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!

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...