Author: Ray Found
Since I first developed an interest in homebrewing, one main piece of advice has remained consistent– yeast should be pitched into well aerated wort. From instructions provided on commercial yeast packaging and recommendations by prolific homebrewers to the amateurish videos readily available all over the web, there seems to be universal agreement that aeration via splashing, shaking, or using a sintered stone connected to an O2 tank is key to achieving a healthy fermentation.
I’m a shaker, have been since the beginning, though I’m aware of several accomplished homebrewers who swear by other methods. For example, Marshall uses a plastic wort spray aerator attached to the end of his kettle-to-carboy hose, while Matt of To Brew A Beer and Olan of Homebrew Dad both prefer pure O2.
The yeast labs, for their part, seem to be fairly uniform in the recommendation to add 8-10 ppm of oxygen to wort, with Wyeast demonstrating that shaking alone can achieve the lower end of this range. I guess the question then is: does it really matter?
| PURPOSE |
To evaluate the differences between a beer aerated by shaking and one made from the same wort with no effort put into aeration.
| METHOD |
With a family full of hop heads, IPA on tap at the house has come to be expected, and I’ll admit, I’ve really come to enjoy a fruity example of the style myself. For this xBmt, I decided to make the 4th iteration of my MACC (Mosaic, Amarillo, Citra, Centennial) IPA, a medium OG beer featuring massive doses of delectable aroma varieties in the whirlpool. The essence of the grain bill for this recipe was stolen shamelessly from Marshall’s A Lil’ Slack IPA.
MACC IPA
| Batch Size | Boil Time | IBU | SRM | OG | FG | ABV |
| 11 gal | 60 min | 95 | 7.0 | 1.068 SG | 1.016 SG | 6.9 % |
Fermentables
| Name | Amount | % |
| Domestic 2-Row | 23 lbs 5 oz | 81.4 |
| Munich (10L) | 3 lbs 14 oz | 13.6 |
| Gambrinus Honey Malt | 1 lbs 7 oz | 5.0 |
Hops
| Name | Amt/IBU | Time | Use | Form | Alpha % |
| Magnum | 35 IBU | First Wort Addition | FWH | Pellet | 12.6 |
| Mosaic | 100 g/19 IBU | Flameout w/ 20 min stand | Boil | Pellet | 11.7 |
| Centennial | 80 g/13 IBU | Flameout w/ 20 min stand | Boil | Pellet | 10.2 |
| Citra | 80g/17 IBU | Flameout w/ 20 min stand | Boil | Pellet | 13.9 |
| Amarillo | 71g/10 IBU | Flameout w/ 20 min stand | Boil | Pellet | 8.8 |
| Mosaic | 120 g | Dryhop 5 Days | Dry | Pellet | 11.7 |
| Centennial | 60 g | Dryhop 5 Days | Dry | Pellet | 10.2 |
| Citra | 100g | Dryhop 5 Days | Dry | Pellet | 13.9 |
Yeast
| Name | Lab | Attenuation | Ferm Temp |
| Dry English Ale Yeast | White Labs 007 | 75% | 66°F |
I followed my normal process and built up an appropriately sized starter a couple days ahead of time, overbuilding it slightly to harvest some for future use.
When brew day arrived, I got my strike water warming and, as I often do, left to tend to another task. I returned to discover it was 20°F warmer than expected. I generally preheat my MLT by adding strike water that’s 7°F to 10°F warmer than my target strike temp, but this was too high, so I reached for a makeshift tool most homebrewing fathers will recognize– frozen Capri Sun pouches! Sadly, I only had a couple handy, so the job was left incomplete. My impatience got the better of me and I mashed in a little early. After some extensive stirring and a handful of ice, the mash temp finally stabilized just under 155°F… my target was 150°F. Not my finest hour.
After a 60 minute mash, the sweet wort met a mound of Magnum sitting in the kettle and I kicked my burner into high gear, achieving a rolling boil in no time. As always, FermCap-S pulled its weight and kept the boil under control. The boil was complete in 1 hour, at which point the flameout hop addition was added and allowed to steep for 20 minutes.
I cranked the water to my Hydra IC to full-blast after a 20 minute steep and 10 short minutes later the wort was sitting at 74°F, about 6°F above the temperature of my groundwater.
After factoring in a .002 correction on my poorly calibrated hydrometer, the OG was revealed to be 1.068.
I usually use a shorter hose to rack the wort, allowing it to fall from the top of the carboy neck for splash aeration as it fills. I did things a little differently on this brew day. Both carboys were very gently filled from the bottom up using a long transfer hose with the “out” end placed on the bottom, similar to the way growlers are often filled in pubs. I believe I achieved my goal of introducing as little O2 as possible, in fact I see no other way a homebrewer could get less aeration using typical practices. The transfer hose was alternated back and forth between the two carboys, something I do for these split-batch xBmts to ensure equivalent amounts of kettle trub.
This was it for the non-aerated batch, it was daintily moved to the 66°F fermentation chamber immediately after being filled. I then proceeded to shake the living hell out of the other carboy for what felt to my feeble arms like an eternity, 180 seconds (3 minutes), before placing it next to the non-aerated carboy in the cool ferm chamber. Yeast was then pitched into both batches.
Fermentation activity appeared similar upon observation the following day.
The shake-aerated batch did produce a small blowoff that was not observed on the non-aerated batch, though it would appear this occurred as a function of the slightly higher volume of wort in that particular fermentor.
A few days into fermentation, I had to do some travelling for work and ignored my the beers for a couple weeks while I visited the California Science Museum and enjoyed a really nice Pilsner on Vancouver Island.
Upon my return home, I found both beers had attenuated to an identical 1.016 FG (corrected), about 4 points higher than where I wanted it to be, which I blame on the whole mash temp fiasco.
The beers were cold crashed, fined with gelatin, and after a few days, kegged and carbonated.
| RESULTS |
Before going into too much detail, there’s something I need to confess…
I fucked up.
You see, I have a family who loves IPA, and frankly, this turned out to be a damn good beer. Pint after forgotten pint consumed, growlers filled, good times had. You know the routine. Only this time, my mental beer level tracking system went awry and one of the kegs kicked after only 7 people completed the evaluation– not even half of our normal goal of 15. Each participant was blindly presented 3 samples, 2 from the aerated batch and 1 from the non-aerated batch, then asked to select the one they perceived as being different.
I don’t mean to polish this turd or make excuses for my obvious miscalculation, but despite my mistake, I think we can still glean something meaningful from these results. Allow me to explain:
With a sample size of 7 participants, a total of 5 (p<0.05) would have had to correctly identify the different beer to imply statistical significance. Only 1 person in this xBmt was able to do so, a surprisingly low result. Now, let’s imagine I administered the evaluation to 8 additional tasters, bringing our sample size up to the expected 15. In order to achieve significance at the same probability level, every single one would have needed to make the correct selection. While extrapolations of this kind aren’t necessarily good statistics, the likelihood that 8 straight panelists would choose the different beer, particularly since only 1 out of 7 was able to do so in reality, seems awfully slim. Make of this what you will, I’ve a hunch of my own I’m comfortable with…
My Impressions: Blinded or not, I could not reliably tell a difference between these beers. I fully agree with the remarks of panelists regarding how difficult it was to tell a difference. Both beers were great, I happily drank from both the non-aerated and aerated kegs… perhaps a bit more often than I should have.
| DISCUSSION |
I am not entirely clear what to make of this. On one hand, the yeast labs seem fairly adamant about pitching into well aerated wort. As easy as this is, especially since it requires no extra equipment, there seems no good reason to recommend skipping this step. I do wonder, though, if good aeration might be more important if one plans to repitch yeast slurry into a fresh batch of wort? Does pitching a constantly stirred (aerated) starter mitigate the need for wort aeration? Do the lipids in the trub act as a substitute for oxygen?
I don’t know.
As for the slightly different appearance during fermentation of the aerated batch, I am not sure what to credit for that, though I wonder if it has anything to do with the fact the yeast was pitched while a bunch of kettle trub remained in suspension. Either way, it wouldn’t appear this had any significant effect on the beer.
This is absolutely one xBmt headed straight for the I-wonder-what-would-happen-if-we-combined-this-with-another-variable folder. I am intrigued, for example, to compare a non-aerated wort with as little trub as possible transferred to the fermentor to an aerated wort fermented with a higher amount of trub. Or, pitch a non-aerated wort with a single vial then compare it to an aerated wort pitched with a yeast starter. Of course, a pure O2 vs. non-aerated xBmt is also high on the list.
What has your experience with aeration been? Are you a shaker, splasher, or user of O2 tanks and wands? Please feel free to share your thoughts in the comments section below. Cheers!
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48 thoughts on “exBEERiment | Wort Aeration: Impact Shake Aeration Has On An American IPA”
Interesting write up despite the small sample size!
For me I use none of the main methods you actually mention for aeration. I use an inline Venturi on my transfer tubing to help aerate the sweet wort as it goes into the fermenter. All it took was two hose clamps (tightened down) on either side of a small but moderate hole punched in the side of the tube about 6-8 inches above the end.
Thanks for the write up! Perhaps an examination of dissolved 02 by method and resultant impact on beer should be planned still keeping to just one variable. Use no shake, shake, Venturi, aquarium pump and pure O2? It would be interesting to see if this made any differences if anything at all.
We try to test one variable at a time, but yes.. There’s some interesting things in works and planning to try and suss out the role of pitch rate/yeast vigor/o2/etc….
Can’t wait to see the next round of experiments! All of them are helping me become a better brewer and for that I am ever so grateful!
This article is relevant. Not exactly a casual Memorial Day read, but relevant nonetheless.
http://www.morebeer.com/articles/oxygen_in_fermentation
The Morebeer article is quite good.
I’d love to see an exBEERiment on over pitching.
It’s coming.
When you use a well sized and well aerated starter the last gen cells have enough lipids etc. to do a ~1070 fermentation of non aerated wort. That’s one of the goals of making a starter, very fit cells, cells with a reserve.
Do the same experiment with harvested slurry without making a starter, you may taste the difference or even have a stuck fermentation
We’re planning a few xBmt designs to try and flesh out the effects.
It is a little bit bananas to me that so many tests reveal that there’s no appreciable difference between “commonly held best practice X” vs “doing the exact opposite.” But I’ve had plenty of stinker homebrews (my own and others) to know there’s clearly something differentiating between the good ones 🙂
As homebrewing and brewing as a whole has evolved many of the ingredients have become better eg: modified malts, smack packs etc.; and with these improvements many of the older practices can be replaced with simpler practices it seems. It is off though how many of the “common” teachings have been shown to have little to no difference in end product though!
It’s just proof that you should question everything you are taught (not just brewing). If the reasons don’t make sense, you don’t understand the reasons or the act itself doesn’t make sense.
Pretty close experiment. Keep up the great work.
I used pure O2 on my last batch and got my first blowoff. I also did my first stater so I don’t know who is to blame. But, it made me feel better using the O2 for fear off an off flavor so I’ll continue to use it. Thanks for this. Cheers!
There’s no doubt in my mind that adding trub to the fermenter makes up for a lack of oxygen. Also, as always, I’m sure some strains are less sensitive to a lack of oxygen or a lack of the metabolites produced when oxygen is around. I like the pure O2 method, as the shake method results in a reduction in the head-forming compounds in the beer according to Palmer.
Reduces head? I don’t understand… Can you expand?
Palmer says that some of the head forming proteins will only form head once, so when you shake it up you’re using those up when creating all that foam. I’m not sure how well this has been tested though. Maybe it’s on your guys’ list, if not, it would be a good one.
…interesting…
The once forming protein phenomenon isn’t a theory – it’s true. It’s also been discussed at good length by Dr. Charles Bamforth “The Pope of Foam”. He has a book out, FOAM: Practical Guides for Beer Quality (Via ASBC – http://www.asbcnet.org/store/Pages/19002.aspx). He is also featured in loads of Youtube and Podcast interviews (http://beersmith.com/blog/2011/09/28/head-retention-with-the-pope-of-foam-beersmith-podcast-23/)
The only issue worth (re)discovering IMO is if at the homebrew level lil’ shaking is enough to noticeably affect foam and retention via the minimal denaturation that occurs during that process. Lots a variables there. I add O2 via an oxygen regulator, wand, and stone – I use the 3 setting (whatever that rate actually is does’t matter – it’s the baseline) for 90 seconds, I kick up serious foam – thus denaturing gobs of the foam proteins – zero beer’s of mine have foam issues unless they are aged for an extremely long time and/ or exposed to brett or bacteria. I have an RIS that is 2 years old and you could shave with the foam.
I guess what I mean to say is – I doubt a little bit of shaking matters unless you are going to extremes.
I hadn’t seen that data, thanks for adding it Malcolm! You’re right though, may not be too big of an issue at our scale.
…and John Palmer was recommending secondaries until not too long ago, until folks like Marshall (and company) started doing side-by-side comparisons challenging all of these long-held beliefs.
I’m at the the point where I’m rolling my eyes whenever someone starts a post “Well, Charlie Bamforth/John Palmer/Jamil says….” I certainly respect their expertise, but I think we are finding that there is alot of differences between commercial brewing where alot of these guys got their recommendations from, and the reality that we are dealing with a different set of parameters at the home brew level.
If anything, these exBEERiments show how careful we need to be with the “argument by authority” fallacy that seems to be commonly invoked in these discussions.
Palmer hasn’t recommended secondary’s for nearly a decade. I think Brewing Classic Styles was copy written in 2007 so the book was started 1-2 yrs before that and he had already rebuffed his certain segments of his own book by then. It happens all the time as science and learning are not stagnant.
I am less hesitant to quote Bamforth as he is an academic and writes peer reviewed texts that are used to teach future industry experts. Similar to how I would question very little Palmer says about metals. And to be fair, Palmer has been writing about this stuff so much and for so long he’s certainly technically proficient. I have little doubt he knows the mechanics of water chem, for example, but techniques and processes evolve. Whether or not everything that they write or talk about actually matters to us or at our level – sure, I agree with you that may be a separate issue.
Malcolm, good points. I did feel there needed to be a counter-balance to the sentiment in the discussion that we should not shake because it destroys the head-retention. I’m sure Charlie and Palmer is correct on paper, but in practice at the home brewer level it appears to be a non-issue.
Obviously, I think we need to be cautious about extrapolating these results given such a small sample size. Having said that, I think a retest would be best in something like a lager or barleywine or DIPA – something that is generally believed to need more aeration. I also like your idea if comparing whether a healthy starter makes more of a difference in unaerated wort.
Another potential endpoint is if there is a delta between the two batches, does it lessen over time? In other words, if aeration does make a difference initially, does the non-aerated batch “catch up” over time.
Are you pitching a yeast starter? You only mention that you pitched yeast and I suspect that a lot of yeast handling good practice may be obviated by pitching a fresh culture of yeast
“I followed my normal process and built up an appropriately sized starter”
Another Great exBEERiment!
I have often wondered what the difference would be as we all have had a few batches we were in a hurry with and you just pitched your yeast and went about your day. I just recently went to using O2 after pitching to aerate the wort. The only difference I can really see is it takes a mere matter of hours to start kicking in vs a 12 hour or longer wait doing the traditional shake rattle or roll !
I have not seen a difference in taste at all. Great job Brulosophy once again!
Nice work here, especially resisting the temptation of not doing a true negative control. Too many times these aeration experiments are done comparing two different methods, and ignore what would happen if you simply did nothing.
This is because we tend to be home brewers first and experimentalists second, so we are biased towards producing beer, not knowledge….we may not want to do the experiment in a way that may produce a bad batch of beer.
This does confirm my thought that the post-boil process does allow some re-introducion of air/oxygen back into the wort after being boiled, or simply that the requirement for post-boil oxygen in the wort is over-stated. An interesting follow-up would be to take dissolved oxygen measurements throughout your process as well as between the two samples.
While you can get a fine fermentation without oxygenation ONCE, the problem arises when repitching the yeast for future batches. The knowledge that homebrewers have about O2 are, like many things, extrapolated from commercial settings. Commercial brewers are repitching their yeast for a dozen or more times so helathy cell walls for multiple budding is very important. If you are a homebrewer using the yeast once and then dumping it, oxygen really doesn’t matter as long as you are pitching an appropriate starter…a fun x-beerment would be to repitch the yeast from this test for three gens and see what the results are.
Yes. That makes a lot of sense… and as homebrewers who build starters, the o2 in the fermenter might not be all that important (or it might be… I just don’t know yet). There are a lot of things from commercial brewing that we just don’t or shouldn’t worry about homebrewing – our process is different, and in some ways BETTER.
With respect to your suggestion: I don’t routinely repitch yeast (unless saved from starter) anyway. On top of which, I am not really interested in chasing a “Bad” practice for repeated fermentations just to prove that it really is bad. I have to drink the beer at the end anyway!
Tip on aerating – put a tennis ball on a square bock of wood on the ground and place the carboy/better bottle on it, and then rock it back and forth. Much easier than holding it. Plastic buckets are easier, just rock them hard, with an undrilled lid.
Time to show your carboy who’s boss. Place a towel on your kitchen counter. Hold a piece of sanitized tinfoil over the mouth of the carboy. Turn the carboy on its side and rock as vigorously and for as long as you like.
One of my favorite sites. Always a fun read.
I have done most all of the various ways to oxygenate and most are a PITA and none seemed to make a lot if any difference. I think people do this mostly because it has been writ to do so and who wants to spend a day making a batch of undrinkable beer.
My current mode is to pump from the boil kettle through a bucket screen. It catches the junk and really froths up the wort. With out some expensive equipment there is no way to really tell how much O2 is getting in there but it’s probably at least as much as shaking. Of the stuff I have read the bigger danger is over oxidising (which you can only really do with pure O2).
I figure it doesn’t do any harm, it’s going to happen anyway if I filter the way I currently do and it is probably a help with higher gravity beers.
Since an experiment awhile back suggested some positive results from more turb in the fermentor… I feel reassured that unless I’m going really big it’s probably fine to just skip the screen. I would still get some oxygenation since I’m pumping and unless I went to a lot of effort there will be a fair amount of agitation.
I agree with others that a lot of the “rules” are very soft. I feel that probably a lot of the problems people have had are with sanitation or old ingredients and then get incorrectly associated with a technique.
When I started LME and hops and yeast (dry and two types “ale” and “lager”) sat in the store unrefrigerated and not sealed the way they are today. Most of the books on homebrewing had you add sugar. I had one recipe that called for all sugar and hops were optional!
So when some of these rules came about people were dealing with all kinds of things we don’t today.
I’m currently a shaker but have been looking into the merits of using a pump so your observations are pretty interesting. I wonder if there might have been more of a detectable difference in a beer where the yeast character is more prominent, something like an English pale.
I’d love to see some of these experiments tried again with just a pitch of rehydrated dry yeast.
Agreed. I use dry yeast more often than not for convenience.
On my home-brew forum in Croatia a guy did a similar test, but was testing attenuation and how much CO2 will be produced during certain time, with different levels of aeration
here is link http://www.pivarstvo.info/forum/viewtopic.php?t=3471
its not only text, there are pictures which will explain pretty much that in same time frame, he got more CO2 and better attenuation if wort was aerated enough
though you encountered no problems, according to his results, you could expect a slower fermentation and lower attenuation, probably even stalling at some point in extreme cases and not reaching desired FG
The point of aeration is to help yeast build up cell numbers by giving them the resources needed to manufacture cell membranes. If you make a starter, this stage has already happened and there’s little point oxygenating the wort. The result might have been different if yeast had been pitched into the wort straight from vials or smack packs. If you use dry yeast, which has less need of starters or aeration, I suspect there would be no sig difference again.
As always, great experiment.
I would really expect most fermentation based results to be highly strain dependent, so I think the most we can conclude from them is that strain S shows/does not show effect with variable x. For this reason, I would like to see yeasts known for their stronger character when doing experiments like this.
I aerate by roughly stirring my wort in the brew kettle while chilling.
I no chill my wort, so my method of aeration involves simply picking up the cube of wort and tipping it into the fermenter from a height. Splashes it around and foams it up quite a bit so I figure it’s good enough. The resultant beers would suggest that it is, though. 🙂 I also do the overbuilt starters for all batches too.
I run off my wort using a pump. I have a recirculating setup for chilling with a copper tube to set down in the kettle with the immersion chiller (like this: http://www.mrmalty.com/chiller.php). Mine has only a single outlet so when it’s time to transfer to the fermentor I just stop the pump, pull the copper tubing out, hold it a few feet above the bucket (or carboy with funnel) and switch the pump back on.
The foot or two fall down into the bottom of the bucket results in plenty of splashing/foaming and probably more aeration then I could get by shaking it up.
Eureka moment yesterday – after I finished transferring from my brew kettle to the carboy with an autosiphon I kept pumping the autosiphon wand to bubble lots of air through the wort in the carboy. No shaking needed!
throwing another spin into this, a few weeks ago, before reading this post, I found another topic on aeration, Using olive oil instead of aerating it the yeast starter. from what I gleam, most big breweries dont aerate wort, but there yeast, to prevent oxidation.
a few interesting links to consider, http://www.winning-homebrew.com/olive-oil.html,
and http://www.kotmf.com/articles/oliveoil.pdf (the PDF is the experiment that they did at new belgian brewing.)
so far, i have been having good luck adding a drop of olive oil to my starters, try to get more yeast growth. but i may have to do an xbmt to really get some good data.
I love all the xBmts on this site and wish I would have found this site a long time ago! It may have saved me a lot of time and equipment/ingredient purchases. As others have cautioned about extrapolating the results of this particular experiment due to the low sample size, I also wanted to point out that the results of this experiment gives us no ability to make inferences relative to an objective estimate of the differences between oxygenation of wort via shaking versus no shaking/oxygenation, such as attenuation level. There is only a single replicate of a paired sample, which results in zero degrees of freedom to test for differences in attenuation. In other words, if we repeated this experiment again, or hundreds of times, we might see a range of differences in the attenuation. I appreciate the great care to only manipulate a single variable, yet there will be slight deviations in the process (e.g. missing your target mash temp), ingredients, and other factors we cannot completely control that will affect the differences observed between the treatments. We would need to replicate the paired samples to get at this. Which sounds awful to do unless you have lots of funding and assistants.
That said, the participants that sample the beer gives us an idea of what I and others likely really care about – whether it makes a difference in the flavor or appearance. Certainly having more participants will be better – it gives us a better understanding of person-to-person variability in ‘detectable’, albeit subjective, differences. Yet, even if you had 100 participants for the taste test, these results still pertain to a single paired sample. So, there are two-levels of variability to consider.
Now that I got the nitpicking out of the way, I will say that I have been oxygenating my wort with pure O2 or years and the similarities shocked me! I might just have to replicate this experiment on my own to add to the sample size 🙂
The one data point issue was brought up in part 2 of the O2 tests (“WORT AERATION – PT. 2: SHAKEN VS. PURE OXYGEN | EXBEERIMENT RESULTS!”), and handled much more concisely than my diatribe above. Keep up the good work, guys!
What we do in our testing brewing room is to use an O2 bottle to aerate the yeast and pull yeast into the wort hose during the wort is flowing through the hose. And also the wort is also aerated with by an air compressor to push the o2 into wort via a ventritube design.
Jana
http://microbrewerysystem.com/Blog/HSA_Hot_side_aeration_905.html
I am new to beer brewing but cooking spirits is a family tradition. In my four batchs of beer I’ve yet to areate and am pleased with the taste thus far. Not much of a drinker though. My employees and co-workers though do hammer them back without complaints yet….