The stopper won’t be removed until after the cold crashing. At that point, why is it any different than not crashing and removing the stopper?
never put much thought to it. guess i will just use a stopper from now on. i assume that’s what you mean by ‘seal’.
because there is now a pressure differential between the inside of the fermenter and the outside. It will always exist if you cold crash because the air inside (and liquid) are contracting. If you have an air lock in place, it equalizes as the air cools sucking air in. if you seal the fermenter it is not able to equalize until you open unseal it but it will equalize by sucking in air when you unseal it.
I suppose though, that the reduced time of contact between the air and the beer could have an impact. if you have the fermenter ‘open’ the beer is potentially in contact with o2 for the whole cooling process while if you seal the fermenter it is only in contact with o2 for the short time between opening and purging in the keg.
+2
Very well said.
Yep.
I can’t imagine that will make any difference. The O2 will sit on top of the beer, right?
I suspect it’s all academic anyway. I know that oxidation is one of the very last things I worry about in my homebrewery most of the time given that I own three kegs and there are 4 adults in my house. A keg very very rarely lasts long enough to get over the hill much less oxidized seriously.
Yes academic IMO
The headspace by the time for cold crashing is about 100% CO2, if the beer shrinks 5%, you draw in 5% air which I’d 20% o2. Pretty infinitesimal. Plus co2 is heavier than o2. I doubt a lab test would show much difference in total dissolved o2.
I think the keg blanketed with CO2 is superior for crashing, followed by a stoppered bucket or carboy ( did this for a while and had good results too) second, with the airlock sucking in air dead last. I started crashing in keg because I felt in theory the oxidation was less, though in practice the stopper worked fine. I did feel crashing in a FV with an airlock caused an oxidized beer or two though. Maybe not.
Maybe I’m misreading your post, but are saying you recently switched from dryhopping at fermentation temperature to cold crashing and then dryhopping at serving temperature?
If so, that could be a factor in loss of hop aroma.
It’s always good to be mindful of where your beer is picking up oxygen. In terms of magnitude, though, I think racking to the keg under pressure would prevent more exposure than anything else. Diffusion through the surface of an un-agitated liquid is going to be pretty slow.