Adding Oxygen To Wort Before Or After Pitching Yeast?

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JBIII

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Can someone explain the science behind the method of adding oxygen to the wort, prior to pitching the yeast?

A couple of days ago while listening to a podcast the person being interviewed was emphatic about adding oxygen BEFORE pitching yeast. So, I've brewed about 180 batches of beer and I've always added oxygen AFTER pitching my yeast and this was the first time hearing about adding oxygen before pitching the yeast. As far as I know, I haven't experienced any issues and my beers have even won competitions.

So...I'm really just looking for an explanation of the science behind adding oxygen to wort, pre and/or post pitch.

Thanks in advance...
 
I cannot explain the science but I do oxygenate before I pitch the yeast. I previously read a post from the forum that said before or after but that it doesn't matter, however, don't oxygenate after fermentation has started....

For what it's worth at 180 batches you are pretty darn experienced, I would do what you think is best and keep moving forward.

https://www.homebrewtalk.com/f39/aerate-wort-before-after-pitching-yeast-132347/
 
Just to be clear, are we talking about oxygenating (pure O2), or aerating (air), or both?

In a recent thread, I said one should oxygenate prior to pitching, because I suspect pure O2 is harmful to the yeast. (But I have no evidence of this whatsoever.) Then, this past weekend I temporarily forgot to oxygenate until I had pitched, so I had to oxygenate post pitch. It is fermenting, for what it's worth, but I suppose it will suck. And I suppose I will drink it anyway.
 
Just to be clear, are we talking about oxygenating (pure O2), or aerating (air), or both?

In a recent thread, I said one should oxygenate prior to pitching, because I suspect pure O2 is harmful to the yeast. (But I have no evidence of this whatsoever.) Then, this past weekend I temporarily forgot to oxygenate until I had pitched, so I had to oxygenate post pitch. It is fermenting, for what it's worth, but I suppose it will suck. And I suppose I will drink it anyway.

Oxygenating....

And I'd be interested in hearing how your post pitch oxygenation batch turns out. What kind of beer is it?
 
IMO, If you are doing this within a minute or so before OR after pitching the yeast. The yeast will come into contact with the same degree of oxygen. So why would it matter????

I feel similarly to how you do, which is why I was surprised at how emphatic the podcast was about oxygenating first and then pitching. There was no explanation given as to why this was the preferred method, other than 'it's bad if you pitch and then immediately add oxygen'.


So...this is the reason I'm looking to understand the science behind it...
 
I don't think there is much scientific difference behind pre and post, as long as you oxygenate very shortly after pitching. Oxygen dissolves into water before and it dissolves into water after. I have done both, but always oxygenate before (unless I forget and do so after pitching). The beer turns out good no matter when I have oxygenated.
 
I can't site the source, but recalling what I've read pure oxygen will kill yeast cells. It won't kill all of the yeast cells but it will reduce the quantity. If you are doing a large enough yeast starter to compensate (or if you aren't seeing any negative effects) than it may not be making a difference for you.

I've always oxygenated prior to pitching for this reason.
 
So I think the warning to oxygenate first, pitch second, is due to this logic: yeast do not like sudden changes in their environment, and tend to lyse or create heatshock proteins when those changes happen. There's also the fact that excess oxygen is toxic to yeast. I can envision a scenario in which oxygenating wort containing yeast exposes some of the yeast to higher-than-desired oxygen levels (ie if a bubble of O2 hits a yeast cell).

Then again this is all "in principle" talk. Until proven, it's conjecture.
 
I oxygenate (pure O2) just before I pitch, mainly because I don't want to submerge my O2 wand and stone into wort that's full of yeast. I clean it after I use it, but still, I figure it's better to not load it up with yeast.
 
I have to imagine that yeast are more robust than to die immediately after being exposed to an oxygen bubble for a fraction of a second in a bunch of wort. If a yeast cell was enveloped in an oxygen bubble and stayed there for a while, then I would think it would die. I would think the larger issue would be over-oxygenating (over 20 mg/L in solution), which should not happen if you oxygenate for 60 seconds (Wyeast indicates you should achieve around 12 ppm at 60 seconds). At that point, doesn't matter if you pitch before or after, as the yeast will be exposed to a sustained environment toxic to them.

Anyhow, pitching after oxygenating is still the safest bet.
 
I wouldn't be surprised at all if a big part of the O2 before yeast comes from the pro brewer scene. I'd wager it is just a lot easier to add O2 in-line as the wort exits the chiller and goes into the cylindroconical than to try and figure out a way to stick a sintered stone down into a 300 bbl tank. For not good reason, I always oxygenate for 1 minute @ 1L/min immediately after pitching yeast slurry from a starter. I use the wand to stir up the yeast as I'm adding the oxygen.

I wager it makes no difference on the final product on the homebrew scale.

**Chemist, not biologist.
 
I read in Yeast of a study in which the actual oxygenation of brewery wort was measured and then compared to the breweries' calculated/target oxygen numbers. a lot of the breweries used inline oxygenation setups. The numbers weren't anywhere near a match, and the conclusion of the study was that using a dissolved oxygen meter is the *only* way to be sure of your oxygen levels.

Food for thought? I've more or less decided to drop the aim of using pure O2 given this knowledge. I'll just stick with a bit of olive oil for estery beers or my aquarium air pump with sanitary filter for the rest.
 
I can't site the source, but recalling what I've read pure oxygen will kill yeast cells. It won't kill all of the yeast cells but it will reduce the quantity. If you are doing a large enough yeast starter to compensate (or if you aren't seeing any negative effects) than it may not be making a difference for you.

I've always oxygenated prior to pitching for this reason.

IMO, if you are adding the oxygen into wort containing yeast you are not subjecting the yeast to "pure oxygen". If you immersed your stone in a slurry of yeast - then yes.

I would chalk this one up to large scale brewing = a concern, homebrew scale = no concern.....

Unless someone post a lab study on a homebrew scale showing definite data I will not be concerned.

That said I am in agreement with another reply that I want a little crud in contact with my diffusion stone so I aerate (pump) before pitching.
 
As far as yeast health goes, I'm not sure that it matters pre vs. post pitching so long as you do it shortly after pitching. Once the colony progresses beyond its initial aerobic respiration (when it consumes the dissolved O2) to anaerobic respiration (aka fermentation), the introduction of oxygen is disruptive to the process.
 
Can someone explain the science behind the method of adding oxygen to the wort, prior to pitching the yeast?

A couple of days ago while listening to a podcast the person being interviewed was emphatic about adding oxygen BEFORE pitching yeast. So, I've brewed about 180 batches of beer and I've always added oxygen AFTER pitching my yeast and this was the first time hearing about adding oxygen before pitching the yeast. As far as I know, I haven't experienced any issues and my beers have even won competitions.

So...I'm really just looking for an explanation of the science behind adding oxygen to wort, pre and/or post pitch.

Thanks in advance...

Yeast are prone to motion sickness. You don't want yeast barf in your beer.

But seriously...how can there possibly be a difference, provided that the wort is oxygenated right after pitching?
 
Yeast are prone to motion sickness. You don't want yeast barf in your beer.

Unless you're brewing a Belgian, in which case yeast barf is the distinguishing characteristic, and you want your yeast to blow chunks all over your beer.
 
Oxygenating....

And I'd be interested in hearing how your post pitch oxygenation batch turns out. What kind of beer is it?

I will try to report back in a month or so, but I may forget. I drink, you know. You may have lost interest by then anyway. There are some good comments in this thread. Somehow, I do think it is different to dose the oxygen directly into the wort/yeast mixture than it is to add yeast immediately afterward, but I'm struggling to explain why. It seems safest to pitch after adding oxygen, so why not?

My beer is similar to Stone's Sublimely... (black IPA). And it will be awesome, regardless of when I added oxygen.
 
I will try to report back in a month or so, but I may forget. I drink, you know. You may have lost interest by then anyway. There are some good comments in this thread. Somehow, I do think it is different to dose the oxygen directly into the wort/yeast mixture than it is to add yeast immediately afterward, but I'm struggling to explain why. It seems safest to pitch after adding oxygen, so why not?

My beer is similar to Stone's Sublimely... (black IPA). And it will be awesome, regardless of when I added oxygen.

How bout that report back? Notice any difference in you beer when you added oxygen post pitching?
 
How bout that report back? Notice any difference in you beer when you added oxygen post pitching?

No difference. So there's another anecdotal data point. Regardless, I will continue to pitch after adding oxygen.
 
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