[narvin]

I still use O2 when I use liquid yeast, and I'm always pitching something out of the fridge that is a few days to a few weeks old (either harvested slurry or a decanted starter).  It may be different if you're pitching a whole starter at high krausen, but I found that using O2 did improve my lager fermentations and didn't hurt ales.  I have a 20 cubic ft welding tank that has lasted years and at this point it's basically free, so why not continue doing what works for me?

[BrewBama]

Not to argue but to clarify:  2) based on the bioreactor experiment with sugar and bread yeast to scavenge O2 from water, wouldn’t the DO in a SnS starter be 0 at ~20 min?  Those trials took 10 gal of room temp water to 0 in 20 min. I realize a SnS starter is not water but the volume is 10x less so would think it would be at 0 far sooner than a cpl hours.

[tommymorris]

Note that Denny is now using SNS starters. That process gives the yeast oxygen before pitching it into the beer. Is it enough oxygen? The inventor of the SNS method says yes, but I am not convinced. I think that some kind of aeration during the transfer from kettle to fermenter is still worthwhile. I have a wine-type aerator that I put on the end of my transfer hose. I no longer use oxygen except for very high gravity beers.

Anybody that knows biochemistry and yeast (and any cell) aerobic metabolism can tell you that there won't be any significant yeast growth if you don't oxygenate at pitching.
If you have enough viable and vital cells at pitching (whatever the method used to produce the cells) to carry the fermentation, then the wort will ferment, if not, it won't ferment completely.

Yeast growth produces secondary flavor compounds, so beer from a fermentation with yeast growth will taste differently from beer produced with no yeast growth.
Better or worse is for the brewer to decide.

Is it enough oxygen?
It depends.
Is NOT enough to produce significant growth during the main fermentation.
It may be enough to produce sufficient cells in your starter depending on many factors including initial count and vitality, nutrients provided and oxygen provided.

Sent from my SM-G981U1 using Tapatalk

If by metabolism you mean respiration, then brewers yeast can't be put in the same category as "any cell". Yeast in beer wort do not use the oxygen for aerobic respiration because of the Crabtree effect. At the sugar concentration found in even weak beer wort, yeast will always use the anaerobic fermentation pathway to multiply, regardless of how much oxygen is present. Oxygenating the wort, whether via splashing or stone, does not necessarily result in more cells, it results in stronger cells that can more easily cross the finish line.

That was not my point.
Cells, including yeast, don't have the ability to store oxygen.
So, you can't give the oxygen "in advance".

The statement "yeast will always use the anaerobic fermentation pathway to multiply" is incorrect.
You can easily disprove this by weighing the yeast biomass pitched and the final yeast biomass after fermentation under different oxygenation rates.
That's why we shake or use stir plates or bioreactors.

Can yeast multiply anaerobically? Yes, of course. But you produce much more yeast with oxygenation.

Sent from my SM-G981U1 using Tapatalk

I indeed must not have seen your point. (You are also omitting some important qualifiers in my comment.)

You implied that yeast are like any other cell in that they multiply via aerobic respiration when oxygen is present. My point was, no they don't. That's only true when the sugar concentration is below the Crabtree threshold (IIRC, <0.2% sugar concentration). Perhaps we have different understandings of the Crabtree effect.

To be honest, I don't understand most of your comment above. However, you are correct that cells do not store oxygen.

It might be worth noting in a yeast propagator there is constant aeration and the yeast produces very little co2 or alcohol in the presence of oxygen. The vast majority of available carbon goes to biomass. Many breweries have a propagator to build their own pitches and this is the considered an ideal condition in which to grow yeast. So yes, yeast do grow in both states, aerobic and anaerobic, but if you want mostly biomass, feed them oxygen. That's why this whole discussion seems a bit ignorant, this is well established biology. Aeration at pitch has a direct impact on yeast health and beer quality. Go to brewing school, they will stress the importance of proper levels of oxygen at pitch. Study the metabolism of yeast and the same thing will be pop up.

I understand it "works" for some people or so it's claimed, but it certainly isn't best practice.

I think the “it works” approach is not saying oxygenation of wort is unnecessary. The question is really does a home brewer need to add more oxygen or is there enough present already. The answer is probably process dependent.

[HighVoltageMan!]

It works sometimes if your process causes lots of splash or pouring from transferring or handling, but the most oxygen you can get into solution is 6-7ppm using that method. That's the bottom end of most ale yeasts. Each strain has different requirements from almost nothing for some Kviek yeasts (3-4ppm) to 20ppm for some lagers yeast. Trying to find the information for the oxygen requirements for each yeast strain is difficult, apparently due to trade secrets of the breweries that use that strain. If you aerate to 12-15ppm, you can be assured that will oxygen provided for nearly every yeast strain, adding to consistency between batches.

So if someone took advice not aerate wort prior to pitch liquid yeast, it may very well work with one strain and bomb on another, leaving the brewer to wonder what went wrong. Rather than asserting that "it works for me", implying that science in this situation is to stringent, the right response would be to educate the brewer so the brewer can make an educated decision as to whether they need to aerate with pure oxygen or to let ride. This topic is covered so much in brewing literature that I can't believe it even debated here.

[Megary]

It works sometimes if your process causes lots of splash or pouring from transferring or handling, but the most oxygen you can get into solution is 6-7ppm using that method. That's the bottom end of most ale yeasts. Each strain has different requirements from almost nothing for some Kviek yeasts (3-4ppm) to 20ppm for some lagers yeast. Trying to find the information for the oxygen requirements for each yeast strain is difficult, apparently due to trade secrets of the breweries that use that strain. If you aerate to 12-15ppm, you can be assured that will oxygen provided for nearly every yeast strain, adding to consistency between batches.

So if someone took advice not aerate wort prior to pitch liquid yeast, it may very well work with one strain and bomb on another, leaving the brewer to wonder what went wrong. Rather than asserting that "it works for me", implying that science in this situation is to stringent, the right response would be to educate the brewer so the brewer can make an educated decision as to whether they need to aerate with pure oxygen or to let ride. This topic is covered so much in brewing literature that I can't believe it even debated here.

Great post.  And I agree, whoever started this thread should be ashamed of themselves.   

Serious Questions:
How do you know that "the most oxygen you can get into solution is 6-7ppm using that (splash) method."?  I'm assuming there have been tests done...
You note that O2 requirements are different depending on yeast, but what about other variables?  Batch size, wort composition, pitch rate...and on and on.

Again, I don't think anyone questions the need for oxygenating wort.  I think the question is simply a matter of how much is enough.  It doesn't appear to be one target ppm number.

[denny]

Note that Denny is now using SNS starters. That process gives the yeast oxygen before pitching it into the beer. Is it enough oxygen? The inventor of the SNS method says yes, but I am not convinced. I think that some kind of aeration during the transfer from kettle to fermenter is still worthwhile. I have a wine-type aerator that I put on the end of my transfer hose. I no longer use oxygen except for very high gravity beers.

Anybody that knows biochemistry and yeast (and any cell) aerobic metabolism can tell you that there won't be any significant yeast growth if you don't oxygenate at pitching.
If you have enough viable and vital cells at pitching (whatever the method used to produce the cells) to carry the fermentation, then the wort will ferment, if not, it won't ferment completely.

Yeast growth produces secondary flavor compounds, so beer from a fermentation with yeast growth will taste differently from beer produced with no yeast growth.
Better or worse is for the brewer to decide.

Is it enough oxygen?
It depends.
Is NOT enough to produce significant growth during the main fermentation.
It may be enough to produce sufficient cells in your starter depending on many factors including initial count and vitality, nutrients provided and oxygen provided.

Sent from my SM-G981U1 using Tapatalk

If by metabolism you mean respiration, then brewers yeast can't be put in the same category as "any cell". Yeast in beer wort do not use the oxygen for aerobic respiration because of the Crabtree effect. At the sugar concentration found in even weak beer wort, yeast will always use the anaerobic fermentation pathway to multiply, regardless of how much oxygen is present. Oxygenating the wort, whether via splashing or stone, does not necessarily result in more cells, it results in stronger cells that can more easily cross the finish line.

That was not my point.
Cells, including yeast, don't have the ability to store oxygen.
So, you can't give the oxygen "in advance".

The statement "yeast will always use the anaerobic fermentation pathway to multiply" is incorrect.
You can easily disprove this by weighing the yeast biomass pitched and the final yeast biomass after fermentation under different oxygenation rates.
That's why we shake or use stir plates or bioreactors.

Can yeast multiply anaerobically? Yes, of course. But you produce much more yeast with oxygenation.

Sent from my SM-G981U1 using Tapatalk

I indeed must not have seen your point. (You are also omitting some important qualifiers in my comment.)

You implied that yeast are like any other cell in that they multiply via aerobic respiration when oxygen is present. My point was, no they don't. That's only true when the sugar concentration is below the Crabtree threshold (IIRC, <0.2% sugar concentration). Perhaps we have different understandings of the Crabtree effect.

To be honest, I don't understand most of your comment above. However, you are correct that cells do not store oxygen.

It might be worth noting in a yeast propagator there is constant aeration and the yeast produces very little co2 or alcohol in the presence of oxygen. The vast majority of available carbon goes to biomass. Many breweries have a propagator to build their own pitches and this is the considered an ideal condition in which to grow yeast. So yes, yeast do grow in both states, aerobic and anaerobic, but if you want mostly biomass, feed them oxygen. That's why this whole discussion seems a bit ignorant, this is well established biology. Aeration at pitch has a direct impact on yeast health and beer quality. Go to brewing school, they will stress the importance of proper levels of oxygen at pitch. Study the metabolism of yeast and the same thing will be pop up.

I understand it "works" for some people or so it's claimed, but it certainly isn't best practice.

I think the “it works” approach is not saying oxygenation of wort is unnecessary. The question is really does a home brewer need to add more oxygen or is there enough present already. The answer is probably process dependent.

That is exactly what I'm saying

[HighVoltageMan!]

It works sometimes if your process causes lots of splash or pouring from transferring or handling, but the most oxygen you can get into solution is 6-7ppm using that method. That's the bottom end of most ale yeasts. Each strain has different requirements from almost nothing for some Kviek yeasts (3-4ppm) to 20ppm for some lagers yeast. Trying to find the information for the oxygen requirements for each yeast strain is difficult, apparently due to trade secrets of the breweries that use that strain. If you aerate to 12-15ppm, you can be assured that will oxygen provided for nearly every yeast strain, adding to consistency between batches.

So if someone took advice not aerate wort prior to pitch liquid yeast, it may very well work with one strain and bomb on another, leaving the brewer to wonder what went wrong. Rather than asserting that "it works for me", implying that science in this situation is to stringent, the right response would be to educate the brewer so the brewer can make an educated decision as to whether they need to aerate with pure oxygen or to let ride. This topic is covered so much in brewing literature that I can't believe it even debated here.

Great post.  And I agree, whoever started this thread should be ashamed of themselves.   

Serious Questions:
How do you know that "the most oxygen you can get into solution is 6-7ppm using that (splash) method."?  I'm assuming there have been tests done...
You note that O2 requirements are different depending on yeast, but what about other variables?  Batch size, wort composition, pitch rate...and on and on.

Again, I don't think anyone questions the need for oxygenating wort.  I think the question is simply a matter of how much is enough.  It doesn't appear to be one target ppm number.

I didn't mean that anyone should be ashamed, it just that it's been covered so much. But it is good to review for someone new to the hobby.

As far as aeration with splashing goes you can get from Wyeast here:

https://wyeastlab.com/resource/home-enthusiast-oxygenation-aeration/

As far as variable oxygen levels, this is can vary due to strain of yeast, gravity, and to some degree temperature (mostly lagers). Typically ale strains are more tolerate to lower oxygen levels than lagers, specific information on strains is hard to find. The higher the gravity, the more oxygen is required. The problem lies in that oxygen does not go into solution easily in higher gravity wort, so longer aeration times apply. Batch sizes does not change oxygen requirements, but knowing how much oxygen is getting into solution may vary from one volume to the next. I don't have a O2 meter, so I guess based on Wyeast's information because my volumes don't change much from batch to batch. You can also get by with lower pitch rates if the wort is aerated properly. If you pitch rate increases, it's likely your brewing a high gravity ale or a lager, so aeration time/ppm increases.

The ppm varies in different situations but it can be adjusted for by aerating longer; to levels 12-18ppm. There is no harm to the yeast, but if you're a LODO brewer, you may argue it harms the beer itself. I dunno, maybe, I guess. So with a 7 gallon batch I aerate 60 seconds for ales which I'm guessing gives me 12ppm or so and 120 seconds for lagers, which I'm guessing comes to 18-20ppm. I think it's more than I need, but the it works really well.

[mchrispen]

Keep in mind that LODO will likely have excess meta-bisulfite in the wort as it is chilled to pitching temp. So cold wort slows the oxidation process and meta-bisulfite adds protection.

Then at pitching temp knock out the excess MTB with pure O2 and oxygenate to 12 ppb at pitch.


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[kramerog]

I have not used O2. I use a stir plate and rely on shaking the fermenter to aerate the wort or use a drill driven mixer to aerate. I don't intend to change that for making ales, but I might do something different for lagers now that I know that lager years generally need more oxygen. Lack of sufficient oxygen might explain why my last lager fermentation took so long although it tastes fine to me.

[Megary]

It works sometimes if your process causes lots of splash or pouring from transferring or handling, but the most oxygen you can get into solution is 6-7ppm using that method. That's the bottom end of most ale yeasts. Each strain has different requirements from almost nothing for some Kviek yeasts (3-4ppm) to 20ppm for some lagers yeast. Trying to find the information for the oxygen requirements for each yeast strain is difficult, apparently due to trade secrets of the breweries that use that strain. If you aerate to 12-15ppm, you can be assured that will oxygen provided for nearly every yeast strain, adding to consistency between batches.

So if someone took advice not aerate wort prior to pitch liquid yeast, it may very well work with one strain and bomb on another, leaving the brewer to wonder what went wrong. Rather than asserting that "it works for me", implying that science in this situation is to stringent, the right response would be to educate the brewer so the brewer can make an educated decision as to whether they need to aerate with pure oxygen or to let ride. This topic is covered so much in brewing literature that I can't believe it even debated here.

Great post.  And I agree, whoever started this thread should be ashamed of themselves.   

Serious Questions:
How do you know that "the most oxygen you can get into solution is 6-7ppm using that (splash) method."?  I'm assuming there have been tests done...
You note that O2 requirements are different depending on yeast, but what about other variables?  Batch size, wort composition, pitch rate...and on and on.

Again, I don't think anyone questions the need for oxygenating wort.  I think the question is simply a matter of how much is enough.  It doesn't appear to be one target ppm number.

I didn't mean that anyone should be ashamed, it just that it's been covered so much. But it is good to review for someone new to the hobby.

As far as aeration with splashing goes you can get from Wyeast here:

https://wyeastlab.com/resource/home-enthusiast-oxygenation-aeration/

As far as variable oxygen levels, this is can vary due to strain of yeast, gravity, and to some degree temperature (mostly lagers). Typically ale strains are more tolerate to lower oxygen levels than lagers, specific information on strains is hard to find. The higher the gravity, the more oxygen is required. The problem lies in that oxygen does not go into solution easily in higher gravity wort, so longer aeration times apply. Batch sizes does not change oxygen requirements, but knowing how much oxygen is getting into solution may vary from one volume to the next. I don't have a O2 meter, so I guess based on Wyeast's information because my volumes don't change much from batch to batch. You can also get by with lower pitch rates if the wort is aerated properly. If you pitch rate increases, it's likely your brewing a high gravity ale or a lager, so aeration time/ppm increases.

The ppm varies in different situations but it can be adjusted for by aerating longer; to levels 12-18ppm. There is no harm to the yeast, but if you're a LODO brewer, you may argue it harms the beer itself. I dunno, maybe, I guess. So with a 7 gallon batch I aerate 60 seconds for ales which I'm guessing gives me 12ppm or so and 120 seconds for lagers, which I'm guessing comes to 18-20ppm. I think it's more than I need, but the it works really well.

Thanks for that link.  Good stuff, but a little unsettling.  Since I have no intention of ever "injecting pure oxygen through a sintered stone", I'll have to hope that - when using liquid yeast - my splashing and swirling gets me by.

What to make of this:
The unsaturated fatty acids found in wort trub can be utilized by yeast and directly incorporated into membranes. If wort trub levels are low, yeast will need to synthesize more of these lipids and therefore will require more oxygen.

[denny]

The unsaturated fatty acids found in wort trub can be utilized by yeast and directly incorporated into membranes. If wort trub levels are low, yeast will need to synthesize more of these lipids and therefore will require more oxygen.

This info has been out there for a very long time.

[Megary]

The unsaturated fatty acids found in wort trub can be utilized by yeast and directly incorporated into membranes. If wort trub levels are low, yeast will need to synthesize more of these lipids and therefore will require more oxygen.

This info has been out there for a very long time.

So the upshot is what exactly?

Don't transfer clear wort if you don't plan on oxygenating??
Or if clear wort is your goal, get some pure Oxygen and a stone??

[denny]

The unsaturated fatty acids found in wort trub can be utilized by yeast and directly incorporated into membranes. If wort trub levels are low, yeast will need to synthesize more of these lipids and therefore will require more oxygen.

This info has been out there for a very long time.

So the upshot is what exactly?

Don't transfer clear wort if you don't plan on oxygenating??
Or if clear wort is your goal, get some pure Oxygen and a stone??

For many years, there has been a debate about how important it is to get clear wort into the fermenter. Your take away seems correct.  I don't worry about clear wort, and I don't oxygenate. Maybe this is part of the explanation of why I get good results.

[ynotbrusum]

I also am confused about getting O2 into the solution (by aeration stone as the only way to achieve sufficient PPM)...isn't the yeast able to scavenge O2 from the foam that is at the top of the wort after swirling/stirring/etc...  That foam is pretty full of bubbles or at least it looks like a ready source of O2 that the yeast could access.

[fredthecat]

For many years, there has been a debate about how important it is to get clear wort into the fermenter. Your take away seems correct.  I don't worry about clear wort, and I don't oxygenate. Maybe this is part of the explanation of why I get good results.

i agree with what was said above about not needing to worry at the homebrew scale, and i don't aerate other than shaking the carboy (if its liquid yeast) for about 30 seconds. i am really hitting what i want from my yeast and finished beers these days tbh.

i know the worst thing to say on a homebrew forum is "well, i just like my beer". but i have experienced the improvement as i've adapted techniques over the years and i am now fully satisfied in comparison to premium commercial beers i enjoyed with many of the beers i make.

so i think qualifying the "good results" as that is important, as i believe some of the 02 injection in-every-case people are trying to state that without oxygen and yeast cell growth, the right esters and traits will not be there. this is something over my head, but again i am fully satisfied with most of the beers i make nowadays, or at least feel i only got one or two areas wrong upon tasting.