Pressure ferment a Quad?

[1Pivoman]

I have a Fermzilla, and have had good success fermenting lagers under pressure and kegging under pressure as well. Haven’t done any ales under pressure, and am brewing a huge Quad next and am contemplating doing it under pressure. Yeast will be White Labs Belgian Strong Ale. I know some styles like Bavarian Weizens are brewed without pressure, not sure about a Belgian Quad. I do plan to bottle it instead of kegging it since I’m splitting the batch with someone. Anyone have any insights?

 

[bjhbrew]

Just spitballing but I would think that pressure fermenting a quad would reduce the yeast derived flavors and aromas that are signature of the style. Also, you mention bottling - I’m thinking that it could be tricky to fill bottles without foaming depending on what pressure you ferment at (how much co2 is in the beer) that being said, I can see why you might want some pressure; I did a quad with wy3787 and the krausen was huge! I did a 4 gallon batch in a 7 gallon fermonster and needed pretty much all of that headspace.

 

[VikeMan]

I have a Fermzilla, and have had good success fermenting lagers under pressure and kegging under pressure as well. Haven’t done any ales under pressure, and am brewing a huge Quad next and am contemplating doing it under pressure. Yeast will be White Labs Belgian Strong Ale. I know some styles like Bavarian Weizens are brewed without pressure, not sure about a Belgian Quad. I do plan to bottle it instead of kegging it since I’m splitting the batch with someone. Anyone have any insights?

When you say "fermenting under pressure," are you talking about lots of pressure, like 10+ PSI? Or just enough pressure for a spunding valve to replace an airlock...say 2 PSI or so?

 

[Pivoman]

I have a spunding valve, so it's about 10-12 psi. I totally forgot about pressure fermentation subduing the esters in certain beers like Bavarian Weizens, which is why they open ferment them in a lot of German breweries. I just feared not getting proper carbonation when bottling, so I picked up some bottle and cask conditioning dry yeast I'll sprinkle in the bottles with some corn sugar tabs when bottling.

 

[VikeMan]

I have a spunding valve, so it's about 10-12 psi.

Yeah, so I would recommend reducing that pressure to the bare minimum (like 2 PSI) for any batches where you are not trying to intentionally suppress esters.

 

[TheMadKing]

Yeah, so I would recommend reducing that pressure to the bare minimum (like 2 PSI) for any batches where you are not trying to intentionally suppress esters.

+1

It would reduce the character of the beer

Also, the reason pressure suppresses esters is because it adds minor stress to the yeast, and the last thing you want to do with a big beer like a quad is intentionally stress your yeast.

 

[luckybeagle]

I know this thread is several months old but... did you end up fermenting the quad under pressure? I’m considering a 5psi fermentation at room temp to hopefully suppress fusels without losing too much by way of desirable esters (wy3787). I’d love to hear your outcome if you ended up doing this, or pressure fermenting any other high gravity ales for that matter!

 

[VikeMan]

I’m considering a 5psi fermentation at room temp to hopefully suppress fusels without losing too much by way of desirable esters (wy3787).

Pressure does suppress the production of higher alcohols. Unfortunately, the esters you are (likely) talking about are made (by the yeast cells) from the higher alcohols. So, pressure also reduces the amount of esters made.

 

[luckybeagle]

Pressure does suppress the production of higher alcohols. Unfortunately, the esters you are (likely) talking about are made (by the yeast cells) from the higher alcohols. So, pressure also reduces the amount of esters made.

That makes sense. I found this article this morning that I found pretty insightful:

Esters and Fusel Alcohols

I suppose a pressure-fermented Quad could be stylistically lifeless and more along the lines of an Imperial Dark Lager or something. It seems to me that there should theoretically be some pressure sweet spot where you can keep a lid on harsh fusels whilst having desirable esters make enough of an appearance though, since we're able to do that with temperature manipulation alone (for example, keeping solventy fusels at a level 2 and esters at a level 8 can be achieved concurrently, and not one at the expense of the other). I wish I had a 20 gallon system, 3 fridges and 4 Fermzillas to run some quality tests.

I'm also thinking about the comparatively tall fermenters at Westvleteren, Rochefort etc, and the head pressure from the volume of wort being fermented in those things. Couldn't a pressurized ferment simulate those massive conicals to some extent? Maybe that also helps them push temperature higher without undesirables (I think Westys hit 80F+). I know if I did that with my 20" tall carboys I'd make a pretty harsh Belgian with all other things being equal to Westvleteren's process.