A Home Brewing experiment with Oxygenation by guest blogger Bruce Benneke.
Oxygen plays a huge role in the early stages of fermentation. It’s vital to yeast growth, helping to build healthy new cells. This ensures lots of little workers to turn sugars into alcohol and CO2. Good yeast growth means less risk of off-flavours, shorter lag times, and faster ferments. Yeast requirements for oxygen can vary slightly, but most yeast strains do well with at least 8-10 ppm of dissolved O2.
Let’s take a little look at the two most common ways homebrewers aerate their wort. We usually start out by splashing the wort by some method, either while transferring the wort from the kettle to the fermenter, or by shaking the fermenter itself. This uses atmospheric oxygen to aerate the wort, and will give you a max of about 6 ppm.
The other method uses pure oxygen. This uses a “stone” or “wand” that contains many tiny holes or pores (measured in microns) to create small bubbles that dissolve into the wort more readily.
Links are available at the end of this article to point you to further info.
To examine differences between a beer that was oxygenated via shaking, vs one that was given pure O2. For this test we decided to use a yeast that likes its oxygen, Escarpment’s Foggy London. Given that this has become a classic yeast for Hazy IPAs, let’s make a split batch of that.
30L (8 gal) batch, split into 2 fermentors
OG - 1.064 : IBU - 29.4 : ABV 6.3% SRM 4.8
Measured OG - 1.061
68% - (13# or 5.9Kg) Maker’s Malt Premium Pale
13.1% - (2.5# or 1.1Kg) Flaked oats
13.1% - (2.5# or 1.1Kg) Wheat malt
2.6% - (8oz or .2Kg) Cara Pils
2.6% - (8oz or .2Kg) Honey Malt (you could sub in all Carapils or all Honey Malt)
.7% - (2oz or .05Kg) Rice Hulls (you could use more or less, but that’s a lot of oats in there)
Mash for 60 min at 154F / 67.7C
.5 oz (14g) - Galena (12.5%) @ 60 min
1.5 oz (42.5g) - Amarillo (9.2%) @ Whirlpool 175F / 79C - 30 min
1.5 oz (42.5g) - Citra (12%) @ Whirlpool 175F / 79C - 30 min
1.5 oz (42.5g) - Mosaic (12.25%) @ Whirlpool 175F / 79C - 30 min
2.5oz (71g) - Amarillo (9.2%) - Dry hop, day 4, for 2 days
2.5oz (71g) - Citra (12%) - Dry hop, day 4, for 2 days
2.5oz (71g) - Mosaic (12.25%) - Dry hop, day 4, for 2 days
Note: The dry hop amounts were split equally between the 2 fermenters.
Whirlfloc @ 15 minutes (boil)
RO water, adding minerals to reach the following:
2 x fresh pouches of Escarpment Foggy London Ale
I mashed for 60 min at 154F / 67.7C, although temp slipped up to 156 at one point, which should result in a lower OG and higher FG, which it did. But not by much. The measured OG was 1.061. I’ve since swapped out the PID in my controller.
I split the batch into 2 separate fermenters, and aerated each, which is where we introduced the variable.
I shook one fermenter VIGOROUSLY for 5 full minutes. I don’t have a D.O. meter, but shaking can give you up to 6 ppm of O2. These round bottom fermenters make the shaking much easier.
The second fermenter got 1 minute of pure O2 through an aeration wand, which should put in the 8-10 ppm range.
The cost of an oxygen rig like the one pictured is quite reasonable. It consists of a small O2 cylinder available from your local hardware store (~$20), plus tubing, a regulator ($52 at my local homebrew store [LHBS]), and an oxygen wand ($40 at my LHBS). You could go for a bigger O2 bottle and flow meter/regulator if you do a lot of brewing or want finer control of the flow of O2 into your wort. Either way, it’s a cheap way to ensure healthy yeast, not only in this batch, but also in successive re-pitches.
For this experiment, two pouches of Foggy London Ale were obtained from the same batch and packaging run. I pitched a fresh pouch of Foggy London into each, tossed a Tilt into each fermenter, and applied a blow off. Each got wrapped with a heater, and temp control was applied.
I used a dry hop method that I’ve never tried. Magnets hold well through the walls of the plastic fermenter. Put the hops in bags, and attach the bags to the walls of the fermenter with (food safe) magnets above the krausen line. When you’re ready to dry hop, pull the outside magnets to drop the bags into the fermenting beer. I normally don’t worry about opening to dry hop, but as this experiment is oxygen based, it seemed like a good idea to limit the wort’s O2 exposure to the variable being tested. This process seemed to work just fine, but I’ll limit the use of this technique to experiments such as this.
This yeast took off like a rocket! Both fermenters had a good krausen within 6 hours, and within 12, the blowoff was overflowing. Thankfully I had taken the precaution of having it sit in a large pan.
So the fermentations were similar, but the shaken batch lagged ever so slightly behind. By the time I pulled the magnets on the dryhop bags on day 4, both yeasts were already finishing up. I let the beers sit on the hops for 4 days before pressure transferring to kegs, cold crashing, and force carbonating.
After patiently waiting for a few days (total lies, I 'tested' it the next day), I sampled each beer and confidently could not tell them apart. So I tried again a couple days later, with similar results. So I tried it again a couple days later, with similar results. Then I decided I better quit “sampling” and save some for science.
This hop and yeast combo produces a really nice juicy beer! It also maintained its haze right to the last drop.
I took sample bottles of each beer to a few locations in SK, namely Let’s Make Wine in Yorkton, Rebellion Brewing in Regina and Prairie Brew Supply in Regina all of whom were able to arrange tasters for me (Thanks guys! You made this sooo much easier!). Plus, I hit up a few friends who enjoy craft beer. So we had a wide variety of tasters,13 in total. Some were long-time professional or home brewers, a few more testers with a beverage tasting background, and some craft beer enthusiasts. Of the 13, only 5 correctly selected the odd beer out, while 8 did not.
Personally, I couldn’t distinguish these beers right until the day the kegs kicked. Which was far too soon. I’ll need to make this recipe again soon!
So while tasters couldn’t reliably distinguish these beers, there were objective, measurable differences between them from a fermentation perspective, if only small ones. I personally find the objective differences interesting. This was very fresh yeast, which is one of the benefits of getting yeast from Escarpment. Older yeast, or successive generations of repitched yeast, would quite possibly have had a more pronounced impact (as seen in Escarpment’s experiment). I saved this yeast from this experiment, so I’ll maybe run it out a couple generations and do another side-by-side.
To the lab!!!
More advice on oxygen and yeast from the experts:
Please note that I resisted making a “shaken not stirred” James Bond reference throughout this entire article, at the expense of a small piece of my soul.
Special thank you to my better half Nicole for taking the photos!