exBEERiment | Lager Fermentation: Traditional vs. Quick Lager Method With Imperial Yeast L09 Que Bueno

Author: Jake Huolihan

Ask any brewer what the difference between an ale and a lager is, and almost certainly the most common response will have something to do with the temperature at which fermentation occurs. It’s well established that ester production is positively correlated with temperature, and seeing as lager styles are known for their clean fermentation character, it makes sense that brewers would opt to keep fermentation temperatures as cool as possible. Historically, lagers were allowed to ferment at a consistently cool temperature over a relative long period of time, though some modern brewers began to develop methods for hastening the process.

Understanding that ester development primarily occurs during the initial phases of fermentation, it was posited by some that maintaining a cool temperature was really only necessary during this time, after which the beer could be gently warmed to encourage activity and thus reduce the overall turnaround time for lager beer. While many have reported positive results using such quick lager methods, a past xBmt showed tasters could tell apart a beer made this way from one fermented consistently cool. However, numerous xBmts since then have indicated certain yeasts may be more sensitive to temperature than others.

I’ve had good experiences with Imperial Yeast L09 Que Bueno, a seasonal strain that is said to be sourced from Grupo Modelo that seems to impart different characteristics based on fermentation temperature. I was curious if these differences might be mitigated by starting fermentation cool then gradually raising the temperature, so I decided to put it to the test.

| PURPOSE |

To evaluate the differences between a pale lager consistently fermented at 50°F/10°C with Imperial Yeast L09 Que Bueno and one fermented with the same yeast using the quick lager method.

| METHODS |

I designed a simple pale lager recipe for this xBmt in hopes of any differences being readily apparent.

¡Ándale!

I started my brew day off by making two equally sized starters of Imperial Yeast L09 Que Bueno.

With the starter spinning, I collected the water, adjusted it to my desired profile, then weighed out and milled the grain.

When the water properly heated, I incorporated the grains then checked to ensure it was at my target mash temperature.

The mash was left alone for 60 minutes.

During the mash rest, I weighed out the kettle hop additions.

With the mash rest complete, I collected the sweet wort in my kettle and boiled it for 60 minutes with hops added as stated in the recipe.

Once the boil was complete, I quickly chilled the wort.

A refractometer reading showed the wort was right at the expected OG.

Identical volumes of wort were then racked to separate sanitized Unitanks.

The filled vessels were connected to my glycol rig and left for about 15 minutes to child to 50°F/10°C, which is when I pitched the yeast starters. Fermentation activity was observed in both batches the following morning. While the temperature for one batch was left alone throughout the fermentation process, I set the controller on the quick lager batch to 56°F/13°C 3 days post-pitch, which took approximately 8 hours for the beer to reach. The next day, I set the controller on the quick lager batch to 64°F/18°C, which the beer had reached by the next morning. The beers were left at their respective temperatures for an additional 10 days before I took hydrometer measurements showing the beer consistently fermented cool finished with a slightly higher FG than the quick lager batch.

I reduced the temperature in in both I proceeded to pressure transfer the beers to CO2 purged kegs.

The filled kegs were placed in my keezer, burst carbonated, and allowed to lager for 4 weeks before being evaluated.

| RESULTS |

Due to social distancing practices as a result of the COVID-19 pandemic, data for this xBmt was unable to be collected in our typical manner. As such, temporary adaptations were made involving the author completing multiple semi-blind triangle tests in as unbiased a way as possible.

Utilizing 4 opaque cups of the same color where 2 were inconspicuously marked, one set was filled with the beer consistently fermented cool while the other set was filled with the beer fermented using the quick lager method. For each triangle test, 3 of the 4 cups were indiscriminately selected, thus randomizing which beer was the unique sample for each trial. Following each attempt, I noted whether I was correct in identifying the unique sample. Out of the 10 semi-blind triangle tests I completed, I needed to identify the unique sample at least 7 times (p<0.05) in order to reach statistical significance. In the end, I correctly identified the unique sample 8 times (p=0.003), indicating my ability to reliably distinguish a pale lager fermented with Imperial Yeast L09 Que Bueno consistently at 50˚F/10˚C from one where the temperature was gradually raised during fermentation.

While I enjoyed drinking both of these beers and didn’t think either was necessarily bad, I perceived a sulfur noted in the one fermented using the quick lager method that was absent in the cool fermented batch, and I preferred the cleaner character of the latter.

| DISCUSSION |

It’s widely accepted that in order to produce the highest quality lager beer, it’s necessary to keep the fermentation temperature as cool as possible to ensure minimal ester development. Given yeast activity is positively correlated with temperature, lager fermentation is known to require quite a bit of time, which when including the traditional lagering process, means the turnaround time for such styles can be upwards of 8 weeks, give or take. Less patient brewers have developed methods for hastening this process, many claiming it has no perceptible impact, though my ability to reliably distinguish a pale lager fermented with Imperial Yeast L09 Que Bueno consistently at 50˚F/10˚C from one where the temperature was gradually raised during fermentation contradicts this claim.

While lager yeasts are typically viewed as a singular class, there are two primary genetic variants known as Saaz and Frohberg, which research has shown do not share the same temperature sensitivities. Given tasters in a previous xBmt were able to reliably distinguish beers fermented with the Grupo Modelo yeast either cool or warm, it seems plausible this strain is of the variant that is more sensitive to temperature, unlike strains such as Imperial Yeast L13 Global.

Despite being able to pretty easily tell these beers apart, my triangle test performance wasn’t 100%, which is an indication of their similarities. The biggest difference I noticed was that the quick lager beer had a slightly stronger sulfur note than the one fermented cool the entire time, and my hunch is this would have dissipated over time, which would have made the beers far more difficult to distinguish. Based on my experience here, when fermenting with Imperial Yeast L09 Que Bueno, I’ll be sticking with a cooler temperature, as I preferred its smoother overall character.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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