Fermenting beer under pressure offers many bonuses to the brewer, including significantly reduced exposure to oxygen, quicker turnaround times for your homebrew and the ability to naturally carbonate. There is one area in which it isn’t so user-friendly however. Dry hopping under pressure can be a tricky endeavour, resulting in a foamy mess and inadvertently adding oxygen to your batch if done wrong.
Don’t worry though, if you’re brewing under pressure you can still dry hop your beers — IPAs are not off the menu! Knowing when to dry hop is important and with a little forward thinking, you can set up systems that prevent oxygen from ever touching your beer post fermentation.
The Benefits of Dry Hopping Under Pressure
As with fermenting under pressure, the main advantage of dry hopping in a closed, pressurized system is that there’s no chance of oxygen getting into your brew. For homebrewers who have become jaded with quickly fading hop bombs, this could offer a solution to this all too common problem.
On top of keeping oxygen out, dry hopping under pressure is said to keep hop aroma within the beer. The theory is that there is nowhere for the delicate aroma compounds to escape to if the vessel is sealed under pressure. Often you can smell hops coming from the airlock during primary fermentation, and many brewers believe that these hop aromas are lost to the atmosphere.
Dry Hopping in a Keg
By far simplest method of dry hopping in a keg is to add your hops into an empty keg that has been purged and sealed with co2. Next, transfer your beer from the primary fermenter directly into the new keg, allowing the beer to wash over the hops.
To avoid clogged up dip tubes or taps, it’s best to put your dry hop addition in a hop sock or tea strainer. This can be hung using string to the top of the keg, or left to sink to the bottom by adding sanitized marbles. If you prefer to let your hops loose, a fine strainer should be fitted around your dip tube.
Dry hopping in a keg is simple to do, though your hops are effectively trapped in the keg until it’s empty. Some brewers believe this can lead to grassy, vegetal off flavours, though there is little evidence to support this. You can use a hop sock and string to pull out your hops whenever you like, though this will involve depressurizing the keg and opening the lid. For the most intense flavour, try dry hopping at room temperature for 5 days or so, before chilling down to serving temperature.
Dry Hopping in a Fermentasaurus
If you are concerned about the hops staying in your keg too long, there are solutions. The fermentasaurus is a pressurized, conical PET fermenting vessel that is ideal for dry hopping under pressure. You can choose when to dry hop, plus make multiple additions, putting you in full control.
Once you feel the hops have been in contact with the beer for long enough, simply transfer into a serving keg. To add your dry hop additions to the fermentasaurus, you have two choices.
Yeast Collection Bottle
The most common method uses the handy yeast collection bottle, fixed to the bottom of the fermenter. This attaches to a butterfly valve and is primarily used to harvest and purge yeast from your beer after fermentation is complete.
To dry hop with the yeast collector, ensure it’s sanitized and add your hops. Purge with a blast of co2 to prevent oxygen entering the beer and attach to the butterfly valve. When you open the valve, beer will flow down and the hops will eventually float up to the top of the beer. After a few days, they will begin to sink back down.
Be advised that with this method, you should ensure you’ve purged as much yeast and trub as possible. If you don’t, the valve can become blocked as the hops and trub are too thick, preventing proper dry hopping. Around 2 bottles worth of trub should be enough, but each batch is different.
Hop Sock and Magnets
This method is a little more DIY, but it allows you to add your hops at any stage you like, rather than waiting for the trub to fully settle. When to dry hop is entirely up to you and you can even place multiple hop socks for larger additions or double dry hopping.
Simply add a magnet and your dry hops to a hop sock, and place in the empty fermentasaurus. Use another magnet to suspend the hop sock above the level the wort will reach. Fill up the fermenter, pitch the yeast and let it ferment as normal. When the time comes to add the hops, remove the outside magnet and watch them drop into your beer.
Just remember, never open a pressurized vessel without depressurizing it first. If you forget, you may soon end up with a fountain of beer foam to remind you!