Do you aerate?

[Agentgonzo]

Watch the new GEB brewery tour. Really interesting.

Thanks. I'll take a look (do you have a link). It'll be interesting to see how stuff has changed over a couple of decades.

 

[hoppyscotty]

Yeah it's mixed. I've done alot of brewery tours over the last couple of years, and spoken to brewers invited to our monthly homebrew club meet and it's mixed. Think it depends on the individual brewers own experiences of the harvesting and maintaining yeast stores. Not sure how many re-pitches you have to do for the strain to mutate sufficiently for it to be considered a 'house strain'. I thought you could only re-pitch the same yeast a certain number of times, say 5 or 6, before it started developing bad flavours...one very small brewery I visited (a friend of a friends) used S05 and re pitched 5 times before ditching and re-pitching fresh. I've no idea how Verdant developed their own strain...pretty sure it took more than just re-pitching the same stuff time and time again.

That is a whole area I've yet to delve into.

 

[Agentgonzo]

Yeah it's mixed. I've done alot of brewery tours over the last couple of years, and spoken to brewers invited to our monthly homebrew club meet and it's mixed. Think it depends on the individual brewers own experiences of the harvesting and maintaining yeast stores. Not sure how many re-pitches you have to do for the strain to mutate sufficiently for it to be considered a 'house strain'. I thought you could only re-pitch the same yeast a certain number of times, say 5 or 6, before it started developing bad flavours...one very small brewery I visited (a friend of a friends) used S05 and re pitched 5 times before ditching and re-pitching fresh. I've no idea how Verdant developed their own strain...pretty sure it took more than just re-pitching the same stuff time and time again.

That is a whole area I've yet to delve into.

The brewers I talked to didn't worry about whether it was different or had mutated from where they got it from. I guess "house strain" is just a fancy word for "the yeast we keep in the bucket in the fridge" . You can keep yeast going indefinitely provided you look after it. I can't remember the exact numbers, but most (if not all) of the ones I visited had kept their yeast going since they opened. Well over a decade in some cases.

I thought you could only re-pitch the same yeast a certain number of times, say 5 or 6, before it started developing bad flavours...one very small brewery I visited (a friend of a friends) used S05 and re pitched 5 times before ditching and re-pitching fresh.

I guess it depends on the source of the yeast

 

[MrJay83]

Well over a decade in some cases.

In that video I mentioned they have been repitching it for 50 years!

 

[MrJay83]

Thanks. I'll take a look (do you have a link). It'll be interesting to see how stuff has changed over a couple of decades.

Sorry. Forgot to include
https://www.geterbrewed.com/blog/2023/04/09/open-top-fermentation/

 

[Sadfield]

Triggers broom.

 

[RoomWithABrew]

To get healthy yeast. Oxygen is needed to make healthy yeast with good reserves. Health and reserves diminish as yeast multiplies.

Yes, but you won't get as much yeast after multiplication as you would with a 'correct' pitch rate so not as. It will ferment, but at a slower rate (and with more off flavours I suspect).


Lots of things happen. Yes, it's aerobic in the lag phase and it starts to multiply, but yeast multiplies more in the fermentation (or 'log') phase, which is generally anaerobic. But if there is any oxygen still present (or even reintroduced at this stage) then the yeast will use it up as well, the same as what would happen if you cropped yeast from fermentation and chucked it into fresh wort. It's a complex process, and not a simple on/off scenario where it stops consuming oxygen suddenly and changes mode.

My questions were really more of a challenge to the non aeraters and all of your answers were the reasons why I aerate starters on a stir plate and also my wort. Your final answer also confirmed my views.
But I'm sure your answers will have helped the believers and will be ignored by the unbelievers.

 

[hoppyscotty]

In that video I mentioned they have been repitching it for 50 years!

And longer than that because they got the original yeast from an already established brewery. However they do ‘maintain’ the yeast which is something they didn’t go into in that video. He did mention they had a lab and for each brew check the viability of the pitch which implies that sometimes the yeast may not be good enough to be re pitched and then maybe they have to refresh it from some other batches they keep in storage or something.

 

[Sadfield]

Bottle conditioning and oxygen uptake.

Active yeasts are known to be capable to metabolize oxygen and subsequently to act as biological oxygen scavengers, which offers the opportunity of enhancing the shelf life of beer in a natural way.

Different yeasts selected from commercially available bottle
conditioned beers showed different speeds in oxygen reduction,
which interestingly did not have an impact on the prevention of stale flavour, as all yeasts proved to be
efficient in this respect.

https://www.researchgate.net/public...ers_Part_2_Screening_of_Yeasts_1_Introduction

 

[Sadfield]

From Lallemand.

While dry yeast can be pitched without aeration (sufficient sterol and unsaturated fatty acid reserves support several cell divisions without requiring oxygen), the re-pitched yeast must be aerated to 8-10 ppm dissolved oxygen.

https://www.lallemandbrewing.com/en...y-yeast-for-quality-consistent-fermentations/
There's aeration and aeration. The way I see it, if you aren't adding pure oxygen to your wort, you are unlikely adding 8-10ppm, which is what yeast manufacturers consider aeration. A normal (splashing) transfer will introduce some oxygen into the worry, which will eventually be used by dry yeast after the initial cell divisions have depleted sterols. If you oxygenated to 8-10pmm then pitched dry yeast, you'll likely have dissolved oxygen carrying over into the finished beer. Likely why the producers recommend not to aerate.

 

[foxy]

Bottle conditioning and oxygen uptake.




https://www.researchgate.net/public...ers_Part_2_Screening_of_Yeasts_1_Introduction

I introducing an active yeast will scavenge any yeast in the bottle most commercials do this in there bottled conditioned beer, Coopers are renown for their bottle conditioned beers and dose the yeast at bottling. Apparently a weaker strain of their fermentation yeast.

From Lallemand.

https://www.lallemandbrewing.com/en...y-yeast-for-quality-consistent-fermentations/
There's aeration and aeration. The way I see it, if you aren't adding pure oxygen to your wort, you are unlikely adding 8-10ppm, which is what yeast manufacturers consider aeration. A normal (splashing) transfer will introduce some oxygen into the worry, which will eventually be used by dry yeast after the initial cell divisions have depleted sterols. If you oxygenated to 8-10pmm then pitched dry yeast, you'll likely have dissolved oxygen carrying over into the finished beer. Likely why the producers recommend not to aerate.

The dried yeast requires no oxygen whatsoever, both Fermentis and Lallemand state this. Any oxygen present, from those who chose not to follow the advice of the two above and aerate the wort the oxygen will be scrubbed out by the fermentation along with everything else we don't want in our finished beer.

 

[MrJay83]

And longer than that because they got the original yeast from an already established brewery. However they do ‘maintain’ the yeast which is something they didn’t go into in that video. He did mention they had a lab and for each brew check the viability of the pitch which implies that sometimes the yeast may not be good enough to be re pitched and then maybe they have to refresh it from some other batches they keep in storage or something.

Yeah I would like to hear more about that. Surely they have a backup for when things go wrong.

 

[Sadfield]

The dried yeast requires no oxygen whatsoever, both Fermentis and Lallemand state this.

I didn't say otherwise. Whether in an fv or a bottle, yeast will use oxygen whether they 'need' it or not. From a yeasts perspective, fermentation is all about survival and growth, they'll take whatever they can use, in order to multiply until they've consumed all that's available. Just making the point that what most people consider aeration doesn't add much oxygen and won't do any harm when using dry yeast.

 

[foxy]

I didn't say otherwise. Whether in an fv or a bottle, yeast will use oxygen whether they 'need' it or not. From a yeasts perspective, fermentation is all about survival and growth, they'll take whatever they can use, in order to multiply until they've consumed all that's available. Just making the point that what most people consider aeration doesn't add much oxygen and won't do any harm when using dry yeast.

Not once they have gone anaerobic, they will consume the sugars in the bottle and that's all. Otherwise beer wouldn't oxidise.
The last thing any brewer would want is a yeast returning to aerobic respiration,

 

[Sadfield]

 

[foxy]

View attachment 84641

Exactly how I feel at times on here.

 

[Agentgonzo]

Not once they have gone anaerobic, they will consume the sugars in the bottle and that's all.

So if you repitch yeast from the end of fermentation into fresh wort, you need to aerate the wort because the yeast needs oxygen to build up reserves and multiply.
But if you have exactly the same yeast and feed it sugar to condition the beer, it won't take up any oxygen at all?

That makes no sense. How would the yeast know to decide on option 1 or 2?

 

[RoomWithABrew]

That makes no sense. How would the yeast know to decide on option 1 or 2?

I reckon it doesn't.

 

[Sadfield]

Indeed. Fermentation is the exponential growth phase of yeast, which requires sterols to form cell walls, regardless of being a new fermentation or secondary fermentation. As a basic survival mechanism yeast must surely do what it needs to be ready for that next potential source of carbohydrate. Absorb oxygen and prepare for the next chance to grow.

This I found interesting from Fermentis, it says aerating can be done if you intend to reuse the yeast, despite it's inbuilt sterols. Impling the above, the yeast will deplete and replace sterols.

 

[foxy]

So if you repitch yeast from the end of fermentation into fresh wort, you need to aerate the wort because the yeast needs oxygen to build up reserves and multiply.
But if you have exactly the same yeast and feed it sugar to condition the beer, it won't take up any oxygen at all?

That makes no sense. How would the yeast know to decide on option 1 or 2?

From Tracy Aquillas article which has been viewed on this forum a number of times.
The article 'Oxygens role in the fermentation of yeast' a must read, its been around a long time.

Although brewers’ yeast is able to use both respiration and fermentation metabolic pathways, it does not respire if a relatively high concentration of fermentable sugar is available, even when ample oxygen is available for respiration.

Brewers’ yeast is able both to respire and ferment, a luxury most organisms do not enjoy. What determines its ability to grow and reproduce is the presence of the required nutrients, independent of whether the environment is aerobic (exposed to air) or anaerobic (without air). Although brewers’ yeast is able to use both respiration and fermentation metabolic pathways, it does not respire if a relatively high concentration of fermentable sugar is available, even when ample oxygen is available for respiration.

The tendency for fermentation: Brewers’ yeast has a very strong tendency toward fermentation and will respire only when the concentration of fermentable sugars is very low and oxygen is available. In beer making, yeast will ferment rather than respire, regardless of the oxygen concentration, because the wort usually supplies an overwhelming abundance of fermentable sugar. The production of ethanol during fermentation may contribute to yeast survival because of its toxicity to other microorganisms.

So making a starter the yeast determines the task in front of it according to the amount of nutrient, with ample amount of nutrient it will respire and reproduce, once it has reached an abundance of cells it goes into aerobic stage of fermentation.
The dried yeast needs no starter, I am pretty sure I read it is 5 billion cells per gram of yeast full of ergo sterols, fatty acids and glycerol to get to work immediately. I doubt they do a head count before they tackle the job in front of them, they just know they have the quantity of cells to do the job.