oxygenating wort - larger capacity systems

[Sadfield]

Not really @peebee. I'm saying there's nothing to scrub. Anyhow, I see your still here.

@Wynne I forgot I knew about crabtree. Aerobic to anaerobic was a mistake on my part. As above, it's not really relevant, the DO has already been removed, as per Wyeast's statement.

https://onlinelibrary.wiley.com/doi/full/10.1002/jib.392

 

[peebee]

Not really @peebee. I'm saying there's nothing to scrub. ...

Aye, and what I'm saying is whether one mechanism or the other is entirely true or only part true, the result is the same so who here cares? We want homebrewing arguments, not geographically distorted or "Physics" arguments. As either side's view ends up with the same result (no oxygen) either side can be brandished about as "correct" for the purpose of brewing beer.

(Says someone - me? - who was once the most intolerant bigot about here but has had to learn to be a little more broad-minded).

 

[Sadfield]

Aye, and what I'm saying is whether one mechanism or the other is entirely true or only part true, the result is the same so who here cares? We want homebrewing arguments, not geographically distorted or "Physics" arguments. As either side's view ends up with the same result (no oxygen) either side can be brandished about as "correct" for the purpose of brewing beer.

(Says someone - me? - who was once the most intolerant bigot about here but has had to learn to be a little more broad-minded).

Well, if oxygen is totally used up during the lag phase and not gased off during the exponential growth phase, then it would be quite significant to home brewers. It would mean that there could be advantages in adding more oxygen, even with dry yeast, if yeast uses up all the available oxygen we can give it, rather than taking a percentage of it. Healthy, happy yeast make better beer, IMO.

 

[Agentgonzo]

Physics steps in (partial pressure) and forces excess O2 in solution that can no longer be held in solution by the partial pressure of O2 over the beer (and isn't nabbed by any passing yeast cells)

So at what point does something change in the yeast cells that will make them take up oxygen again?

ie, according to the above, yeast does this

1. Gets pitched into a starter. Yeast takes up oxygen
2. Gets pitched into the wort. Yeast takes up more oxygen during the lag phase
3. Growth phase of yeast. Yeast continues to take up oxygen?
4. Fermentation phase. According to the above, yeast will not take up oxygen, even if it is present

What happens if I crop actively fermenting yeast from the above and throw it straight into a new batch of oxygenated wort? According to the above, it "won't take up the oxygen", but we know this isn't the case because brewers have been repitching yeast like this for centuries, and repitching yeast needs the wort to be oxygenated (it's just putting the yeast back to stage 2/3 above in fresh wort).

 

[peebee]

Fermentation phase. According to the above, yeast will not take up oxygen, even if it is present

But it will! As I've found to my cost! (Also learnt silicone tube is transparent to oxygen so those tubes all caked up solid with yeast).

The yeast doesn't operate to our clear-cut ideas. If there is oxygen to build more cells, that's what it will do! And it will carry on fermenting sugar (anaerobically) too.

 

[Agentgonzo]

But it will! As I've found to my cost! (Also learnt silicone tube is transparent to oxygen so those tubes all caked up solid with yeast).

The yeast doesn't operate to our clear-cut ideas. If there is oxygen to build more cells, that's what it will do! And it will carry on fermenting sugar (anaerobically) too.

So then this (the bolded bit) is wrong ?

Physics steps in (partial pressure) and forces excess O2 in solution that can no longer be held in solution by the partial pressure of O2 over the beer (and isn't nabbed by any passing yeast cells) to escape from the beer.

ie, should it be "as well as any passing yeast cells"?

 

[peebee]

No? But it could have been better to say "an' ain't nabbed by any passing yeasty loons".

"Inclusiveness"; I'm trying to support both lines of thought.

 

[Weizenberg]

Excess oxygen can have an unwanted, toxic, side-effect on yeast.

This so-called oxidative stress that occurs at concentrations over 30 ppm, may lead to formation of radicals and to peroxidation of the lipids and thus to an impairment of the functionality of the yeast cell membrane.

I experienced it first hand due to a faulty instrument. The end-result ended up in the drain. It tasted awful.

 

[Agentgonzo]

well this thread has left me none-the-wiser about whether yeast uses up excess oxygen during fermentation.
From a practical point of view, it doesnt' matter because it does "go away" during fermentation, but I do like to understand things!

"Inclusiveness"; I'm trying to support both lines of thought.

This seems a futile endeavour given the arguments on the thread (and forum)

 

[Agentgonzo]

Excess oxygen can have an unwanted, toxic, side-effect on yeast.

This so-called oxidative stress that occurs at concentrations over 30 ppm, may lead to formation of radicals and to peroxidation of the lipids and thus to an impairment of the functionality of the yeast cell membrane.

I experienced it first hand due to a faulty instrument. The end-result ended up in the drain. It tasted awful.

Fortunately, it's very hard to get that high levels of oxygen. And even more fortunately, impossible without using pure O2

 

[Weizenberg]

Fortunately, it's very hard to get that high levels of oxygen. And even more fortunately, impossible without using pure O2

Absoultely. You'd need pure O2 indeed.

The fermentation process can be divided into two stages: the initial period and the Embden-Meyerhof-Parnes (EMP) pathway.

Once the fermentation begins, it is important to exclude oxygen because the EMP pathway is an anaerobic process. In fact, if oxygen is introduced during fermentation, the yeast cells will tend to revert to respiration. This process is often called the Pasteur effect.

You can read about this in more detail in: Principles of Brewing Science, George Fix, (p. 93).

Hope this helps.

 

[peebee]

... You can read about this in more detail in: Principles of Brewing Science, George Fix, (p. 93). ...

"George Fix"? As in the late Dr George Fix!!! Now ... you're just trying to stir up controversy, aren't you?

Beer colour. (Rant!). - Jim's Beer Kit

I think I'm out of here ... runnnnnn...

 

[Weizenberg]

Looks like I found a new button to press