Calling those fermenting under pressure!

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lukey_brews

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Hi Folks,

After one too many oxidised brews I've adapted a corny keg to allow for closed fermentation, initially I'd planned to just use a blow of tube.

When I realised you could make a spunding valve cheaply I decided to give fermenting under pressure a go.

I'm reaching out for any information regarding yeast types, psi and temperature ranges as I'm keen to experiment fermenting at higher temperatures.

Do you ferment under pressure? Does it improve your beer? Is it worth it?

I'm planning a SIPA with chico yeast if anyone has any advice I'd love to hear it.

Any help would be really great.

Cheers! 🍺
 

DocAnna

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There was a recent thread here with quite a bit of discussion about fermenting with top pressure Fermenting under pressure
I think it's fair to say there is some disagreement about whether it is a panacea to improve beer in a generic way. There is agreement that it speeds up fermentation, reduces fusel alcohols and allows for closed transfer. Others are clear that excellent beer can of course be made without using pressure, but that it does make fermenting and transferring NEIPA easier to avoid oxidation.

Personally my experience is mixed but that's more around process and how to work with a closed fermenter, which I reckon to be getting the hang of now.

Anna
 

phildo79

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I recently bought a 23L corny keg and have a brew in it right now. It is a 7.6% stout. It went off like a rocket and was sitting at about 13 psi after 12 hours, on Friday morning. I put a spunding valve on it and dialled it down to 3 psi. After about ten mins, krausen started coming out. I had to switch to a blow-off tube. It bubbled like crazy for a couple of days and has now slowed but the bubbles are still coming about every one second.

I think I will now cap it with the spunding valve and increase the psi to about 8 and then up to the 12 psi mark, if it'll get there. Might take a hydrometer reading first, just to see where it's at.
 

SteveB.

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I have been thinking about trying to ferment under pressure in a corny keg but just to try it out. I don't want to buy any special equipment yet just in case I don't get on with it. I have a spare pressure gauge and gas in connector. I don't have a pressure release/ spunding vale so I was wondering could the pressure release valve fitted to the corny keg lid be modified to do the job?
Anyone tried doing this? Cheers..
 
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I don't have a pressure release/ spunding vale so I was wondering could the pressure release valve fitted to the corny keg lid be modified to do the job?

I've not tried it (I do ferment in a corny, but use an adjustable spunding valve) but noticed that you can now get two types of PRV which would probably enable this:


 

SteveB.

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Cheers SteveH that looks like a great option and a cheap way of trying pressure fermentation with the corny keg.
I am assuming that these PRV's will fit the corny keg lid.
 
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Fermenting under pressure is something which strikes me a bit strange. I can understand a few of the arguments for it but if your techniques are correct, you won't oxidize your batch anyway. The extra pressure (which elevates CO2 saturation) can and will mutate the yeast. It's not a true concern if you don't maintain your yeast crop but if you try to keep a yeast stable, you'll quickly be starting over. Even using an airlock or blow-off tube will cause the extra CO2 in solution and force the yeast to mutate within 8 - 10 generations. The 3 - 10 psi I usually read about might mutate the yeast in far less generations than that. Just something to think about. Remember, most commercial brewers throughout the UK and Europe used open fermentation FOREVER.
 

krispn

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I've just made a batch and it was a quick turnaround, it looks bright (hazy 'bright’ as opposed to clear bright) and it was all done under pressure/closed transfer. Is it a necessity? No! but with any new hobby it's good to try out a new process/technique and one which I hope to experiment with a little more over the coming months. My current focus is on some recipes I've made before and trying to see if there are any noticeable differences. At this stage it's not about better or worse just different techniques to hopefully get the same end result - good beer! If there are incremental improvements along the way that's even better.
After some research and reading what's becoming apparent to me is that the benefits are speeding up the turnaround time on a brew, closed transfers from fv to keg (or serving from the pressurised fv) and there might be an advantage to less ester heavy styles. Really looking forward to doing some big beers like Imperial Stout, lager styles and redoing my last NEIPA as I had some oxidation after a few weeks.
 

Brew_DD2

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I've not tried it (I do ferment in a corny, but use an adjustable spunding valve) but noticed that you can now get two types of PRV which would probably enable this:



I've not had a proper look, but are the PRVs on the Fermzilla the same as the ones on Corny kegs? I'll maybe grab one of these to try out.
 

SteveB.

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Don't know if these PRV's fit the corny keg yet But as they are so cheap I decided to order a couple anyway and take a chance. They look the same as the corny PRV in the pictures. So I will know the answer to the question as soon as they arrive.
One question I have is how much headspace should I leave in the keg when fermenting. The weld line seems to be the obvious answer but what do you guys use?
 

spigley

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Don't know if these PRV's fit the corny keg yet But as they are so cheap I decided to order a couple anyway and take a chance. They look the same as the corny PRV in the pictures. So I will know the answer to the question as soon as they arrive.
One question I have is how much headspace should I leave in the keg when fermenting. The weld line seems to be the obvious answer but what do you guys use?
 

spigley

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I like using these from brew2bottle £50. Good as you can see exactly what is happening. I have 17L of Golden ale using Wyeast London 111 and pressure is about 10psi. This is day 5
 

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Fermenting under pressure is something which strikes me a bit strange. I can understand a few of the arguments for it but if your techniques are correct, you won't oxidize your batch anyway. The extra pressure (which elevates CO2 saturation) can and will mutate the yeast. It's not a true concern if you don't maintain your yeast crop but if you try to keep a yeast stable, you'll quickly be starting over. Even using an airlock or blow-off tube will cause the extra CO2 in solution and force the yeast to mutate within 8 - 10 generations. The 3 - 10 psi I usually read about might mutate the yeast in far less generations than that. Just something to think about. Remember, most commercial brewers throughout the UK and Europe used open fermentation FOREVER.
Please would you provide references regarding fermenting under pressure causing yeast mutation?
 

phildo79

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The weld line seems to be the obvious answer but what do you guys use?
That sounds too high to me. Someone here gave me some advice about fermenting in a keg and said that about 15L was the max you should do in a standard 19L keg. I have a 23L keg so I aim for 19L batches and use a blow-off tube. Currently on my second brew with a keg but the krausen had reached the lid on my first brew.
 
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I use a blow-off tube until the fermentation is well under way then fit a spunding valve. I tend fill to about 8-10cm below the weld and that seems to work. I have tried filling to the weld and got wort coming out through the blow-off tube.
 
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Please would you provide references regarding fermenting under pressure causing yeast mutation?
Read Eric Warner's "German Wheat Beer" pg 71, 72; C. White & J. Zainasheff "Yeast" pg 87.

With open fermentation, brewers may get hundreds of generations from their yeast. As soon as you start over-saturating the fermenting wort with CO2, it stresses the yeast leading to mutation. Even The Alchemist who brews Heady Topper in Vermont used his yeast for up to 15 or so generations, now pitches new yeast after only about 8 generations because of mutation.

Don't get me wrong; I've always tried different things but if you're maintaining a yeast strain, this can be detrimental. I've really just noticed how much interest there is in pressurized fermentation and don't think most have thought of the consequences or that there are any. If it's working for you, great!
 

DocAnna

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Just a short note on CO2 stress and mutation - high pressure slows down cell division and overall cell mass, reducing the number of generations in the wort and the cells may eventually after multiple generations adapt to the CO2. Stresses to the cells in this regard don't actually cause mutations, rather it provides a selection pressure for genetic drift towards CO2 tolerant types. Sorry to be a pedant but stresses don't cause mutations in yeast, and will only select out mutations if they are caused as a steady state. The viability of yeast under CO2 pressure was questioned in anecdotal reports in 1983 but subsequent studies on yeast response to stresses hasn't shown this to be the case.

Paper of interest if anyone keen to read about this:
Richard, Lannig, Guillouet, Stéphane E & Uribelarrea, Jean-Louis, 2014. Quantification of the transient and long-term response of Saccharomyces cerevisiae to carbon dioxide stresses of various intensities. Process biochemistry (1991), 49(11), pp.1808–1818.
Consequently, yeast cells grown in presence of CO2 enrichment showed a different short-term response to a CO2 step-increase of same intensity than yeast cells grown without CO2 enrichment. The response to the second CO2 shift-up was much lower than the response to the first step-increase pointing out that yeast cells may have acquired a resistance to CO2 stress during the A-SS2. This increase of the resistance to a CO2 stress may be similar to the increased resistance of yeast cells to H2O2 observed during four to five generation after exposure to an initial 0.7 M NaCl stress [60]. However in the present case the long-term effect was observed after stabilization of a new steady-state.
 

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