Partial natural carbonation on keg to prevent oxydation?

I've kegged a few batches, and they've all been carbonated with a Co2 bottle. On most of them I've purged the keg with Co2 first, and also used the safety valve to vent out oxygen.

I am not sure if this is good enough, and I'm therefore considering to partially carbonate my next kegged batch with sugar. Hoping that the yeast will use the oxygen.

Have you guys and gals tried it?

If I do my best to keep oxygen out, how much of the carbonation should be naturally? 1/4, 1/3, 1/2?

Never had oxygenation issues transferring into the "out" tube of a purged keg. Keg conditioning is an option, but the extra yeast layer can be a PIA. Usually use 2/3 as much priming sugar as it your were bottling. Not sure if the yeast will consume all of the dissolved oxygen present. That calls for Science!

kiwipen said:

I've kegged a few batches, and they've all been carbonated with a Co2 bottle. On most of them I've purged the keg with Co2 first, and also used the safety valve to vent out oxygen.

I am not sure if this is good enough, and I'm therefore considering to partially carbonate my next kegged batch with sugar. Hoping that the yeast will use the oxygen.

Have you guys and gals tried it?

If I do my best to keep oxygen out, how much of the carbonation should be naturally? 1/4, 1/3, 1/2?

Click to expand...

Purging your keg is completely effective and can be qualitatively demonstrated via physics. Dougcz did the math in another thread that I don't feel like digging up right now, but basically you need to charge your headspace with 30 PSI and purge 10-15 times to reduce the oxygen content to less than .1ppm.

EDIT: I guess I'm not as lazy as I thought

https://www.homebrewtalk.com/showthread.php?t=565834

and its less than .001 ppm

TheMadKing said:

Purging your keg is completely effective and can be qualitatively demonstrated via physics. Dougcz did the math in another thread that I don't feel like digging up right now, but basically you need to charge your headspace with 30 PSI and purge 10-15 times to reduce the oxygen content to less than .1ppm.

EDIT: I guess I'm not as lazy as I thought

https://www.homebrewtalk.com/showthread.php?t=565834

and its less than .001 ppm

Click to expand...

You linked the first version of the analysis and chart, which used "Percent of Original O2 Remaining" rather than ppm O2 in the headspace. The "New and Improved" versions which show ppm O2 in the headspace are below:





One complicating factor is the analysis assumes that the CO2 being used is 0 ppm O2. All CO2 has come level of O2, and you can't purge to lower O2 levels than what is in your CO2.

You can get lower O2 levels by kegging prior to completion of fermentation, and using a spunding valve to control excess CO2 build up. I haven't done an analysis on that method (yet.)

Brew on

What exactly is a purge cycle?

kiwipen said:

What exactly is a purge cycle?

Click to expand...

Pressurize the keg with CO2
Shut off, or disconnect the CO2
Vent the keg to 0 psi

Each repetition of the above sequence is one purge cycle.

Brew on

You can 100% natural carb in the keg. I use around 2.5oz +/- corn sugar, and hit it with some CO2 to seal the lid. 7-10 days later it's carbed and ready to go in the cold.

doug293cz said:

You linked the first version of the analysis and chart, which used "Percent of Original O2 Remaining" rather than ppm O2 in the headspace.

Click to expand...

I did mention that I was lazy... I saw the chart but didn't read it carefully because it looked familiar

Thanks for the correction!