Author Topic: Why does cold crashing work?  (Read 898 times)

Offline Biran

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Why does cold crashing work?
« on: January 23, 2016, 08:04:15 PM »
I have never thought of this before but today I was trying to think of why chilling the beer causes particles to drop out of solution and I could not think of a reason.  It works, obviously, I do it all the time.  But how?

Offline charles1968

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Re: Why does cold crashing work?
« Reply #1 on: January 23, 2016, 10:15:14 PM »
Gases are more soluble in colder water, so when you chill beer (which is saturated with CO2 as a result of fermentation), more CO2 can stay in solution rather than leaving as bubbles. Hence bubbles stop forming and rising. It's the continual rise of tiny CO2 bubbles that keeps yeast cells and other particles suspended and that creates krausen during peak fermentation activity and a head on freshly poured beer. Take away the bubbles and the sediment drops out a lot faster than if you waited for the solution to fully degas first.

The cold also makes yeast dormant, stopping fermentation (though if yeast are still active, you might be cold crashing prematurely).
« Last Edit: January 23, 2016, 10:18:52 PM by charles1968 »

Offline hopfenundmalz

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Re: Why does cold crashing work?
« Reply #2 on: January 23, 2016, 11:08:39 PM »
Proteins and polyphynols combine at low temperature, bigger partials form as you go lower in temperature. Look up Stokes Law, which says larger partials will settle faster.
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Offline denny

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Re: Why does cold crashing work?
« Reply #3 on: January 24, 2016, 04:48:12 PM »
Proteins and polyphynols combine at low temperature, bigger partials form as you go lower in temperature. Look up Stokes Law, which says larger partials will settle faster.

THIS^^^^ is the correct answer.
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Offline charles1968

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Re: Why does cold crashing work?
« Reply #4 on: January 24, 2016, 05:27:28 PM »
Proteins and polyphynols combine at low temperature, bigger partials form as you go lower in temperature. Look up Stokes Law, which says larger partials will settle faster.

THIS^^^^ is the correct answer.

It doesn't answer the OP's question though, which is why does chilling make particles drop out. It's the answer to a slightly different question: why does chilling remove chill haze.

Hopfenundmalz is right that chilling precipitates protein-polyphenol complexes, which helps get rid of chill haze, but those don't exist as particles in beer before chilling as they're soluble at fermentation temperatures. Most of the suspended gunk is yeast, which doesn't drop until CO2 bubbles stop rising.
« Last Edit: January 24, 2016, 05:31:27 PM by charles1968 »

Offline narvin

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Re: Why does cold crashing work?
« Reply #5 on: January 24, 2016, 05:39:51 PM »
Yeast flocculates at lower temperatures.  Bigger clumps means the same reaction a la Stokes. Rising bubbles has little to do with it.
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Offline charles1968

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Re: Why does cold crashing work?
« Reply #6 on: January 24, 2016, 06:29:09 PM »
Yeast flocculates at lower temperatures.  Bigger clumps means the same reaction a la Stokes. Rising bubbles has little to do with it.

Yes that's another factor, more so for flocculant ale yeasts than lager. Turbidity is related to CO2 release though. Anything that forces CO2 back into solution allows sediment to fall, eg putting beer under pressure or chilling.