In a nutshell, Pressure fermentation is the practice of fermenting your beer inside a closed and pressurized barrel. As opposed to a closed-lid fermenter with a airlock which allows the CO2 to escape but allowing no Oxygen inside, a pressure fermentation chamber will not allow the CO2 to escape thus reducing to practically nothing the chance of oxidization as well as ester development to occur.
Pressurizing the chamber is also a way of oxygen-free keg transferring which once again eliminates any contact with oxygen. Pressure transferring to bottle can be a little more challenging, but this can be lessened with the help of a counter-pressure bottle filler. Pressure fermenting also dramatically shortens fermentation time as well as some flexibility when it comes to temperature range. Another great advantage of pressure fermenting is that it stops ester development, which is perhaps a reason why you should be cautious with what you brew.
For example, beers such as Hazy IPA’s, Belgian Dubbels, Saisons and the like are not suitable for pressurized fermentation as their profile is typically driven by ester and phenolic flavours. Lagers especially thrive in this environment and usually come out of the fermenter with a very clean taste profile. This is also true with aroma retention as well as there is no potential ‘scrubbing’ which goes through the airlock, and the aroma naturally stays inside the chamber. Alternatively, applying too much pressure will have a detrimental affect on your beer. Too much pressure will lead to lack of cell growth which leads to poor attenuation which in turn can lead to a sweeter beer than anticipated.
It should be noted that different strains of yeast will behave differently under pressure, many brewers tend to shoot for 10–12psi range. Another factor to consider is the taller your fermentation vessel the more pressure it will put on the yeast cake. Finding which strains perform best under pressure is a series to trial and error, saying this lager yeasts such as Lallemand Diamond Lager and Fermentis W34/70 which are both dry lager yeasts will happily ferment up to 18psi. And the American West Coast Ale Yeast BRY-97 is another example of a yeast that thrives under pressure.
In an exhaustive series of experiments author and co-founder of Sapwood Cellers, Scott Janish compared several yeast strains to observe their behaviour under different pressures, its well worth a read. What equipment is required with Pressure Fermentation? There are a plethora of products available out there and we will go into detail about the various products you can use in a future article.
Of course it will depend on which method of pressure fermentation you are going to adopt, conical, fastferment, P.E.T the list goes on. One constant is that most pressure fermenters are fitted with a Cornelius-type ball lock post, and replacing the airlock is the spunding valve, a spunding valve allows you to release the gas that you don’t want to hold inside the pressure fermenter.
Spunding valves come in a vast variety of designs. The spunding valve is placed on the ball lock valve, some sits at a 90 degree angle and some at a 45 degree angle depending on what material they are made of. Next, you set it to your desired level of pressure, the spunding valve is connected to a cylinder of CO2.
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