Pressurizing FV with oxygen instead of co2?

[Smellyglove]

I ferment some of my beers in cornys. I was thinking, is it a bad idea to pressurze the corny with o2 instead of pure co2? Co2 is "poison" to yeast. And yeast needs oxygen..

About it being "to much", one could maybe dillute the co2 to pressurize if you want to ferment under pressure (lagers) with o2?

My Imp stout is always getting a boost of o2 on day three, just before krausen. I was thinking maybe instead of this day 3 boost, if I pressurize it with pure o2, it would be maybe better, since the o2 would be steady, instead of giving the beer 02, it uses it up, and I give it some more, and it uses that up again.. What If I found a "golden" pressure to use so the o2 would be just perfect?

 

[Bilsch]

I think you will easily overrun the 8ppm O2 in solution recommended with a pure oxygen headspace under pressure. You'd be better off getting a gas syringe and doing some math to figure out how many CC of O2 (@stp) you would need to inject in the keg headspace. Then just shake it up a bit. The only way to be more accurate then this would be to use a DO meter.

 

[Smellyglove]

I think you will easily overrun the 8ppm O2 in solution recommended with a pure oxygen headspace under pressure. You'd be better off getting a gas syringe and doing some math to figure out how many CC of O2 (@stp) you would need to inject in the keg headspace. Then just shake it up a bit. The only way to be more accurate then this would be to use a DO meter.

But. Let's say I flow 60 seconds / 0.5L of 02 into my batch (I know this works) with a wand. Is there a reason I wouldn't, or shouldn't do this into the headspace?

the difference would be that the 02 comes out of solution in an open keg and out the "window".

I feel I need to test this.


Besides, 8PPM once will not cut it in an imperial stout how I see it.

 

[Bilsch]

The problem is that most of the oxygen your bubbling into your wort just escapes out the top. If it didn't you would never see bubbles breaking the surface from your wand/stone. Conversely in a keg it's all trapped in there and under pressure is going to diffuse at an even greater rate then it did at atmospheric pressure. You could very quickly go past the level that's damaging to yeast. Whereas if you put a known qty of o2 in the keg theoretically you cannot over do it.

 

[Smellyglove]

The problem is that most of the oxygen your bubbling into your wort just escapes out the top. If it didn't you would never see bubbles breaking the surface from your wand/stone. Conversely in a keg it's all trapped in there and under pressure is going to diffuse at an even greater rate then it did at atmospheric pressure. You could very quickly go past the level that's damaging to yeast. Whereas if you put a known qty of o2 in the keg theoretically you cannot over do it.

I'm with you on that. Meaning that less 02 would be needed, right?

I'm not much of a mathematician, at all, so I'll just try this by trial and error when I find a window to do so. A split batch into to cornys, and give them different amount of o2.

 

[day_trippr]

fwiw, I believe Chris White in Yeast claims there is no measurable toxicity at up to 40ppm...

Cheers!

 

[TechFanMD]

I assume you're releasing pressure either through a spunding valve or have a way to use an airlock/blowoff on the corny. Since you mention 'pressurizing' with O2 I'm guessing spunding.

Either way the yeast will quickly make CO2 which will just mix with your oxygen and quickly dilute it and push it out making the whole exercise a waste of 02.

I don't think they would ever use any of that surface oxygen in the time before it is all blown out through the spunding valve.

 

[Bilsch]

I'm with you on that. Meaning that less 02 would be needed, right?

I'm not much of a mathematician, at all, so I'll just try this by trial and error when I find a window to do so. A split batch into to cornys, and give them different amount of o2.

Yes if you trapped it in the keg you would need a LOT less oxygen then if you were bubbling it through.

 

[Bilsch]

I assume you're releasing pressure either through a spunding valve or have a way to use an airlock/blowoff on the corny. Since you mention 'pressurizing' with O2 I'm guessing spunding.

Either way the yeast will quickly make CO2 which will just mix with your oxygen and quickly dilute it and push it out making the whole exercise a waste of 02.

I don't think they would ever use any of that surface oxygen in the time before it is all blown out through the spunding valve.

Well not exactly spunding the O2 but holding it there to give it time to diffuse in the wort. By enriching the O2 in the atmosphere and or increasing it's pressure above the wort you creating a higher partial pressure and thus forcing more in faster. Surface area plays a big role here too. If you shake the keg diffusion will accelerate.

The yeast will only produce CO2 when they have finished taking up O2 so any dilution and sweeping out of O2 after that point by CO2 would be a good thing actually.

Well that depends on the factors above whether they would use the surface oxygen as you called it. If we take air (~20%O2) and let it sit in contact with the wort in the keg at standard temperature and 1 atmosphere then yes the rate that oxygen will diffuse into that wort will be slow. To speed that process up we could do several things.
1) Increase the concentration of oxygen in the headspace.
2) Increase the pressure of oxygen in the headspace.
3) Increase the surface (contact) area between the gas and liquid.
The only problem is that without active measurement you could quickly overrun the the amount of oxygen the yeast need and either damage the yeast or damage the beer.

What I proposed was to put a known quantity of O2 in the sealed keg and that way you theoretically should not be able to over oxygenate your wort.

To be clear.. I have never tried this except with starters but have always thought of testing the idea out in a keg. In theory it should be a simple matter of putting x amount of oxygen in a sealed keg and waiting a specified time and then venting. Or shaking and waiting a shorter period of time.

 

[TechFanMD]

Where do you get the idea that yeast don’t produce CO2 until after they have finished taking up O2? I think that any time they are consuming sugar and ‘breathing’ O2 they are producing CO2 just like any other living thing.

 

[Bilsch]

Interesting. Where do you get the idea that yeast produce CO2 while they are in the lag phase?

 

[TechFanMD]

They do not, but they aren't swimming to the surface and gulping for air like gold fish either. The lag period is short enough that I think the headspace oxygen would be pushed out before it had any affect on oxygen levels in the wort - especially on a wort made by someone like the OP who is clearly advanced, very careful, likely has an appropriately sized starter and oxygenates well to begin with.

 

[TechFanMD]

I found this article interesting. I also had not heard of someone doing what the OP does (adding more O2 after 3 days) so I am reading up on why one might or might not do this. What is the benefit of adding oxygen once fermentation has begun?

https://www.morebeer.com/articles/how_yeast_use_oxygen

 

[Smellyglove]

I found this article interesting. I also had not heard of someone doing what the OP does (adding more O2 after 3 days) so I am reading up on why one might or might not do this. What is the benefit of adding oxygen once fermentation has begun?

https://www.morebeer.com/articles/how_yeast_use_oxygen

I only do that to my imperial stout. I ferment it "slowly" with a slow temp-rise to avoid creating to much "crap", and on the day three mark it's starting to hit high krausen. I just do it to maybe help a potential "last" cell division on it's way.

 

[Smellyglove]

But. The point in pressurizing with either 100% o2, or a mix of co2/o2 is also to dillute the co2 those times I ferment under pressure. 1.5 bar of pure co2 can't be super healthy for the yeast from the get-go. I can aerate the wort normally before pitch as usually.

 

[Smellyglove]

I assume you're releasing pressure either through a spunding valve or have a way to use an airlock/blowoff on the corny. Since you mention 'pressurizing' with O2 I'm guessing spunding.

Either way the yeast will quickly make CO2 which will just mix with your oxygen and quickly dilute it and push it out making the whole exercise a waste of 02.

I don't think they would ever use any of that surface oxygen in the time before it is all blown out through the spunding valve.

Yes I'm using a spunding valve.

 

[TechFanMD]

Thanks Smellyglove. You may be right - I just have trouble wrapping my head around the tiny surface contact area on a corny with the small headspace filled with CO2 having much negative impact, or filling with O2 having a positive impact.

I did not know that you ferment at 1.5bar (22psi) - I've never read of anyone doing the initial ferment that high. I thought that when you ferment under pressure it was like 6-9psi, then you adjust it higher later in the ferment if you want to carbonate it.

 

[Smellyglove]

Thanks Smellyglove. You may be right - I just have trouble wrapping my head around the tiny surface contact area on a corny with the small headspace filled with CO2 having much negative impact, or filling with O2 having a positive impact.

I did not know that you ferment at 1.5bar (22psi) - I've never read of anyone doing the initial ferment that high. I thought that when you ferment under pressure it was like 6-9psi, then you adjust it higher later in the ferment if you want to carbonate it.

1.5 bar was just from the top of my head since I have a batch going at that pressure right now, and it's the first attempt at pressurizing from the start with that amount of pressure. One needs to experiment

EDIT: But I actually started this one at 0.9 bar when I think of it, and the wort absorbed the co2 so it went down to about 0.8-ish bar before it started to ferment the wort and I could observe a rising pressure again, which is spunded at 1.5 bar. For at least two days there was no pressure buildup, until when I came back from a job late day three and I saw it was at 1.5 bar.

But, I've done 9 PSI (0.6 bar) before a few times, but I want to go further, just to see how it works out. I'm trying this to see if it's viable to suppress the esters "enough" at 14C with 34/70, as warm fermented lagers tastes nothing like lagers to me.