Pressure fermentation is a hot topic in home brewing communities, but even micro and macro breweries use pressure fermentation, too.
Simply put, pressure fermentation is a process that ferments beer under pressure that higher than 0 PSI [R]. Usually, this is done by fermenting beer inside a closed vessel, which is then pressurized.
Pressure fermenting isn’t as straightforward as it seems, though. Read on to find out everything you need to know so you don’t put yourself under pressure!
Why Is Fermentation Pressurized?
Brewers ferment beer under pressure because it offers plenty of benefits that traditional fermentation doesn’t.
In traditional gravity fermentation, CO2 from the beer is allowed to escape [R]. While the process is straightforward, it also requires a lot of transferring, from the primary fermentation vessel to the secondary vessel to bottling and kegging.
The transfer process exposes the beer to unwanted oxygen while fermenting, which isn’t ideal.
In pressure fermentation, the fermenter is completely sealed off, and the CO2 is trapped inside the fermenter.
Should I Ferment Under Pressure?
Pressure fermentation is a process that any homebrewer should try. There are several theoretical benefits to pressure fermentation, like:
- The ability to ferment at higher temperatures
- Beer can naturally carbonate inside the vessel
- Fewer esters and fusel flavors in your beer
These theoretical benefits really just add up to one practical upside for homebrewing hobbyists: quicker and more efficient fermentation. By using pressure, you get to finish your beer in the same vessel you started fermenting in.
Read about the practical benefits that pressure fermentation can add to your beer below!
Benefits During Fermentation
Pressure fermentation allows you to ferment yeast at high temperatures faster, without losing flavor.
Higher temperatures mean faster fermentation [R], but this means that you may get more unpleasant flavors because of increased ester production.
Brewers want to avoid esters in their beer because esters give beers a solvent-like flavor [R]. With ester fermentation, this results in fewer esters because less yeast grows inside your vessel during fermentation [R].
Brewers also want to avoid oxidation in their beer. Oxidation is bad in beer brewing because oxygen gives bad, papery flavors to the beer. Oxygen, when combined with certain flavor compounds and yeast, gives the beer an unpleasant, cardboard taste [R].
Pressure fermentation is a closed system, so oxygen can’t interact with your fermenting yeast.
With traditional fermentation processes, you’ll have to transfer your beer to another vessel for the second fermentation. You wouldn’t have to avoid that with pressure fermentation.
Another advantage of the “closed system” nature of fermenting under pressure is that it’s more sanitary. There is less air exposure, less exposure to hands, and is just cleaner to manage overall.
Benefits After Fermentation
Beer is carbonated either naturally or by force.
There might not be enough carbon dioxide in traditional fermentation to carbonate the drink, especially if the brewer went through second fermentation because gases escape in the transfer process [R].
So brewers add carbon dioxide to carbonate their beer in the second fermentation container.
Pressure fermentation saves you the hassle of transferring your beer and needing multiple vessels. You can also save up on CO2 because you can naturally carbonate your beer using a spunding valve.
Because fermenting under pressure naturally carbonates your beer, you can serve the beer straight from your keg.
What Does This All Mean?
This all means that with fermentation under pressure, you get to:
- Save time
- Save money
- Streamline your fermentation process
The faster fermentation of this method saves valuable time you can use to make more batches of beer.
You also reduce costs with this method because you will need fewer vessels and fewer CO2 tanks. This is especially the case if it’s hard to get CO2 in your area.
The process is also more sanitary because it reduces your yeast exposure and your beer to outside elements, like oxygen and, yes, human hands.
All of these upsides make fermenting under pressure a good draw even for homebrewers.
Though there are some upfront costs with more specialized homebrewing equipment (you can’t just use glass carboys for this method!), you get to save in CO2 tanks and time spent down the line.
The Downsides of Fermenting Under Pressure
Fermenting under pressure has some downsides you should watch out for. For one, you’ll have to be very careful about yeast health because higher pressures can reduce yeast cell division.
For another, you also have to purchase more kegs because you’ll be using your kegs as your first ferment and second ferment vessel.
Pressure ferments are also more difficult to bottle since they already come naturally carbonated. You’ll have to make sure that you have a counter-pressure bottle filler so that your beer stays its best and doesn’t lose that characteristic fizz.
However, these downsides aren’t so bad if you think about the benefits of a faster, cleaner fermentation method.
Which Beers are Best for Pressurized Fermentation?
The first thing you’ll have to remember is that pressure fermentation isn’t necessarily ideal for all beer styles.
Some yeasts respond really well to pressure fermentation. Lager yeast, in particular, makes very good beer when pressure fermented.
Lagers taste clean and are made quickly, so this kind of beer really benefits from pressure fermentation. Ale yeast also responds well to pressure fermentation.
German-style beers also benefit from this method because of improved natural carbonation. Germany has a 500-year-old law called the Reinheitsgebot [R], so brewers aren’t allowed to force-carbonate their beer. They can’t even add sugar [R] to help carbonate their beer!
So pressure brewing is a good workaround for German-style brewers to keep natural carbonation in their beer.
Although, this method isn’t ideal for some German-style beers like hefeweizens, where ester production is important [R]. Esters are bad in excess but are also responsible for fruity compounds in beer [R].
For IPAs, it depends on your preference. Pressure fermentation gives better hop flavors to your brew, so they’re suited for British style IPAs.
To sum it up,lager yeasts respond really well to pressure fermentation. For other beer styles, it’s really up to your preference, depending on the flavors you want to achieve and the kind of yeast you’ll be using.
How to Get Started With Fermenting Under Pressure
Choosing A Vessel
The first thing you need to do is to choose a vessel to ferment in. While most homebrewers ferment in a carboy, glass and pressure don’t mix. You’ll end up wasting precious beer when the glass shatters!
Instead, we suggest that you ferment in a suitable keg. Ensure that you check the keg rating or other container you’ll use to ferment in.
As a general rule, most Cornelius kegs can take around 35PSI of pressure. Preferably, check the manufacturer’s labels for the proper pressure rating of the container.
You can opt to use a Cornelius keg for this process, but you can also try using a Fermentasaurus for larger volumes.
When it comes to pressure, you will want to consider two things: the ideal pressure which promotes yeast growth and the pressure that your vessel can take.
It’s when you have to adjust the pressure to promote yeast growth that it gets a little tricky. Different kinds of yeast respond to different levels of pressure.
It actually takes a lot of pressure for yeast to die. Yeast dies at around 50 MPa, which is roughly around 7,252 PSI [R]. But that doesn’t mean that you should be subjecting your ferment to pressures this high.
While your yeast won’t die, it will stop growing at 2.5atm (around 37 PSI) [R]. Yeast cell division becomes impossible at this point. As a result, while your fusel alcohols are reduced, it can lead to reduced metabolism of sugars and alcohols and give you problems with fermentation down the line.
A good rule of thumb is to start experimenting with lower pressures and then increase as you go along until you get the result you want. Most people find that 10-12 PSI is a good number, but cap it off at 15 PSI.
At these levels, you wouldn’t have to worry all too much about yeast growth, and these levels are enough to gain the benefits of pressure fermentation.
You may also want to start with lower pressures during the first fermentation, which will take around 4 days. After that, you can raise the pressure to your desired outcome.
To adjust the pressure of your vessel, we suggest getting a spunding valve [R]. This way, you can adjust the pressure parameters as preferred. You can even adjust for carbonation!
A spunding valve works best with corny kegs. If you try using the Fermentasaurus, you can opt for the Fermentasaurus Pressure Kit instead.
If you dry hop your beer, pressure fermentation can be a problem.
Dry hops added in pressurized ferments can lead to a disaster if you’re not careful. Because ferments under pressure are naturally carbonated, the dry hops provide more nucleation points. The result? Something called a dry hop volcano [R].
So if you’re dry-hopping, remember to be careful when adding your hops to the beer.
What About Pressurized Dry-Hopping?
When you talk about “pressure fermentation,” it means fermenting your yeast in a pressurized vessel for the duration of your fermenting process. The fermentation vessel itself is subject to pressure.
Lately, some brewers started dry hopping under pressure. Dry-hopping under pressure offers the same benefits as fermenting under pressure.
It reduces the risk of oxidizing your beer and exposes your yeast to less oxygen. That’s always a good thing for great tasting beer.
You can try putting dry hop in a vessel under pressure, with the same rules as fermenting under pressure. See if you’ll like it.
Now you have an idea about pressure ferments and why homebrewers like using this method. Many homebrewers like fermenting under pressure because it saves money and time and gives excellent tasting results.
It can be as simple as putting your ferment in a closed container and putting pressure. With these tips, you can safely experiment with pressure fermenting at home.