Author Topic: Fermenting under pressure.  (Read 6582 times)

Offline oscarvan

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Fermenting under pressure.
« on: May 21, 2012, 12:13:15 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?
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Offline morticaixavier

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Re: Fermenting under pressure.
« Reply #1 on: May 21, 2012, 12:47:42 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.
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Offline jmcamerlengo

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Re: Fermenting under pressure.
« Reply #2 on: May 21, 2012, 12:50:40 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...
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Offline oscarvan

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Re: Fermenting under pressure.
« Reply #3 on: May 21, 2012, 01:25:53 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.
Wooden Shoe Brew Works (not a commercial operation) Bethlehem, PA
http://www.woodenshoemusic.com/WSBW/WSBW_All_grain_Setup.html
I brew WITH style..... not necessarily TO style.....

Offline tschmidlin

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Re: Fermenting under pressure.
« Reply #4 on: May 21, 2012, 01:35:59 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.
Tom Schmidlin

Offline lornemagill

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Re: Fermenting under pressure.
« Reply #5 on: May 21, 2012, 01:44:08 PM »
ive heard you can ferment at higher temps with no off flavors, no experience or data to back it up though.

Offline dak0415

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Re: Fermenting under pressure.
« Reply #6 on: May 21, 2012, 01:56:05 PM »
Somewhere, just don't remember, I heard there was a special yeast designed (selected) for fermenting under pressure.
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Offline tschmidlin

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Re: Fermenting under pressure.
« Reply #7 on: May 21, 2012, 01:57:52 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.
Tom Schmidlin

Offline hopfenundmalz

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Re: Fermenting under pressure.
« Reply #8 on: May 21, 2012, 02:22:14 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
« Last Edit: May 21, 2012, 02:25:54 PM by hopfenundmalz »
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Offline oscarvan

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Re: Fermenting under pressure.
« Reply #9 on: May 21, 2012, 03:39:04 PM »
No dilution going on here.
Wooden Shoe Brew Works (not a commercial operation) Bethlehem, PA
http://www.woodenshoemusic.com/WSBW/WSBW_All_grain_Setup.html
I brew WITH style..... not necessarily TO style.....

Offline tom

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Re: Fermenting under pressure.
« Reply #10 on: May 21, 2012, 06:31:46 PM »
What was the pressure?
Brew on

Offline tomsawyer

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Re: Fermenting under pressure.
« Reply #11 on: May 22, 2012, 04:21:57 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.
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Offline kylekohlmorgen

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Re: Fermenting under pressure.
« Reply #12 on: May 22, 2012, 08:30:14 AM »
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.
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Offline tschmidlin

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Re: Fermenting under pressure.
« Reply #13 on: May 22, 2012, 12:27:39 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.
Tom Schmidlin

Offline phillamb168

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Re: Fermenting under pressure.
« Reply #14 on: May 23, 2012, 01:05:02 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?
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