The definitive aeration/oxygenation experiment

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Bobby_M

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Ok, so you can trust my science or not, but the results of this test will determine whether I continue to pump pure O2 into my wort from now on.

First, the setup:

2 gallon batch boiled down to a final volume of 1.75g.

2.42 pounds of Pale LME (someone gave me a Mr Beer refill kit so I had to do something with it.)

Boiled bottled water and threw in 1/2oz Cascade and let it go for 30 mins.

Added LME and let that boil for 10 minutes. (in the meantime, rehydrated half a pack of Safale S-04 dry yeast in 80dF water)

With 5 minutes left in a 45 minute boil, I threw in another 1/2oz Cascade.

Cooled with an icebath to 75dF then gently poured the wort through a straining funnel into 3 one-gallon fermenters to which I added exactly 2 tablespoons of suspended yeast. The OG was 1.050 exactly. Each fermenter got the following "aeration" activity after pitching:

#1 No deliberate aeration. It foamed a little from falling through the funnel.

#2 Capped the fermenter and shook it vigorously for exactly 2 minutes.

#3 Ran O2 through an aquarium stone for exactly 2 minutes (which was the point at which the foam was about to rise out of the neck of the fermenter.)

After the above, I rubberbanded a santized latex glove on top of the fermenters to act as a visual indicator of fermentation. The test involves a timelapse camera so an airlock would not show fermentation properly.

I set up the fermenters in front of my webcam and had it take an image every 10 seconds. I have some preliminary results that I found really interesting but I'll wait to share them when I can post the video later tonight. Hope it helps some of you make decisions. Stay tuned.
 
Now, before I post results, I'd like to discuss a few things.

1. What do you expect the lag time characteristics to be for each?

2. Which should have the lowest OG after 24 hours in the fermenter?

3. Are there any aspects of my methods that may tarnish the results that I just haven't thought of? The only one I've recognized is that a 45 minute boil may not have fully depleted the disolved oxygen. I should have boiled the water for 30 minutes prior to adding anything.

Discuss.
 
I expect #3 to produce the longest lag time and #1 the lowest gravity at 24 hours. I might be wrong, but more oxygen should mean more cell growth and less oxygen an earlier switch to alcohol production.

I probably would have added the yeast & stirred a little before splitting the batch up. On the other hand, I chose a Schwarzbier recipe for a lager/ale experiment & the carafal III dominates the flavor in both.
 
I was concerned with unbalanced yeast cell addition but I stirred the hydrated yeast really well and measured the liquid additions very carefully. If any fermenter got more or less yeast, it couldn't be by too much. I'm guessing the variance could easily occur stirred into the wort as well.

I'm yet to analyze the entire time lapse, but I can say that #2 showed signs of offgassing first.
 
I recently got an o2 system ( 5 micron airstone, filter, o2 regulator and hosing) and aerated my wort this past brewday using it. I pitched my usual amount of yeast and my temps are consistant with my previous brews (ambient 62f). I got action 12 hours after pitching vs 36 hours usual when using dry yeast sprinkled onto wort.
That was enough of an endorsement for me.
 
Can't wait to see the results, I've had bad luck so far with my O2 system, both brews stopped short in the .020's. Never had this happen until now, tommorrow I'm making a murphy's clone, almost the same as the Guinness I did 2 weeks ago (which started @ 1.042 and stopped @ 1.024 used O2 and airstone) but will use my old method of rack and splash, no O2 aeration, well see.
 
boo boo said:
vs 36 hours usual when using dry yeast sprinkled onto wort.

You should ALWAYS rehydrate dry yeast in boiled/cooled tap water. Rehydrating in wort, which contains high levels of sugars, sends the yeast into osmotic shock and you only recover about 30% of the viable yeast you would if you rehydrate in water before pitching.
 
I spent some time creating the timelapse video and I'm going to share it here. Keep in mind though that I believe the real result most of you would be interested in is the gravity of each at the 48 hour mark. That time is coming up later this evening.

 
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Nice porn music. :rockin:
Good work, it seams not much between 2 & 3. The real test will come with the hydrometer. Number one is obviously gentler but that is no bad thing. It's not failed and it is going well.
If you look, there's less gunk on the foam of #1

Can't wait for the money shot.:D
 
Orfy,
I don't know what kind of porn you watch but I thought that was more of a corporate ethics training video track. I had access to more tracks that were more 70's porn slanted so maybe I should have gone with those.

Right though. I'd call #1 maybe the tortoise in the tortoise and the hare. In theory, it should ferment all the way out but probably take a long time to do so. It's far from vigorous.

If the gravity at the 24 hour mark (and even the FG at say 1 week) are exactly the same between #2 and #3, I think the conclusion is leaning towards O2 systems being somewhat unnecessary. Of course, if you're doing 10 gallon batches, shaking the crap out of the fermenter might be a problem.

I'm wondering if 45 minutes of boiling was enough to fully deplete the oxygen. Then I wonder if 2 minutes of O2 is really getting the most out of the process. I usually hit my 5g batches with 2 minutes on, 5 minute rest, another 2 minutes of O2 on. Also, maybe #2 started quickly because of how well the yeast was dispersed througout the wort from all the shaking. In other words, would a quick shake of the #3 after O2 injection make a big difference?
 
GREAT video! I watched it twice! It makes me want to do that with every batch of mine so I get to see the magic happen.

I'm looking forward to the gravity results.
 
Can you believe I'm only showing every 10th frame of what I captured? I set the webcam to take one frame every 10 seconds so that's 6 a minute, 360 an hour, 8640 per day. It was just taking too long to import and render that many frames so I grabbed every 10th instead. Even with that I'm showing you 864 frames. At one frame per second it would be a 14 minute clip. After rendering I sped it up x5 and rerendered to make it under 3 minutes. By the way, I used a shareware version of Flix for the timelapse. I don't know exactly where I found it. I did all my post in Ulead video studio 9.
 
I think the video shows exactly what is expected from a growth / fermentation perspective...

Yeast in #1 likely depleats the dissolved O2 first, but the resulting yeast growth is not sufficient to show much fermentation activity after O2 depletion. Resulting fermentation is slow.

Yeast in #2 depleats the dissolved O2 prior to yeast in #3 (less O2 in #2). Yeast growth in #2 is adequate to produce a fairly vigorous fermentation.

#3 shows the longest lag, (due to the extended respiration phase / high dissolved O2 concentration). Yeast population in #3 is much greater than in #2 as shown by the extremely vigorous fermentation.

You mentioned that the SG of #2 and #3 were identical when you measured. When did you take the measurement and what was the value? I'd be interested to see how it compares to the FG. Regardless, I think it's safe to say that pure O2 is not required for a vigorous fermentation.

As a follow-up to your experiment, I would be interested to see the time-laps on the same three bottles (same aeration procedures) pitched with a starter instead of rehydrated yeast.
 
Ok, so this first pass at it took quite a lot of effort. Anyone else inclined to try some additional versions?

I suppose I could have split a 5 gallon batch to 7 different 1gal fermenters and tried all kinds of variables.

Dry pitched into wort, half cell count pitch, double pitch, starter pitch, liquid yeast without starter. I also avoided an airstone driven by a pump because I just don't have one. You could also do longer boils, longer O2 injection (to ensure saturation) etc.
 
Awesome video and awesome experiment (I have a science background so this stuff really appeals to me!).

I have a two comments worth considering:

1. It will be very interesting to see the attenuation rates -- that may lead to slightly different information than the video. But I think the visible rates of krausening are quite interesting on their own -- I am surprised that the oxygenated fermenter didn't perform noticably better than the shaken fermenter (but see next comment).

2. Your yeast pitching rates were actually pretty high. Aeration/02 conditioning is likely most needed when pitched yeast quantities are on the low side (e.g., may be more relevant to pitching liquid yeast, particularly directly from a smack pack instead of from a starter). Lots of O2 in the wort promotes an extended aerobic phase which will then promote higher yeast propagation (i.e. increase the total quantity of yeast). There may be little apparent difference between the shaken and oxygenated fermenters because both had plenty of yeast to begin with. An interesting twist on this experiment would be to repeat it using lower quantities of liquid yeast to see if the fermentation rates show a more marked difference.

I also wanted to add that I loved the videography. Nice time-lapse rate. Nice use of the rubber gloves as a visual aid to examine CO2 production.

Thanks for sharing this with us all!
 
Thanks guys. I have some more ideas in response to flyguy's comments.

Given the assumption that yeast's exposure to O2 creates a reproductive cycle and delays fermentation, I think there's a threshold where pitching rates and O2 saturation stop working to your advantage and start becoming a detriment. Hear me out. If you pitch a starter with a huge cell count, one in which they are fully capable of reaching max attenuation, exposure to O2 will only cause a longer lag.

On the other hand, if you pitching rate is on the other end of the spectrum like a non starter liquid pitch, the lower cell count will likely cause a low attenuation. That is, each yeast cell is likely only capable of converting a fixed amount of sugar before it dies. The short lag time may give you false hope but it's only because there was no reproductive cycle.

I'm making this conclusion prior to taking additional SG readings (of course I can modify this later), but I think:

1. Very high pitch rates (starter) perform well in oxygen depleated wort.

2. Medium pitch rates (dry yeast) perform well in moderately oxyenated wort (shaken fermenter, airpump, etc). If oxygen is too depleted, attenuation may suffer. That's not to say that oxygen rich wort would be a problem, the lag would just be longer than necessary to reach the same full attenuation.

3. Low pitch rates (liquid yeasts without starter) perform well in O2 saturated wort. Cell count is first increased and as O2 is consumed, the ferments begin with an adequate cell count to reach full attenuation.

I'll call that my theory. Maybe this one experiment is not quite enough to prove all points. As mentioned above, I think a single 11g pack of dry yeast is a moderate pitch rate for a 5 gal batch so half a pack in a 2 gal batch really is on the upper end, but probably lower than a starter.

JCC, I only took an OG from this batch before I split it into the different fermenters. It was 1.050. I plan to take an intermediate reading tonight at around 45 hours after pitching.
 
Good work. I'm not trying to diminish anything here. But I do have to laugh about the prospect of...

The definitive aeration/oxygenation experiment II
The definitive aeration/oxygenation experiment III
...

or would that be definitiver, definitivest, more definitiver?
 
Yeah, so I was ambitious in the naming of the experiment. It'll only be definitive in my own level of acceptance of the results. To others it's probably has a slight edge over otherwise unsubstantiated rumors going around.
 
Excellent work. Please post the final gravities when you can. It would also be interesting to know how long each takes to finish.
 
bnutting said:
So is it better to aerate and then pitch or pitch and then aerate?

There's likely no difference at all except aerating after pitching will likely mix the yeast in just a bit more. Net effect, nothing except maybe a ferment that starts minutes sooner?
 
I always aerate (by shaking) first, then I take my gravity reading, then I pitch. That way I know it's well mixed and I'm getting as accurate a reading as possible. I'd hate to take a reading after pitching and lose some of the precious yeast. Also, I did shake it up a bit after pitching some dry yeast directly, and some got stuck on the sides of the carboy. That really bothered me a LOT. :(
 
clayof2day said:
You should ALWAYS rehydrate dry yeast in boiled/cooled tap water. Rehydrating in wort, which contains high levels of sugars, sends the yeast into osmotic shock and you only recover about 30% of the viable yeast you would if you rehydrate in water before pitching.

The only thing about that is that I personally have found when pitching dry, I get a shorter lag time and my attenuation still don't suffer. I know this flys in the face of conventual(sp) wisdom but it works for me.
 
To answer that last question, I pitched then aerated #2 and #3. Remember, I didn't do anything to disturb #1 except for the initial pour through the straining funnel.

Here are the SG readings (temp corrected) at 45 hours after pitching (remember the OG was 1.050):

#1 = 1.018 (64% attenuation)
#2 = 1.019 (62% attenuation)
#3 = 1.016 (68% attenuation)

Safale S-04 is claimed to attenuate in the low 70's so the O2 injected batch is nearly done. I think I'll wait until 72 hours to take the next reading. This does confirm that an oxygen rich wort, though adding somewhat to the lag time (an hour) will eventually explode into action. This is kinda like amassing a large army and attacking together rather than sending in stragglers to be slaughtered one at a time.

I'm a little surprised that #2 is the slowest. To be honest, there's a good chance they were less than a full point apart but I'm quite certain #1 was ahead by at least a noticeable margin. However, if I'm figuring correctly, #2 should catch up at some point and finish drier than #1 which should have the least attenuation at the end.
 
Good job, and great idea whith the gloves.

Bobby_M said:
Safale S-04 is claimed to attenuate in the low 70's so the O2 injected batch is nearly done.

Since you don't know the composition of the wort and fermentation conditions when they measured atteniuation for the yeast, you won't really know where your batches will finish.

Kai
 
Also, 1018 and 1019 are pretty darn close. If we really wanted to be accurate, each method (1,2, and 3) would have to be done in triplicate and the average gravities taken at each timepoint. This is not to take anything away from your experiment, however, I think it was great to watch and very informative. I'm just saying, with all the variables that could be present in pitch rate, volume measurement, etc. I would have to say that at this point 1018 and 1019 probably aren't statistically significant in their difference. The other thing to consider is that 2 minutes of shaking isn't very much. Air is only about 20% oxygen and depending on how the carboy was shaken it may not have maximized the surface area to volume ratio of the wort and thus affected the solubility of gasses in the wort. Remeber the O2 had a diffusion stone. #2 did take off first though, indicating that the had indeed done something.

I'm excited to see the FG numbers, great work!
 
Bobby_M said:
Right on Kaiser, I realize that estimated attenuation figures are bull until they're measured.

I didn't want to be a smart-ass, but some brewers do take these attenuation numbers way to seriously.

Kai
 
IMHO I would expect #2 to start "off gassing" as you put it first because of the amount of gas that was not disolved but instead suspended in the wort.

When I am cleaning my carboys (or even rinsing them out) I cover the opening with my hand and shake the hell out of them and get a pretty decent presure release. Depending on the size of your airstone (mine is 2 microns) I would expect those bubles to be disolved more and faster then just shaking.

Still interesting, nice work
 
I really see no difference in your numbers, although I respect you for the effort put into this experiment. I have been seeing a lot of non-scientific stuff on this board, a lot of speculation, and a lot of opinions that are unfoundd. A difference of .003 is really nothing in the large sense of things (n=1, standard deviations, etc), and as clayof2day said, you need to repeat this experiment a bunch of times...

Personally, as far as my 'brewery' goes, I am going to try to spend as little money and keep it as simple as possible, and this includes pitching and shaking. But then again, boys love their toys, I drive a jeep with well over $5000 in modifications that are totally not necessary...to each their own.

That being said, I am not even close to hitting most attenuation numbers, i think the LME from my shop sucks, but I am still going to bottle it when SG's are steady and bottles will not explode.
 
ColoradoXJ13 said:
That being said, I am not even close to hitting most attenuation numbers, i think the LME from my shop sucks, but I am still going to bottle it when SG's are steady and bottles will not explode.
What LHBS do you shop at for your LME? Have you tried DME?
 
First, I want to say that constructive criticisms are welcome, expecially in the methods so that the next brewer to take this on can be more accurate. However, I don't want anyone slamming my results unless they're willing to disprove them with their own test. It's easy to talk about variables and controls all day long than it is to put it into practice especially when my last experience with scientific method was 14 years ago in high school. That being said, here are some more comments.

clay said: I'm just saying, with all the variables that could be present in pitch rate, volume measurement, etc. I would have to say that at this point 1018 and 1019 probably aren't statistically significant in their difference. The other thing to consider is that 2 minutes of shaking isn't very much. Air is only about 20% oxygen and depending on how the carboy was shaken it may not have maximized the surface area to volume ratio of the wort and thus affected the solubility of gasses in the wort. Remeber the O2 had a diffusion stone. #2 did take off first though, indicating that the had indeed done something.

Agreed. I said above that I really can't be positive that #1 & #2 are different enough to make any claims. In fact, to take any possible bias away, it would be nice for the gravity tester to not know which sample was which. I personally can't imagine I would WANT any particular result except to confirm that using my O2 system is useful. However, I didn't pay for my O2 bottle so I really have no vested interest. Still, bad science abound.

If shaking was my usual method, there's no way I'd do it for more than 2 minutes. Besides, in a typical 5 gallon batch, you'd never be able to shake with the same vigor as I did on this one gallon bottle. There was only foam, almost no liquid wort could be seen at the bottom. I believe I got all the air from the headspace pretty well in contact with the wort in that container.

To your last comment about #2 taking off first, it says nothing about the benefit of aeration though. As we discussed earlier, taking off first suggests that the reproductive cycle simply didn't happen or didn't last very long.
 
Pumbaa said:
IMHO I would expect #2 to start "off gassing" as you put it first because of the amount of gas that was not disolved but instead suspended in the wort.
I used the term off gassing but I really meant fermenting. Any gas that was in the container prior to shaking was just redistributed (suspended). It's not the same as if I compressed the gas first. If this is your aeration method you really just hope that some of the O2 in that air dissolves into the wort. I'm not sure I'm saying it right but I don't think the inition pressure build up you see on #2 has anything to do with suspended air coming out of solution. I believe it is CO2 being created via fermentation.


Pumbaa said:
When I am cleaning my carboys (or even rinsing them out) I cover the opening with my hand and shake the hell out of them and get a pretty decent presure release.
I'm taking a guess, but I think that has a lot more to do with the temperature of the water. Try it this way, heat up the carboy with warm water. Then put cold water in and shake it up. I bet you get a vacuum on your hand.

Pumbaa said:
Depending on the size of your airstone (mine is 2 microns) I would expect those bubles to be disolved more and faster then just shaking.
Yeah, who knows. It's too bad I don't have a pump/airstone. I THINK it's about the same as shaking in how much O2 you end up with. The real benefit to airpump systems is the ability to filter the air which you can't do with the shake method. No matter how small the risk, the shake method takes possibly contaminated air from the headspace and completely distributes it throughout your wort.
 
You're also supposed to get beter results (more o2 absorption) by having the o2 bubbles barely break the surface. By having a lower pressure and smaller bubbles, they stay in contact with the liquid longer allowing more to be absorbed. Also the vigorus bubbling at the surface knocks gas out of solution lowering the total disolved gasses.
 

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