum and tamarind as Indian souring ingredients in beer

Souring without bacteria

Most sour beers are soured by microbes. Lactobacillus produces lactic acid, either in a kettle sour or a mixed fermentation. Our guide to kettle souring covers that route.

Fruit and fruit acids offer another way. Adding an acidic ingredient lowers pH and adds tartness directly. The result is less complex than a long mixed fermentation, but faster, more predictable and free from the risk of bacteria spreading through the brewery. Kokum and tamarind each bring their own flavour as well as acid.

Kokum

Kokum is the fruit of Garcinia indica, a tree of the Western Ghats and the Konkan coast, common in Goan, Konkani and coastal Karnataka cooking. The dried rind, sometimes called amsul, is deep purple to almost black. Soaked in water it releases a pink to red colour and a gentle, fruity sourness.

Its main acid is hydroxycitric acid, which gives a softer tang than citric or lactic acid. Kokum also contains pigments that colour beer pink to deep red. Like many fruit pigments, the colour is sensitive to pH and oxygen.

Kokum is sold as dried rind (sometimes salted) or as concentrate or syrup (often sweetened and salted). Read labels. Salted kokum can suit a gose, where salt is part of the style. Sweetened syrups add sugar that will ferment if the beer is not stable.

Tamarind

Tamarind is the pod of Tamarindus indica, used across India in sambar, rasam, chutneys and chaat. The pulp is brown, sticky and intensely sour, with dried fruit, date and caramel notes.

Its main acid is tartaric acid, which tastes sharper than lactic acid. Tamarind also carries a lot of sugar, fibre and pectin. That means it adds body and fermentable sugar. It can also leave haze and sediment.

Buy seedless tamarind blocks or plain concentrate without added salt, sugar or spices unless you want them. Tamarind suits amber and brown sours, spiced ales and beers served with Indian food.

When and how to add them

Adding acid to wort before fermentation lowers pH, which can stress yeast if it falls too far. For most ale yeasts, starting fermentation with pH well below about 4 can lead to sluggish or stuck fermentation.

The safer approach is to add kokum or tamarind after primary fermentation, in the conditioning tank. To sanitise, make an extract first: simmer kokum rind or tamarind pulp in a little water, strain through a fine cloth and cool. Add the extract to the beer.

For a fruitier, more integrated result, some brewers add part of the ingredient in the whirlpool and the rest after fermentation. Whirlpool additions extract colour and flavour and are sanitised by heat, but some tartness and pectin will carry into fermentation.

Dosing and measuring

Do a bench trial. Make an extract of known strength, add measured amounts to samples of finished beer and taste blind. Measure the pH of the samples you like.

Many fruited sours finish around pH 3.2 to 3.6. Lower than that, beer can taste harsh. Higher than that, it may taste flat rather than sour. Record pH and taste together, because tartaric, hydroxycitric and lactic acids feel different at the same pH.

Tamarind's sugar will ferment if live yeast is present, which raises carbonation in package. Allow fermentation of the added sugar to finish in tank before packaging, or account for it.

Styles to try

• Kokum gose: a light wheat beer with salted kokum for tang, salt and a pink colour. See our gose guide.
• Kokum wheat or saison: unsalted kokum in a light, dry beer for colour and soft acidity.
• Tamarind brown sour: an amber or brown ale with tamarind for dried fruit and a sharp finish.
• Tamarind and jaggery ale: tamarind with a little jaggery for a sweet and sour profile.

Stability and storage

Pink and red colour from kokum fades with warmth, oxygen and light. Package with low oxygen, in cans or brown bottles. Keep it cold. Tamarind adds haze and sediment. Settle and crash cool before packaging.

Record supplier, form, dose and resulting pH for each batch. Natural ingredients vary between harvests, so a repeat recipe needs a repeat bench trial.

Common questions

Can kokum sour a beer?

Yes. Kokum adds hydroxycitric acid for a soft tang and a pink to red colour. It is best added after fermentation as a sanitised extract.

What acid is in tamarind?

Mainly tartaric acid, which tastes sharper than lactic acid. Tamarind also adds sugar, body and dried fruit flavour.

When should I add tamarind to beer?

Usually after primary fermentation, as a strained and heated extract, so the acid does not stress the yeast.