Author: Greg Foster

I don’t brew very many lagers. It’s not that I don’t like them, though I generally do prefer ales, it’s mainly because I’m incredibly impatient. I simply don’t want to tie up my fermentation chamber for a month or two waiting for a lager to crawl to completion. It should come as no surprise that I’ve been keenly following the developments of the quick lager method and have successfully used it multiple times. This got me wondering just how far one could push lager fermentation before noticeable off flavors developed. Then the results of the last fermentation temperature xBmt were published demonstrating a lager fermented at ale temperature was indistinguishable from the same beer fermented at a traditional lager temperature.

I’m not entirely sure what’s going on with all the breaking of brewtonian laws of lager yeast, but I have a suspicion it has something to do with the seemingly magical strain, Saflager W-34/70. Fellow contributor, Malcolm Frazer, did some internet sleuthing and found that 34/70 seems to be a sort of hybrid strain, mimicking characteristics of both ale and lager yeasts. Cool! Curious to know just how impervious 34/70 is to high temperatures, I designed a torture test involving a rather absurd fermentation temperature usually reserved only for Belgian ales.

| PURPOSE |

To evaluate the differences between 2 beers of the same recipe split into separate fermentors and fermented with the same lager yeast strain at different temperatures, half at a cooler 60˚F/16˚C and the other half at a much warmer 82˚F/28˚C.

| METHODS |

Desiring a clean beer that would allow any off-flavors to shine, I brewed Marshall’s popular Munich Helles recipe for this xBmt, swapping out the noble hops for some Fuggles I happened to find in the back of my freezer. Everything in place, my brew day began with the crushing of the grain.

I adjusted my water profile with minerals and acid while the strike water was warming then, once to temp, mashed in and came close enough to hitting my intended 150°F/66°C mash temperature.

The wort was recirculated through my RIMS tube for a 60 minute single infusion rest after which I pumped it over to the kettle and brought it to a boil. Bagged kettle hops were added per the recipe and when the hour was up, I removed the hops and tossed in my immersion chiller.

With the assistance of a pump, the wort quickly fell to my desired pitching temperature. Despite previous xBmt’s questioning the importance of oxygenation, I still chose to hit my wort with 1 minute of pure O2.

The wort was then split between three identical corny kegs (2 xBmts in one) that would all be used as primary fermentors. I dissolved four packets of 34/70 yeast in a single volume of lukewarm water before splitting the slurry evenly between the three fermentors.

The fermentors used for this particular xBmt were placed in separate fermentation chambers, one set to 60°F/16°C and the other 82°F/27°C. I noticed the warm ferment batch had begun to show airlock activity within a couple hours. At 24 hours in, the warm ferment batch was going crazy with rapid fire bubbles in the airlock, while the cool ferment batch was moving along with demonstrably less vigor. By 2 days post-pitch, the airlock activity on the warm ferment batch had halted. I waited another day before checking the SG and discovered it had attenuated to the expected FG. To keep things equal, that beer was left waiting for its cooler counterpart to catch up. After a week, I slowly began bringing the cool ferment beer up to 68°F/20°C, this took 3 days. Airlock activity being absent, I took a hydrometer measurement. Sure enough, both beers had fermented to the same expected FG.

A couple days later, I cold crashed overnight then pressure transferred both to serving kegs.

It was at this point I realized I’d forgotten to fine with gelatin, which proved to be the perfect opportunity to test out another unnecessary and ridiculous creation of mine– the gelatin injector!

While both beers maintained a slight degree of haze when it came time to have them evaluated two weeks later, I observed the cool fermented batch to be noticeably clearer.

| RESULTS |

A total of 21 Strand Brewers Club members participated in this xBmt, each blindly served 1 sample of the beer fermented cool and and 2 samples of the warm fermented beer in opaque cups then asked to identify the one that was different. To reach statistical significance with this sample size, 12 accurate selections (p<0.05) would be required, and exactly that many were capable of doing so (p=0.021), suggesting participants were able to reliably distinguish between a beer fermented with 34/70 at 60°F/16°C from one fermented at 82°F/27°C. Finally.

When those who were correct on the triangle test were asked which beer they preferred, 7 selected the warm ferment sample, 2 chose the cool ferment beer, 2 felt there was a difference but had no preference, and 1 thought there was no difference.

My Impressions: When I first sampled these beers, I was taken aback by just how similar I experienced them to be. I fully expected 82°F/27°C to have been far too warm of a fermentation temperature to make an acceptable lager, but after my initial taste, I was honestly unsure if I would be able to pass a triangle test. However, after noticing a distinct sulfur aroma, I was consistently able to pick out the unique sample in multiple blind triangle tests. It was actually quite easy, as the aroma gave it away every time.

| DISCUSSION |

The results of this xBmt suggest there may indeed by an upper limit to the temperature at which Saflager W-34/70 can be fermented without producing noticeable characteristics, as tasters were capable of distinguishing a Munich Helles fermented at 82°F/28°C from one fermented at 60°F/16°C. Not that this comes as a huge surprise, the packaging does recommend a max temperature of 71.6F/22°C after all, but I have to admit these results feel somewhat validating, particularly given the findings of the last few xBmts evaluating the same variable.

I can understand how some might view these results as largely meaningless since the chances anyone would intentionally ferment a beer, particularly a lager style, as warm as 82°F/28°C are slim. And while I also understand how easy it might be for those who didn’t sample these beers to assume they would have been among those who were accurate on the triangle test, I’ve got to say, the difference between the batches wasn’t nearly as vast I expected. Outside of exBEERimentation, I won’t be fermenting warm like this anymore, though for me, these results add more support to the idea that at least some lager yeasts may not be as sensitive to warmer fermentation temperatures as we’ve been taught.

Please feel free to share your thoughts on this xBmt in the comments section below!

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