[denny]

So the Wyeast info says that 10ish ppm is good.  And yes, SN does make a lager....Glissade.

[tygo]

I’ll see if I can taste anything that I could attribute to the excess O2.

Kai

I definitely be interested to hear the results of that taste test.  Up until the last batch I've just been shaking the hell out of the carboy for maybe a minute.  I'm guessing that method gets you less than 8 ppm.

For the last batch I aerated with pure O2 and based on this discussion I'm sure I over-aerated.  It'll be interesting to see what the effects on the beer will be.

[denny]

According to Wyeast (sorry for the poor formatting)

Method     DO ppm     Time
Siphon Spray    4 ppm    0 sec.
Splashing & Shaking    8 ppm    40 sec.
Aquarium Pump w/ stone    8 ppm    5 min
Pure Oxygen w/ stone    0-26ppm    60 sec (12ppm)

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.

[Kaiser]

Here is a page from a German brewing text that I still aspire to own: Technologie der Wuerzebereitung: http://books.google.de/books?id=rlcwl7aS8KYC&lpg=PA791&ots=HfVnzIkiIn&dq=w%C3%BCrzebel%C3%BCftung%20venturi&pg=PA661#v=onepage&q=w%C3%BCrzebel%C3%BCftung%20venturi&f=false

Tab 8.1 shows how much O2 (mg/l = ppm) can be dissolved in water and wort based on its temperature if air is used.

Kai

[a10t2]

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO.

I'm not sure their data really support that. Of course, they're making the assumption that 10 ppm is "adequate" and anything less than 10 ppm is therefore "inadequate". I can't argue for or against that particular target, but brewing isn't a binary process.

I've also always wondered how fast O2 will diffuse out of the wort, relative to how fast the yeast can become active and start utilizing it. I guess filling the headspace with O2 would be the best way to ensure that didn't happen.

[babalu87]

Here is a page from a German brewing text that I still aspire to own: Technologie der Wuerzebereitung: http://books.google.de/books?id=rlcwl7aS8KYC&lpg=PA791&ots=HfVnzIkiIn&dq=w%C3%BCrzebel%C3%BCftung%20venturi&pg=PA661#v=onepage&q=w%C3%BCrzebel%C3%BCftung%20venturi&f=false

Tab 8.1 shows how much O2 (mg/l = ppm) can be dissolved in water and wort based on its temperature if air is used.

Kai

Maybe WYeast didnt perform their tests at a cold enough temperature then?

[tygo]

Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.

Thanks Denny.  That's good to know.

[ndcube]

I made a Tripel with pure O2 and it wasn't as estery as I expected.  I'mswitching back to whipping the wort for those styles.

Kai,
A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.

[Kaiser]

A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.

I don't think any of the O2 will be driven off. The yeast consumes it well before there is enough CO2 production that would purge the O2.

Kai

[ndcube]

A good experiment would be to see how quickly and completely O2 is driven off by fermentation if one over oxygenates their wort.

I don't think any of the O2 will be driven off. The yeast consumes it well before there is enough CO2 production that would purge the O2.

Kai

So there can never be too much O2 present that the yeast won't use it all?

[Kaiser]

The concern with too much O2 is not beer oxidation but adverse effects on the yeast including excessive growth.

Kai

[ndcube]

The concern with too much O2 is not beer oxidation but adverse effects on the yeast including excessive growth.

Kai

So the yeast will always grow until all available O2 is consumed regardless of gravity?

[tom]

I used to oxygenate throughout my chilling, maybe 5-10 minutes and I got some very oxidized beers. I know everyone will say that the oxygen will dissipate, etc., but I transfer into cornies filled with CO2 (sanitizer filled to the top and then pushed out with CO2). I don't think the oxidation could come from anywhere else.

[Kaiser]

They keep growing until one of the essential nutrients for growth is gone. Those nutrients are:

- carbon source: sugar or ethanol. The
latter only aerobically
- nitrogen source: generally amino acids but ammonium works too
- sterols: O2 is needed for their synthesis and they are accumulated during the phase when O2 is available. Later the pool is split between mother and daughter

nitrogen and O2 (sterols) tend to be the growth limiting factor in brewing.

Kai

[marcopolo]

THANKS TO ALL FOR RESPONDING TO MY QUESTION.  Obviously this topic is subject to further research & review !  I especially appreciate your insight, Denny.  You made me a fan of batch sparging, and now the MIxStir...
Cheers !!!
Marco