Aeration (Basic Brewing Radio)

[menschmaschine]

I just listened to the August 7th Podcast:
http://www.basicbrewing.com/index.php?page=radio

... and looked at the results here:
http://media.libsyn.com/media/basicbrewing/AerationMethods.pdf

Very interesting results. Aside from a few possible outlying variables not discussed and not experimenting with pure O2, it looks like simply shaking the fermenter is not so bad after all.

In summary, he got 92% O2 saturation in water (not wort) after 5 minutes of shaking. Results with an aquarium pump weren't near as good.

Anybody want to chime in on the validity (or lack thereof) of the results of this experiment?

(Revvy, heard your email to the show. Good plug for HBT!)

 

[JVD_X]

I've never had a problem with shaking the fermenter and I haven't seen a noticable difference when I use pure O2... with one exception... for my glass carboys I don't want to shake them!

 

[menschmaschine]

I've never had a problem with shaking the fermenter and I haven't seen a noticable difference when I use pure O2... with one exception... for my glass carboys I don't want to shake them!

Yeah, I use Better Bottles and shake with the ol' tennis ball underneath. I've been seriously contemplating getting an O2 system, but after reading this, now I'm not so sure.

 

[FlyGuy]

Wyeast has done these tests in the lab, and the results from BBR seem to agree. See here for the Wyeast aeration guidelines:
http://wyeastlab.com/hb_oxygenation.cfm

On a side-note, while shaking your carboy is a decent method compared to splashing or an aeration pump, you need to inject pure O2 using a oxygenation system to get more than 8 ppm O2 (atmospheric concentration of O2). For higher gravity brews, 10 - 20 ppm O2 may be necessary for ideal fermentation conditions. For low to moderate gravity brews, the carboy shaking method does work well, though -- particularly if you use a good pitch of healthy yeast.

 

[Revvy]

I was dissapointed that he didn't measure post boil/pre aeration oxygen levels in the wort, nor did he conduct the same experiment with airstone and O2 bottle... He wrote about it but kinda glossed over it on the podcast...I think more of us use bottled O2 than airpumps, or at least it seems like it on here.

Thanks

I was actaully more impressed with sme of the stuff the Chris White of Whitelabs is comong out with...he has been pitching the notion or adding another 2 minutes of O2 between 10-12 hours after pitching yeast for worts with an og over 1.060...

 

[flyangler18]

Perhaps I being my normal 'science numpty' self, but wouldn't there be measurable differences with the oxygen-holding capacities of wort vs. pre-boiled water? Surely the fermentables and isomerized AA would have an effect.

 

[menschmaschine]

His units of measure were % saturation as opposed to ppm of dissolved oxygen. How does, say, 95% saturation compare with ppm? If we put these two studies together (Wyeast and BBN), it seems that flushing the headspace with oxygen and shaking (repeating several times) would get the most dissolved oxygen.(?) That might be good to not have to mess with an aeration stone.

 

[Special Hops]

I just make sure I get a nice vigorous pour from the kettle to the fermenter.

Seems to do just fine like that. No shaking or injecting.

 

[ColoradoXJ13]

I like how there is a typo in the abstract of that pdf.

 

[menschmaschine]

Perhaps I being my normal 'science numpty' self, but wouldn't there be measurable differences with the oxygen-holding capacities of wort vs. pre-boiled water? Surely the fermentables and isomerized AA would have an effect.

No, no... I'm the same way. I thought about that too. I would think water would be a better solvent than wort, but is it a significant difference? And if we compare method to method qualitatively rather than the numbers themselves, it's still pretty interesting. But I guess it's nothing Wyeast didn't already tell us.

 

[Bobby_M]

"Results: Boiled and cooled water contained a significant amount of
dissolved oxygen after it was delivered to the fermentor even before active aeration was initiated."

But...

"Preparation of Oxygen-poor Water
In all experiments, the method of aeration was
tested using tap water. Approximately six gallons
of tap water was boiled for several minutes,"

WTF is "several minutes"? 5, 10, 90? Nice science. How do you test for the efficiency of various methods when you don't ensure the water is just as devoid of O2 as wort that was boiled for 60-90 minutes?


90% saturation in 70F wort is about 8ppm. Someone asked about that.

Oxygen is also less easily dissolved in higher gravity liquids so testing with water is poor science.
They admit to it in the summary:
"The purpose of these experiments was to evaluate
the effectiveness of different methods of aerating
wort for beer production. However, these
experiments were conducted using water rather
than wort, solely because of the significantly
greater expense of using wort. The solubility of
oxygen in a 12 °Plato wort is about 15-25% less
than in water, depending upon the temperature.i It
is unlikely that this difference in oxygen solubility
would significantly affect the conclusions about
the aeration methods themselves."

You can't make up a little 1.050 wort for the experiment because it's too expensive? I don't know where the figures came from on the percentage of oxygen solubility difference but if it's accurate, it really matters.

Using water, he started at 4ppm already by not boiling off enough O2 in the first place. Using the shake method, they got up to 8ppm in 5 minutes of shaking. If wort starts at 0ppm and is up to 25% more resistent to dissolving O2, 5 minutes of shaking would get you to 3ppm.

The million dollar question is, if they're going to discount the use of oxygen, why not use oxygen in one or two samples as a comparison? Go ahead and show me how close shaking gets you to the oxygenated sample and I'll bite. Then again, if a little DME for making wort is too expensive, I don't expect anyone to run out and buy an oxygen bottle either.

 

[menschmaschine]

WTF is "several minutes"? 5, 10, 90? Nice science. How do you test for the efficiency of various methods when you don't ensure the water is just as devoid of O2 as wort that was boiled for 60-90 minutes?

IIRC, in the interview he mentioned around 10 minutes. He might have made the assumption, based on previous experience/knowledge that water boils off oxygen rather quickly.

I'm not trying to defend the guy, but I think the podcast is worth a listen if you haven't listened yet. He isn't new to science/laboratory... I believe he currently works in a laboratory in the pharmaceutical industry. But one thing I think he failed to do was enough controls in the experiment... and also, to explain in the text, any scientific assumptions he might have made and taken for granted that others know. For instance, if a given volume of "water" is known to boil off all dissolved O2 in a matter of, say, 2 minutes, he could have mentioned that fact and explained why he only boiled for "several minutes". He just didn't cover all his bases.

But I don't think that makes his results completely invalid. It's really just nothing new.

 

[Kaiser]

How does, say, 95% saturation compare with ppm? .

I e-mailed him after the paper was posted on HBD and told me saturation was about 8 ppm DO. I also asked him if he could run more real world measurements with actual wort. Shouldn't be a cost issue when brewing anyway.

I guess shaking provides a far greater surface area.

If you are interested in the math:

O2 has a density of 1.44g/l at atmospheric pressure. To get 8 ppm in 20l (~5 gal wort) you need 160mg O2. This is 110 ml pure O2 or 500 ml (little more than a pint) of air. Based on these numbers (please check if I may have gotten some of them wrong) there is plenty of O2 in the head space.

But I still use O2 and a stone on a wand. Mostly because I'm lazy and don't want to shake the carboy.

Kai

 

[menschmaschine]

I e-mailed him after the paper was posted on HBD and told me saturation was about 8 ppm DO.

Thanks, Kai. If, 8ppm is 100% saturation, where are all these numbers like 10 to 20+ ppm coming from (Wyeast experiment)?

If this is all true, as long as one has a liter or two of head space, a good 5-10 minute shake is as good as pure O2?

 

[FlyGuy]

Thanks, Kai. If, 8ppm is 100% saturation, where are all these numbers like 10 to 20+ ppm coming from (Wyeast experiment)?

If this is all true, as long as one has a liter or two of head space, a good 5-10 minute shake is as good as pure O2?

Atmospheric O2 is 8 ppm. If shaking, you can't dissolve more than that, so 100% saturation = 8 ppm.

If you want to get more than that in your beer, you can inject PURE O2 and get levels up to 26 ppm. So no, shaking will never be as good as oxygenation.

 

[JVD_X]

Yea - the PPM may be higher but how long before it comes out of solution? And can the yeast really make use of the excess oxygen before it comes out of solution?

I've used both methods (shaking and O2) and they both work fine. However, as was pointed out... big beers might benefit more.

 

[Piotr]

The conclusion of the experiment might be that aquarium pump is almost useless. Strangely enough, Wyeast experiment doesn't confirm that.

For me, most interesting was the sentence:
"Even when splashing was minimized by allowing the water to flow into the bottom of the plastic fermenter bucket oxygen content was significant (43% of saturation)"
Does that mean, that even with carefull racking (i.e. to secondary) we get some 3ppm oxygenation of wort?

 

[menschmaschine]

Atmospheric O2 is 8 ppm. If shaking, you can't dissolve more than that, so 100% saturation = 8 ppm.

This doesn't add up to me. Atmospheric O2 is roughly 21% or 210,000 ppm. In my experience, I would expect saturation in this case to refer to how much the solvent is capable of dissolving, rather than how much is available.

 

[FlyGuy]

This doesn't add up to me. Atmospheric O2 is roughly 21% or 210,000 ppm. In my experience, I would expect saturation in this case to refer to how much the solvent is capable of dissolving, rather than how much is available.

Yeah, it doesn't quite work like that. You need to consider the solubility of oxygen in a liquid (i.e. water or wort).

But you are correct to point out that my statement was misleading. I should have stated that the maximum amount of atmospheric O2 you can get dissolved is 8 ppm (assuming room temperature), not that concentration of O2 in the atmosphere is 8 ppm.

 

[menschmaschine]

Yeah, it doesn't quite work like that. You need to consider the solubility of oxygen in a liquid (i.e. water or wort).

But you are correct to point out that my statement was misleading. I should have stated that the maximum amount of atmospheric O2 you can get dissolved is 8 ppm (assuming room temperature), not that concentration of O2 in the atmosphere is 8 ppm.

OK, I think we're on the same page now. But I still don't understand why water can only take on 8ppm DO from the atmosphere, but can take on more from more from pure O2.

I did a water quality study in college for acid mine drainage were one of the parameters measured was DO, but 10 years have made remembering all those details quite difficult!

 

[Kaiser]

OK, I think we're on the same page now. But I still don't understand why water can only take on 8ppm DO from the atmosphere, but can take on more from more from pure O2.

That has to do with the concept of partial pressure. For each liquid, there is a relationship between the amount of gas dissolved (at equilibrium), the liquid's temp and the gases pressure outside the liquid. We know that for beer and CO2 and it's called a carbonation table.

At the molecular level this works by gas constantly leaving and entering the liquid. If the amount that leaves is equal to the amount that enters we have an equilibrium and the total amount in the liquid will not change.

But the pressure that is used for this calulation is not the pressure of the gas mix (i.e. air) but the partial pressure of the oxygen. In case of atmospheric air pressure (1 bar) the partial pressure of O2 is only 0.21 bar because only 21% of the 1 bar pressure comes from O2. So you need to use a partial pressure of 0.21 bar when determining the saruration level of O2 in water. If you use pure O2 at 1 bar, you will get a O2 partial pressure of 1 bar and your saturation level will now be much higher. As soon as there is not a 100% O2 atmosphere around the water/wort anymore the O2 will come out of solution b/c more O2 leaves the water than enters it. But that is a slow process. Just think how long it takes for a beer to go flat.

For the carbonation tables, we can work with the actual pressure of the CO2, but only because it is 100% CO2.

Kai

 

[menschmaschine]

As soon as there is not a 100% O2 atmosphere around the water/wort anymore the O2 will come out of solution b/c more O2 leaves the water than enters it. But that is a slow process. Just think how long it takes for a beer to go flat.

Thanks a lot, Kai. That's very helpful. Wyeast states: "Over-oxygenation is generally not a concern as the yeast will use all available oxygen within 3 to 9 hours of pitching and oxygen will come out of solution during that time as well."

The reason I'm interested in all of this is because my FGs generally end up being anywhere from 1 to 3 points of SG high. And since I've ruled out most other issues, I'm trying to either fix or rule out this one as well. Most of my beers are at or under 12 Plato and I'm pretty sure I'm getting as much DO as one can get from shaking. So, if the rule of thumb is that yeast need at least 10ppm DO, how much affect on attenuation would 8ppm have?

 

[Kaiser]

The reason I'm interested in all of this is because my FGs generally end up being anywhere from 1 to 3 points of SG high.

Do a fast ferment test. This will tell you how far the yeast would be able to go. And tells you for sure if fermentation or mashing is the problem. For German beers I know that in darker and stronger beers the beer attenuation will be a little lower than the FFT attenuation. But for low gravity lighter beers the beer attenuation pretty much matches the FFT attenuation.

I generally have to warm up my lagers towards the end to push the yeast towards the FG expected from the FFT. But I'm trying to eliminate this.

Kai

 

[menschmaschine]

Do a fast ferment test. This will tell you how far the yeast would be able to go. And tells you for sure if fermentation or mashing is the problem. For German beers I know that in darker and stronger beers the beer attenuation will be a little lower than the FFT attenuation. But for low gravity lighter beers the beer attenuation pretty much matches the FFT attenuation.

I generally have to warm up my lagers towards the end to push the yeast towards the FG expected from the FFT. But I'm trying to eliminate this.

Kai

Huh, that fast ferment test is a great idea. I'll try that on my next batch. I know what you mean about lagers and attenuation. My decocted lagers are always worse at attenuating than my lighter ales, even after lagering is complete.

 

[Seawolfe]

Theres also the idea that cool water/wort can hold more O2 that warm water/wort.

I have a big old "availability of ppm oxygen in distilled water (saturated with air) at various temperatures and elevations" chart stuck on my wall here at work (yeah yeah, posting at work).

Note the differences at different temperatures. Even if the saturation is different for wort vs water, cooled wort will hold more 02 that warm wort.

Heres part of it for sea level:
Temp (deg F)______ppm 02
59_______________10.2
64_______________9.5
69_______________9.0
73_______________8.7
77_______________8.4
81_______________8.1
84_______________7.8