Fermentation under pressure question.

[jetfixr]

I have never fermented under pressure but I would like to give it a shot. I still have a bit of confusion that I have not been able to sort out through searching the forums. I know it is crucial to oxygenate prior to pitching the yeast. But as the yeast starts to create CO2 and the oxygen is depleted, at what point is the yeast cell division and growth inhibited by lack of oxygen and the CO2 being driven into the solution? Do use the spunding valve from the start of the fermentation? Went transferring under pressure there will inevitably be some slight differential pressure in the primary and secondary, does that allow the CO2 to come out of solutions and disturb the trub. What is the best amount of pressure to ferment under? I am seeing around 10 psi kicked around alot.

 

[VikeMan]

The yeast will take in all the oxygen they need (or is available, whichever is less) in about the first hour after pitching, before CO2 production really begins. They use the O2 to make sterols, which are used to build cell walls to facilitate budding. They don't need O2 to be replenished during fermentation.

 

[DuncB]

If I want the yeast to express itself then I ferment the bulk of the sugars open. Then spund at the end to the target vols of CO2 corrected for temperature.
To squash yeast expression say for a quick " lager " then I oxygenate and then spund from the start letting it build to 15 psi and then higher towards end of ferment.
Closed transfer I use the ferment gas to purge the starsan from the target keg and then build pressure in the keg with the spund valve on the keg.
You need a small pressure difference in receiving keg to start the closed siphon but then just transfer with gas to gas and liquid to liquid. No trub should really get stirred up and no need to add gas.
But some will ferment at different pressures, others drive their transfer with CO2 from a cylinder and bleed or spund the gas out during the transfer.

 

[Yesfan]

I'm on my second attempt at pressure fermentaton. This time, I spunded from the start. I've got about 6-6.5G in my all rounder and 4G in one of my kegs (with a floating dip tube). Recipe is a pale ale with Galaxy, Mosaic, and Comet hops (Centennial for bittering). I pitched 2 pks of US-05 in the All Rounder and K-97 in the keg. Both are currently at 17psi at 66F.

I brewed this beer on the 3/4. With pressure fermentation, how long until I can package and serve? I'm fermenting at my typical temperature, but was wondering if a pressure fermentation will still finish quicker compared to a non-pressure fermentation if the temp remains the same.

 

[DuncB]

Use gravity readings to check the ferment progress. Picnic tap on the liquid post will allow sampling.
Ferment will be same time or slower than usual ferment of that beer. Unless you are warm fermenting a lager in which case it will be quicker.
2 or 3 days without change plus a diacetyl temperature raise, then cold crash and transfer.