You really can’t with O2 if you are following normal procedures. If you continuously oxygenate it’s bad, but no one does that. The solubility limit of O2 in wort is fine for yeast if you are pitching the proper amount of healthy yeast. The solubility of O2 in wort is less than in water.
Pretty sure you aren’t supposed to aerate/oxygenate hot wort. I’m surprised no one else caught this comment earlier?!? Aerating/oxygenating is for cooled wort. Isn’t that where the (bad) term hot-side aeration comes from?
I’ve used the red O2 tanks for years. Recently acquired a cheap decommisioned small medical O2 tank. Holds way more than those disposible red ones. Yes, oxygenating costs more. But I figure the yeast want oxygen not just air. Not that good results can’t be had with aerating.
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I think the idea is to stir the wort for a whirlpool effect and to speed cooling. I have poured hot wort from one bucket to another on several occasions and never noticed and apparent HSA effects. Not denying that it is real just saying that I have not had a problem with it even what doing things that one would think should cause it!
Can that be reconciled with the statement in the recent Zymurgy “Brew Lager like a German” article…
“It is easy to over-oxygenate the wort in a small vessel with pure O2, so tread carefully. Levels of oxygen over 12 mg/l can have a toxic effect on the yeast and result in stopped fermentation”
…haven’t people been talking about pure O2 being able to get as high as 26 or so? regular air only being able to reach 8 ?
That’s going to strongly depend on pitching rate among other things, but let’s just say I’d like to see the primary research for that statement.
Yeah, I don’t really know much about it. I’ve just seen that “you can overdo it with pure O2” statement in lots of different places, hence my original post. It was just a coincidence that I finally got around to that Zymurgy article yesterday morning and dang if I don’t see that very statement again 
Here’s the main reason I don’t believe it. We know that yeast can survive in air, and in a saturated liquid that’s supposed to be 8 ppm O2. We also know that when first pitched yeast will rapidly take up ALL of the available O2, and if brewers are oxygenating to 12 ppm that’s 12 ppm they can remove. So hypothetically, if the yeast can drop the level to 8 ppm they’re fine, thus 20 ppm should be no problem at all. And that is considerably higher than 12 ppm. Further, a healthy pitch of lager yeast (which is recommended to be twice as much as ale yeast) should be able to handle twice as much O2. So I call BS on the 12 ppm number without seeing the original data.
I suspect that the primary research will indicate some factor that will make it irrelevant for our purposes - probably that the media was continuously oxygenated, which is not what we do.
FWIW I don’t think I’ve ever seen 12 ppm referenced as an upper limit. And I know I’ve read several independent sources that recommend ~15 ppm for high-gravity beers.
OTOH, saturation of pure O2 in water is ~50 ppm even at ale pitching temperatures (~60 ppm for lagers). I would have no trouble believing that could be detrimental.
Maybe. I’d really have to see the research that indicates it’s actually bad at 50 ppm before I’ll believe it. I know it sounds high, but the level will start dropping as the yeast take it up. And as far as I know, the toxicity will generally come from reactive oxygen species which are generated by respiration, and respiration should be suppressed because of the sugar level in the wort.
Pretty sure you aren’t supposed to aerate/oxygenate hot wort. I’m surprised no one else caught this comment earlier?!? Aerating/oxygenating is for cooled wort. Isn’t that where the (bad) term hot-side aeration comes from?
I’ve used the red O2 tanks for years. Recently acquired a cheap decommisioned small medical O2 tank. Holds way more than those disposible red ones. Yes, oxygenating costs more. But I figure the yeast want oxygen not just air. Not that good results can’t be had with aerating.
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Thread drift. I was responding to theDarkSide’s question about whirlpooling. I would never aerate or oxygenate hot wort. Back to your regularly scheduled thread…