Wort Aeration for Fermentation- Test Results

[micraftbeer]

A while back I was making a NEIPA and trying out Imperial's A38 Juice (it came out great by the way, very similar to my favorite Wyeast 1318 but slightly less sweet). On their website they said the yeast did best with higher DO levels of 20-25 PPM. From reading other experiments and other literature, I knew I needed to use bottled oxygen through a stone rather than my aquarium pump through a stone. My "process" for wort aeration has (had) been to just put the stone in the wort in the fermentor, and let it sit for 12-15 minutes when using my aquarium pump, and if I used bottled oxygen with its stone, I would let it sit for 3 minutes.

On the NEIPA I brewed, I used my new Milwaukee MW600 Dissolved Oxygen meter (hands on review here), and only read 8.1 ppm of DO after the 3 minutes of bottled oxygen through the aeration stone. I reached out to Imperial Yeast, and they were good enough to get back to me as we discussed my aeration process. After talking to Jess Caudill (Imperial's technical guy), the conclusion was I needed to "stir" my aeration wand/stone in the fermentor to get better oxygen levels. Even though I'm sure Jess is way more competent and experienced in the ways of yeast wrangling than me, I had a hard time believing that would make a difference.

So as a part of my review process of the MW600 meter, I set up a little experiment where I split my wort into 3 fermentors and then oxygenated them 3 ways. First was my aquarium pump that was left mainly stationary, other than shifting its position 3 times during an 18 minute aeration session. That got 7.1 ppm. Next was bottled oxygen and wand, with just putting the wand in the bottom of the fermentor and letting it sit for 3 minutes- 9.6 ppm. The last fermentor I used the bottled oxygen again for 3 minutes, but I continually moved the wand around in various directions continually- 19.6 ppm.

In hindsight I felt dumb to question the expert, but I just assumed everything was getting all mixed up with the stone on the bottom and bubbles rising to the top. Anyway, I thought I'd pass along this technique in case there were other out there unaware like I was.

 

[MaxStout]

Caudill's suggestion makes sense and it seems intuitive. If the stone is simply kept in one location in the wort, you get a plume of O2 rising and dissolving in that area, but not as much going into solution farther away.

My method has always been to slowly move the O2 wand around the fermenter, with the idea of getting O2 into as much of the wort volume as possible. Your measurements bear that out. Thanks for sharing this experiment.

 

[day_trippr]

I use a Williams Brewing .5 micron aeration wand hooked to my O2 system at .5 lpm for four minutes, swirling the whole time. Just seemed intuitively the right thing to do, but this confirms it. Thanks for that

Cheers!

 

[hotbeer]

Since it's a NEIPA I'm assuming hopped heavily at the end of the boil (as well as later in the fermenter). So is it even desirable to do a lot of aeration? Or is the time spent aerating not doing much oxidizing of the hop aroma/flavors? If it does, then wouldn't dry yeast that needs no aeration preferable?

And since you are in to experimenting, how bout one that sees how quick the DO drops after pitch and/or at peak krausen.

 

[day_trippr]

Peak krausen? Lol!
The yeast will consume all of the free oxygen within a hour or two, and won't leave appreciable O2 to dull your dry hopping later.
It's really stunning how fast a proper pitch will gobble the O2 all up.

Cheers!

 

[hotbeer]

Yeah, but I was really thinking about the time it takes to aerate, not just how soon it disappears after pitch, though I was curious about it, hence the question.

As for aerating in general, I'm sure there are some that think if 10 minute is good, then 20 is better and 30 to 60 minutes fabulous.

How quick does oxidation happen? Is it over a long exposure, or short exposure to large enough concentration of DO?

 

[day_trippr]

I had one of those Milwaukee O2 meters for a month and found I could hit 12 ppm O2 in 4 minutes at .5 lpm while moderately stirring.
I would think it takes time to fully inflict damage - way more time than the yeast would allow
Higher content likely means faster damage but ultimately more, regardless of rate...

Cheers!

 

[jtgoral]

And how did the beers taste? Were they better or worse because of the aeration method?

 

[day_trippr]

They reached their attenuation goals with no evidence of oxidative damage.
Over the last few years I've had kegs of neipas last for months so I don't think there is a down-side here wrt oxygen exposure at the right time

Cheers!

 

[micraftbeer]

And how did the beers taste? Were they better or worse because of the aeration method?

I'll take the bait... This experiment wasn't about taste, as I don't expect there to be a direct correlation. Wort aeration is about making the ideal environment for your yeast to work in. There are obviously a lot of other factors that go into ideal yeast fermentation. Yeast strain, age of your yeast, wort composition, temperature. I could probably go dig up a reference from John Palmer's How to Brew book to describe why oxygen is important to fermentation health- but I won't.

Whether or not aeration affects your finished beer flavor will depend on all of these things.

I doubled up this experiment with an experiment looking at beer transfer methods on the way out of the fermentor, so the data would be convoluted anyway.

The point here wasn't to convince you to aerate or not aerate, but if you do aerate, stirring vs. non-stirring of your aeration stone makes a significant difference in the amount of DO you get in your beer.

 

[TLaffey]

I use a Williams Brewing .5 micron aeration wand hooked to my O2 system at .5 lpm for four minutes, swirling the whole time. Just seemed intuitively the right thing to do, but this confirms it. Thanks for that

Cheers!

Is this in 5-6 gallons? I'm doing almost exactly this now (with 6G in fermenter) but I don't have a way to measure the DO, so interested in the data point.

 

[McMullan]

I'll take the bait... This experiment wasn't about taste, as I don't expect there to be a direct correlation. Wort aeration is about making the ideal environment for your yeast to work in. There are obviously a lot of other factors that go into ideal yeast fermentation. Yeast strain, age of your yeast, wort composition, temperature. I could probably go dig up a reference from John Palmer's How to Brew book to describe why oxygen is important to fermentation health- but I won't.

Whether or not aeration affects your finished beer flavor will depend on all of these things.

I doubled up this experiment with an experiment looking at beer transfer methods on the way out of the fermentor, so the data would be convoluted anyway.

The point here wasn't to convince you to aerate or not aerate, but if you do aerate, stirring vs. non-stirring of your aeration stone makes a significant difference in the amount of DO you get in your beer.

Your sampling strategy (for beer) might have biased the DO detected in the beer, in terms of O2 pickup during pouring from keg to glass. Key to most experiments is a well designed sampling strategy.

 

[micraftbeer]

For this one, I sanitized a small sampling glass and dipped it into the fermentor after I oxygenated to scoop out my sample.

 

[day_trippr]

Is this in 5-6 gallons? I'm doing almost exactly this now (with 6G in fermenter) but I don't have a way to measure the DO, so interested in the data point.

Typically, 5.5 gallons in the fermentor to start...

Cheers!

 

[McMullan]

For this one, I sanitized a small sampling glass and dipped it into the fermentor after I oxygenated to scoop out my sample.

I was referring to the correlation observed between wort aeration and DO detected in the beer. I think measuring low DO levels in wort and beer might be too much of a challenge for this instrument, which is probably designed more for measuring DO in water samples. Although your results for wort DO here seem to agree with expectations. I’d like to know how an in-line O2 stone compares with a stirred wand.