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Environment and yeast in ale conditioning

I’ve been thinking a lot lately about what goes on during the aging/conditioning of ales, specifically the period between the end of complete primary fermentation (as defined by SG stability) and final packaging (either in a bottle or sealed, chilled and carbonated keg).

Correct the following if I have it wrong, please, and add anything you think relevant to improve my understanding.

An advantage of conditioning would be diacetyl reduction by the yeast that are still alive although metabolizing at a greatly reduced rate, “scrubbing” the beer of any remaining compounds they can digest. Cellaring temperatures (50’s) are preferred over serving temperatures (30-40’s) because yeast metabolism rates will be greater at the higher temperatures and so the conditioning process will proceed more quickly.

The vessel in which the beer is conditioned (glass carboy or steel keg) does not need an airlock to benefit the yeast. A steel keg could be purged with CO2 and sealed. A glass carboy needs an airlock to release the slow CO2 pressure build-up from the very slow yeast respiration, but this release of gas is not a necessary component of the environment the yeast need. The yeast don’t need to “breath”, rather the airlock just keeps the bung from being expelled from the carboy.

By extension, the same concepts apply to lagers. More time is required for conditioning because the lager yeast are working more slowly at colder temperatures.

Am I getting close to understanding this?

[quote=“Tom_B”]An advantage of conditioning would be diacetyl reduction by the yeast that are still alive although metabolizing at a greatly reduced rate, “scrubbing” the beer of any remaining compounds they can digest. Cellaring temperatures (50’s) are preferred over serving temperatures (30-40’s) because yeast metabolism rates will be greater at the higher temperatures and so the conditioning process will proceed more quickly. [/quote]Reducing diacetyl should be done before conditioning the beer at cellar temps. You need to be in the mid to upper 60s for a D-rest and since most ales are fermented in that range a D-rest is usually unnecessary. I bring all my beers up to around 70° after primary fermentation is finished to get the yeast active and clean up after themselves. As for conditioning, I do it at whatever the temperature is in my basement, right now it’s in the mid 50s but in the summer it gets over 70° I don’t brew much in the summer though.

Bottle conditioning is best done at 68F+. It’ll proceed faster at the higher temperature, but at some point, you run into diminishing returns, as high heat can stale beer prematurely - 68F seems to offer the best balance between preventing staling and allowing the yeast to work quickly.

As has been said, diacetyl reduction should happen before bottling. I’m not sure what else it is you’re trying to figure out.

My interest regards bulk conditioning, either in a glass carboy or corny keg. I’ll be force-carbonating the beer in the keg. While I want to learn more about what actually happens over time to the beer (conditioning), I want to know whether I need an airlock on a corny keg while allowing it to bulk condition in either 1) my basement at 64 degrees or 2) my keezer at 40 degrees? The forums give conflicting opinions on this.

In the past when bottling a beer, I found that racking the beer from the primary to a secondary carboy with an airlock where it conditioned for 2 weeks greatly clarified the beer and shortened the time needed for conditioning in the bottle. Now that I am kegging, I would like to capture the benefits of this period of bulk conditioning but am unsure what environmental conditions are required.

For example, I just racked the beer to the keg after 2 weeks in the primary. The keg has been sealed and purged with CO2 and is sitting in a basement corner without a blow-off tube or airlock with the headspace under about 11 psi. Rather than put the keg into the keezer immediately, my plan is to leave at basement temperature for 1-2 weeks, then move it to the keezer where it will be force carbonated. The idea is that conditioning will proceed more rapidly at 64 degrees than it would at 40 degrees.

Am I wasting time, effort and thought on this?

[quote=“Tom_B”]My interest regards bulk conditioning, either in a glass carboy or corny keg. I’ll be force-carbonating the beer in the keg. While I want to learn more about what actually happens over time to the beer (conditioning), I want to know whether I need an airlock on a corny keg while allowing it to bulk condition in either 1) my basement at 64 degrees or 2) my keezer at 40 degrees? The forums give conflicting opinions on this.

In the past when bottling a beer, I found that racking the beer from the primary to a secondary carboy with an airlock where it conditioned for 2 weeks greatly clarified the beer and shortened the time needed for conditioning in the bottle. Now that I am kegging, I would like to capture the benefits of this period of bulk conditioning but am unsure what environmental conditions are required.

For example, I just racked the beer to the keg after 2 weeks in the primary. The keg has been sealed and purged with CO2 and is sitting in a basement corner without a blow-off tube or airlock with the headspace under about 11 psi. Rather than put the keg into the keezer immediately, my plan is to leave at basement temperature for 1-2 weeks, then move it to the keezer where it will be force carbonated. The idea is that conditioning will proceed more rapidly at 64 degrees than it would at 40 degrees.

Am I wasting time, effort and thought on this?[/quote]

Kegs are rated up to 100+ PSI, so there’s no need for an airlock as long as the beer is in the condition you want it to be. If you wanted to blow off sulfur or other off-flavors, you’d want a way to let gases escape. Otherwise you’re just conditioning. Don’t over-think it.

Yep, that is pretty much what I’ve concluded. My concern was the freer exchange of gases in a carboy than in a keg. Once off-gassing or respiration by the yeast is completed, kegging is the way to go for letting a beer rest and condition/mellow before final packaging. I’ve had an Irish ale resting in a sealed keg in the basement at 64 degrees that will get placed in the keezer tomorrow for chilling and carbonation.

Overthinking things is what this forum is all about, Vaughn. I’d inset a smily here but they aren’t working on this computer, so here it is old-school : )

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