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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