If they put it on the label, then they have to follow the law. I can see air contact but since they are not allowed to add CO2, I can't imagine they can use pure O2.
Yeast Pre-Oxygenation - Oxygenate your yeast, not your wort.
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It really is not a law so it would help to stop calling it a law.
Co2 is a bit of a different story, it stays within the final product. You see the bubbles. Try finding the oxygen after removing the yeast.
There are fining agents used that don't show up on the label. They get removed before bottling... More or less.
Sorry, I meant that once it is stated, it becomes a truth in advertising sort of situation which is more of the law I was referring to.
I am sure breweries either try to get around it or don't want to follow it etc... I guess I am thinking "what does Weihenstephan do"? I have heard their head brewer state "oxygenate the yeast, not the wort" in a podcast. Not sure if that is the end process or not though.
I am sure breweries either try to get around it or don't want to follow it etc... I guess I am thinking "what does Weihenstephan do"? I have heard their head brewer state "oxygenate the yeast, not the wort" in a podcast. Not sure if that is the end process or not though.
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Let’s put it this way: keep it simple. Oxygenation inline is done because it’s easy and highly effective. And, O2 is generally more cost-effective than additional yeast. If your pitch is adequate and there is enough DO to feed the yeast, you will get a clean fermentation for your desired flavor profile. If after fermentation is complete (not just active bubbling, REALLY completed) you can taste the effects of over-oxygenation pre-fermentation, then you need to go take the Master Sommelier or Master of Coffee tests.
And yes, the O2 is introduced inline between the chiller and the FV, at pitching temperature.
The best beers arise from one word: SIMPLIFY. Simplify the recipe, simplify the process, simplify the ingredients.
And yes, the O2 is introduced inline between the chiller and the FV, at pitching temperature.
The best beers arise from one word: SIMPLIFY. Simplify the recipe, simplify the process, simplify the ingredients.
Sorry, I didn't mean you directly with "stop calling it a law". It was more a statement towards that Reinheitsgebot gets generally translated to "purity law", which is incorrect as it is not a law. The German word for law is "Gesetz". The word "Gebot" is more like "commandment".
Anyway, I agree. My question is also what the big breweries do and controlled oxygenation of the yeast makes way more sense to me. At least if you can reach a cell count high enough this way.
There are specific terms under which you can write "gebraut nach dem deutschen Reinheitsgebot" on your beer in Germany. And as us Germans love it, these terms are defined into the very details. You can use all sort of fining agents for example, as long as you can show that you remove them before packaging. A lot of micro plastic is being used in the big breweries for this specific reason. They filter it out before packaging or remove it via sedimentation. There are other fining agents than that, but the plastic one is very common. Therefore I doubt that using oxygen or air before fermentation would make a difference. It's basically the same as with the fining agents. Once the yeast gets removed, the oxygen is gone as well. At least if you remove the yeast.
So I wouldn't discard the possibility of oxygenation just because of the Reinheitsgebot. Still, I don't think that the big breweries do it to the wort.
Thanks. I was surprised to learn that the purity law only extends to lager brewing. Top fermenting yeast driven beers can be brewed with whatever the brewery sees fit. But in the end, the Reinheistgebot is responsible for the art of German brewing being so developed imho. So I do not see it as a bad thing. It might be more a challenge commercially when your competitors are using less expensive methods. But from a beer quality perspective, it is the highest bar.
If you really want to dig into it, ask google to translate this article for you:
https://slow-brewing.com/blog_post/die-reinheitsgebote-im-rechtlichen-kontext/
OP
OP
Adequate is the question. If your pack of yeast is already pretty close to what you need, getting that number of cells "full" of sterols is your goal.
This is a pragmatic path forward, but you "suspect" you haven't had any oxidation problems. A lot of brewing improvement is somewhat intangible until you can pick it out later. Maybe what I mean, is for the past 15 years I've been telling myself "this is it, this is the best my beer will ever be" and I've been wrong most of the time. Maybe there is ZERO oxidation. Maybe there is SLIGHT oxidation below your ability to taste it. I guess they're the same thing pragmatically.
I know you meant oxygenate. It could be the most convenient way to do it at commercial scales, but it also doesn't "prove" that it's the best way to do it.
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This oxygen discussion goes way back in history. One day Julius Caesar was making an early version of Pliny the Elder and it had a funny taste to it.
Caesar took a sip and asked his brewmeister what gives. He said -
O2 Bruté?
Caesar took a sip and asked his brewmeister what gives. He said -
O2 Bruté?
I agree.
It is always the question of what one wants to achieve. Fix obvious flaws (for example the dreaded almond flavour I was experiencing) or further improve a beer that one thinks is already great.
If there is this little bit more nice grainyness or malt character that one might be after in a low hopped and already pretty clean beer like in a Helles for example, then this oxygenating wort or starter question might be one which might be of importance.
You "technically" don't need the oxygen to go into the wort.
Yesterday I brewed a Schwarzbier. I took ~1 Liter of leftover wort and heated it up in the microwave to 75°F and then pitched my sachet of S-189. Within two hours with intermittent shaking there was significant white foam that would form on top of the starter, visible activity. I'm leaving the top of the erlenmeyer open to the air. The yeast are on top of the beer starting to ferment it and pulling the oxygen directly from the atmosphere as they would in nature or in open fermentors. Given gas kinetics are way way faster than liquid kinetics, I would think this would be ideal.
This is in the neighborhood of what I was trying to say earlier. Perhaps the "problem" of getting those cell walls built up was created by modern fermentation techniques. Somebody should be able to do the math (not I), but I wonder if there is more happening at the beer-air interface at the start of an open fermentation than we homebrewers have tended to include in our models. If the yeast on or near the surface is gobbling up oxygen, maybe the resulting concentration gradient would push more into the system than simple diffusion would suggest. Maybe even enough to keep the yeast cell walls built up pitch after pitch, year after year. And just maybe, that mechanism brings just enough in for the yeast when they need it, and no more later when it would be detrimental to beer quality.
One thing is for certain: all the strains we have available now survived by repitching only for years and years, WITHOUT O2 injection, because there was no such thing as yeast propagation outside of brewing another batch, and no O2 bottles. They had to get oxygen from somewhere, and enough to thrive.
OP
OP
I think it's intuitive that the need for O2 injection is correlated to the increasing brewing capacity, tall closed fermenters, etc. The conclusion might be that wide, shallow open fermenters is the way to go but the required controls for contamination and oxidation make it a difficult proposition and it wouldn't be suitable for all beer styles anyway.
HighVoltageMan!
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This kind of doesn't count. The yeast can get by without oxygen as long as it has sufficient lipids, dry yeast has enough lipids to make excellent beer without oxygen provided the pitch rate is right. You're right about the yeast taking off quickly since it's a massive over pitch in a small starter. By proofing the dry yeast the way you did, you reduced your lag time.
They don't need oxygen if the lipid cell reserve is high enough or the yeast has another source of lipids. Barley malt has lipids available, although it may not be enough after boiling. Lipids drop out as the brewing process progresses and the finished wort may be deficient of lipids, in addition not all the lipids are completely available to the yeast. Technically, the yeast can reproduce and survive without oxygen, but the conditions are not ideal.
The idea behind the use of oxygen was to get the yeast in an ideal state to produce the best product (beer), yeast can survive and make beer without oxygen, but the it may or may not produce the beer you want.
When oxygen is added to the wort or yeast slurry, the yeast does not go into an aerobic state, it simply uses the oxygen to for lipid production if needed.
Brewers yeast is almost always in an anaerobic state despite the presence of oxygen. The conditions to put the yeast in a aerobic state requires a gravity of less than 1.010. Anything higher and the yeast immediately into a Crabtree mode or effect. When dry yeast manufacturers grow yeast, they get them to go into an aerobic state, which requires a slow feeding of the yeast. When yeast are in this state, almost all carbon (sugar) goes into yeast reproduction. Very little co2 or alcohol is produced. In an anaerobic state, most carbon (sugar) goes into production of co2 and alcohol, some carbon goes into cell reproduction.
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Why doesn't it count? I do the same thing with liquid strains. Same results. Are you suggesting that because it's dry yeast, it isn't taking up oxygen when exposed to it? Of course it is. I'm still growing more yeast and presumably improving fermentation performance for free, which is the point I am trying to make.
Why would the yeast take up oxygen if they don't need it? I've always wondered about yeast assimilating oxygen introduced during bottling for example. Yeast will ferment even in the presence of oxygen; they don't need an anaerobic environment to do anaerobic sugar metabolism. If they're not replicating and aren't sterol depleted, what are they doing with the oxygen?
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HighVoltageMan!
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This my point. Dry yeast have lipid reserves from the packet. Liquid yeast lack these reserves as well as sterol reserves. Dry yeast are going to do really well in a low oxygen environment, liquid yeast will not do as well. This is a well established in the brewing world and not a new revelation.
If you use this method for the beer you like for both liquid and dry yeast, than the debate is over for you. But in my case, I will not make a beer with liquid yeast without aerating the wort. I've been burnt too many times with low attenuation, super slow starts and off flavors. When I use dry yeast, I don't aerate because the yeast really doesn't need it.
Trying to catch up here. Isn't this what a starter does, stirred or shaken, add a bunch of O2 to the yeast as well as increase the cell count? So you don't really need to do anything different here or you need to add more O2 to the starter? This replaces any O2 necessary in the wort? Cold side O2 is bad, which is an easy fix for most of us.
If that's right seems like a pretty easy split batch, half with O2, half without. Need a light clean beer. I don't have anything in my brewing lineup for a few months like that. Working my through 2 kegs of kolsch, although that sounds like a good style?
If that's right seems like a pretty easy split batch, half with O2, half without. Need a light clean beer. I don't have anything in my brewing lineup for a few months like that. Working my through 2 kegs of kolsch, although that sounds like a good style?
HighVoltageMan!
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No. The starter gets enough oxygen for itself, but not the entire beer. The growth of the yeast in the beer requires enough nutrients for the yeast to grow and thrive. Oxygen is kind of a catalyst for the production of lipids the yeast needs for cell wall production, the yeast can produce lipids but it needs a source of oxygen. The beer will require more cells to be produce during fermentation and so more lipids are needed for healthy yeast cell walls.
If the lipid reserves in the yeast cells are sufficient, no oxygen is needed. Dry yeast has enough lipids and sterol reserves for one fermentation, if it's re-pitched, oxygen is needed just like any liquid yeast.
The starter builds healthy biomass. If done correctly it will build sterol and glycine reserves necessary for proper cell reproduction and metabolism, but more oxygen is needed in the wort so the yeast can continue to have healthy reproduction.
It is possible to aerate the yeast slurry just prior to pitching, but most US breweries add the oxygen to the wort. Which makes sense, because the oxygen is available to the yeast for a longer period allowing them more time to uptake the oxygen. One thing to keep in mind, really high levels of oxygen is hard on yeast because it may act as a sanitizer.
AdjunctBrewer
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How does one measure the detriment of oxygenating a volume of wort with active yeast. The rate and amount of oxygen uptake combined with the amount of remaining O2 could be had with an O2 meter. Is the uptake faster and intaked amount more with less remaining O2 in a smaller volume of wort -or- does the volume of wort not play a role?
Simple sensory observation probably won't produce a noticeable difference unless an artificially high amount of oxygen is introduced into the wort (of which dissolved O2 has its own limit).
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Indian_villager
Well-Known Member
Thanks for the neat article! I think this touches on what Brulosophy was calling a Vitality Starter a while ago, see attached HBT thread.
https://www.homebrewtalk.com/threads/vitality-starters.689064/
I've personally been using this method for a while now and can confirm that I have had reduced lag times and healthy fermentations without off flavors I have pretty much stopped pumping in O2 into wort unless the OG is above 1.100.
For the specific process I use, I cold crash and decant my starter. Give it some wort coming off the counterflow chiller ~1-1.5L. If the chiller did not get the wort down to pitching temp I'll pitch the aerated starter after my ferm chamber gets the wort down to temp, if the CFC did get it down to target temp, I'll usually wait 1-2 hours to pitch.
I'll fully admit that I only skimmed the article and plan on giving it a through read tonight. From what I did read though there were some degreadations noted after one hour of oxygenation without fermentables present. So I am wondering if adding a bit of the wort is going into will help with that. But on the flip side, it sounds like the tests run without sugars during oxygenation made the yeast hardier against oxidative stress. Wonder how it plays out when you have a preoxygenation with sugars.
https://www.homebrewtalk.com/threads/vitality-starters.689064/
I've personally been using this method for a while now and can confirm that I have had reduced lag times and healthy fermentations without off flavors I have pretty much stopped pumping in O2 into wort unless the OG is above 1.100.
For the specific process I use, I cold crash and decant my starter. Give it some wort coming off the counterflow chiller ~1-1.5L. If the chiller did not get the wort down to pitching temp I'll pitch the aerated starter after my ferm chamber gets the wort down to temp, if the CFC did get it down to target temp, I'll usually wait 1-2 hours to pitch.
I'll fully admit that I only skimmed the article and plan on giving it a through read tonight. From what I did read though there were some degreadations noted after one hour of oxygenation without fermentables present. So I am wondering if adding a bit of the wort is going into will help with that. But on the flip side, it sounds like the tests run without sugars during oxygenation made the yeast hardier against oxidative stress. Wonder how it plays out when you have a preoxygenation with sugars.
Anyone know how many successive generations of yeast occur during an "average" fermentation?
Cheers!
Cheers!
But the whole point of the thread (and the article that prompted it) is "Oxygenate your yeast, not your wort."
AdjunctBrewer
Well-Known Member
In the long process of troubleshooting a lack of ester development in my Hefeweizens in 2023, I went down the rabbit hole of looking into this. This is where it turns it into a brain bash. It's dependent on both oxygenation and pitch rate. Given a fixed amount of dissolved O2, if you pitch less cells, there can be more generations because there's more oxygen available on a per-cell basis.
HighVoltageMan!
Well-Known Member
A starter provides enough oxygen for itself. The conditions in a starter are not the same as the beer. In a typical stir plate type starter, the stir bar drives off the co2 produced, that same agitation adds small amount of oxygen. The level of oxygen in the starter is limited by the atmosphere, the maximum amount it can get into solution is 8 ppm, With c02 being produced and mixing in the air available in the starter, that level would presumably be much lower. The level of oxygen is based on volume and is limited. The growth of the cells consumes the available oxygen in the starter and so no oxygen is available to them during the lag phase after pitching when the yeast cells are preparing for fermentation (log phase). The combination of driving off co2 and adding small amount of oxygen is what makes starters so effective in building biomass.
A lot of research has been done with yeast both inside and outside the brewing industry, yeast metabolism is very complicated. You can add oxygen to the yeast slurry itself and it has been done by some brewers, but it brings up several important questions. One, is there sufficient levels of oxygen? Two, is the level of oxygen getting so high as to harm the yeast? A high concentration of oxygen can act as a antimicrobial. Three, is it really going to have a positive impact on the beer? The last question is obviously the most important.
If oxygen was to be added to the slurry, it would need to be a higher concentration than just the atmosphere. Once the yeast slurry is aerated, it needs to pitched as soon as possible because the exposure to oxygen triggers the yeast to use their glycogen to prepare for reproduction and fermentation.
Is there an advantage to aerating the slurry rather than the wort? I don't know. In my mind, the standard convention of aerating wort makes more sense overall (it's also a proven and very effective method). I would seriously doubt anyone would be able to tell the difference between the two methods assuming slurry aeration works as well as wort aeration.
That's how I read it too, thus my questions.
Yeast are fascinating. This has been a great thread for general yeast information. The crux of all this for me is starter vs batch size. If you oxygenate the starter, you are only feeding the first round of cells. But you need to feed all of the cells after cell division is complete. Unless you are pitching a complete slurry and do not want/need any cell growth, it seems you need to provide oxygen once the yeast get in the batch.
Growth is where a lot of flavor comes from. Even in repitching, growth is desired. So I do not think this method stands up to reason for most applications.
Growth is where a lot of flavor comes from. Even in repitching, growth is desired. So I do not think this method stands up to reason for most applications.
I think so. If you are doing a vitality starter or a shaken-not-stirred starter where you are pitching a reasonable amount of yeast that are actively fermenting, it seems likely that they need a limited amount of oxygen to support the needed reproduction. If you have let the starter ferment out, there is a good chance you have enough healthy yeast that, again, needs limited oxygen. It seems like an area where use homebrewers making small batches have an advantage...vs trying to shake or spin enough yeast for a 20 barrel pitch.
I will admit I had a hard time understanding the linked article enough to figure out how it might impact my process.
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I think this analysis applies only to a sealed starter flask. However, if your starter flask uses a permeable foam stopper, or is simply loosely covered by foil as many people do, gas kinetics will ensure that ~21% of the air in the flask will be O2 throughout the entire process (the CO2 barrier myth has been debunked many times). As a result, the dissolved oxygen in the starter wort will remain at ~8 ppm from beginning to end, no matter how much O2 the yeast take up or how much CO2 they produce.
Interestingly, the original paper linked in post #1 targets 8 mg of O2 per liter of yeast slurry, which is roughly the same as 8 ppm of O2.
HighVoltageMan!
Well-Known Member
I wonder if it can maintain 21% oxygen during peak fermentation. It would be reasonable to believe the oxygen, along with the atmosphere in general would be partially displaced by the off gassing of the starter. It could be measured fairly easily with a gas detector used for confined entry. You got me curious now.
It's exactly the same, .008 grams into 1000 grams or 8 per 1,000,000.
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Not to get too pedantic, but you are assuming the yeast slurry has a density of 1 gram/ml. According to Wyeast, a “typical” 40% yeast slurry has a density of about 1.1 g/ml.
I've started doing this the last few times I've used liquid yeast. I do not have an O2 setup yet, and so I've been over pitching liquid yeasts and I take about 2L of chilled wort and spin it on the stir plate while I clean. I usually pitch after about 2-4 hrs, depending mostly on how long it takes to clean up or to finish chilling the wort down (lager).
Very anecdotal, but the beers have been good.
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