Yeast Pre-Oxygenation - Oxygenate your yeast, not your wort.

[sibelman]

To me, this idea seems sensible: yeast need oxygen to reproduce. Once there's enough yeast cells, no more need, I guess. Anaerobic respiration thereafter.

In other words start with enough cells somehow, and skip aeration/oxygenation.

I'm not seeing this as a revolutionary change. The main idea: do any needed cell reproduction outside the main body of wort, which never gets aerated/oxygenated cuz there's no need and it might be a bad thing. Cool.

 

[mashdar]

(Assuming a clean yeast profile,) Is there any need for aerobic activity in the wort at all if there is a sufficient quantity of healthy yeast present? And how many is that? 4.5 million cells per mL per degree P for a normal gravity ale? (6x normal calculator value)

 

[sibelman]

Is there any need for aerobic activity in the wort at all if there is a sufficient quantity of healthy yeast present?

This is a fine question. I've imagined active fermentation being aerobic, followed by slower anaerobic fermentation. Based on no relevant knowledge whatsoever. I read most of Yeast by Chris White a few years ago, but don't recall...

Many claim dry yeast doesn't require (added) oxygen. Of course, even freshly chilled wort is gonna have considerable oxygen in it...

 

[Bobby_M]

I get successful results with moderate to excessive pitches of top crop slurry that is 2-4 weeks old, no starter, no O2. I say "successful" because, not having a point of comparison, my process might be good or bad. I like the beer, at least, and I get consistency with attenuation and flavor. Based on what I read here, I have short lag times.

I've always wanted to schedule brews so I could pitch directly from one batch to the other, as God intended, just to see what would happen, but I've never done it. I suspect that real direct repitching of clean, active yeast covers a multitude of sins.

I think being happy with the beer consistently is a good enough reason to not change anything.

The thing I can't wrap my head around is that a colony of yeast that never sees any oxygen shouldn't really be sustainable in theory because it shouldn't be able to reproduce and it doesn't live forever. I assume that typical wort handling is getting SOME oxygen in play.

 

[Bobby_M]

Many claim dry yeast doesn't require (added) oxygen. Of course, even freshly chilled wort is gonna have considerable oxygen in it...

The claim is true enough I think. The sterol reserves are "full" at the time the cells are dried so when they are properly revived/rehydrated, they can reproduce in the batch wort "AS IF" you had just given fresh oxygen to a liquid slurry that was somewhat sterol-depleted.

The nuance though, is how much yeast you pitch vs. how much is needed. The extreme example is, one dry yeast cell, no matter how fat and happy is is going in will not have the horsepower to ferment anything and certainly not enough sterols to reproduce enough.

One pack is often not enough for high gravity ales or normal to high gravity lagers and if it is enough to get the job done, it may not ferment as clean as it would with more. Clean isn't always the goal, but just sayin.

 

[sibelman]

A thing I wonder: don't the yeast "want" to reproduce even if there's more than enough to ferment the wort? They don't know how many yeast cells there are, and don't decide to not reproduce just 'cuz I pitched more than enough healthy cells. They just do what yeast do.

I imagine a happy yeast cell has all it needs to do what yeast does: ingest sugar, excrete alcohol & CO2, and divide. I don't need my yeasties to be happy, as long as there's enough of 'em to get the job done. But I want them to be happy. Don't I?

 

[mashdar]

They don't know how many yeast cells there are, and don't decide to not reproduce just 'cuz I pitched more than enough healthy cells. They just do what yeast do.

Based on Kai's results for starter populations, they do seem to have some sense of population density.

 

[oldschool]

I’ve read about this in a few different books or at least it is touched on. I was always under the impression that this is done in a brewery when they don’t have a sufficient way to “rouse” the harvest yeast. Essentially they don’t have a yeast dosing system that adequately disperses the yeast into the cold wort. So they add the pitching about of yeast to a dedicated tanks, then add wort, then mix and/or aerate, then pitch the entire contents to the fermenter. I never read that they avoid aeration of the main wort in this process.
I always pitched chilled starters. Decant leaving the yeast, add in some wort to the flask when I start filling the fermenter giving it some shakes while tinkering with the temp and then pitch when it’s completely dispersed- some strains take a lot of shaking. But then I hit the fermenter with O2 anyway.
That said once I realized that I didn’t have any oxygen so I just repeated the process as usual and didn’t hit the fermenter with anything O2. The fermented out clean and completely like normal but took two extra days or so. Omega west coast 1

 

[Bassman2003]

This is good to hear. I've probably been under-dosing for fear of toxicity but post #18 and this one allay those fears a good deal. I want a DO meter so bad.

This is the one I got. Keep your eyes on Ebay as I found a seller that was selling them new for $120-$180. https://www.vernier.com/product/go-direct-optical-dissolved-oxygen-probe/

Optical is the only way you want to go and it is basically only useful for oxygenation due to the temperature constraints. But that is the most important place to use a DO meter anyway outside of experiments and system testing. This model is in use with others' I know and it is accurate and easy to use with its app.

 

[corncob]

I think being happy with the beer consistently is a good enough reason to not change anything.

The thing I can't wrap my head around is that a colony of yeast that never sees any oxygen shouldn't really be sustainable in theory because it shouldn't be able to reproduce and it doesn't live forever. I assume that typical wort handling is getting SOME oxygen in play.

Exactly. We now have the technology (and the desire) to keep DO in the ppb range throughout. But we're using yeast that adapted in a very different environment. I wonder if we would still be able to keep these old cultures going without the parallel development of microscopes, glycol, and propagation methods. Certainly, we homebrewers would be out in the cold no matter what--I'm thinking about small commercial brewers.

I think about that picture of the open fermentation in wooden vats in the pilsner urquell basement. I bet that Culture is stable and vital as long as they keep brewing with it. But I bet that beer would be all cardboard dull caramel if they sent a bottle to my local store.

I think, as homebrewers, we're trying to do two different things, fundamentally, with yeast. This method gets at that concept.

 

[Miraculix]

Exactly. We now have the technology (and the desire) to keep DO in the ppb range throughout. But we're using yeast that adapted in a very different environment. I wonder if we would still be able to keep these old cultures going without the parallel development of microscopes, glycol, and propagation methods. Certainly, we homebrewers would be out in the cold no matter what--I'm thinking about small commercial brewers.

I think about that picture of the open fermentation in wooden vats in the pilsner urquell basement. I bet that Culture is stable and vital as long as they keep brewing with it. But I bet that beer would be all cardboard dull caramel if they sent a bottle to my local store.

I think, as homebrewers, we're trying to do two different things, fundamentally, with yeast. This method gets at that concept.

Open fermentation does not imply oxidised beer. The trick is to keg/bottle/move to closed tank, before fermentation is completely finished. Afaik, that's what's being practised in these commercial open fermenting breweries here in Europe.

 

[VTMongoose]

I had possession of a decent DO meter about a decade ago and did a few experiments while I had it. One was seeing how fast the O2 was removed from strike liquor using bakers yeast with a bit of corn sugar; the other was seeing how fast the O2 I added to a carboy of freshly pitched wort disappeared. In both cases there was very little O2 remaining after 6 hours, and within 12 hours there was no measurable O2 remaining (I was actually pretty impressed with the strike water deaeration thing)...

Cheers!

This is an interesting data point, however I would point out that in the example using wort, you do not technically know what amount of that oxygen is being taken up and used by the yeast as opposed to reacting with the wort. One of the fundamental frustrations I'm sure that all of us in this thread have when discussing a topic like this, is that we do not have access to instrumentation that would allow us to quantify nonenal (from oxidation of unsaturated fatty acids from malt) or hop aroma compounds like linalool that can be oxidized, in the final beer to determine to what degree oxygenation of the main body of wort is actually oxidizing the wort.

To me, this idea seems sensible: yeast need oxygen to reproduce. Once there's enough yeast cells, no more need, I guess. Anaerobic respiration thereafter.

In other words start with enough cells somehow, and skip aeration/oxygenation.

I'm not seeing this as a revolutionary change. The main idea: do any needed cell reproduction outside the main body of wort, which never gets aerated/oxygenated cuz there's no need and it might be a bad thing. Cool.

This is my exact general feeling on the totality of the topic. A healthy fermentation requires a certain minimum population and the data in the original study supports this idea where oxygenating more than a certain amount didn't yield further benefits.

I believe the purpose of the historical practice of adding oxygen to the wort is that it gives you a free and significant boost in yeast cell count. If I was a commercial brewery needing 4 bricks of US-05 to ferment a batch, and could get away with pitching two and adding oxygen instead, that's a no-brainer. You're using the free raw materials floating around in your wort and a few bucks worth of gas to make more yeast.

Now on the homebrew scale, the cost of yeast is not as big a factor, and as well our homebrew pitches these days are bigger and healthier on average than they used to be (caveats in my next point), and we almost always have access to the small amounts of wort we require to make starters. So then it just becomes a question of best practice where I'm with Bobby that pitching a healthy and active population of yeast must have some quantifiable benefit even if it would of course fail a Brulosophy triangle test.

One pack is often not enough for high gravity ales or normal to high gravity lagers and if it is enough to get the job done, it may not ferment as clean as it would with more. Clean isn't always the goal, but just sayin.

I know that you know, better than me, that there is still tremendous variability in what "one pack" means, but here are some highlights from the last 25 batches I brewed in the past 6 months:

1. I direct pitched an expired Omega Witbier pack from Brew Hardware that took off within 20 hours and showed all signs of an extremely healthy fermentation
2. I direct pitched two full dry yeast sachets of Lallemand WLP860 expiration Oct2025 obtained from the late Atlantic Brew Supply and absolutely nothing happened. After 6 days I krausened a liter off the top of a 34/70 batch that was fermenting. Within 12 hours that took off but showed all signs during fermentation that it was an underpitch as it took FOREVER to ferment.
3. I used a fresh pitch of Wyeast 1099 from ABS. The smack pack never inflated and the fermentation was slow to start and slow to finish.
4. I brewed multiple 1.045ish lagers using a single sachet of either 34/70 or S-189 and every single beer fermented out in about 7-9 days, no esters, fusels, or diacetyl.
5. Every single starter I pitched, regardless of how much yeast I started with, took off within 12-24 hours, and showed all signs of a healthy fermentation - I make 1 Liter starters and shake vigorously every hour or two to encourage oxygenation and replication.

I learned my lesson. The only way to ensure you have enough yeast, and healthy yeast, is to rehydrate or make a starter and monitor the activity.

I still have never oxygenated a single batch beyond what I pick up while chilling and transferring. I cannot say that this is good/bad or right/wrong. I never discourage other brewers from oxygenating unless it's an ester-driven style of beer. However, in years past I've made some very fruity/esterey ales and lagers where it was not desired. Now my beers are more or less all clean when I want them to be, and it's purely a combination of pitching more and controlling temperature better than I used to.

 

[sibelman]

I cannot say that this is good/bad or right/wrong.

Years ago, an experienced guy at my LHBS asked about aeration. I said I hadn't seen a difference, and had abandoned it. More recently, I've resumed aeration when pitching a single liquid yeast pack. When I make a 1 liter/quart starter, it's not needed and lag time is brief. I also don't aerate when pitching rehydrated dry yeast.

So, my practice is fairly well aligned with Bobby's and VTMongoose's thoughts. I should stop being lazy with single liquid yeast packs, and always make starters for them, even when they're frsh and claim 200 billion cells.

 

[Bassman2003]

I have come to believe that yeast management is the most important part of higher level brewing. Once one gets sanitation, temperature & process down, focus on yeast health and propagation. Once you do this hobby for a while, using tired and/or outnumbered yeast is frustrating and counterproductive. Take the extra time to always make a starter and pitch more yeast than the norm. Underpitching is way more harmful than too many cells.

 

[mashdar]

I used to aerate my stirplate, and I know Kai did some work showing it increased cell counts. I wonder if you could end up with dry-yeast-style lipid-saturated yeast doing that. I don't know that Kai looked at cell size/viability/vigor; I'll have to look for his post about it.

 

[Bobby_M]

I know that you know, better than me, that there is still tremendous variability in what "one pack" means,

This is absolutely true. I have about the best intel on the condition and handling of the liquid yeast since I'm early on in the "chain of custody" but there's still UPS and FEDEX in between and not all labs publish viability reports on each pack to begin with. If I were ordering packs from retailers for my own brewing, I'd be making starters for EVERY SINGLE BEER.

I do use intuition a bit. If I'm using Omega, and the pack is a week old, I assume I have about 180B cells to work with. If that's about what Brewfather's calculator says I need to pitch, I PREVIOUSLY would have direct pitched it and added 30 seconds of O2 with a stone directly into the fermenter. After giving it thought, I will be basically be making a viability starter. I agree with previous posters that it's basically what you're doing if you oxygenate your yeast with a bit of added wort on brew day.

As the packs get older, I'm more likely to assume the worst case scenario on the degradation of viability and will lean towards running full growth starters. This is an insurance that has more upside (a successful batch) than downside (20 minutes to get a starter stirring).

 

[CascadesBrewer]

To me, this idea seems sensible: yeast need oxygen to reproduce. Once there's enough yeast cells, no more need, I guess. Anaerobic respiration thereafter.

This statement does not match my understanding. What I understand is that yeast will process oxygen because the aerobic pathway produces much more energy than anerobic. They will use this energy to build up their cell structure and these healthy cells will be in a good position for the needed reproduction that occurs during a fermentation. The oxygen introduced into the wort will be consumed well before the growth phase. (A yeast lab may continually feed sugar and oxygen to force continuous yeast growth.)

I have not yet read through the linked paper, but this thread hits on lots of interesting topics for me. There was an off hand comment in an Escarpment Labs webinar like "The goal is oxygenate the yeast, not the wort" which has stuck with me. It made me realize why I had good success in years past with simple "vitality starters" made the night before brew day, or when I adopted shaken-not-stirred methods.

I am pretty sure if I pitch heathy yeast into my wort shortly after chilling, it will consume the oxygen present. I have wondered how short that needs to be to prevent oxidation. What if I chill to 85F, transfer to the fermenter, and let the wort chill for a few hours or overnight? What about cases where it takes over 24 hours before fermentation kicks in?

 

[VTMongoose]

I am pretty sure if I pitch heathy yeast into my wort shortly after chilling, it will consume the oxygen present. I have wondered how short that needs to be to prevent oxidation. What if I chill to 85F, transfer to the fermenter, and let the wort chill for a few hours or overnight? What about cases where it takes over 24 hours before fermentation kicks in?

I would not recommend doing this. Pitching hot will almost always yield fermentation off-flavors like esters and especially fusel alcohols in my experience. It's one thing to ferment a liter at room temperature in a starter, pretty harmless even if you don't discard the spent wort IMO, but you are talking about active fermentation starting in 20 times the volume. Kinetics are way way faster as a function of temperature and you could be hitting the growth phase in 1/4 of the time as at 50°F for a lager. So then your yeast is entering the growth phase where it produces the most esters and fusel alcohols and you're actually fighting trying to chill it down and get it to slow down as it's producing more heat and all these off-flavors. See "Timing of Ester and Alcohol Production & Fluctuating Temperatures" in this article by Scott Janish.

I was drinking a pint of a Czech Pils at a local brewery and talking to one of the head brewers. The beer had numerous problems, but for the sake of this thread, the esters and fusel alcohols were high for the style (the fermentation profile was just generally not clean). I came to find out he was chilling to 65 and waiting for the yeast to take off, then chilling to 50 to finish fermentation. He claimed this practice was because when they direct pitched at 50, the yeast would "not take off". I guarantee all of this is down to poor yeast management on their part. I have observed that if I direct pitch lagers with inactive yeast, liquid or dry, I can expect a 2-3 day lag time regardless of how healthy/large the pitch was.

Edit: Never mind, I literally misread the thing I'm quoting apparently. I'm still not sure what he was trying to describe.

 

[mac_1103]

What if I chill to 85F, transfer to the fermenter, and let the wort chill for a few hours or overnight?

I would not recommend doing this. Pitching hot will almost always yield fermentation off-flavors like esters and especially fusel alcohols in my experience.

He didn't say anything about pitching hot.

 

[Bassman2003]

I am pretty sure if I pitch heathy yeast into my wort shortly after chilling, it will consume the oxygen present. I have wondered how short that needs to be to prevent oxidation. What if I chill to 85F, transfer to the fermenter, and let the wort chill for a few hours or overnight? What about cases where it takes over 24 hours before fermentation kicks in?

From a low oxygen point of view this is not that bad if:

You have a floating cap to limit surface area
Do not oxygenate until you are ready to pitch

Since the temperature is low, oxygen ingress will be slower. This plays into your favor. Once cooled, pitch your yeast then oxygenate and you should be off to the races.

 

[tracer bullet]

Brulosophy* has done some testing on this over time. Looking back, there was one time where the reviewer could tell a difference, and 4 other times that there was no difference able to be detected. The one time a difference was determined was with a barleywine... That could be related to the high OG perhaps? It seems with more common beers that various methods, or a lack of altogether, didn't make enough change to be noticed.

* I know a lot of folks question the knowledge of the people doing the sampling, and their statistics, and that's fine. But I'm actually referring to the author doing the testing for the above. I like to think that they are avid homebrewers and fairly experienced beer drinkers, and so I tend to pay attention to their own personal notes much like if one of us here reported on their own testing.

I don't mean to say it's proof oxygen is not important, but just for the sake of sharing some data points, if you consider it to be data.

 

[Bassman2003]

Do you mean Brulosophy testing oxygen ingress into wort from various chilling methods? Unless they had a DO meter, I would not think the tests would show much. Flavor wise, one would need to start with a low oxygen wort to see any differences.

 

[tracer bullet]

Do you mean Brulosophy testing oxygen ingress into wort from various chilling methods?

Good question, looking back at my post I wasn't clear at all. Sorry. It was various oxygenation methods performed at the time the yeast was pitched.

 

[sibelman]

floating cap to limit surface area

temperature is low, oxygen ingress will be slower

DO meter

Am I right in thinking that you (or someone) used a DO meter to measure the effect of the floating cap, and of the lower temperature? There's data?

 

[Bassman2003]

Good question, looking back at my post I wasn't clear at all. Sorry. It was various oxygenation methods performed at the time the yeast was pitched.

That is better then. As I posted before, I think the pre-oxygenation is a good way to get oxygen to the yeast, but how long it will fuel them is the big question for me. If they start strong and whimper out because they are looking for more oxygen to replicate, it would not be a positive. That is more lab level testing and beyond my capabilities.

 

[Bassman2003]

Am I right in thinking that you (or someone) used a DO meter to measure the effect of the floating cap, and of the lower temperature? There's data?

Yes. On another forum not to be named in a separate universe. That method has been verified as bona fide

 

[CascadesBrewer]

I'm still not sure what he was trying to describe.

I think it is fairly common for people to chill the wort down to ~10F above their ground water temp, transfer into a fermenter, and let their fermentation chamber get down to pitching temps before adding the yeast. For me this often took 3-4 hours, but I have also pitched the yeast the following morning. These days I can usually get down to pitching temps by recirculating ice water through my immersion chiller. Worries about oxidation was a primary driver in changing my process here.

From a low oxygen point of view this is not that bad if:

One would also have to take care about introducing oxygen during the chilling process and the transfer into the fermenter. My chilling process has involved a lot of manual stirring (though I recently added a pump for recirculation during chilling). I would also want to use a transfer tube that reached the bottom of my fermenter.

 

[Bassman2003]

One would also have to take care about introducing oxygen during the chilling process and the transfer into the fermenter. My chilling process has involved a lot of manual stirring (though I recently added a pump for recirculation during chilling). I would also want to use a transfer tube that reached the bottom of my fermenter.

Your are correct but that is why the low oxygen crowd uses sulfites to protect from unavoidable oxygen "events"

 

[beer'd_meadeator]

I'm going to change my user name to "innocently ignorant."

 

[Miraculix]

I think it is fairly common for people to chill the wort down to ~10F above their ground water temp, transfer into a fermenter, and let their fermentation chamber get down to pitching temps before adding the yeast. For me this often took 3-4 hours, but I have also pitched the yeast the following morning. These days I can usually get down to pitching temps by recirculating ice water through my immersion chiller. Worries about oxidation was a primary driver in changing my process here.


One would also have to take care about introducing oxygen during the chilling process and the transfer into the fermenter. My chilling process has involved a lot of manual stirring (though I recently added a pump for recirculation during chilling). I would also want to use a transfer tube that reached the bottom of my fermenter.

Just to throw in one personal observation p(o)int here, I also used to do A LOT of stirring during the use of a normal immersion chiller.

And you might have seen my "dreaded almond flavour" thread elsewhere..... there was an interesting correlation between these two.

Once I stopped stirring while the wort is truely hot (let's say above 45 c ), a big portion of this almond flavour disappeared.

When I started milling my own grain, and did not use malt that was stored crushed for extended time, the rest of the almond disappeared.

So stirring while hot seems really to oxidise the wort.