[Herminator]

So I visited another forum just to check it out.  Then a thread grabbed my attention.  The thread was about cold crashing causing oxidation.  Basically what was discussed is that cold temperatures cause air to be sucked in and thus O2 and CO2 mix together.  Additionally the conversation indicated only cold crash under pressure.  Anyone have any experience with this? 

This jumped out to me because the last two beers I have cold crashed in the carboy have a slight oxidation flavor that I just couldn't figure out. 

Thoughts?

[morticaixavier]

this is an issue that invites endless discussion.

It is true that when you cold crash a fermenter that is not sealed it will draw in a small amount of air. and it theory this could cause oxidation reactions but I personally have never noticed this happening and I cold crash pretty much all my beers.

There are those that will seal the fermenter first which is fine as long as it's not glass. Air will still be sucked in when you unseal the fermenter but it will be in contact with the beer for a much much shorter time this way.

Or, if you keg, you can keg first and then cold crash in a pressurized environment.

It just isn't worth the worry to me as I have never had a problem arise from it.

[ynotbrusum]

Like Mort, I never had a problem Hermen.  But for the last several years I keg, apply significant head pressure, then crash.  If I was to cold crash, I guess I would do it in the primary with the hope that the existing CO2 layer would cover the incoming O2.  Watch out for fully sealed containers - they will crush in an environment where the temp is dropped without venting!

[morticaixavier]

Like Mort, I never had a problem Hermen.  But for the last several years I keg, apply significant head pressure, then crash.  If I was to cold crash, I guess I would do it in the primary with the hope that the existing CO2 layer would cover the incoming O2.  Watch out for fully sealed containers - they will crush in an environment where the temp is dropped without venting!

I would not trust a glass container to hold the negative pressure but I doubt very much if the shrinkage caused by a drop from 65 to 32 would implode a 7 gallon bucket or better bottle. I have been wrong in the past though. 

[HoosierBrew]

  But for the last several years I keg, apply significant head pressure, then crash.

+1.  Easily enough avoided if you keg.

[duboman]

I crash just about every beer and do it in a bucket with a blow off attached usually, not one beer has ever had any oxidation issue, not saying it can't happen, just not my experience. Neither have I experienced any suck back of the blow off vessel contents which has been reported to be an issue for some. Maybe I'm just lucky

[Herminator]

Thanks for the thoughts.  I don't keg at this point and have started to crash my past few batches and was wondering if this was an issue and the cause of my slight oxidation taste I was getting. 

I have always removed my blow off tube after fermentation is complete in place of a airlock.  I guess all the more reason to get the kegging system started. 

Cheers!

[HoosierBrew]

Thanks for the thoughts.  I don't keg at this point and have started to crash my past few batches and was wondering if this was an issue and the cause of my slight oxidation taste I was getting. 

I have always removed my blow off tube after fermentation is complete in place of a airlock.  I guess all the more reason to get the kegging system started. 

Cheers!

FWIW, I did crash in fermenter for many years and did not notice a difference. I always assumed that what small amount of oxygen that got sucked in sat on top of the heavier blanket of CO2 from fermentation. I just started crashing in the keg to remove the worry.

[ynotbrusum]

As to the crushing, I was thinking about the one time I put a solid bung on a Better Bottle... Caught it before a full disaster, but it did crumple significantly!

[majorvices]

I don't think it is a big concern and have cold crashed in carboys for years and never had a problem. Much more of a concern is picking up oxidation from racking to secondary, bottling buckets and bottles for packaging.

[Jeff M]

If you cold crash in an open container and then bottle condition the small fermentation to carbonate the bottles should scrub the majority of the oxygen from the beer, no?

[majorvices]

If you cold crash in an open container and then bottle condition the small fermentation to carbonate the bottles should scrub the majority of the oxygen from the beer, no?

It certainly scrubs oxygen but I think it's a mistake to think that all that o2 pick up homebrewers do is just magically cleaned up during natural carbonation. And, of course, sone styles can handle oxygen pick up better than others. Best to try to eliminate it as best as possible at every chance.