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Brews & Views Bulletin Board Service * Brews and Views Archive 2006 * Archive through June 28, 2006 * O2 coming out of solution in aerated wort? < Previous Next >

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Black Beard
New Member
Username: Jollyroger

Post Number: 2
Registered: 06-2004
Posted From: 204.194.37.78
Posted on Thursday, June 15, 2006 - 06:23 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

i read on another board that after being aerated, O2 dissipates from wort fairly quickly -- within a few hours. is that true? if it is, it would totally change my procedure for lagers because right now i aerate after cooling, and don't pitch until the next day (the soonest that i can get the wort to lager pitching temps here in sunny FL). do ya'll aerate right after cooling, or right before pitching?
 

Graham Cox
Advanced Member
Username: T2driver

Post Number: 574
Registered: 11-2004
Posted From: 68.32.248.92
Posted on Thursday, June 15, 2006 - 07:15 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Right before (or after) pitching. It's the yeast that need the O2, not the wort.
 

Paul Edwards
Senior Member
Username: Pedwards

Post Number: 1044
Registered: 03-2003
Posted From: 70.225.129.141
Posted on Thursday, June 15, 2006 - 07:52 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Dittoes. Some people recommend a second blast of oxygen a few hours after pitching.
 

Ken Anderson
Senior Member
Username: Ken75

Post Number: 1573
Registered: 11-2002
Posted From: 69.168.141.10
Posted on Thursday, June 15, 2006 - 08:03 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I once hit an underpitched batch with the Mix-Stir aerator at 38 hours. I figured the yeast needed it for further growth. I assume it helped. Nothing detrimental that I could tell.
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 2957
Registered: 03-2004
Posted From: 216.23.59.245
Posted on Thursday, June 15, 2006 - 08:12 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ken, do the arms of your Maxi-Stir stay on opposite sides or does one flip over to the wrong side. I just tried one of these things the other day and had to reconfigure it more than once.

On second thought, it did not seem to matter.

Dan

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Ken Anderson
Senior Member
Username: Ken75

Post Number: 1575
Registered: 11-2002
Posted From: 69.168.141.10
Posted on Friday, June 16, 2006 - 04:10 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

In case anyone doesn't know how they work, the two "wings" move independently. They both hang straight down when the thing isn't spinning. In this position, they will fit down the neck of a carboy (how convenient, ay?). When you spin it with a drill they move out to the horizontal position and whip up a batch of wort like crazy. There are stops at each end of this 90 degree movement.

Dan, I've never had the malfunction you mention.

I have this guy:
http://www.thegrape.net/browse.cfm/4,8175.htm

Ken
 

Richard Nye
Senior Member
Username: Yeasty_boy

Post Number: 1451
Registered: 01-2004
Posted From: 68.4.202.69
Posted on Friday, June 16, 2006 - 12:53 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

BlackBeard...I don't think the O2 dissipates. It's dissolved into the wort, and like CO2, will stay dissolved unless the conditions change (temperature increases, or there's some mechanical disturbance). But I would still aerate just before you pitch the yeast, particularly since you're chilling the wort. You want to aerate the wort when it's coldest so it dissolves the most O2 (colder liquids can dissolve more O2 than warmer ones).
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 2959
Registered: 03-2004
Posted From: 216.23.59.245
Posted on Friday, June 16, 2006 - 01:04 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

That is different from mine. We quit carrying those because the drive stem kept shearing off. Maybe they have figured out a fix now.

Mine has a stainless shaft and plastic rods that fly out as it spins. Sometimes they end up on the same side. This is not right, but it does not seem to be a problem either.

Dan

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J. Steinhauer
Advanced Member
Username: Jstein6870

Post Number: 874
Registered: 03-2002
Posted From: 216.70.45.1
Posted on Friday, June 16, 2006 - 01:27 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

BB,

Simply because the oxygen is more soluble in the colder wort, I would wait until you pitch. If you oxygenate earlier and you store the wort in a sealed container, outgassing should not be much of a problem, though, since the headspace over the oxygenated wort would remain supersaturated with oxygen as well. If your fermenter is not sealed, though, it will gradually reach equilibrium levels with the atmosphere.

Steinhauer
 

Fredrik
Senior Member
Username: Fredrik

Post Number: 3230
Registered: 03-2003
Posted From: 213.114.44.200
Posted on Saturday, June 17, 2006 - 11:14 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

FWIW, here are some more comments... I don't have any good references for data, so I can't supply any numbers, but as far as dissipating from the wort there are two possibilities.

1) Like Steinhauers mentions, a supersaturated wort (having more dissolved oxygen than that governed by the equilibrium with air) will obviously loose some oxygen over time... I have no good time data though.

But I think you need a darn small headspace to effectuvely prevent release of supersaturated gas.

Considering that 16 ppm O2 in 5 gallons is only 0.24 l O2 (0.06 gallons) it seems like the release of some of this into a gallon of air heagspace, will only marginally increase the oxygen content in the headspace in order to keep the wort supersaturated.

This is because the total amount of oxygen is so ridicilously small.

2) The other possibility is that dissolved oxygen is used up in wort oxidations. Yes, supposedly this is pretty slow at cool wort temps as compared to the rate at which yeast consume it, but probably not zero. I don't have any references at hand though.

Wort oxidations probably doesn't have any other direct effects besides flavour stability and shelf life.

In either case it seems to me beyond most doubt that aerating the wort and then let it sit is not going to improve anything.

Only semirelated, there is one interesting ASBC paper investigating the link between a modern method of measuring the reducing power of the wort, and wort aeration techniques as well as flavour stability as in oxidations in lager beer.

It was found that sulphur production increase with lower aeration along with lower performance but the good part was that the yeast sulfite production actually increased the shelf life.

They found in this limited that the interesting thing that underaerated beer, had some undesirable flavour BUT it had better shelf life.

So they suggested a balanced aeration to balance performance, desirable flavour production, and shelf life. The also note that timing is essential. I think the less total oxygen you need to add, the better. And with the right timing with respect to yeast growht phases you can achieve the proper yeast aeration with less excess oxygen. They also suggest that if you do a second aeration, it should be balanced against the first aeration, in order to not overaerate.

The overaeration as it seems had marginal effects on performance, but significant effects on the beers reducing power and thus resistance to oxidations during storage.

This may seem less important to homebrewers but I am no longer so sure about that. Probably the single most important factor for storage is temperature. Those of you who store your beers fridgerated at all times can probably get away with more than if it's stored at room temp.

I have to admit that I am not happy with the flavour stability of all my beers. I am currently investigating why. Sure the fact that I use PET may be a factor (I'm going to get a keg eventually to make a comparasion) but OTOH, I think there are more to it, I do not think the PEt alone is the main factor, but I could be wrong. I remember some beers I've made that were different... and I am starting to see patterns.

Some homebrewers seem to have the opinion that the change of flavour over time is charming. Maybe that's true, but I find it annoying.

/Fredrik
 

Tom Gardner
Advanced Member
Username: Tom

Post Number: 815
Registered: 01-2001
Posted From: 67.190.165.26
Posted on Saturday, June 17, 2006 - 03:22 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

What Richard Nye said. I think "they" were referring to the O2 being used up in 4 hours by the yeast. Brew on, Tom