Fermenting Under Pressure?
It Might Actually Reduce Your Pressure Level When Fermenting a Batch of Beer
by John Lowry (aka WortMonger)
Every time I brew up a batch of beer, and start the flow of rich worty goodness towards my Sanke fermentor, I start to hear that infamous bass line from one of my favorite songs. That’s right, it’s Queen and David Bowie singing “Under Pressure.” The reason for this is justifiable enough… I ferment in a completely closed 15.5 gallon Sanke keg under pressure. Why? Well, that’s the reason I decided to write this article. I am excited to tell you a little about my process, with the hope you decide to gather further information on the subject later if you choose to attempt it. Please allow me to walk you through the more general and basic approach to this technique, and I will leave it up to you. If you are hungry for more, feel free to check out my thread devoted to the process at
https://www.homebrewtalk.com/f13/closed-system-pressurized-fermentation-technique-44344/. I warn you though, it is a mammoth read filled with way more specific information on the subject from a number of people currently having success with the technique.
My process may look at first like some sort of complicated procedure, but honestly it really isn’t that much different than what most everyone does right now. The biggest difference is that I am doing some steps at the same time, and that I do everything under a positive pressure environment. First there is my fermentor, a Sanke beer keg, that I utilize to build up CO2 pressure allowing a slightly lower krausen height, lower ester production, and natural carbonation.
Then we have what makes my process controllable, so I don’t create a fermenting beer A-Bomb!!! I am talking about my handy-dandy spunding valve. Some German brewers utilize this device on their lagering tanks to get natural carbonation towards the end of fermentation. This is nothing more than an adjustable back-pressure relief valve with an attached pressure gauge for reading the pressure inside their lager tank. With this device, they can release a measured amount of excess pressure from the fermentation process to accurately carbonate their beers to a desired volume of CO2. There is a wealth of searchable knowledge for what to buy when making your own spunding valve, including an article in the Jan/Feb 2007 issue of BYO magazine by Marc Martin and an even earlier article in a Nov 2006 issue by Chris Colby. I think you will find these articles as interesting as I did, and so I won’t go into specifics on what part numbers to purchase and the likes. Believe me, there are several ways to skin this cat… just read the thread I referenced earlier and see how many combinations or different parts there are possible. All the spunding valve parts are easily purchased from online vendors and range in price according to how fancy you want to make yours. Mine cost me around $35, which isn’t bad considering I also use it when counter-pressure transferring kegs with carbonated beer. Who doesn’t like owning multitasking tools?
Last is the Sanke tap connector, or other connector sold by vendors that connect you to the keg and hold in pressure. For the sake of simplicity, I will stick to talking about what everyone with a keg should already own… a Sanke tap connector. That’s it, that’s all that is involved in doing your very own pressurized fermentation. Now let’s delve into the reasons anyone might want to do this in the first place.
Most who use spunding valves do so towards the very end of primary fermentation, like the Germans and the BYO authors I mentioned earlier, and only to carbonate the finishing beer. When I use my spunding valve, I do so to create a slight positive pressure at the beginning of fermentation to mimic the hydrostatic pressure the Big Boys have when using such large fermentors. This allows me to keep the krausen height down a bit more than an open or air-locked fermentation would, as well as some other positive aspects I would like to elaborate on. I have seen from personal experience the ability to raise the fermentation temperature a few degrees higher in a pressurized fermentation and still have the flavor profile of a lower temperature “normal fermentation.” It was through my research though, were I found other possible benefits to a pressurized over non-pressurized fermentation.
Ray Daniels was the first trusted brewing author I came across in my research when I was just starting to wonder if this would work or not. He forced me to want to dig further, after I read his response to a question when he was asked about fermenting under pressure in the July 11, 2002 web version #3986 issue of The Homebrew Digest . Basically, he states that in his opinion bitterness might be a bit more due to krausen staying in the fermentor vs. a blow off fermentation and that he saw nothing else that would cause him to think any other factors were negative due to the pressure. The study he referenced had variables (such as pitching rates and fermentation temperatures) that led him to say he thought it, “exceedingly unlikely that you would discern any consistent bias in your results under pressure fermentation versus non-pressure.” He also spoke of diacetyl being increased, which I will talk about in a minute.
After reading Mr. Daniels article, I found another that sealed the deal for me. Up until I read this next article, I was honestly hesitant on trying this without confidence I wasn‘t going to just waste a batch of beer. I found a publication written by Teri Fahrendorf on her website about Closed System Pressurized Fermentation (
http://www.terifahrendorf.com/Closed-Pressurized-Fermenatation), in which she makes the statement, “The best home brewing system is the simplest to use. The less complicated your technique, the more you can concentrate on the joy of the art of home brewing.” I cannot agree with her more. While this system seems more intricate and complicated than the “norm,” it is an extremely streamlined and completely sanitary way to brew beer. Less messing with the beer and less introduction to the atmosphere means less possibility of infection… which, makes this a less worrisome and simpler brewing method in my mind. Immediately after reading this article I bought my spunding valve, started brewing Closed System, and haven’t looked back since.
Ok, picking back up where I left off at the beginning of this strange article. The music playing in my head as I transfer my cooled, aerated, pitched wort into my Sanke fermentor. It is located in an electronically controlled temperature chest freezer with the Sanke placed inside prior to kettle knock-out. After the beer enters the keg, I seal it up and attach my spunding valve to the gas-in port on my tap connector (gas check valve removed of course). After primary fermentation is over I am “naturally carbonated” and ready to mature my beer for whatever length it needs, saving time by not having to later carbonate my beer. I follow this with a crash cooling for ales before transferring with a filter into my smaller serving kegs. For lagers, I will transfer into a lagering keg to store right after primary fermentation is over. Then I transfer with a filter to my serving kegs. I like to set my spunding valve to 5-7 psi while purging serving kegs, so that I know what my starting set pressure will be when I place it on my fermentor. 5-7 psi seems to be a good starting point for a fermentation at typical ale yeast temperatures. I have a testing spigot set up on the beer-out port of my spunding tap connector, so that I can test gravity and know when to crank up the valve for wanted carbonation volume at the end of fermentation. It is just that easy! I have thrown in different variables from time to time such as pumping the kettle into a already sealed keg, or other little things I choose to do differently. That is the fun part. As soon as you get comfortable knowing that your only major concern is keeping the beer away from the outside atmosphere under a positive pressure, you can come up with lots of different things to try on your own.
EDIT: I had to separate it so that means two posts.
Sorry WortMonger
