Pressure fermentation are a method of fermenting beer under controlled pressure. By using pressure fermentation, brewers can accomplish brewing certain types of beer in a shorter period of time then with traditional fermentation methods. Traditional brewing methods requires the beer to be brewed at very cold temperatures for long periods of time.
During pressure fermentation, though, the beer can be brewed at warmer temperatures due to the change in the behavior of the yeast when exposed to the carbon dioxide that is trapped inside a pressure rated vessel. The carbon dioxide lead to a physiological shift in the yeast that reduce the production of esters by the yeast. Because the brewer suppresses the production of esters, the beer will not contain any off-flavors associate with the production of those compounds.
How Pressure Fermentation Lets You Brew Beer Faster
Thus, using pressure fermentation, it is possible to brew a clean tasting lager even at warmer temperatures, which would lead to an ale if brewed under traditional methods. Beyond carbonation, pressure also impact the yeast and the resulting beers clarity. Due to the fact that carbon dioxide affect the yeast’s membranes, the beer clears of particulates more quick.
This shortening of the brewing timeline allow for the brewing process to be completed in only a few week rather than several. Thus, pressure fermentation allows for time to be save for those that may not have the space to refrigerate the beer enough to complete the traditional brewing process. In order to perform pressure fermentation, brewers must utilize certain equipment.
Equipment such as a pressure-rated vessel (corny keg, unitank), a pressure gauge, a spunding valve, and a digital temperature controller must be purchased and utilized in the brewing process. The spunding valve allow for the release of gas from the vessel early in the brewing process, but also allows for the retention of the gas in the vessel after the yeast has completed its initial brewing stage. The digital temperature controller allow for the maintenance of the proper brewing temperatures.
In order to manage the yeast, there are specific step to be performed during the brewing process. The brewer must leave the spunding valve open during the lag phase of the brewing process. After the beer reach a certain level of attenuation, the brewer must close the spunding valve to allow the yeast to produce carbon dioxide.
Should the spunding valve be closed too early, the yeast will be stunned. Should it be closed too late, the beer will not become sufficiently carbonated. Different style of beer require different level of pressure to achieve their flavor, and each style require a different temperature curve to accomplish its desired flavor.
For instance, a German Pilsner may require a specific level of pressure to its composition for it to remain crisp, but a Belgian Saison may require a different level of pressure in order to preserve its own characteristics. Brewing is considered to be finish when the gravity of the beer stabilize to the target gravity of the beer. After brewing is finished, a cold crash under pressure can be performed to allow the beer to clear of any suspended yeast or protein.
Dropping the temperature of the beer while it is sealed within the pressure vessel will allow for the yeast and proteins to settle to the bottom of the vessel. As a result, the beer will be clear, and this process will occur at a more fast rate than traditional methods of allowing the beer to lag. Finally, when the beer is transferred to the serving keg, it will be carbonated due to the amount of carbon dioxide that was trapped within the liquid during the fermentation process.