[marcopolo]

Does using pure O2 offer any significant advantages over aerating with plain air ?  The only advantage I can see is that pure O2 only takes seconds to oxygenate the wort whereas natural air takes minutes.  Is that the only difference ?
Thanks,
Marco

[denny]

I haven't done a side by side, but I can tell you that aerating with my MixStir I get results as good as friends who use O2.  If I didn't get that kind of result, I'd look at switching.  It only takes a couple minutes with the Mixstir.

[tubercle]

My tiny mind tells me O2 is just that regardless of the source.

[Kaiser]

The only problem with natural air is that you can’t get past 8-10 ppm. But this is what is recommended anyway. Even large lager breweries aerate with sterile air and must be getting to the recommended 12 ppm. I think this is because the wort is quite cold when they aerate.

I recently added a DO meter to my testing equipment and have started playing around with various aeration techniques. Here is data from a MixStir aeration:

Wort temp: 11 C
Gravity 11.5 Plato

Unaerated wort: 1.5 ppm DO (there is a lot of error in low DO readings, so don’t put too much into this.

30s MixStir, 2 min settling time: 5.2 ppm
another 30s MixStir, 2 min settling: 7 ppm
another 30s MixStir, 2 min settling: 7.6 ppm
additional 60s MixStir, 2 min settling: 8.0 ppm

Another batch with pure O2:

Wort temp 10C
Gravity 11.5 Plato

Unaerated: 1.6 ppm
1 min pure O2 -> 20 + ppm

In this case I maxed out the DO meter range. Based on earlier experiences with aerating starters with pure O2 I thought it would take much longer than 1 min to max out the DO meter. I’ll be oxygenating shorter next time around.

The advantage of air is that you cannot overaerate the wort. But I don’t necessarily like all that foam when using the MixStir. It makes it hard for me to see when low Kraeusen starts.

[babalu87]

That tube with the holes in it on the end of my kettle to fermenter hose aerates the hell out of the wort.

Foam out the top everytime

[Matt B]

There's no real advantage. It's faster, since you have to pump less 'air' into it, and possibly more sanitary as not a whole lot can live in a pure O2 environment, but with the right precautions (sanitary filter) with a good fish tank pump is almost just as effective. For me it was more convenient, I have an O2 tank, didn't have to buy a pump, done.

[Kaiser]

... and possibly more sanitary as not a whole lot can live in a pure O2 environment...

I’m trying to look at this as well. The idea is to take a wort sample before and after the aeration process and perform a wort stability test on it.

Kai

[bluesman]

Kai,

Based on your crude experiment you are getting almost three times as much dissolved O2 in your wort using pure O2 vs mix-stir. My question to you is did you determine any flavor contribution by increased DO in the beer. Did you do a side by side tasting? By the way...nice work as usual.

[denny]

I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?

[Kaiser]

Based on your crude experiment you are getting almost three times as much dissolved O2 in your wort using pure O2 vs mix-stir. My question to you is did you determine any flavor contribution by increased DO in the beer. Did you do a side by side tasting? By the way...nice work as usual.

I only know that I got more than 20 ppm O2 into the wort. It may have been much more since the meter quickly jumped to “overflow”. The way these meters work is by having O2 diffuse through a membrane into an electrolyte. The meter than measures the O2 content in the electrolyte. The time it takes for the O2 concentration in the electrolyte to rise or fall depends on the O2 gradient between the electrolyte and wort. Since it jumped to 20+ pretty quickly I assume that the wort may have been aerated with well over 20 ppm.

Obviously that was not my intention. The two beers are intended to evaluate the benefit of removing the Kraeusen. I wanted to aerate both to ~8 ppm DO but way overshot my target on the 2nd one. One suspicion I have with the pure O2 method is that it is difficult to set a flow rate that is constant between all the beers you brew. You may be able to set a constant pressure by making the regulator but that means nothing if your stone gets more and more clogged over time. I’ll get a better idea about that in future batches.

If you a medical O2 bottle and regulator you can set a flow rate but I don’t think that flow rate will be accurate once you force the O2 though an aeration stone since that will restrict the flow by an unknown amount.

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

Kai

[Kaiser]

I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?

8 - 10 is considered optimal for ales and 10-12 is optimal for lagers. I think these numbers are in line with the air saturation DO values at their respective pitching temperatures.

Once you go to high gravity beers you want more than that. But I don't know how much more.

Kai

[bluesman]

I seem to recall reading somewhere that 8 ppm is optimal.  Can anybody confirm or correct that?

Good Question Denny.

Here's a study on the effect of DO on wort fermentation and yeasy health. Unfortunately, one must pay to get it.

http://cat.inist.fr/?aModele=afficheN&cpsidt=1355176

[Kaiser]

Here's a study on the effect of DO on wort fermentation and yeasy health. Unfortunately, one must pay to get it.
http://cat.inist.fr/?aModele=afficheN&cpsidt=1355176

This is a really good one. It's from the MBAA and you'll have to find someone who is a MBAA member. There aren't many papers that are readily apllicable to home brewing, but this one looks like one that would be.

Kai

[beerocd]

http://www.wyeastlab.com/hb_oxygenation.cfm/1949-aerating-wort-techniques

There's a table of DO towards the bottom.

[babalu87]

On the Wyeast table:

Sierra Nevada uses just air (filtered of course) but then again do they make any lagers...............?

Top of my head I cant remember.

I recently brewed a Pils and using just the tube with holes at angles on the end of my hose, had it just hanging in the carboy neck.

5.25 gallons of wort went into this carboy and wort foam came out the carboy neck during the last 1/2 gallon or so.
I'd say thats pretty well aerated. We'll see in about 6 weeks I guess.