Heard Sarah talking about this, looks pretty awesome.
I see James' and Rob's pants just got a little shorter:
Fri, Dec 25, 2015 - 3:03pm
#1
White labs yeast vault
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This is very interesting. How do you ferment at 14 psi? If in a keg, as the gas is expelled it would raise that pressure constantly. You'd need a special kind of blow-off valve to make this work?
Also, who came up with the tests to even realize this possiblity?
Neat though. I'd be stoked to see how this comes out.
This is very interesting. How do you ferment at 14 psi? If in a keg, as the gas is expelled it would raise that pressure constantly. You'd need a special kind of blow-off valve to make this work?
Also, who came up with the tests to even realize this possiblity?
Neat though. I'd be stoked to see how this comes out.
No idea. You would need some kind of pressure relief valve you were talking about, or hook up to 14 psi co2, let the yeast build pressure and gas off every day?
Can we ask Sarah for their method?
I found this: http://byo.com/color/item/397-build-your-own-spunding-valve-to-carbonate...
But even if you did this, you'd still have to rack it and re-pressurize it.
https://www.wyeastlab.com/rw_yeaststrain_detail.cfm?ID=30 is known to work well at room temp (68 and under). I can say I've used it before with good results (still requries 4-6 weeks of lagering). Although, I've found that the simplest thing to do is create a starter for s-05 and pitch when it's really active. That's usually good to drink in 3 weeks.
I would assume the easiest way is to calculate the pressure excerted by a column of water, and then make sure that the blowoff tube is kept under that amount of water. If there is 14psi of water pushing down against the blowoff, then only once the internal pressure hits 14psi would gas be able to escape.
As for Chris' question of "who came up with these test?", it's probably commercial guys using a giant chonical fermenter who were worried about hydrostatic pressure on their yeast. Remember, lager yeast sits at the bottom of all this water.
EDIT:
Yup, as I suspected, using vertical water will work. however, you run into a problem.
1 inch of water exerts in the neighborhood of +0.04psi. This is about the amount of water in an airlock and is enough to maintain positive pressure inside a fermenting carboy. It also means that to get to +1psi, you would need a 2.3' vertical column of water. Which I guess is no big deal. you could do that by running a tube into a large-ish pot.
I believe in a passage from the book "Yeast" by Chris White and Jami Z---something, he mentions that 2 psi is enough to put some stress on lager yeast (ale yeast is top fermenting, so only the pressure from the airlock is applied after it starts to gas off).
But by that calculation, the carboys we use are far smaller than anything which would exert close to that much hydrostatic pressure. Using the estimation above, the liquid from the carboy itself is only likely to exert in the neighborhood of +1psi onto the yeast cake.
In other words, this yeast is probably only practical for commercial applications when hydrostatic pressures of 10psi and above are concerns. Since nobody at the brewhouse is rocking a 20-foot conical, I think this is a non-issue.
But what if we wanted to push this lager strain to its theoretical factory recommended maximum of 14 psi?
To 14psi, you that means you would need about a 35 foot column of water vertically pushing down onto your blowoff. That's taller than the brewhouse, even if we assume that you use Mike's giant 15 gallon fermenter (which we conservatively estimate to provide about 2.5 feet vertically of water).
In general, though, I would assume that hydrostatic pressure is something you want to avoid because it stresses out the yeast. If you consider the analogue, think about what happens when your own body is exposed to pressure? The bends can kill you if you're not being really careful. Even if you could do it, doesn't mean you should actively go trying to push the boundaries, and I would assume the same applies to yeast.