The definitive aeration/oxygenation experiment

[Orfy]

The figures speak for themselves.

Cheers Bobby.

 

[brehm21]

I'm jumping in on this thread late, and I'm rookie compared to most in this forum; but I wanted to throw in my $.02. Coming from a biology/natural resources background, this caught my attention and the geek lobe of my brain went into temporary overdrive.

Although this is not what the scientific community would consider "good science", I think it speaks enough to be continued.

I raise fish. Fish need oxygen to live/eat/reproduce. So does yeast. I spend a lot of my time in the summer making sure my fish have enough 02 dissolved into the water (Dissolved Oxygen, or DO), almost always measured in Parts Per Million, or ppm (same as mg/L).
So, couldn't we just brew up some wort, pitch, aerate with the different methods, then measure the DO for each method?
Does anyone know of a specific DO level that is best for the yeast, or is it simply more=better? I would assume that just like all other types of organisms (fish, crustaceans, insects), certain species, or strains of species, in the case of our yeasts, would outperform other strains at lower DO levels. If we knew the answer to that, people could choose yeast varieties based on whether they choose to aerate or not, and still achieve best possible results.

I'm thinking that the next time I brew, I'll drop my DO meter into some wort, to see if it will even measure the DO in a solution such as beer wort. I can't see why it wouldn't. Then I could possibly move on to finding out which DO level would work best.

I also would imagine that the yeast companies have already done some work like this, and the results were either irrelevant and not worth publishing to the public OR MAYBE so important that technically advanced breweries pay top dollar for the information. ????? Hmmm.

Way to get our attention BobbyM!! I think your experiment could lead to more experiments and hopefully a better understanding of what the hell is really going on inside that carboy!

 

[FlyGuy]

Hey Brehm21, if you have the equipment to measure dissolved oxygen, then you could do your own test to help out on this question. A fundamental question (precursor to asking what effect different oxygenation methods have on fermentation) would be 'How do different oxygenation methods perform at increasing the dissolved oxygen content in wort?'

You could replicate Bobby_M's basic design by making three identical batches of wort, measuring the DO in each (to ensure consistency), and then using shaking to aerate one, then direct oxygenation with an aeration stone for the third. Let sit for a half hour, then measure the DO content in each.

Of course, you could also replicate the rest of Bob's experiment by taking gravity readings, pitching yeast, and tracking fermentation. That would be interesting, too. Perhaps you could even pitch a smaller amount of yeast as per Bob's suggestion.

 

[Bobby_M]

I raise fish. Fish need oxygen to live/eat/reproduce. So does yeast. .....

Way to get our attention BobbyM!! I think your experiment could lead to more experiments and hopefully a better understanding of what the hell is really going on inside that carboy!

Thanks. Everything I've read says that they need O2 to reproduce, but they only begin to eat/convert sugars in an anaerobic environment. That would suggest that if you already have enough yeast cells to get through all the fermentables (who knows exactly how much that is), you really don't need O2. That's why I was suggesting that this experiment would have been better if I underpitched.

I tend to think that the simple answer, if you don't want to go buying an O2 system, is to simply pitch more yeast. This is basically what you're doing when you make a starter.

Testing DO is a reasonable idea but I wonder if it will be accurate in a higher gravity liquid. Maybe it's calibrated for fresh/sea water? Well, at least you'd have reasonable relative figures. Maybe just boil a bunch of water for an hour to deplete the O2, then try the different methods to aerate and then retest DO.

I was unable to test this intermediate data. I was testing the end fermentation results of different aeration methods but I don't know how much O2 saturation I actually acheived. You could break this down to a few other experiments to be more conclusive.

1a: Which methods produce the highest O2 saturation. 1b: If equal, which ones are faster.

2a. Under low pitch rates, which DO levels produce the shortest lag time? 2b: which DO levels produce the best attenuation.

3. Repeat 2a and 2b with high pitch rates.

I'd volunteer to run the test again if someone wants to loan me a refractometer (to take more frequent gravity readings without pulling huge samples) and a DO meter.

 

[brehm21]

I'll have to get my DO meter out and read up on testing liquids other than water. I know it will read DO in some really nasty water, but the sugars could possibly play havoc with the sensor.
I'll check it out. Unfortunately, I won't brew until next week at the earliest.

 

[Pumbaa]

Room air is 21% O2, Medical O2 is 100%. In your video was the O2 cylinder filled with room air or was it filled with medical O2? What rate did you have your regulator set? You can set those things anywhere from 1 lpm to over 25 lpm. Just curious. I wonder if adjusting the rate of flow out of your O2 cylinder would affect your outcome?

The welding O2 is 100% O2 as far as I know and the regulator he used cannot be set to a particular flow rate like the one on medical O2 equipment.

Oddly enuff I found out at my last Mortality and Morbidity confrence that industrial O2 is actually cleaner and more "pure" then medical O2. I guess the reasons behind it are your body can handle some contamination (it's built for it) but in industrial purposes the tolerances are stricter becuase the materials it's used for cant compensate.

I dont know how true the info presented to me was but i found it interesting.

 

[FxdGrMind]

Holy Molly.. WOW.

My brain hurts now.... The inner geek is flush with envy.

I had a question and WOW what an answer... Got to love the Search and the people on this forum!

 

[KingHippo]

Great job Bob
The vid looks great!

 

[nowise]

I know this was done back on 07, but I just found it and I wanted to say thanks for your time and effort to apply science to such a controversial issue. Great read and much appreciated!

 

[Ryush806]

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.

You mentioned this early on but I don't think anybody responded. I want to put your concerns at ease in regards to not fully depleting the oxygen in the wort.

I am an engineer at a power plant. We boil water to make steam and send that through a turbine. In that process, it is very important to remove oxygen from the water prior to putting it into the boiler to prevent corrosion in the boiler tubes. To remove the oxygen, we use a contraption called a deaerator. Basically, this uses steam to heat the water up to right before the boiling point. This process actually brings the oxygen level under 1 part per billion (essentially no oxygen left in the water). So, your wort was most likely devoid of oxygen as soon as (or before) it started boiling.

 

[wonderbread23]

My major criticism is using gloves instead of condoms. I think seeing which condom got erect first would have truly been the definitive proof of fermentation that is needed. That being said, great experiment!

 

[Bensiff]

I just caught onto this thread. I tried reading through it and as best I can tell everything is based off the idea that the value of O2 is in a fast fermentation and high attenuation. Below is an excerpt from some of my research that I am too lazy to retype so its directly quoted,

"Oxygen is critical for yeast health. The aerobic respiration yields far more energy than anaerobic fermentation, which is exactly what yeast need as they multiply. As well, oxygen is used during the lag phase to desaturate fatty acids which is critical to maintain cell membrane fluidity as the yeast multiply. This fluidity is critical since if the membrane is too rigid it can not as readily reabsorb diacetyl."

So, what you do at the onset of fermentation pays dividends at the end of the process with healthier yeast. If you re-pitch yeast it is that much more of a benefit.

 

[sailrat]

This was a great thread. Thanks to Bobby M and the others for their input, even though it was 3 years ago.

Wonderbread23: I'd get nervous about the part where he puts holes in the gloves, (think about holes in condoms)
Good info.