Is an extra dose of oxygen a good idea?

[Finn Berger]

When fermenting lager at low temperatures you need a lot of yeast - and sometimes I think even a lot is not enough. The limiting factor for the yeast growth in the beer is it's stores of stuff it sythesizes using oxygen, like sterols and fatty acids, which are vital to building and maintaining membranes. And as it can only store so much, we can't fix the problem with dosing the wort with large amounts of oxygen.

But if we bide our time and wait for the yeast to go through it's first cycle of cell division, the yeast won't have full stores any more. And so, presumably, it will take up more oxygen if it gets the chance. So why don't we give it that chance by adding a new dose of oxygen? If the yeast replenishes it's stores, then it will have added the potential for one extra cell division, and that should - if I'm right - equal pitching the double amount of yeast compared to what we did.

Now we actually do this when brewing very strong beer, though then at least part of the rationale is that it's hard to saturate a high gravity wort with enough oxygen. But I don't see the harm it can do, so why don't we do it when brewing beers of lower gravity? Or maybe some actually are doing it?

I picked up the idea from a Masterbrewers podcast a year or two ago, but that was advice to professional brewers, of course. I have had it in the back of my mind since, but I haven't tried it until just recently when I started the autumn/winter pils brewing season. The beer isn't finished yet, but seems fine.

So what about it? Any thoughts or experiences?

edit: This should probably have been posted in the "Yeast and Starters" part of the forum. Sorry.

 

[MaxStout]

I oxygenate with pure O2 for all beers, regardless of OG. For lower gravity worts, about 60 seconds from a 0.5 micron stone, and for higher gravity, about 90 seconds. I've always done this, so I don't have a non-O2 baseline to compare to. To me, it's cheap insurance and easy to do. For very high gravity worts--over 1.100--I will even oxygenate a second time about 12-24 hours after the pitch.

As an aside, I'm reading some conflicting advice on some of the forums re oxygenating for dry yeast. Some do and some don't. Those who don't claim that you only need to dump in the yeast and let 'er rip, that the yeast has all the nutrients it needs. For most of my beers I pitch dry yeast so I'm skeptical of that and am more in the "give the yeast as much help as you can" camp and opt to oxygenate.

But that's my process. I'll be curious to see what others do and how that works out.

 

[BeerSmith]

I've heard of this technique but only in association with very high gravity beers, wines and meads. The second oxygen addition is typically done at 12 hours.

 

[Finn Berger]

I oxygenate with pure O2 for all beers, regardless of OG. For lower gravity worts, about 60 seconds from a 0.5 micron stone, and for higher gravity, about 90 seconds. I've always done this, so I don't have a non-O2 baseline to compare to. To me, it's cheap insurance and easy to do. For very high gravity worts--over 1.100--I will even oxygenate a second time about 12-24 hours after the pitch.

As an aside, I'm reading some conflicting advice on some of the forums re oxygenating for dry yeast. Some do and some don't. Those who don't claim that you only need to dump in the yeast and let 'er rip, that the yeast has all the nutrients it needs. For most of my beers I pitch dry yeast so I'm skeptical of that and am more in the "give the yeast as much help as you can" camp and opt to oxygenate.

But that's my process. I'll be curious to see what others do and how that works out.

I use pure oxygen - should have stated that, of course. What I wondered about was whether there might be reasons not to give that extra dose, as it seems a very simple way of - in practice - doubling your yeast resources. And as it takes a lot of yeast when you ferment a beer like a pilsner at low temepratures, that would be nice.

When both Fermentis and Lallemand say that you do not need to oxygenate when using their dry yeast, I see no need to doubt that they are right. The reason you don't need to do it, is that the yeast is stacked up with full stores of sterols and fatty acids and so do not need the oxygen, as they can't use it. Fermentis actually advices against it, because what you actually do when you give oxygen to their yeast, is to pretty drastically over-oxygenate. So you don't give the yeast extra help, you just risk possible fermentation flaws.

 

[Finn Berger]

I've heard of this technique but only in association with very high gravity beers, wines and meads. The second oxygen addition is typically done at 12 hours.

Yeah, the problem is timing it right, I guess. It will depend on the lag time, as it should be done when the first doubling of the cell count has occured. That might actullay be even earlier than 12 hours - maybe as early as 6-7 hours if you pitch a live starter, as I do. I'm not sure what signs I should go by to decide that the right moment has come, though. That's what is holding me back. But I don't know how critical that is, either - maybe it doesn't matter, just as long as I don't do it too early?
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The problem is that I'll have to get up in the middle of the night to do this trick if the right timing is critical, and I hate the idea. I brewed yesterday and thought I could sneak down in basement in the morning with oxygen wand in hand, but the brew was already bubbling rather energetically, so I dropped the idea. I guess I'll just wait a bit next time and not add the yeast until late at night, just before I go to bed. The risk of an infection getting started in the meantime is probably rather small,.