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General Category => General Homebrew Discussion => Topic started by: oscarvan on May 21, 2012, 07:13:15 PM

Title: Fermenting under pressure.
Post by: oscarvan on May 21, 2012, 07:13:15 PM
As per my post in "equipment" yesterday I spent a day slaving at a large-ish (10bbl) brewery in Holland. One of the big surprises was that these folks ferment under pressure. It' all goes in a large SS conical fermenter, and the thing is sealed. Dry yeast is re-hydrated in a cornie sized keg, and then forced in with CO2 through a little valve on the side of the thing. Then it ferments....no airlock, no blow off. After a week or so it gets racked to a lagering tank. (They call it lagering, although most of it's ale....the word is used for what we call lagering as well as for what we call conditioning.) The result is a carbonated beer.

Thoughts on fermenting without blowing off CO2?
Title: Re: Fermenting under pressure.
Post by: morticaixavier on May 21, 2012, 07:47:42 PM
I've heard of this, but I was under the impression a set level of pressure was maintained, 15psi if I recall.

By the way, good to have you back Oscar.
Title: Re: Fermenting under pressure.
Post by: jmcamerlengo on May 21, 2012, 07:50:40 PM
i thought what you thought mort.

I have also heard it produces a unique characteristic to the beer since the yeast are under constant stress and pressure. I'd think the ester level would be significantly higher...
Title: Re: Fermenting under pressure.
Post by: oscarvan on May 21, 2012, 08:25:53 PM
By the way, good to have you back Oscar.


Never left, was in the bathroom. Long line. ;)
Seriously, still brewing strong. Just tapped the first dry hopped version of my IPA....it ROCKS.
Title: Re: Fermenting under pressure.
Post by: tschmidlin on May 21, 2012, 08:35:59 PM
i thought what you thought mort.

I have also heard it produces a unique characteristic to the beer since the yeast are under constant stress and pressure. I'd think the ester level would be significantly higher...
I believe it is the opposite - the ester level is greatly reduced.
Title: Re: Fermenting under pressure.
Post by: lornemagill on May 21, 2012, 08:44:08 PM
ive heard you can ferment at higher temps with no off flavors, no experience or data to back it up though.
Title: Re: Fermenting under pressure.
Post by: dak0415 on May 21, 2012, 08:56:05 PM
Somewhere, just don't remember, I heard there was a special yeast designed (selected) for fermenting under pressure.
Title: Re: Fermenting under pressure.
Post by: tschmidlin on May 21, 2012, 08:57:52 PM
ive heard you can ferment at higher temps with no off flavors, no experience or data to back it up though.
yes, this is what the larger breweries supposedly do - higher temps and gravity then dilute back to "normal" strength.  The higher temps and gravity would lead to increased esters, but it is under pressure so it is reduced.  End result is the "same" flavor profile as if it were open fermented at regular strength in small batches and at lower temps.
Title: Re: Fermenting under pressure.
Post by: hopfenundmalz on May 21, 2012, 09:22:14 PM
Somewhere, just don't remember, I heard there was a special yeast designed (selected) for fermenting under pressure.
This stuff.
http://www.whitelabs.com/beer/strains_wlp925.html

Don't try fermenting without a pressure releif valve. You would set it for 15 PSI. Otherwise you could blow up your fermenter. It has happened in production breweries.

Edit - same reason you are required to have a pressure relief on your hot water tank. Anyone see the Mythbuster where they blew one through the roof of the structure built to code? It came down a far way off.

Edit 2 - http://www.probrewer.com/vbulletin/showthread.php?t=23197
Title: Re: Fermenting under pressure.
Post by: oscarvan on May 21, 2012, 10:39:04 PM
No dilution going on here.
Title: Re: Fermenting under pressure.
Post by: tom on May 22, 2012, 01:31:46 AM
What was the pressure?
Title: Re: Fermenting under pressure.
Post by: tomsawyer on May 22, 2012, 11:21:57 AM
I've done several pressurized fermentations, in fact I do all my Brewhemoth batches this way.  Also do small batches in cornies.  Works well, although I must report that my ester levels haven't been noticeably lower.  Maybe the increased temp is offsetting as said earlier.  I ferment at 7psi and then ramp to 15 towards the end.  The Brewhemoth is tested to 100psi.  This is supposed to mimic the higher pressures seen by yeast in large fermentors.

I don't believe they don't have a pressure relief device, theres way too much CO2 produced to hold it all in.  You can get to 30psi quickly.
Title: Re: Fermenting under pressure.
Post by: kylekohlmorgen on May 22, 2012, 03:30:14 PM
Some pressure in the fermenting vessel might reduce esters because it keeps the yeast from foaming up above the heat sink (jacket, cooler, etc.). I can't really think of any reason yeast would benefit from additional pressure during fermentation.

Too much pressure is probably a bad thing - not only would there be mechanical yeast stress, but you would hold in a lot of CO2. This creates chemical/osmostic stress on the yeast and its tough to transfer highly carbonated beer.
Title: Re: Fermenting under pressure.
Post by: tschmidlin on May 22, 2012, 07:27:39 PM
Some pressure in the fermenting vessel might reduce esters because it keeps the yeast from foaming up above the heat sink (jacket, cooler, etc.). I can't really think of any reason yeast would benefit from additional pressure during fermentation.
Who says the yeast are benefiting?  Increased pressure will activate pathways that affect metabolism.  It seems these pathways reduce esters, but that doesn't mean the yeast like it.  Remember, we often ferment in the mid 60s, but if the yeast had their choice from a reproductive standpoint the temp would be more like 85 or 90F.
Title: Re: Fermenting under pressure.
Post by: phillamb168 on May 23, 2012, 08:05:02 AM
Related to this, can someone remind me what the thing is called that you put on a corny gas out valve to regulate the pressure inside? Setting it to 15 PSI and then it vents when it goes over, until it goes back down to 15?

I typically ferment all of my lagers under some pressure, because I have to ferment them in cornies (not a very big fridge, only two will fit, carboys don't fit, etc). I would be very interested in seeing how fermenting under pressure at ale temps would affect ales. Perhaps a fun exbeeriment?
Title: Re: Fermenting under pressure.
Post by: tschmidlin on May 23, 2012, 08:30:55 AM
Related to this, can someone remind me what the thing is called that you put on a corny gas out valve to regulate the pressure inside? Setting it to 15 PSI and then it vents when it goes over, until it goes back down to 15?
You mean a pressure relief valve?
Title: Re: Fermenting under pressure.
Post by: phillamb168 on May 23, 2012, 08:45:58 AM
Related to this, can someone remind me what the thing is called that you put on a corny gas out valve to regulate the pressure inside? Setting it to 15 PSI and then it vents when it goes over, until it goes back down to 15?
You mean a pressure relief valve?

Yeah, but the one I'm thinking of has a regulator built-in so you can adjust the pressure at which it vents automatically.
Title: Re: Fermenting under pressure.
Post by: tschmidlin on May 23, 2012, 08:51:09 AM
Related to this, can someone remind me what the thing is called that you put on a corny gas out valve to regulate the pressure inside? Setting it to 15 PSI and then it vents when it goes over, until it goes back down to 15?
You mean a pressure relief valve?

Yeah, but the one I'm thinking of has a regulator built-in so you can adjust the pressure at which it vents automatically.
That is called an adjustable pressure relief valve ;)

morebeer has them, some with gauges.  You don't adjust with the gauge, that just tells you what you've adjusted it to.  So I'd pressurize to 20 psi, then adjust the prv down until the gauge reads 15 psi.

http://morebeer.com/view_product/16772//Ball_Lock_QD_Adjustable_Pressure_Valve_W_Gauge
http://morebeer.com/view_product/16771//Adjustable_Pressure_Relief_Valve
Title: Re: Fermenting under pressure.
Post by: stlaleman on May 23, 2012, 09:29:35 AM
The Brewhemoth sells one  http://brewhemoth.com/spunding-valve   it works quite well.
Title: Re: Fermenting under pressure.
Post by: tomsawyer on May 23, 2012, 12:33:50 PM
Its called a spunding valve.  The adjustable pressure relief device is spring-loaded, and you can screw down to increase the pressure it takes to release.

I have a relief valve from McMaster Carr, its plastic but does a good job and goes to 30psi.  I also have the one they used on the Brewhemoth spunding valve attachment, it comes from Grainger.  Its brass, has markings that approximate the pressure setting, runs all the way to 100psi, and was a little cheaper.
Title: Re: Fermenting under pressure.
Post by: jmcamerlengo on May 23, 2012, 01:44:14 PM
good info in here! Can always learn new stuff. I may try this in a small batch of a Scottish Ale. I think that would be a great test beer for this. You want it very clean, yet generally have to ferment around 60 degrees to achieve that, and it takes a bit longer than usual to get to terminal gravity at those temps. So this would be a good test batch.
Title: Re: Fermenting under pressure.
Post by: MDixon on May 24, 2012, 12:05:47 PM
Long ago I did some experiments with fermenting under pressure. I haven't updated my site in forever and most of my links are broken. First off high pressure may be dangerous depending upon how the container is rated. I seem to recall 45 psi was the pressure Doric yeast reached before it stopped fermenting and then once the pressure was released fermentation started again. I was not trying to see if esters were reduced or any of that jazz.

I found the linky
http://carboyclub.com/recipes/experimental1.htm
Title: Re: Fermenting under pressure.
Post by: tomsawyer on May 24, 2012, 02:23:11 PM
I agree about pressure being potentially dangerous, thats why I like a fermentor that has a pressure relief valve in addition to the adjustable spunding valve.

I think Chris White has indicated that yeast health is negatively affected above 15psi, interesting that they can still go up to 45psi.  I hope you lowered the pressure slowly, I'd hate to see yeasties get the bends.  Plus the beer foams up to beat the band if you just release the pressure all at once.
Title: Re: Fermenting under pressure.
Post by: jimrod on May 25, 2012, 06:47:13 AM
So what is the verdict? Is it worth it to ferment under pressure? Lagers or Ale? What is the optimum pressure for what yeast?
Title: Re: Fermenting under pressure.
Post by: phillamb168 on May 25, 2012, 08:20:22 AM
So what is the verdict? Is it worth it to ferment under pressure? Lagers or Ale? What is the optimum pressure for what yeast?

Personally it sounds to me like I'll buy buying a spunding valve set to 15 PSI and doing everything that way from now on.

Keeps the krausen down, meaning less cleanup, and I can do it in cornies, which means oxygen-free transfer AND free rhienheitsgebot-safe carbonation!
Title: Re: Fermenting under pressure.
Post by: tomsawyer on May 25, 2012, 01:30:54 PM
The technique has been applied more for lagers than ales but it works for both.  Supposedly 7psi is typical of the pressures in a large fermentor anyway, and 15psi is the limit above which yeast health starts to suffer.  Not sure that means the yeast start producing bad stuff though.

The lowered krausen is really a non-issue, you still have to have some head space above your wort to avoid blowoff and blowoff into your spunding valve does cause clogs.  I haven't really seen a significantly faster fermentation rate, it may get done a little faster but the yeast still have to drop clear and that time isn't accelerated by pressure.  The free carbonation is a slight benefit over what you get with conventional ferms, I haven't been dialing the pressure up to 30psi to take full advantage.  With an ale its tricky to time this, with a lager    The O2-free environment/transfers are probably a bigger benefit than anything else.  Thats what attracted me.  I've been troubleshooting my malt-forward beers that don't seem to have quite the flavor they could, and I hypothesized that oxidation was a culprit (after getting my water chemistry in order).  I still haven't concluded anything for sure (have to keep hoppy brews in the rotation) but I've made a few pretty tasty malty beers now so I've been sticking with it.  All in all, I am not seeing a huge difference but its no more difficult so I am doing it on the conical just to allow me to live with slightly higher ferm temps.

All in all its an interesting technique to play with but it doesn't seem to be head and shoulders above conventional methods.