Venturi Aeration Experiment

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As a homebrew beer crafter, one of the biggest challenges that we have to overcome in proper aeration. Here is one tale sent in from a forum member that addresses his own journey down this wort road.-Ed
Hello everyone,
Please let me allow you to introduce myself and create a little background for this article. I have been brewing for nearly 1 year at the time of this article and have brewed a total of 12 five gallon batches of different types of beer. I have also made mead and wine. I am a strong believer in"If you can buy it you can build it" and randomly came across the following article by aarong:
Wort Aeration & How To Build A Free Pump
In his article he describes the use of the venturi effect to aerate wort without the use of aeration stones or other techniques commonly employed in home brewing.
In this article I would like to present my findings and experiences of this technique.
aarong's principle uses two worm clamps and a single circular hole in between these two clamps. Using a common auto-siphon found in most every homebrew kitchens, he succeeds in adding oxygen/different colored fluid to plain water.
For my own experiment I created a batch of Bavarian "Dampfbier", which I had brewed previously to test the effect of oxygenation and compare the findings to my previous method of stirring/shaking the carboy. The recipe is as follows:
  • 8 lbs German pilsen
  • 4 lbs munich malt
  • 1 oz 4.0% AA Tettnang (60 min)
  • 0.25 oz 4.0% AA Tettnang (15 min)
  • 0.25 oz 4.0% AA Tettnang (5 min)
  • 0.25 oz 10.0% AA Zythos (5 min)
Mashed 30 mins at 145F
Steped up to 154F using boiling water for 30 mins
Batch sparged and boiled for 60 mins. The wort was cooled in the snow from boiling to 90F in 15 mins outside (I do not have a wort chiller yet)
Wyeast 3068 Wheinstephan was activated at the beginning of the mash and pitched without stirring into the wort that was aerated with the technique described by aarong. In my previous batch the yeast was pitched, and the wort aerated using a mashpadded inside the carboy.
In order to recreate the technique described by aarong, I attached the two worm clamps towards the bottom end of a 1/4" ID, 6ft long plastic hose (food grade plastic hose obtained from my local homebrew store and identical to the one used in aarong's article). I tightened the clamps as far as it was possible without having an accurate measurement of how wide the gap had to be. I proceeded to cut a small 2 mm big hole into the middle of the two clamps with a pocket knife. I was unsure as to how big the hole needed to be and was afraid that a too big hole would spill wort instead of suck oxygen in.
I sanitized the hose inside and out with starsan and made sure to spray the clamps just in case the wort would run out of the hose. I sanitized my autosiphon and attached the hose to it.
The following pictures show the process of using the technique.

The wort was racked out of the aluminum 9 gal pot using the autosiphon. The wort was clear without trub.

The technique worked as described by aarong. The little hole sucked up air (it had a bubbling noise to it) and mixed it with the wort to create a cloudy looking wort going into the fermentor (6 gallon plastic bucket).

Close up of the clamp assembly. The wort definitely was getting oxygenated.

Halfway through racking the wort. A healthy layer of foam similar to "splashing" around the beer formed.
The yeast was pitched into the wort without stirring up. A single smackpack (activated) was pitched into 90F (yeah, a little warm but it was getting late) wort. The same beer was brewed with the same conditions (pitched yeast at 90F also) but stirred that one.
The lag phase was a lot shorter. first fermentation activity started after 3 hours. The beer had a healthy 1 1/2 in krausen layer after 8 hours. In the previous batch that was stirred, the lag phase took about 4-5 hours with a smaller krausen after 8 hours.
Discussion and conclusion:
This technique is very useful for aerating wort at a budget and reduces the need for sanitization and contact of wort with additional equipment like an aeration pump. Similarly the process reduces the physical effort and increases the quality of oxygenation for people on a budget. The only shortcomings come from time spent. It took twice as long to rack 5 gallons into the fermenter.
This is a great technique and further testing should be done. 2 clamps from the hardware store are only about 50 cent and the wort is being exposed to less contamination sources. Further testing would be needed to determine the actual amount of O2 added to the wort by brewing more badges.
Hope this will is informative for people.
woot :) my article was posted. I hope everyone can enjoy and benefit from it ... and I hope no one is offended by all the numerous typos in the document haha.
Someone correct me if I'm wrong, but I thought the addition of oxygen actually increases the "lag phase." In the presence of oxygen, yeast cells are focused on reproduction, and while they are multiplying, they are not expelling ethanol and CO2, at least not at the same rate as during anaerobic respiration. Which means, with proper aeration, while the yeast are multiplying, there won't be any significant krausen.
In my experience, adding oxygen after krausen has formed has caused the krausen to fall, which means the yeast are switching from anaerobic respiration (producing enthanol and CO2, which causes krausen to form) to aerobic respiration (reproduction.)
If that's the case, and you had two separate batches, one aerated, one not, all else equal, the one aerated should have a longer "lag time" or take longer to form krausen because the yeast are focused on reproduction rather than expelling ethanol and CO2.
Or am I wrong? Have you all experienced shorter lag times with the addition of oxygen (all else equal, of course)?
Reproduction is extremely important if you are pitching a single smack pack w/o a starter into 5 gallons of wort. Maybe the lag period will be longer if you aerate but w/o aeration overall fermentation time will be longer- may not even finish if the yeast pop is too low. Not to mention off flavor city.
Really with a good sized starter lag is a non issue I pitch the night of or morning after brewday and I typically have a nice krausen within 8-12 hrs.
OP- nice writeup. I would say pitching at 90F is more than a 'little' high. If the wort cools to ambient quickly enough the yeast in suspension might flocc early. If it's still hot just seal up you fermenter- go to bed if it's late- and pitch in the morning when your wort is at fermentation temp. If your sanitation is good it won't become contaminated overnight.
interesting write up! I'm excited to hear what others have to say about it. If people think it's a brilliant idea, I may be on my way to the hardware store today :)
@prohl84: Right, I didn't mean to imply that the lag phase was a bad thing, or that we should want to see krausen as quickly as possible. I'm only questioning the OP's conclusion that the shorter lag phase was and indication of higher oxygen content. From my understanding, and again, I could be wrong, I would expect to see a longer lag phase with more oxygen.
I agree, 90F is a bit high for sure but since the first time I made it it was 90F as well I figured that I should reduce the variables. Just as an additional note, there were no noticeable off flavors in this batch and it won 2nd place in the specialty beer category (23A) out of 28 entries in the Calgary, AB, Canada YeastWranglers Cowtown Roundup. A local big competition that had 500+ entries.
Since I have no scientific way of measuring oxygen amount in the beer or cell counts in the beer, I was judging my success based on lag phase. Theoretically, if ambient air temp and pitching temperature are the same, you would assume that first kraeusen marks the end of the reproduction phase of the yeast. My thinking is that if the lag phase is over the reproduction cycle is mostly done and fermentation starts. If the lag phase is shorter, the yeast reached that point faster due to higher amounts of oxygen available. Please correct me if I am wrong thou. Either way for this experiment, that was the only gauge of success but I will definitely do some reading up on this and may adjust the experiment in the future.
Here is a video I took 2 years back. Basically before I got pure O2 I was just putting a hop sock on the auto syphon to create some air in the flow.
Wouldn't contamination from airborne particulate be more of an issue with this method? All in all though, it's definitely an awesome option.
@zeptrey I was wondering about that also but then if you think about the general stir and shake method, you would be adding the same oxygen as you would with this technique. I would assume it is just as high a risk as racking your beer into your carboy unless you sanitize and flood your carboy with CO2 and keep it sealed until you rack into it.
@LeapingLamb I was thinking the same thing, but it does seem you would have more wort in contact with more air with this method too. Hard to really say but I think from all the articles I have read on this that the contamination risks really aren't mentioned much. I am assuming it doesn't happen any more often than the average freak occurrence.
@HappiBrew you are probably right, I always mix them up. I use 1/4 OD for my mash tun and it must be 3/8 for the siphon. It should still work just fine either way.
I wonder... what if you were to expand the aeration space using a T-join. Off the T, slap on a secondary hose that is hooked up to an oxygen tank so you are introducing a slow flow of O2 with the aeration (instead of just room-air). This would remove the need for an oxygenation after cooling and aeration as well as it would kill two birds with one stone.
Heck, slap a counterflow chiller upstream so you are cooling down to pitching temp. Cooling and aerating (with O2) at the same time... sounds like that could shave off a little bit of time to the brew day...
For those concerned about contamination, use a Tee and attach a short piece of tubing to the end used for sucking in the air. Then place an inline filter (0.45 or 0.2 M) at the end of the tubing. Just make sure you don't let the wort creep up into the filter and block it... happens to me frequently and those buggers are expensive to replace!
I also like the idea of attaching an O2 source to the air intake and oxygenate the wort in situ during the flow into the fermenter. Pressure regulation might be the only issue.
Just a question about hops and the aerator. Did you remove the hops before Putin it through the aerator or did you just whirlpool it?
Ps side note (i work in a Wine boutique) would putting one of these wine aerator somewhere in the piping or on the end also work....
@ChristiaanS I cooled the wort in my bathtub ice bath and stirred it occasionally. most of the hop debris was left in the pot. There was only minor hop matter in the fermenter after I was done. It ran off pretty clear. I have done this technique several times since with similar results, the hop pellets I use just settle to the bottom of the pot.
As for the wine aerator, it looks like it is using the same principle. Perhaps give it a try and compare. I would think it would be a bit more work to attach the aerator to the hose and run the wort through it. I'd be curios to see if you can get it to work.
The Zymurgist: A BYO article discusses aeration and lag time: http://byo.com/stories/article/indices/7-aeration/1949-aerating-wort-techniques
This article states "Overlooking proper wort aeration can lead to problems such as long lag times before the start of fermentation, stuck or incomplete fermentation, or excessive ester (fruit flavor) production, any of which would produce less than desired results." Maybe this answers your question?
I think I just did this by chance. My hose clamp was no as tight as i usually have it. I noticed tons on air in the hose mixing with the coole wort. There was more bubbles than usual. I am pretty certain it was sucking o2 this way.
Good write up! It seems like a common trend to be concerned with contamination during aeration. The amount of possible airborn bacteria/ dust etc getting in the wort through the tube is very low compared to the amount of dust that will fall into the wort from having an open bucket sit out. Just my 2 Cents.
To be fair even Palmer manages to be (apparently) contradictory on this topic within two sentences:
"Thus, an oxygen-rich wort shortens the adaptation phase, and allows the yeast to quickly reproduce to levels that will ensure a good fermentation. When the oxygen is used up, the yeast switch metabolic pathways and begin what we consider to be fermentation - the anaerobic metabolism of sugar to alcohol. This pathway is less energy efficient, so the yeast cannot reproduce as proficiently as during the adaptation phase."
"Oxygen shortens the adaptation phase," but the adaptation phase ends when "oxygen is used up". So obviously there is a nonlinear relationship here, and there are one or more factors that determine the length of adaptation other than just oxygen content. And most likely the end of adaptation is not precisely when oxygen is used up, but when some other threshold is met (glycol depletion?), and it is met more quickly with the assistance of oxygen, with more cell reproduction to show for it.
I don't think the method described above is as sanitary or effective as pouring between buckets. The most serious risk of contamination is never, ever, ever airborne. It is direct contact with a surface. You are engaging in more physical contact with more surfaces here. That said, if they're properly sanitized, everything will probably be OK, but you're going through a lot more trouble than simply sanitizing a second pour bucket.
The exception to the "never airborne" thing is that dust particles, and especially grain dust, are definitely a source of infection, and if you want to call them airborne, you can. Pouring in a clean location will eliminate most of that risk. Mainly, don't do it near your mill or anything that just came from your mill, and preferably not your kitchen. Your bathroom's probably better than your kitchen, for likely beer contaminants. If you get infections, especially lacto, consider changing your clothes if you mill and boil in the same day.
While its not cheaper than two 50 cent clamps, as a friend of the creator of the Wort Wizard I feel like his product should at least get some credit here. Its something he brought to market years ago utilizing the venturi effect. His racks very quickly though so not sure why some mentioned this taking longer than usual for them as its the same concept.
I saw something similar to this on youtube. instead of slits he just drilled very small holes in the tube up by the siphon. about 6 1/32" hole and it pulls in air as the wort goes by.