What are the Differences Between Tap and Cask Beer?
Cask beer and tap—also known as draft or draught—beer are not different styles of beer. Virtually any beer can be either a cask beer or a tap beer, depending on how it is brewed, stored, dispensed, and served. The main differences between tap and cask beer are due to the process by which these beers are produced. However, these processes can also bring out a wide range of varying flavors in beer. Beer on tap often tastes different from the same style of beer brewed as a cask beer.
The steps of the primary brewing process are identical for both tap and cask beer up until the beer is ready to be stored. Both types of beer undergo primary fermentation catalyzed by the live yeast inside it.
After beer on tap is brewed, it is filtered and pasteurized to remove all of its live yeast. Cask beer, on the other hand, is not filtered or pasteurized. Live yeast remains in cask beer after it is sealed and stored and continues to undergo its natural metabolic activity up until the moment the beer is dispensed.
Tap beer is stored in a keg that feature valves and internal tubes to accommodate the pressurized release of the beer when it is ready to be served. The process of dispensing tap beer by pushing it out of its keg with the help of carbon dioxide keeps the keg sealed and prevents the beer from being exposed to oxygen.
Cask beer, on the other hand, is stored in a cask that is equipped with a manual hand pump and spout. This hand pump is not pressurized and allows the beer inside the cask to oxidize once the cask is opened and beer is dispensed from it. A sparkler is often attached to the spout of a cask to aerate the beer as it is dispensed for a foamier texture.
Cask beer is much more delicate than tap beer. Unlike beer on tap, cask beer includes live, active yeast even after it is sealed and stored. It is also completely natural and does not include any artificial ingredients, like the carbon dioxide that is eventually infused into tap beer.
Due to its living, natural state, cask beer has a shorter shelf life than tap beer. Because cask beer is dispensed through a hand pump instead of a pressurized tap system, it needs to be served almost immediately. Once a cask is opened and the beer inside is exposed to air, the cask beer needs to be served within one to two days at most. After this time period, cask beer loses all of its carbonation and spoils. Since live yeast is filtered out of tap beer before it is stored and its carbonation is artificial, tap beer can be kept longer without spoiling.
A sealed cask can be kept for about six weeks, as long as it is stored at the right temperature. Because tap beer is not oxidized and its keg remains sealed even after it is dispensed, it can remain fresh for three to six months even after its keg has been tapped.
Tap beer and cask beer are usually served at different temperatures. The serving temperature of cask beer is approximately 55 degrees F, and the optimal serving temperature of tap beer is significantly lower at about 38 degrees F.
The 17-degree F difference between the ideal serving temperatures of tap and cask beer can noticeably alter the flavor of these beers. Certain flavors in the beer are more recognizable depending on the temperature at which the beer is served.
Both cask beer and beer on tap undergo primary fermentation during the brewing process. This initial fermentation lightly carbonates the beer due to the metabolic activities of the live yeast inside it. After tap beer is brewed, all of the yeast is filtered out of it and its fermentation process ends.
Cask beer undergoes a secondary fermentation after it is brewed because of the live yeast that remains active in the beer once it is stored. This secondary fermentation process gives cask beer a very gentle fizz. All of the carbonation in cask beer is natural and stems from the metabolic activity of the yeast in the beer.
Cask beer is about half as carbonated as tap beer. The heavier carbonation in tap beer is artificial. This carbonation stems from the blend of carbon dioxide and nitrogen that is used to push the beer out of its keg through its pressurized tap system.
The different processes of brewing, storing, and dispensing tap beer and cask beer can result in beer with noticeably different flavors. Cask beer tends to have a deeper, more complex flavor than tap beer.
The filtration and pasteurization process of tap beer stops the development of the beer’s flavor and strips the beer of some of its existing flavor and aroma. Because cask beer does not undergo filtration, the live yeast that remains in it continues to develop its flavor. This development can create more flavorful, aromatic beers.