What level CO2 pressure inhibits yeast activity?

[Dland]

I've got an ale that I racked before it was quite finished working, as have been spunding lately. Well, this brew fermented a little warmer than it should have, and I believe has acetaldahyde in it. I added some yeast from working wort from the next week's brew and it is working again, hope the sour flavor burns off. Am using spunding valves instead of air lock, and have them set at 5 PSI.

At what CO2 pressure, in PSI or volumes, is yeast activity hampered? I know it will happily build up to 3 vols and beyond in regular fermentation, but do not want carbonation get into way of yeast cleaning up contaminants. But if it does not matter, I'd set the spunding valves higher to carbonate as well.

 

[specharka]

I've got an ale that I racked before it was quite finished working, as have been spunding lately. Well, this brew fermented a little warmer than it should have, and I believe has acetaldahyde in it. I added some yeast from working wort from the next week's brew and it is working again, hope the sour flavor burns off. Am using spunding valves instead of air lock, and have them set at 5 PSI.

At what CO2 pressure, in PSI or volumes, is yeast activity hampered? I know it will happily build up to 3 vols and beyond in regular fermentation, but do not want carbonation get into way of yeast cleaning up contaminants. But if it does not matter, I'd set the spunding valves higher to carbonate as well.

It depends on the strain and temperature you are fermenting at. Some strains, like high-pressure lager yeast, will actually ferment faster and cleaner under pressure, even at elevated temperatures. There are other strains like Saison DuPont and Weissbier that are incredibly sensitive to back pressure and will stall with an airlock attached (0.25 in H20 ~ 0.01 psi).

I think 5 psi is acceptable for most ale strains and shouldn’t interfere with yeast health or fermentation. If you’re detecting acetaldehyde, increase the fermentation temperature and give it more time — it will clean itself up with some encouragement. I have noticed yeast stall with some American and British strains north of 2.0 volumes, so you can’t necessarily ferment at serving pressures. But you’re nowhere close to that. Carry on!

 

[RPh_Guy]

I routinely bottle carb to around 2.5 volumes (31psi at 74F).
My most recent weissbier I carbed to 3.6 vol (50psi at 74F).

This obviously would not be possible if the yeast stalled at high pressure.

(Used this calc)

 

[zipster222]

I have a related question. Does CO2 pressure inhibit the aging process of aged beers (e.g., RIS and barleywine)? Is it OK to age in a keg at full carbonation? Should you reduce the carbonation during aging? Should aging be done in a secondary fermenter with no pressure?

 

[Dland]

Usually I start carbing them up when I crash. It is good to have back pressure on the keg seal, at least with these old C kegs.