Author: Greg Foster

It seems every couple of months some “breakthrough” technology is announced that will supposedly change brewing forever. Geek that I am, I always find these new technologies incredibly interesting despite knowing full well that most will never escape the confines of a lab. A few months back, one such announcement quickly caught the attention of the blog circuit. Apparently, students from the University of Pennsylvania had discovered a way to ferment beer 9 times faster than usual by harnessing the power of “microfluidics.” Since waiting for beer to ferment is my least favorite part of brewing, I thought this was awesome!

What the hell is microfluidics? I did a little research and couldn’t find much information on precisely how it works to speed up the fermentation process, but according to one source who interviewed the Fermento team:

Using the microfluidics technology, which can produce nanoparticles of liquid with extremely precise specifications, the team devised a way to concentrate sugar liquids around individual yeast cells. This technique greatly increases the surface area of the yeast exposed to the sugar, accelerating fermentation by 70%. The end result, they say, tastes and looks identical to the traditionally-brewed stuff.

I have no idea what these smart students are actually up to, but the idea of increasing yeasts exposure to sugar to hasten fermentation sounded awfully similar to a method many of us brewers are already employing– yeast starters on a stir plate. Inspired and curious to try spinning a full 5 gallon batch during fermentation, I was doubtful any of the stir plates I use would be up to the challenge. Turns out I was wrong. On a whim, I put a smooth bottomed corny keg full of water on my cigar box stir plate, tossed in a standard stir bar, and turned the unit on.

It actually worked! I couldn’t quite get a full vortex going, but the powerful stir plate had little trouble producing a vigorous spin. Armed with the knowledge of my stir plate’s capabilities, I designed an xBmt to test the impact of continuous agitation during fermentation.

| PURPOSE |

To evaluate the differences between two batches of the same recipe where was fermented under continuous agitation while the other was fermented with no agitation.

| METHODS |

Feeling a tinge of sadness due to not having an Amber Ale on tap, I selected this as the style for the current xBmt and based the recipe off of a NHC winning beer.

Amber Waves of Grain

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5 gal 60 min 55.3 IBUs 18.6 SRM 1.075 1.010 8.5 % Actuals 1.072 1.014 7.7 % Fermentables Name Amount % ESB Pale Malt (Gambrinus) 11 lbs 78.22 Caramel/Crystal Malt - 40L 1 lbs 7.11 Munich Malt - 10L 1 lbs 7.11 Victory Malt 8 oz 3.56 Caramel/Crystal Malt -120L 6 oz 2.67 Chocolate Malt 3 oz 1.33 Hops Name Amount Time Use Form Alpha % Magnum 29 g 60 min Boil Pellet 8 Cascade 29 g 5 min Boil Pellet 5.5 Centennial 29 g 5 min Boil Pellet 10 Mosaic (HBC 369) 29 g 5 min Boil Pellet 12.3 Yeast Name Lab Attenuation Temperature San Diego Super Yeast (WLP090) White Labs 80% 65°F - 68°F

I began my brew day by weighing out and milling the grains for a 10 gallon batch.

While I usually use a complicated eRIMS setup, I opted for a more simple approach for this xBmt and use my old cooler MLT. I added the proper volume of strike water to the cooler then used a heat stick to bring it to temperature, after which I stirred in the grains to achieve a mash temperature a bit lower than I planned.

An hour later, I opened the valve to drain cooler, an effort that was tragically thwarted by an infuriatingly persistent stuck sparge, so I ditched the cooler in favor of the safe predictability of my stainless keggle. After transferring the entire mash, I stirred in some rice hulls and was quickly back in business.

Hops were added during a 1 hour boil, after which I rapidly chilled the wort to my target fermentation temperature.

A preliminary hydrometer reading showed I’d achieved slightly better efficiency than I planned for, which was fine by me.

I equally divided the wort between two keg fermentors and hit both with a dose of pure oxygen before pitching the yeast.

Both beers were fermented in the same chamber, one keg being placed on the floor while the other was placed on my stir plate, which was turned on to provide continuous agitation of the beer throughout fermentation. The purported purposes of using a stir plate to make yeast starters is to keep the yeast suspended in the beer as well as introduce a constant flow of oxygen, the latter of which was not a variable I was interested in looking at in this xBmt. While kegs are largely impermeable to oxygen, I used CO2 to purge the headspace of each fermentor 10 times just to be sure.

I turned the stir plate on and left the beers to ferment, returning 1 day later to check how they were progressing. While both beers were fermenting like crazy, the continuous agitation batch was winning the race by a margin of 9 points!

I came back for another SG check the following day to find the standard batch was still lagging a bit, though not by nearly as much.

Three days after pitching the yeast, I noticed the airlock on the continuous agitation beer had stopped bubbling while the airlock on the standard batch continued to slowly bubble.

Seemingly finished fermenting, I turned the stir plate off and left the beers alone for another day before taking additional hydrometer measurements. Surprisingly, both were sitting at the same target FG.

After another week at fermentation temperature and confirming no change in FG, I cold crashed overnight then pressure transferred the beers to their final serving kegs.

By the time the beers were fully carbonated a few days later, they’d both cleared to the point I was unable to distinguish them on appearance alone.

| RESULTS |

A panel of 15 awesome brewers with various levels of experience participated in this xBmt during a Pacific Gravity Homebrew Club meeting.

Each blind taster was served 2 samples of the beer fermented under standard conditions and 1 sample of the beer that was continuously agitated during fermentation in different colored opaque cups then were instructed to select the sample they perceived as being different. Given the sample size, 9 participants (p<0.05) would have had to identify the unique sample in order to achieve statistical significance. However, only 4 participants (p=0.79) made the accurate selection, suggesting participants were unable to reliably distinguish a beer that was continuously agitated during fermentation from one that fermented under more typical conditions.

My Impressions: I attempted multiple “blind” triangle tests and was unable to reliably detect the beer that was different. I carefully evaluated the aroma each sample, I closely monitored their taste and mouthfeel, I even tried to test myself using full sized glasses with normal pours. Alas, no matter what method I tried, I simply could not tell these beers apart.

| DISCUSSION |

I was warned before attempting this xBmt that fermenting a full-sized batch on a stir plate would likely lead to some nasty off flavors, so I have to admit I was quite pleased that the final beer turned out delicious. The results from this xBmt seem to imply continuous agitation may initially accelerate fermentation while having less of an effect toward the latter portion of the process, as both batches were sitting at the same FG just 4 days after yeast pitch. This along with the fact participants were unable to reliably distinguish the beers leads me to believe that continuous agitation during fermentation, for one, doesn’t replicate the proposed effect of microfluidics, and thus may be a futile endeavor.

I certainly didn’t expect anything like the 9 times faster fermentation the university students reported, but I was admittedly hoping for a little more. Of course, the implications of these results are limited by my use of the notably clean yeast WLP090 San Diego Super Yeast in an ale, which got me wondering how continuous agitation during fermentation might influence other styles such as cold fermented lager. I likely won’t be throwing stir bars into primary fermentors very often in the future because the risk and added complication wasn’t worth the reward.

If you have any experience fermenting beers under unconventional conditions such as continuous agitations, we’d love to hear from you in the comments section below!

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