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Pilsner Urquell: Triple Decoction

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Ever noticed a caramelised sweetness when you drink Pilsner Urquell? That flavour comes from a process that we use called ‘decoction’. It’s a classic part of Czech brewing, something that’s been done for centuries, and something we still do today, where the qualities we get from decoction mashing are considered a key factor in the taste of our beer and most other Czech lagers.

If we look back to the first brew of Pilsner Urquell, Josef Groll may have had his golden malt but the science of brewing was still catching up with the daily processes that were happening in breweries around the world. Thermometers and saccharometers (these measure sugar in the brew) weren’t widely used and little was known about the actual science of brewing – brewers knew what worked but not necessarily why it worked.

Because of this, they developed different processes to get the best-tasting beers they could. One of the most important processes was the mash. This is the mix of water with malt where brewers extract all the important starches which will later be turned into alcohol by the yeast. Brewers developed many different mashing techniques to help them, but Czechs considered decoction the most effective.

Decoction works like this: while the Pilsner malt is mixing with hot water in the mash tun, a portion of that mash is separated and pushed into another vessel, where it’s brought to the boil. This is then returned into the mash tun with the rest of the liquid, where it has the impact of raising the overall temperature. That’s a single decoction. At Pilsner Urquell we do three decoctions on each brew.

The process developed because it meant brewers could ensure they got the high temperatures they needed in their mash, helping extract the best starches and ensuring better consistency before technology advanced. Crucially for the flavour, the extra heat gives a richer texture, more malt depth and a caramel sweetness, something characteristic of Pilsner Urquell and other Czech lagers.

It’s no longer common practice in brewhouses because it’s time-consuming, uses lots of energy and requires extra vessels to be able to go through the process, but triple decoction is an important part of the original Pilsner recipe and it’s something that’s we’ve always done and will always continue to do.