Author Topic: Yeast Autolysis & Pressure  (Read 1017 times)

Offline Kit B

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Yeast Autolysis & Pressure
« on: January 25, 2012, 07:54:37 AM »
In another thread, I was reading about pressurized fermentations & got to wondering...
At what pressures do yeast typically undergo autolysis?
Are pressurized fermentations a potential recipe for disaster?

How much pressure is too much?
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Offline tomsawyer

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Re: Yeast Autolysis & Pressure
« Reply #1 on: January 25, 2012, 09:29:49 AM »
I'm no expert on the subject but I'll pass on my second-hand info.  Its my understanding that yeast can take considerable pressure without bursting.  Consider the fact that bottle conditioned beer is at something like 30psi (I think).  Above 15psi there are some negative effects on genetic stability so you don't necessarily want to go higher if you are saving/reusing yeast cake.  And if you are reusing cake you want to release the pressure slowly prior to harvesting, otherwise this can cause some lysis.
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Offline tschmidlin

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Re: Yeast Autolysis & Pressure
« Reply #2 on: January 25, 2012, 10:59:34 AM »
There is a cell lysis method called a cell bomb - the cells are placed under something like 25,000 psi and then the pressure is released quickly, which blows up the cells.  It does NOT work well with yeast.  When we want yeast DNA we use a smash-n-grab, which uses beads and a vortexer to vibrate the beads and physically smash the cells.  The grab comes later ;)

Anyway, the point is yeast can withstand a lot of pressure, it has more to do with pressure over time (and pH and ABV) than a specific psi.
Tom Schmidlin

Offline hopfenundmalz

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Re: Yeast Autolysis & Pressure
« Reply #3 on: January 25, 2012, 02:28:26 PM »
Tom doesn't temperature come into play also?  Remember that "Yeast" said the higher pressure and temperature in the cone of a big conical can be a problem.  Or am I out in left field? 
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Offline Kit B

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Re: Yeast Autolysis & Pressure
« Reply #4 on: January 25, 2012, 02:41:16 PM »
Tom doesn't temperature come into play also?  Remember that "Yeast" said the higher pressure and temperature in the cone of a big conical can be a problem.  Or am I out in left field? 

That is the issue I was hoping would be addressed.
My curiosity was sparked.
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Offline bluesman

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Re: Yeast Autolysis & Pressure
« Reply #5 on: January 25, 2012, 03:07:26 PM »
I know that Gordon Biersch allows their lagers to pressurize to 10psi (or thereabouts) during the krausening stage to promote natural carbonation.
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Offline tschmidlin

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Re: Yeast Autolysis & Pressure
« Reply #6 on: January 25, 2012, 04:31:36 PM »
Tom doesn't temperature come into play also?  Remember that "Yeast" said the higher pressure and temperature in the cone of a big conical can be a problem.  Or am I out in left field? 
No, you're totally right.  Temp will play a role too, I should have included it in the list.  I don't know of a temp/pressure/viability chart vs. time has been generated - it would be pretty cool I think.
Tom Schmidlin

Offline tomsawyer

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Re: Yeast Autolysis & Pressure
« Reply #7 on: January 25, 2012, 05:58:45 PM »
Cold would render the yeast less susceptible to pressure, or more?  I'm guessing less, as in lower temp at a given pressure would preserve viability.
Lennie
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Offline tschmidlin

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Re: Yeast Autolysis & Pressure
« Reply #8 on: January 25, 2012, 06:08:19 PM »
Yes, lower temperature should help preserve the yeast from the pressure.
Tom Schmidlin