Cask ale or cask-conditioned ale is beer that is both conditioned in and served from a cask. Cask conditioned ales are not filtered or pasteurized, and contain live yeast which adds to the complexity, flavour and aroma of the beer. Think of it as a bottle-conditioned beer but in a big metal bottle.
The brewing process for cask ale is the same as other beers up until it is placed in the cask: mash, boil, ferment. Once the beer is finished primary fermentation, it is added to a cask with sugar and finings. Finings bind yeast cells and other organic matter, dragging them to the bottom of the cask to clarify the beer.
Sugar is added to the cask for secondary fermentation that carbonate the beer. If additional sugar isn’t added before the beer reaches terminal gravity (no more fermentables for the yeast to eat) it can be transferred to cask to finish up and carbonate. After this, the beer is then conditioned.
Sufficient conditioning allows the beer to mature, clarify and carbonate. With cask conditioned beer, a small amount of yeast remains that allows the secondary fermentation and carbonation of the beer. Conditioning time depends on the style of beer and lasts between 3-16 days. After maturing, the yeast and other sediment settles to the bottom. The beer is now carbonated and ready to serve directly from the cask.
When you think of casks, you usually think of low-strength English styles like bitter, milds, and ESBs, but higher-strength cask beers like barley wines and Imperial stouts also condition in casks extremely well.
How is cask ale different?
The differences vary from beer to beer, but the texture of a cask beer is often creamier and smoother on your palette than non-cask beer. Unlike your standard keg beer, which is delivered from the brewery in a finished state, cask ale doesn’t finish its fermenting until just before it is delivered to the drinker,fermentation continues in the cask from which the beer will be poured. By sealing the cask and trapping all the volatile compounds inside the cask, more of the flavours remain within the beer. When beer is fore carbonated, CO2 is bubbled through the beer, pushing out some of the aroma compounds. Before you tap a cask, it is vented from the top, allowing excess gas to escape (this is why cask ale is less carbonated than other beer).
If you’d like to learn more about cask ale, check out Adam Chatburn’s article Casks: An Introduction where he debunks popular myths about casks.
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