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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 ?

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.

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

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.

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


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