Sometimes. Sometimes not. It's a process, not that everything happens individually. Sometimes the first sign of oxidation is that "sweet" flavor, which may be a "loss of hops" to some. That can happen before darkening, concurrently, or after.
IPA 's Darkening with Age
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Sometimes. Sometimes not. It's a process, not that everything happens individually. Sometimes the first sign of oxidation is that "sweet" flavor, which may be a "loss of hops" to some. That can happen before darkening, concurrently, or after.
No to swirling! Whenever a carboy is opened, particularly after fermentation slows, there is just as much oxygen as anything else. I guess in theory that some of the dissolved c02 could be released during swirling, but it's much more likely that swirling would provide greater surface area for room air and oxygen to impact the beer. If the airlock bubbles, that just means that the pressure inside is greater than the pressure outside, and not that it's only c02 being released.
It's posted elsewhere in the forum in graph form, but it takes like 30 purges at 30 psi to really get rid most of the oxygen. Most of us don't do that. It's helpful to purge the keg first and do a closed transfer, to avoid oxygen pickup.
inkman15
Well-Known Member
I'm interested as to why there's hesitancy to use a solid bung during cold crash. Can someone explain that to me?
I had this darkening happen to me recently with a Galaxy IPA that I bottled. It was delicious at the gravity sample but after 2 weeks in the bottle, it took on that dark hue and the flavors got muted.
Followed the same process (cold crash with solid bung) on a recent IPA that I kegged and the beer is still delicious after a month.
Clearly I oxidized the Galaxy one, but I'm thinking it happened during the bottling process and not during cold crash.
I had this darkening happen to me recently with a Galaxy IPA that I bottled. It was delicious at the gravity sample but after 2 weeks in the bottle, it took on that dark hue and the flavors got muted.
Followed the same process (cold crash with solid bung) on a recent IPA that I kegged and the beer is still delicious after a month.
Clearly I oxidized the Galaxy one, but I'm thinking it happened during the bottling process and not during cold crash.
OK, so if you put a solid bung into the top of the carboy and actually seal you will develop 2psi pressure on the outside of your carboy due to the vacuum created from the gas cooling. If glass you don't want 2psi pressure, if plasic you will collapse the carboy, if you have a conical you are already set up for positive pressure. If you do not create a vacuum then you have an air leak and oxidize the beer, if you pull the bung before the temperature (and pressure) returns to normal you will pull air into the vacuum and oxidize the beer.
inkman15
Well-Known Member
So, I use Better Bottles. I don't care, aesthetically speaking, if the carboy collapses at all since they are so durable. What you're saying is that if I don't allow it to "un-collapse" before pulling the bung, there's a rush of O2 introduced?
As long as you don't care that your fermenter collapses, you actually get it to fully seal and allow the CO2 that is in the head space to come back to temperature I suppose not.
You may find that this takes a long time though. The solubility of CO2 into beer increases as temperature goes down and increases as pressure goes down. If you allow the pressure to stay the same by collapsing the fermenter some (probably a small amount) of the CO2 in the headspace will go into solution into the beer. When the headspace returns to temperature the CO2 will expand most of the way back to it's original volume but some of the CO2 will remain dissolved in the beer. You will either have to wait for the CO2 to offgas from the warmer beer or allow some of the air to come in and take its place.
Certainly better than allowing air to come in during cold crash, and better than a vacuum on a carboy.... but I'd still just get the minimum amount of hardware necessary to cold crash under pressure.
You may find that this takes a long time though. The solubility of CO2 into beer increases as temperature goes down and increases as pressure goes down. If you allow the pressure to stay the same by collapsing the fermenter some (probably a small amount) of the CO2 in the headspace will go into solution into the beer. When the headspace returns to temperature the CO2 will expand most of the way back to it's original volume but some of the CO2 will remain dissolved in the beer. You will either have to wait for the CO2 to offgas from the warmer beer or allow some of the air to come in and take its place.
Certainly better than allowing air to come in during cold crash, and better than a vacuum on a carboy.... but I'd still just get the minimum amount of hardware necessary to cold crash under pressure.
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Just an update to anyone who comes across this thread...
I stopped cold crashing & the issue disappeared. My IPA's are tasting infinitely better. Thank you to everyone who offered their ideas! It feels great to have that one resolved!
that's great news. is it still working out good just by skipping the cold crash?
old topic but i have been researching for cases like this since i have been going through this issue with lots of batches. the beers get darker with very little time (even if stored in the fridge) and completely lose their hop aroma and taste. some bottles turn out good, some don't (most).
I thought just letting it sit for a few days or weeks in the fridge would solve my problem. Turns out it didn't.
i did skip cold crashing one time and the batch came out nice. will do that again and hope it works out.
Just an update to anyone who comes across this thread...
I stopped cold crashing & the issue disappeared. My IPA's are tasting infinitely better. Thank you to everyone who offered their ideas! It feels great to have that one resolved!
Good info! Glad I came across this, as I was recently wondering what would work better between cold crashing and putting a filter / rubber band over my siphon when transferring to a bucket.
I'm guessing the suck back caused by cold crashing causes the oxidation?
