Weyermann Sour Wort: biological acidification in a can

What Sour Wort is

Weyermann Sour Wort is made from light barley malt extract that has been fermented without alcohol to produce lactic acid. It is a liquid, not a malt. Weyermann packs it aseptically. Its manufacturing and filling leave no living microorganisms in the product. That is the big difference from kettle souring: you get the acid without bringing live bacteria into the brewhouse.

Where Acidulated Malt adjusts mash pH, Sour Wort is designed for adjusting wort pH, especially at the end of the boil. Both are natural, malt-derived acids that German brewers can use within the purity law.

The spec sheet

• Lactic acid: 52 to 58 g/l.
• pH: 2.9 to 3.2.
• Density: 1.271 to 1.317 g/cm³. It is heavy, which is why a 16 litre box weighs about 20 kg.
• Refraction: 58 to 65 °Bx. It is a dense sugar solution as well as an acid, so it adds a little extract.
• Packaging: 16 litre (20 kg) bag in box.
• Shelf life unopened: 540 days at 4 to 8 °C, 360 days at 20 °C.

Weyermann describes its sensory character as a fine malt aroma with pleasant acidity.

Dosing for mash and kettle

Weyermann gives two dosing figures, both per tonne of malt in the grist:

• Mash acidification: about 10 litres per 1,000 kg of malt lowers pH by 0.1.
• Kettle acidification: about 6 litres per 1,000 kg of malt lowers pH by 0.1.

For a 210 kg grist, that works out at about 2.1 litres in the mash or about 1.26 litres in the kettle for each 0.1 drop in pH. Treat these as starting points. Buffering in the wort means the response is not perfectly linear, especially for large drops. Measure with a calibrated pH meter on a cooled sample and adjust.

For normal beers the aim is to hit the target pH at knockout, typically around 5.0 to 5.2 for a pale lager, which helps protein break and gives a crisper finish. Mash pH targets of 5.2 to 5.6 are covered in our mash pH guide.

Using it for sour styles

Weyermann lists Gose and Berliner Weisse style beers among its uses, along with non-alcoholic beers and malt drinks. For a properly sour beer you need a much larger dose than for a pH correction. The pH drop slows as you add more, so do not scale the rule of thumb in a straight line.

Run a bench trial instead. Take a litre of your finished wort, add Sour Wort in measured millilitres, read the pH after each addition and scale up from what you learnt. It is ten minutes with a measuring syringe and a meter. It can save a batch.

A worked grist: Gose, 1,000 litres

For a 1,000 litre brewpub batch at around 10 °P with a brewhouse yield near 75%.

• Pilsner malt: 87.5 kg (50%)
• Pale wheat malt: 87.5 kg (50%)
• Total: 175 kg (100%)

Add Sour Wort to the kettle after the boil, guided by your bench trial, then salt and coriander as the style suggests. The volume of Sour Wort will be much larger than for a simple pH correction, so add its extract to your gravity sums.

Designing a beer like this means balancing grist, acid and salt so the sourness reads clean and bright. That balance is what we teach in depth, because a recipe alone does not explain it.

Using Sour Wort in India

Storage is the main issue. Weyermann's shelf life drops from 540 days at 4 to 8 °C to 360 days at 20 °C. Weyermann also asks for protection from extreme heat. An Indian storeroom can sit at 35 °C in May. If you have a cold room, keep the boxes there. If not, buy smaller quantities more often.

Once a bag in box is opened, use it promptly and keep the tap clean. Its low pH is hostile to most microbes, but good practice still applies.

If you cannot get it, food-grade lactic acid does the same chemical job outside the purity law. For more on the Weyermann range, see the Weyermann malts guide.