A Home Brewing experiment with Krispy: Ferment Under 10 PSI Pressure vs Atmospheric
A while back, Richard Priess wrote a post on the Fermenting with Escarpment Labs Facebook page looking for someone to do some experimental side by side homebrewing. Being the eternal optimist that I am, I immediately contacted him. After a bit of “geeking out” about yeast (and microscopes), I offered to take a stab at brewing an experiment for Escarpment Labs. We decided I’d test pressure fermentation vs no pressure using their KRISPY yeast, which I hadn’t used since they updated it to a new lab-evolved strain.
Why ferment under pressure?
Pressure fermentation in a homebrew setting has grown in popularity lately, as more and more brewers discover the benefits, such as reduced ester production. This can allow lager strains to be fermented warmer, and help ale strains produce a cleaner, more lager like beer. Caveat: If you’re trying to ferment an ester-driven style like Hefeweizen, or some English Ales etc., pressure fermentation may not give you the results you’re after.
For this experiment, I would brew a split batch of a German Pilsner recipe, separated into two fermenters, and let them ride at 20ºC (68ºF). One would remain at atmospheric pressure, and the other would be under 10psi of CO2 pressure for the duration. Each would receive a full pouch of KRISPY.
I recently completed a split batch experiment (on my own) with two different lager strains, both fermented on the warmer side, and under no pressure, to drive up ester production. For that experiment, I made a fairly simplistic German Pilsner. I thought I’d use a similar recipe here, as it gives the variable nothing to hide behind.
8 gal (30L) batch
BIAB, with a 400 micron bag in a keggle.
Est OG = 1.047
IBU’s (Tinseth) = 32.3
Colour = 3 SRM
Est FG = 1.011
Est ABV = 4.7%
I started with 11.27 gal (42.7 L) of R.O. water, and added minerals to get close to Kai’s pils profile, because I’ve had good luck with it in the past. I added 4.6g Calcium Sulfate, 3.8 g of Calcium Chloride, 3.2 grams Magnesium Sulfate, and 1 ml of lactic acid, which according to Bru’n Water should leave me with:
Ca - 59 ppm, Mg - 7, Na - 8, Sulfate - 90ppm, Chloride - 61ppm, and a mash pH of close to 5.4.
Kveik strains seem to drop pH a bit more than other brewing yeasts, so 5.4 to 5.5 should be good.
Super simple. 15 pounds (6.8 kg) CMC Superior Pilsen. Why mess with a good thing?
Also not terribly complicated.
- 1 oz (28g) of Magnum(12.0% A.A.) at 60 min
- 1 oz (28g) Hallertau Mittelfruh (4.4% A,A,) @ 10 min
- 1 oz (28g) Hallertau Mittelfruh (4.4% A,A,) @ 1 min
Whirlfloc and 4g DAP at 15 minutes in the boil.
Mashed for 60 min at 150deg F, or 65.6C, which should give a nice fermentable wort. I ran the recirculation pump throughout the mash.
Boiled for 90 minutes, for reasons I’ll discuss later.
Mashed in and hit my temp pretty close on my prototype controller. so I did the traditional “I hit my numbers exactly happy dance” (video not included)
After 60 min of circulation, I lifted the bag, let it drip for a bit, and gave it a gentle squeeze. Est pre-boil gravity was 1.041, and this batch hit 1.041 (10.2 P). (Cue the happy dance again, and no, I’m still not videoing it. It frightens livestock.)
My pH meter decided it had enough, and died when trying to test this wort, so I couldn’t confirm mash pH. Bru’n Water always gets me close, so I’ll imagine the mash pH was close to the 5.4 mark.
I boiled for 90 minutes for 2 reasons:
- First, there are traditionalists out there who will say ‘but you’re going to get DMS if you don’t boil an all pilsner malt for 90 minutes’. I figured I’d nip that one in the bud. Probably the last time I’ll ever boil for that long, because I’ve never really had a DMS issue with a 60 min boil, even with an all pilsner malt grist.
- Second, I wanted to further dial in my system's boil off calculation. As it turned out, I over-boiled a bit, and ended up higher than I’d like to be. I added boiled water to get to an FG of 1.049 which is still above my target of 1.047, but I thought that would be in the ballpark.
All boil ingredients were added at the times listed in the recipe above.
After the boil, the wort was chilled with my immersion chiller. I racked equal(ish) amounts of wort into two separate 30L FermZilla All Rounders. Each is equipped with a pressure kit, a floating dip tube, and a thermowell.
Each wort was hit with 60 seconds of pure oxygen through a 10 micron Anvil aeration wand, and a Tilt hydrometer was added to each. This was my first time using Tilts, and I have a few changes to make in my data collection procedure using these. I’m thinking of having a dedicated Raspberry Pi running TiltPi sitting between the two fermenters full time. If anyone has any other ideas that don’t involve an old android device that likes to shut itself off periodically, please feel free to contact me.
I pitched one full pouch of KRISPY into each fermenter, and sealed them. Heat mats and jackets were placed around each fermenter, and temperature was controlled with my STC-3008 powered dual temp controller. Each fermenter has thermowells to allow the monitoring of the temp in the middle of the fermenter. I have a few touch ups to do on this system, but overall it behaved itself. I set them both to 20C, which is in the lower end of the range for this yeast, and is actually the lowest temperature I have ever fermented a kveik strain. We are going for a lager-like beer, afterall.
From here on, the two fermenters were treated differently in only respect. The atmospheric fermenter had a blow off attached to the gas post into a growler full of starsan, which is a typical homebrewer practice.The pressurised fermenter had 10 psi of CO2 applied to the headspace, rather than just allowing the yeast to pressurise the fermenter on its own. It was then kept under 10 psi with a spunding valve attached to the gas post.
The atmospheric beer took off like a rocket. Nine hours after pitch, it was bubbling through the blowoff, and had the beginnings of krausen. The pressure beer didn’t have any visual signs of fermentation until the next day.
In general, the pressure fermented beer appeared to lag a bit behind the atmospheric beer, but they both chewed their way down to 1.009.
I let them sit at FG for a bit, pressure transferred them both into CO2 purged kegs (equipped with floating dip tubes), and cold crashed for 24 hours. Forgoing my usual gelatin fining routine, I applied peer pressure. I mean, I applied CO2 to 12 psi, and let the two beers carbonate for a week or so in my lagering fridge.
My initial impressions
I pulled samples of each about 2 weeks after kegging.
The first sips of the pressure fermented beer were very lager-like. Quite remarkably so. Malt shines through, and those noble hops pop nicely.
The atmospheric beer was still really clean, but I could swear it was a bit more ale-like, but that might just be my prior knowledge of the variable being tested. I’m naturally suspicious of results that adhere too closely to my preconceived ideas, so I was more than happy to refrain from forming any solid opinions and move along to some blind triangle testing.
I poured two opaque glasses of each beer, then had my better half randomise them for me. I then selected 3 glasses at random. I repeated this 5 times. And was only right on three out of 5. I then had my better half perform the same test, and she was only correct twice. As the beers aged, the differences began a bit more readily apparent, and we could both pick the odd one out.
After letting the beers settle down a bit further, I borrowed the palates of a few friends, who weren’t told of the variable beforehand. (Special thanks to ‘Let’s Make Wine’ in Yorkton for all their help in providing tasters)
The total number of tasters was 10, and 7 tasters were able to pick the odd sample out. So it appears in my limited sensory panel, participants were able to distinguish between beers fermented with KRISPY, one under atmospheric pressure, and one under 10 psi.
Samples of the finished beers were also shipped to Escarpment Labs. Tasters at Escarpment Labs also noted that the pressure-fermented beer was "cleaner" with less apple-like ester than the atmospheric beer. Preference was pretty much an even split, with some tasters preferring the fruitier atmospheric sample and some preferring the cleaner pressure-fermented sample.
Editor's note: Escarpment Labs is still waiting for our academic partner to clear through their GC-MS backlog, otherwise we would have run these beers to measure ester content!
I quite enjoyed both of these beers, but if I had to pick one, I’d take the pressure fermented beer. It just felt cleaner and crisper, and closer to a classic German Pilsner. The atmospheric pressure beer was still a great beer, and I’m sure I’d be able to drink multiples. The vast majority of testers who correctly selected the odd beer out agreed with us. Again, this was a very small sample size, so take any preferences with a grain of salt. I’d be curious to see if there were any objective differences between these two beers.
I am loving this new KRISPY! Enough that I may be retiring my workhorse lager strain to produce lawnmower beers for my friends who prefer the mass market light lagers.
I may just brew another batch of this beer and ferment it a bit warmer, and with a bit more yeast nutrient. I’m sure that combination of factors restrained KRISPY from getting in touch with its rapid-fermenting kveik roots. I’ll ferment under pressure, but this time start it at atmospheric pressure, and allow the yeast to bring the headspace up to pressure in its own time.
In this experiment, I found that KRISPY fermented under pressure fermented slightly slower than at atmospheric pressure, but that pressure fermentation resulted in a cleaner flavour profile.
About The Author
Bruce Benneke lives in Yorkton, Saskatchewan with his extremely tolerant better half and his family. He has a background working in R&D and QC for a biocomposites company, and also spent a number of years working as a primary care paramedic for a rural service in SK., giving up both to operate an ice cream store, in one of the coldest places in Canada.
Bruce is extremely passionate about improving his brewing, and takes almost every learning opportunity that comes his way. He’s been experimenting with brewing right from his very first all grain batch.
When not making beer or developing new flavours of ice cream, Bruce is an amateur writer, currently in search of an editor and literary agent. He also enjoys running extremely silly long distances in his ‘spare’ time.
Great job Bruce. I have been wanting to pressure ferment for a while and you have made my mind up. What great, valuable information you provided. More experiments like this help us home brewers. Cheers!