Author Topic: too soon to cold crash?  (Read 450 times)

Offline spurviance

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too soon to cold crash?
« on: February 09, 2022, 10:09:26 am »
I have a Pilsner that I brewed 12 days ago, fermented with 34/70.  I kept the temp in the mid 50's and according to my Tilt SG stopped at 1.013 after 5 days.   I raised temp to mid 60's, went on a work trip for a week, and came home to find SG at 1.012.  Ordinarily I would call fermentation complete and cold trash, then transfer.  I hesitate to do this as there is still activity in the airlock, bubbling about once every couple minutes.  Ordinarily I'd simply wait a while longer as I assume the yeast is 'cleaning up' and why rush things.  But I was hoping to use the yeast cake to ferment a Vienna lager I plan to brew in 2 days.   I'm thinking I'll probably transfer to keg before cold crashing and let conditioning in the keg continue a while longer before cold crashing.  There should be plenty of yeast that has dropped to the bottom that I can re pitch onto my Vienna.  Any thoughts?
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Offline Bob357

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Re: too soon to cold crash?
« Reply #1 on: February 09, 2022, 10:20:41 am »
If it's going to be 2 days before you need the yeast cake, why not wait another day or so and take another gravity reading just to ease your mind, if nothing else. It's surely finished after a week in the mid 60s and that 1 degree over a week wouldn't bother me at all. It's kind of like beating a dead horse but never rely on airlock activity as an indication of fermentation. Your beer is likely just off gassing due to a slight temperature and/or barometric temperature change.
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Offline denny

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Re: too soon to cold crash?
« Reply #2 on: February 09, 2022, 11:28:49 am »
You raised the temp so it's likely what you're seeing is dissolved CO2 coming out of solution.
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Offline RC

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Re: too soon to cold crash?
« Reply #3 on: February 09, 2022, 01:53:04 pm »
You raised the temp so it's likely what you're seeing is dissolved CO2 coming out of solution.

^ This for sure, but also, even though the yeast have gone dormant, they are still metabolizing their stored glycogen reserves, albeit very, very slowly--just enough to stay alive. They are still generating CO2. They will do so until they have exhausted their glycogen reserves and die. A small bubble every few minutes, long after final gravity has been reached, is to be expected while the beer is sitting on the yeast cake.

Yeast only clean up while they are active. If the beer has reached FG, the yeast are no longer active and no more clean up will occur. The risk of kegging it and keeping it at room temp is you are giving ingressed O2 more opportunity to damage the beer. If you are going to keg it, I'd cold crash the keg right away.

If the concern is that off flavors are present, just take a sample and taste/smell it, or better yet do a forced VDK test on it. If there is no diacetyl present, you're good to crash it.

Offline denny

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Re: too soon to cold crash?
« Reply #4 on: February 09, 2022, 02:21:59 pm »
You raised the temp so it's likely what you're seeing is dissolved CO2 coming out of solution.

^ This for sure, but also, even though the yeast have gone dormant, they are still metabolizing their stored glycogen reserves, albeit very, very slowly--just enough to stay alive. They are still generating CO2. They will do so until they have exhausted their glycogen reserves and die. A small bubble every few minutes, long after final gravity has been reached, is to be expected while the beer is sitting on the yeast cake.

Yeast only clean up while they are active. If the beer has reached FG, the yeast are no longer active and no more clean up will occur. The risk of kegging it and keeping it at room temp is you are giving ingressed O2 more opportunity to damage the beer. If you are going to keg it, I'd cold crash the keg right away.

If the concern is that off flavors are present, just take a sample and taste/smell it, or better yet do a forced VDK test on it. If there is no diacetyl present, you're good to crash it.

That middle paragraph is so true and so obvious, yet so many people don't realize it.  How many times have we heard of people leaving beer in the fermenter long past fermentation to "clean up".
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Offline BrewBama

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Re: too soon to cold crash?
« Reply #5 on: February 10, 2022, 09:00:13 am »

Yeast only clean up while they are active. If the beer has reached FG, the yeast are no longer active and no more clean up will occur. The risk of kegging it and keeping it at room temp is you are giving ingressed O2 more opportunity to damage the beer. If you are going to keg it, I'd cold crash the keg right away.



+1. When it’s done it’s done.

Offline Steve Ruch

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Re: too soon to cold crash?
« Reply #6 on: February 10, 2022, 09:09:16 am »
You raised the temp so it's likely what you're seeing is dissolved CO2 coming out of solution.
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Offline spurviance

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Re: too soon to cold crash?
« Reply #7 on: February 10, 2022, 12:52:59 pm »
Thanks for the feedback.  Just tasted the sample that I used for a manual hydrometer check.  All good.  No obvious off flavors detected.  Going to cold crash for 24 hours before kegging and use the yeast cake for tomorrow's brew.
On tap,  Vienna Lager, Doppelbock, Dortmunder Export, Pale Ale, Porter, Saison

Fermenting, Saison