Author: Jake Huolihan
Of the many variables we’ve tested over the years, one we can’t seem to leave alone is fermentation temperature, particularly when using traditional lager yeasts. While it seems certain strains may in fact be more sensitive to fermentation temperature than others, I think it’s fair to say the xBmt results on this topic overall have been very surprising. In addition to cries of invalid methodology, suggestions that participants have shitty palates, and accusations that we’re aligned with Beelzebub, some have constructively posited these results, which have typically shown lagers fermented warm to be indistinguishable from those fermented cool, may have to do with yeast pitch rates.
It’s well known that fermentation activity is positively correlated with temperature and hence brewers are advised to pitch larger volumes of yeast into cool fermented lagers to ensure a quick start, which many contend reduces the risk of ester and phenol development. Indeed, all prior xBmts on lager fermentation temperature have involved yeast being pitched at calculated lager rates into both batches. Could it be that the absence of expected esters and other off-flavors in our warm fermented lagers is due to overpitching?
To explore this hypothesis, I decided to replicate previous xBmts on the topic using ale instead of lager pitch rates with Imperial Organics L13 Global yeast, which is purportedly sourced from the famed Weihenstephaner Brewery.
| PURPOSE |
To evaluate the differences between beers fermented with a single pack of Imperial Organic L13 Global yeast at either 50°F/10°C or 72°F/22°C.
| METHODS |
Given the time of year, I went with an easy drinking Märzen for this xBmt, a reminder of everything I was missing out on in Bavaria.
Masochism
Recipe Details
| Batch Size | Boil Time | IBU | SRM | Est. OG | Est. FG | ABV |
|---|---|---|---|---|---|---|
| 5.5 gal | 20 min | 24.8 IBUs | 9.3 SRM | 1.056 | 1.015 | 5.3 % |
| Actuals | 1.056 | 1.017 | 5.1 % | |||
Fermentables
| Name | Amount | % |
|---|---|---|
| Munich Malt | 4.5 lbs | 32.43 |
| Weyermann Pilsner Malt | 4.5 lbs | 32.43 |
| Weyermann Vienna | 4.5 lbs | 32.43 |
| Caramunich Malt | 6 oz | 2.7 |
Hops
| Name | Amount | Time | Use | Form | Alpha % |
|---|---|---|---|---|---|
| Hallertau Magnum | 28 g | 20 min | Boil | Pellet | 11.5 |
| Hallertauer Mittelfrueh | 10 g | 10 min | Boil | Pellet | 4 |
Yeast
| Name | Lab | Attenuation | Temperature |
|---|---|---|---|
| Global (L13) | Imperial Yeast | 75% | 46°F - 56°F |
Notes
| Water Profile: Ca 71 | Mg 0 | Na 8 | SO4 75 | Cl 74 |
Download
| Download this recipe's BeerXML file |
The day before brewing, I weighed out the grains while the RO water was being collected.
After adjusting the water to my desired profile and turning the element on to heat it up, I ran the grains through my mill.
When the water was at strike temperature, I stirred the grains in before checking the mash temperature– slightly higher than planned, but nothing too concerning.
The wort was recirculated throughout the abbreviated 20 minute mash step, after which I removed the grain bag and let it drip into the kettle while the wort was heating.
The wort was boiled for 20 minutes with hops added as noted in the recipe.
With the boil complete, I ran the wort through my plate chiller into separate fermentors, filling each with the same volume.
Hydrometer measurements revealed my brewhouse efficiency was 65%, which is quite respectable given the abbreviated mash and boil.
One fermentor was placed in a fermentation chamber set to 50°F/10°C and the other went into a chamber set to 72°F/22°C.
The following morning, once both batches had stabilized at their respective target fermentation temperatures, I pitched a single can of IOY L13 Global yeast into each before hitting them with 90 seconds of pure oxygen.
Predictably, the warm ferment beer was very active just 12 hours later while the cool ferment batch took another day to show signs of fermentation. I took hydrometer measurements 3 days after pitching just to see how things were progressing and discovered the warm ferment batch was quite a bit lower than its cool ferment counterpart.
I checked again 3 days later and found the cool ferment beer had dropped to 1.020 SG while the warm ferment beer was still sitting at 1.017 SG, an indication it had reached FG.
Accepting 1.017 SG as the limit of attenuation for these beers meant the cool ferment batch was almost done, so I raised the temperature in that chamber up to 60°F/16°C for a diacetyl rest. This is also when I moved the warm ferment beer, whose SG hadn’t changed since 3 days post-pitch, into the same chamber as the cool ferment beer. I left the beers alone for another 36 hours before confirming both had reached the same 1.017 FG.
With both batches done fermenting, I racked them to kegs.
I placed the filled kegs in my keezer where they were chilled and briefly burst carbonated. I opted to skip fining these beers with gelatin and let them lager in my keezer for a month instead. When it came time to collect data, they equally clear and carbonated.
| RESULTS |
A total of 22 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the cool ferment beer and 2 samples of the warm ferment beer then asked to identify the one that was unique. Given this sample size, 12 tasters (p<0.05) would have had to correctly identify the unique sample in order to reach statistical significance. Ultimately, only 8 tasters (p=0.46) made the correct selection, indicating participants in this xBmt were unable to reliably distinguish a Märzen fermented with a single pack of IOY L13 Global yeast at 50°F/10°C from one fermented at 72°F/22°C.
My Impressions: Having been able to tell apart the lagers fermented with WLP940 Mexican Lager yeast at different temps, I was pretty confident I’d be able to do the same with these beers. However, over multiple triangle test attempts, I simply could not tell the beers apart, they smelled and tasted exactly the same to me. And that was a great thing, both beers were so good, possessing what I perceived as a very nice blend of toast and hay with a crisp lager finish. I’ll certainly be brewing this again using similar methods, may even enter it into some competitions!
| DISCUSSION |
I’m not sure what to say that hasn’t already been said in past fermentation temperature xBmts involving the Weihenstephan yeast. To the chagrin of some, the evidence continues to stack up in favor of this strain being incredibly hearty and consistent, not only producing a clean lager when fermented in an unconventionally warm environment, but apparently unaffected by being underpitched into cool wort. This yeast is a beast!
The fact other xBmts with different yeasts fermented at varying temperatures have returned significant results has me wondering what it is about the Weihenstephan strain that makes it so seemingly insensitive to certain environmental pressures. I’m really curious about the genetics of this strain compared to others in the lager family as well as exploring how traditional ale yeasts perform when fermented at cooler temperatures. As was discussed on episode 015 of The Brülosophy Podcast, the Weihenstephan strain is said to be of the Frohberg-type, which appears to be a tetraploid with 2 parts each S. cerevisiae and S. eubayanus, as opposed to the Saaz-type strains that appears to be a triploid with 1 part S. cerevisiae and 2 parts S. eubayanus. Perhaps this difference is why the Weihenstephan strain is capable of performing equally as well at warmer temperatures as it does at cooler temperatures. Either way, the grip with which I once held onto the idea that all lagers require cool fermentation temperatures has certainly loosened, especially when it comes to this strain, which I definitely plan to continue using often.
If you have thoughts about this xBmt, please feel free to share in the comments section below!
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22 thoughts on “exBEERiment | Fermentation Temperature: Imperial Yeast L13 Global In A Märzen”
How do you open the Imperial yeast cans? I’ve always had trouble with them either spraying yeast everywhere or exploding when the lid is popped.
I follow the instructions given with the can: don’t shake, open cold, reserve and swirl a small amount of liquid
Any particular reason for the short and shoddy mash and boil lengths?
Hmmm, I wonder… What do you think Curtiss? 2 in 1??
Because it doesn’t seem to make beer subjectively worse to me, and I didn’t have 4 hours to devote to brewing that day.
Thank you for the experiment. Now, how did the participants rate the beer itself?
I brew a Märzen based off of a published recipe that won NHC Gold in 2014, which is almost 3 parts Vienna to one part Munich and no Pilsner, and a little Acidulated for pH and Melanoidin to simulate a decoction. And similar IBUs, but using Perl. And I use a shit-ton of WLP833.
I don’t usually ask participants how they enjoyed the beer. I think it’s quite good though, friends have enjoyed it
I don’t think there’s much doubt left that the Weihenstephan lager yeast strain strain (L13 Global, W34/70, WLP830, Wyeast 2124) gives good lager at ale temps. However, of the two other lager strains tested for fermentation temp in Brulosophy experiments, one (WLP800) showed no significant difference and the other (WLP940) did show a difference. So the jury is out on whether lagers are OK fermented warm – it could well be strain dependant and might be a frohberg/saaz thing as you suggest.
I recently made a lager with saflager S-189 and the temp crept up to 61 F during fermentation. It certainly smells estery at the moment but is still very green, so I don’t yet know how clean the final beer will taste.
Reassuring that pitch rate made no difference – again.
Off topic: I’m considering upgrading my system to add a pump + plate chiller. What’s your sanitation process look like for that equipment?
Shawn
I really don’t like using the pumps and plate chiller to be honest, jaded IC is much better imo.
However, I run wort through them for the final 15 min of the boil to sanitize. Need to bag your hops though or the chiller can clog pretty quickly, it’s annoying.
The Jaded Hydra chiller is amazing. Literally cooled my beer down to 68 degrees this weekend in less than 10 minutes. Well worth the money! Since buying this chiller, I can do a complete brew-day in 1 evening after work with no preparation and be in bed by 10:30.
It seems to me that this is partly a pitch rate experiment, in that you’re comparing the results of the other (possibly overpitched) temperature experiments to the results of using a single can (and possible underpitching). But what was the pitch rate for this post’s batches vs. the other batches? Do you have a sense of how many millions of cells per ml per degree Plato you’re pitching as compared to the other exbeeriments? That might make some difference to the outcome–if the cans for this post’s batches was extremely fresh and the other batches used old yeast run through a starter, you may well have ended up with a comparable pitching rate.
Good question
I just brewed a marzen that ended up at boch 1.062.
It was my first attempt at a lager and was hoping the beer would be fine in my 60 degree basement. Well it hit 73 degrees and I had pitched three packs of 34/70. It ran through the wort In less than three days!!!! Your experience gives me hope that maybe this beer will be ok.
Andy, your beer will be fine. In my experience with 34/70 it is very accommodating with temperature. If you hit final gravity, start dropping it down. 34/70 is an absolute go-to and keep on hand lager yeast.
It has a really beautiful color. Do you think this beer recipe would do well with 34/70 instead?
They are reportedly the same yeast strain
Sorry I didn’t realize that. Since this strain has been tested here in Brulosophy I’m fermenting my beers in ale temperature with great results. It’s specially good beacuse I’m using only one fridge with temperature control, so I’m able now to make an IPA and a lager beer simultaneously.
Can you gather data on SG during the fermentation ? Maybe a SG reading once a day until complete. You can compare against other yeasts and processes the fermentation rates.
thx for all the experiments.
Do you have this recipe in a non xml format? I want to make it but can’t figure out how to use the xml. Thanks
Most recipe design software use xml. Shoot me an email and I’ll get you another version this weekend!
Ah no problem, dude. i was able to figure out how to use the xml file. The beer tastes pretty good! Thanks!