exBEERiment | Fermentation Temperature: Imperial Yeast L13 Global In A West Coast Pilsner

Author: Jordan Folks

Fermentation temperature is widely viewed as being one of the most important factors in producing quality beer, and this is particularly true when it comes to lagers. Whereas concerns regarding cooler fermentation temperatures tend to be associated with yeast activity, for example sluggish fermentation and poor attenuation, warmer temperatures are correlated with increased esters, which are especially out of place in lagers. As such, commonly suggested fermentation temperatures when using lager yeasts are around 20°F/11°C cooler than when using ale yeasts.

A handful of new styles have recently been introduced that blend aspects of other more common styles, one being West Coast Pilsner. Typically made with mostly Pilsner malt and an aggressive late hopping strategy, a key feature of West Coast Pilsner is that it’s fermented with lager yeast anywhere from around 50˚F/10˚C up to 68°F/20°C, the ultimate goal being to end up with a crisp, highly drinkable finished beer.

I love hoppy beers and brew a lot of them, especially West Coast Pilsner, and my go-to yeast strain for this style has been Imperial Yeast L13 Global. Given my desire to produce the crispest, most crushable examples of this style possible, I’ve tended to ferment my West Coast Pilsners around the same temperature I do other lagers, which I’ve learned is not a universally accepted approach. Curious to see what, if any, impact fermentation temperature has on a West Coast Pilsner, I designed an xBmt to test it out.

| PURPOSE |

To evaluate the differences between a West Coast Pilsner fermented with Imperial Yeast L13 Global at 46°F/8°C and one fermented at 66°F/19°C.

| METHODS |

For this xBmt, I came up with a West Coast Pilsner recipe that uses a blend of modern American and New Zealand hop varieties. Special thanks to F.H. Steinbart for hooking me up with the malt for this batch!

Burning Shore

After collecting the full volume of water for two 5 gallon/19 liter batches, adjusting each to the same desired profile, and flipping the switch on the controllers to get them heating up, I milled the grain.

I decided to perform a step mash with rests at 147°F/64°C, 157°F/69°C, and 170°F/77°C.

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

Once the mashes were finished, I collected the worts and proceeded to boil them for 60 minutes, adding hops at the times listed in the recipe. When the boils were complete, I quickly chilled them with my JaDeD Brewing SS Coil Hydra.

Refractometer readings indicated both worts were at the same target OG.

At this point, I transferred the worts to separate fermenters and placed one in a chamber controlled to 46°F/8°C while the other was put in a different chamber controlled to 66°F/19°C.

When the worts were stabilized at their respective temperatures, I pitched identical volumes of Imperial Yeast L13 Global slurry into each one.

I noticed activity in the warm fermented batch within 12 hours, while it took around 48 hours for a similar amount of activity to be observed in the cool fermented version. After 5 days, I took hydrometer measurements showing the beer fermenting at 46°F/8°C still had a ways to go, while the batch fermenting at 66°F/19°C appeared to be done.

I left the beers alone for another 10 days before setting both controllers to 60°F/16°C, and once both had reached that temperature, I added the dry hops.

The beers were left to mingle with the dry hops for 24 hours, after which I cold-crashed both to 32°F/0°C before pressure-transferring each to CO2 purged serving kegs along with gelatin fining. Hydrometer measurements confirmed the beers had finished at a similar FG.

The filled kegs were placed on gas in my keezer and left for 10 days, after which they were mostly clear, well carbonated, and ready to drink.

| RESULTS |

A total of 28 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of beer fermented at 46°F/8°C and 2 samples of the beer fermented at 66°F/19°C in different colored opaque cups then asked to identify the unique sample. While 15 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 11 did (p=0.31), indicating participants in this xBmt were unable to reliably distinguish a West Coast Pilsner fermented at 46°F/8°C from one fermented at 66°F/19°C.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I correctly identified the odd-beer-out every time. I perceived the warm fermented batch as having a slightly sharper bite compared to the cool fermented version, which was more lager-like. I also felt the aroma was a bit more muted in the beer fermented cool. While I felt both were great examples of West Coast Pilsner, I personally preferred the cool fermented one, though I was perfectly happy to have both on tap.

| DISCUSSION |

Ask a group of brewers what the most important aspect to making good beer is and it’s likely the most common response will have something to do with fermentation temperature. Indeed, it’s well established that warmer temperatures tend to coax out more esters while cooler temperature suppress such development, particularly when using lager yeast. Interestingly, tasters in this xBmt were unable to reliably distinguish a West Coast Pilsner fermented at 46°F/8°C from one fermented at 66°F/19°C.

Some plausible explanations for this result are that the 20°F/11°C temperature delta wasn’t vast enough to produce a noticeable difference, or that lager yeast requires even cooler temperatures to suppress ester formation, or perhaps the higher hopping rate of this West Coast Pilsner hid any perceptible differences. Then again, seeing as several past xBmts also fail to uphold these claims, it seems at least marginally more likely that the particular yeast strain is robust enough to tolerate a fairly wide temperature range without producing off-flavors.

For a few years now, I’ve been relying heavily on the Weihenstephan lager yeast strain, which includes Imperial Yeast L13 Global, for many styles including ales like IPA, specifically due to its ability to ferment clean at warmer temperatures. While the results of this xBmt seem to add further confirmation to this claim, I’m still hesitant to completely ditch cool fermentation, at least when making traditional lagers, but my conviction that it’s absolutely necessary has certainly softened.

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

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