What is Cask Beer?
Have you ever been at a bar that had cask beer, but you didn’t really know what that meant? Well, cask beer is one of the most interesting, and certainly oldest, ways of making beer. In Britain it is lovingly referred to as “real ale.” The cask itself is simply the container which holds the beer. Casks are barrel-shaped, though structurally different from kegs. They are most often made of stainless steel, as opposed to the wood used in previous centuries. The smallest size, a firkin, is the most commonly used you’ll see around here. But why all the fuss over cask beer?
Well, modern beers are often filtered and/or pasteurized at the brewery, then artificially carbonated using carbon dioxide. The yeast in these beers has been killed off, along with any beer-spoiling microorganisms that may have been present. Cask beers, on the other hand, are treated differently. As was done in centuries past, the beer is transferred into the cask while it is still young. The beer will finish fermenting and mature before being served directly from the cask when it is ready. This beer is a living product because yeast is still present and alive in the beer. These yeast contribute many nuanced flavours and aromas to the brew. Filtration and pasteurization, although beneficial for extending the shelf life of a beer, strip away some of the flavours and aromas of living beers (colour, too, if you get too crazy about it — but that’s a different story).
Cask beers are more delicate than other beers for a few reasons. First, because the beer finishes fermentation in the cask, it naturally carbonates, meaning that the only carbon dioxide present is the by-product of the yeast fermenting sugars. This gives a softer texture than beers that have been force-carbonated. (They are also served between 10 – 13 degrees Celsius, as opposed to 4-degree-Celsius keg beer, which is where the rumour that Brits drink warm and flat beer comes from).
As a rule, cask beer has no extra carbon dioxide used to carbonate the beer, nor to dispense the beer. Which leads me to the second reason why cask beers are more delicate. When the beer leaves the cask, it is replaced with oxygen. Oxygen will spoil beer over time, causing it to taste flat, stale and like cardboard. Because of this, casks are typically served within a few days of tapping. This is also the reason why many brewers opt for the small firkin-sized cask.
Any beer can be cask-conditioned, but you’ll mostly see ales. Some brewers use the opportunity to condition their beer with ingredients like herbs, flowers or fruit. Some have even added gummy worms to the cask! From bitters to barley wines, British ales, in particular, are a natural fit for cask conditioning. It’s especially fun to try a cask beer side-by-side with a keg or bottled version of the same beer.
So the next time you see a cask version of a beer being offered, try it and raise your glass to real ale!