Author: Greg Foster

The results of the prior oxygenation xBmts were confounding to me, as I’d been convinced oxygen (O2) played an integral role in healthy yeast growth and fermentation. While this definitely got me thinking, it wasn’t enough to stop me from using pure O2 in my brewing. And it’s worked fine, my beers have been good, though that skeptical voice in my head continues to nag me– is it really making a difference?

Following the Shaken vs. Pure O2 xBmt, we received many suggestions to focus these types of tests on beers purported to require higher concentrations of O2 in order to ensure the best fermentation, particularly high OG styles known for stalling early. While preparing to get this going, I embarked on a search for valid evidence demonstrating the positive impact of O2 that wasn’t focused solely on the commercial brewing scale, though what I discovered certainly didn’t confirm my presumptions. About a year ago, an article by Tracy Aquilla called Oxygen’s Role in Beer Fermentation appeared on MoreBeer.com that seemed to imply O2 isn’t nearly as important as I’d come to believe. From the author:

It is true that aerating or oxygenating wort is generally beneficial to fermentation, but it is untrue to say that yeast requires oxygen to reproduce or that yeast uses oxygen to respire during fermentation.

Generally beneficial? Yeast doesn’t require oxygen to reproduce? I highly recommend everyone read the article, it provides a truly thought provoking look at the biochemistry of yeast. Changing such a strongly held belief isn’t easy and, despite the evidence Tracy shared, the part of me that finds comfort doing what I’ve been told, appealing to authority, has convinced me there must be situations where wort oxygenation makes a difference.

| PURPOSE |

To evaluate the differences between a split batch of the same beer where half was oxygenated with pure O2 while no attempt to oxygenate was made on the other half.

| METHODS |

I designed my recipe with one goal in mind– go big! I wanted to achieve a momentus 1.100 starting gravity without a ton of roasted malts, so American Barleywine seemed like an excellent choice. I started with a simple Sierra Nevada Bigfoot clone, mixed up the grain bill a wee bit, then finished my recipe off with some dry English yeast. The dextrose and DME weren’t a part of my original recipe, the reasons for their use will become clear shortly…

American Barleywine

Batch Size Boil Time IBU SRM OG FG ABV 5.5 gal 140 min 114 14 1.100 SG 1.020 SG 10.38%

Fermentables

Name Amount % Domestic 2-Row Malt 17 lbs 81 Aromatic Malt 1 lb 4.8 Crystal 60 1 lb 4.8 Dextrose (Corn Sugar) 1 lb 4.8 CaraMunich 8 oz 2.3 Extra Light DME 8 oz 2.3

Hops

Name Amt/IBU (Tinseth) Time Use Form Alpha % Centennial 43 g/47 IBU 60 Min Boil Pellet 9.9% Cascade 43 g/32 IBU 60 Min Boil Pellet 6.7% Chinook 43 g/24 IBU 20 Min Boil Pellet 9.0% Chinook 43 g/12 IBU Flameout w/ 20 min steep Boil Pellet 9.0%

Yeast

Name Lab Attenuation Ferm Temp WLP007 Dry English Ale Yeast White Labs ~79% 65°F

Two days prior to brewing, I spun up a couple 1.5 liter starters using previously canned wort then split a single vial of WLP007 Dry English Ale yeast between them, they were propagated on stir plates for 24 hours before being placed in my fridge to cold crash.

With the yeast taken care of, it was time to get brewing! I mashed in at my desired 154°F and set my RIMS to hold this temperature for 10 minutes.

It was at this point a strange brewing neurosis overcame me and I decided to lower the mash temp to 152°F for the remaining 50 minutes. Once the saccharification rest was complete, I collected the first runnings, performed a routine batch sparge, then transferred the rest of the sweet wort to my kettle and began to heat it up. The boil proceeded as expected with hops added per the recipe. At 15 minutes left until flameout, I checked the gravity and realized some shitty errors I’d made had resulted in the SG being lower than expected. This was supposed to be a big Barleywine! In an attempt to remedy this issue, I added the 8 ounces of DME I had on-hand to the boiling wort. Presuming this wouldn’t be enough to get me where I wanted to be, I desperately threw in 1 lb of dextrose. Before I could take another SG reading, the time had come to chill. I was super excited to try out my new Hydra IC from JaDeD Brewing.

I couldn’t believe how fast this bad boy worked! Equal amounts of the chilled wort were transferred to two 3 gallon Better Bottles, filling from the bottom up as gently as possible in order to limit the introduction of any oxygen for the no O2 batch.

I decanted the starters then pitched the remaining slurry into each of the carboys. It was time to get to the crux of the xBmt. While one of the carboys was left completely alone, the other was hit with a 5 minute dose of O2 dispersed using a 0.5 micron stone. The regulator was set to 1 liter per minute for the first 3 minutes, after which I cranked it up to 2 liters/minute for the remainder of the time.

I took a hydrometer reading at this point and was a little miffed to find I didn’t quite achieve the magical 1.100 OG I was hoping for, but rather came in a few points shy at 1.096 SG.

The carboys were placed in my fermentation chamber controlled to 65°F. I eagerly watched over them the following week to see if there were any observable differences in fermentation. Fermentation kicked off within 6 hours for both beers and appeared pretty much identical to start, then at 28 hours in the kräusen on the pure O2 batch began to creep slightly higher than the no O2 batch, to the point of creating a minuscule blow off.

After 3 days of fermentation, I noticed the kräusen on each beer had completely dropped and signs of activity were all but absent, so I decided to take an initial hydrometer reading.

There was actually a difference! The pure O2 batch had dropped crystal clear and finished at an acceptable 1.021 SG while the murky looking no O2 sample had only managed to ferment down to 1.026 SG. I checked on the no O2 carboy and was surprised to discover small bubbles popping on the surface of the beer, possibly just CO2 off-gassing, but I figured it’d be best to give both batches a bit more time to be sure. When I returned for a follow-up hydrometer measurement a week later, I found the no O2 batch dropped to 1.024 SG, just a fewpoints higher than its pure O2 counterpart. Both batches were cold crashed, fined with gelatin, then kegged and force carbonated. They were looking good when it came time to present them to tasters for evaluation later that week.

| RESULTS |

A total of 36 people participated in this xBmt, a panel consisting of numerous BJCP judges, experienced homebrewers, and long-time craft beer drinkers attending Strand Brewers Club and Pacific Gravity meetings.

Each participant, blind to the nature of the xBmt, was served 1 sample of the pure O2 beer and 2 of the no O2 beer then asked to select the unique sample. In order to achieve statistical significance given the sample size, 17 (p<0.05) tasters would be required to correctly identify the odd-beer-out. In the end, a total of 16 people (p=0.079) correctly selected the pure O2 sample as being different, allowing for the interpretation that using pure O2 on a high OG beer doesn’t appear to produce a reliably distinguishable difference from the same beer that wasn’t oxygenated at all.

My Impressions: I tested my ability to distinguish between the beers before I presented them to any participants. I was at an obvious advantage since on top of being aware of the nature of the xBmt, I poured myself large samples of each beer and compared them side-by-side rather than in a triangle. My hopes weren’t high, but to my surprise, I perceived a difference in aroma alone. For the sake of confirmation, I “blindly” tested myself 6 more times by marking one of the glasses and closing by eyes while whiffing. I remained able to identify the pure O2 beer every time, which I perceived as having a sweeter and less muddled malt aroma than the no O2 sample. Likewise, my results were the same when I focused on flavor alone, though I experienced more difficulty with this than with aroma. It’s possible that my performance was a result of bias, but to my taste buds the no O2 batch had a very slight yeasty off-flavor while the pure O2 batch was clean and smooth. Don’t get me wrong, these beers were incredibly similar, but personally, I preferred the pure O2 batch.

| DISCUSSION |

Yet again, my belief that using pure O2 has a significant impact on the flavor of beer has been shaken, tasters could not reliably perceive a difference between a beer dosed with “proper” amounts of oxygen and one that wasn’t oxygenated at all. As biased as I was, even I detected only the subtlest of differences. Taken alone, these results, when combined with those of prior xBmts, suggest homebrewers may not have to worry about oxygenation nearly as much as some of us do.

But this wasn’t the only data gleaned from this xBmt.

The objectively measurable differences I observed throughout the process lead me to conclude that oxygenation may in fact play a positive role, particularly when it comes to fermentation. The fact the pure O2 batch reached terminal SG nearly a week prior to, and finished .003 points lower than, the no O2 beer supports the notion that oxygen does have an arguably beneficial effect on fermentation and overall yeast health. Moreover, the pure O2 batch dropped clear much quicker than the no O2 batch, even without the assistance of gelatin. To me, this alone is enough evidence to keep me pumping my wort, especially those of higher OG, full of oxygen.

Finally, I’m curious how this xBmt might have played out had I utilized a vitality starter, as I’ve heard this method compensates for a lack of oxygen and contributes to better yeast performance. A future xBmt, indeed.

If you have any thoughts about this xBmt, please don’t hesitate to share them in the comments section below!

Support Brülosophy In Style!

All designs are available in various colors and sizes on Amazon!

Follow Brülosophy on:

If you enjoy this stuff and feel compelled to support Brulosophy.com, please check out the Support Us page for details on how you can very easily do so. Thanks!

Advertisements

Share this: Facebook

Twitter

Pinterest

Tumblr

Email



Like this: Like Loading...