Aeration question - pure O2 not needed?

[ArcLight]

In the Yeast book by Chris White and Jamil Zainasheff they mention that for high gravity beers you can add more Oxygen at around 9-13 hours. That during the lag phase the yeast are absorbing all the Oxygen in the wort.

So why not instead aerate by shaking/rocking the bucket/carboy, then at 9 hours, opening it up, so the head space gas is replenished from the atmosphere, and shaking it again for 45 seconds. that will re-oxygenate the wort.

How is pure O2 better than this method?
The only downside is the small risk of contamination when opening it the second time for 15 seconds.

 

[BigEd]

You can do that. I use the atmosphere all the time to aerate my wort/beer. The advantage of pure O2 is that it is pure O2. Air is 21% oxygen so compared to bottled O2 it's less efficient to deliver the O2 to the yeast.

 

[aiptasia]

There's usually less risk of infection from airborn contaminants as well.

 

[RM-MN]

I believe the absolute best oxygenation by shaking or pouring is about 7 ppm. The usual with shaking a carboy is more like 2 ppm. With pure oxygen you can easily go over 10 ppm and with a bit more time can actually get too much oxygen dissolved in the wort.

 

[aiptasia]

That's why you limit your pure O2 exposure to about a minute. Also, i'd like to know your technique for measuring your O2 ppm in the wort?!

 

[E_Marquez]

So where (when) is the cut off, from aerate wort is good, Oxidizing wort/ beer is bad? 10 hours after pitching? 20? 2 days? 10 days?


To the OP's question..
aerating wort would be done real easy with O2 and a .5 micron stone on the end of a SS tube as can be bought from several HBS places.
If your using carboys or buckets with the larger hole for the air lock stopper (my choice as i can drop a thief in that same hole).. It would be super simple to sanitize the hole and stopper, remove stopper, drop in the sanitized air stone wand, aerate for 1 min or so (ask 10 people, get 12 answers on how long is "best" ), sanitize stopper and airlock and put back in place.

Doing it that way with O2 would pose no more infection risk then pulling a sample to SG readings.

 

[ArcLight]

The reason i ask this is in Mead and Wine making they Oxygenate the must (thats what they call their wort), a few times after yeast pitching. I use a bucket and rock it and get say 8ppm O2. Why not do that again after 7 hours, when the lag phase is just about over), since most of the O2 is now absorbed by the yeast.
There is a slight risk of contamination.

The only problem with the Oxygen stone is they no longer sell the 2.1 Oz O2 bottles. The 1.4 Oz bottles have 1/3rd less O2, but cost 2 $ less, so the cost per use is up a lot.

(Why did Bernzomatic stop selling the 2.1 Oz O2 bottles?)

 

[E_Marquez]

The reason i ask this is in Mead and Wine making they Oxygenate the must (thats what they call their wort), a few times after yeast pitching. I use a bucket and rock it and get say 8ppm O2. Why not do that again after 7 hours, when the lag phase is just about over), since most of the O2 is now absorbed by the yeast.
There is a slight risk of contamination.

The only problem with the Oxygen stone is they no longer sell the 2.1 Oz O2 bottles. The 1.4 Oz bottles have 1/3rd less O2, but cost 2 $ less, so the cost per use is up a lot.

(Why did Bernzomatic stop selling the 2.1 Oz O2 bottles?)

Hunt CL, or local ads, auctions.. Pick up a used O2 cylinder and regulator..
Can be had for cheap, and then just swap a cylinder at your local welding gas store when needed (if only using for beer, you may never need a second refill, depending on size tank you find and how much you brew.)

 

[E_Marquez]

(Why did Bernzomatic stop selling the 2.1 Oz O2 bottles?)

Supplier in NJ still lists the 2.1
http://www.njsupply.com/Bernzomatic-21Oz-Ox9-O2-Cylinder_p_13401.html

 

[ArcLight]

What type of used O2 cylinder and regulator should I get?
Doe sit matter?
It looks like the 1/4 plastic tube taht connects to teh 2 micron stone wouldn't attach to some of the regulators.

 

[E_Marquez]

Common size for O2 regulator output is 9/16" - 18 (RH Male), you can get a barbed fitting that screws into that outlet, sized to fit your tubing size, or an adapter the will then screw in to a barbed fitting.

I cheated and turned down a fitting to work with 1/4 ID hose..

 

[corax]

So why not instead aerate by shaking/rocking the bucket/carboy, then at 9 hours, opening it up, so the head space gas is replenished from the atmosphere, and shaking it again for 45 seconds.

You'd probably be OK with a bucket, but avoid this method with carboys.

I tried it once, but enough fermentation had already occurred that there was a bunch of CO2 already in the wort. When I shook the carboy, it went off like a warm bottle of Champagne!

 

[corax]

So where (when) is the cut off, from aerate wort is good, Oxidizing wort/ beer is bad? 10 hours after pitching? 20? 2 days? 10 days?

It has more to do with gravity (ie, sugar concentration) than it does time. When sugar concentration is high enough, yeast will ferment even in the presence of oxygen -- hence, open fermentation works.

But when sugar concentration drops low enough, if oxygen is present the yeast will switch from fermentation to respiration, and consume alcohol as fuel (I don't know the exact point where they switch, but certainly 1.020 or higher is well above the critical level).

This says nothing about how late you can safely pump pure oxygen into fermenting wort -- just that you shouldn't worry too much about exposing the wort to atmospheric oxygen until late in the game.