Author: Matt Del Fiacco

Shock. Disbelief. Head scratching. All adequate descriptions of how I felt about prior xBmts showing participants were unable to distinguish lagers fermented warm from the same beers fermented cool with both WLP800 Pilsner Lager and Saflager W-34/70 yeasts. Conventional wisdom, which I admittedly accepted without question, has it that lagers require cooler fermentation temperatures in order to restrain ester development such that the resultant beer is clean and crisp, yet the results from the aforementioned xBmts suggest any differences caused by rather disparate fermentation temperatures weren’t large enough for tasters to reliably tell them apart.

Indeed, a follow-up xBmt designed to test the extremes by comparing beers fermented with Saflager W-34/70 at either 60˚F/16˚C or 82˚F/28˚C did return significant results, but only by a small margin, and surprisingly, a majority of tasters who got the triangle test correct preferred the warm fermented sample. After xBmt results suggested participants could reliably distinguish a beer fermented with WLP001 California Ale yeast from the same beer fermented with Safale US-05, I wondered if results from the aforementioned fermentation temperature xBmts using Saflager W-34/70 might be specific to that particular strain and not necessarily other versions said to be from the same source. Loaded with skepticism, I designed an xBmt to test out the impact fermentation temperature has on one of my favorite yeasts, Wyeast 2124 Bohemian Lager.



| PURPOSE |

To evaluate the differences between a lager fermented cool (48˚F/9˚C) and the same lager fermented warm (72˚F/22˚C) with Wyeast 2124 Bohemian Lager yeast.

| METHODS |

I wanted to use a recipe I’d brewed many times before and knew well for this xBmt, so I went with a house staple.

Na Zdravi Czech Premium Pale Lager

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 33.2 IBUs 3.9 SRM 1.047 1.011 4.7 % Actuals 1.047 1.013 4.5 % Fermentables Name Amount % Pilsner (Weyermann) 8.75 lbs 92.72 Carafoam (Weyermann) 4 oz 2.65 Carahell (Weyermann) 4 oz 2.65 Melanoidin (Weyermann) 3 oz 1.99 Hops Name Amount Time Use Form Alpha % Saaz 25 g 60 min Boil Pellet 4 Saaz 31 g 30 min Boil Pellet 4 Saaz 62 g 15 min Boil Pellet 4 Saaz 62 g 0 min Boil Pellet 4 Yeast Name Lab Attenuation Temperature Bohemian Lager (2124) Wyeast Labs 71% 48°F - 58°F Notes Water Profile: Yellow Balanced in Bru’n Water Spreadsheet

A few days before brewing, I made a single starter of a Wyeast 2124 Bohemian Lager yeast that I stepped up to ensure enough cells for two 5 gallon batches. At the start of my brew day, I set both eBIAB systems to heat the mash water, which I’d adjusted to my desired profile.

While the water was heating, I weighed out and milled the grains for each batch

When strike temperature was reached, I dropped the grain baskets into either kettle, stirring to fully incorporate, then checked to see if I hit my target mash temperature.

I typically employ a Hochkurz step mash for this beer, so I did raise the temperature to 160˚F/71˚C thirty minutes into the mash.

After another 10 minutes, I bumped the temperature up again for a mash out before removing the grain baskets and letting them drain while the wort was heating to a boil. During the wait, I weighed out my hop additions.

Hops were added as stated in the recipe, each addition followed by the familiar smell of boiling hops– never gets old!

When the 90 minute boils were complete, I chilled each wort with a stainless immersion chiller to 80°F/27°C then ran equal amounts from each batch into separate fermentation kegs, which were placed in separate chambers to finish cooling. Hydrometer measurements confirmed both batches achieved the same OG.

With both beers stabilized at their respective fermentation temperatures of 48˚F/9˚C and 72˚F/22˚C 6 hours later, I decanted the yeast starter then evenly split the remaining yeast between the batches. The cool ferment beer was left alone for 7 days before I gently ramped the temperature to 72˚F/22˚C for a diacetyl rest while the warm ferment batch was controlled to 72˚F/22˚C throughout fermentation.

Both beers were spunded for natural carbonation over the final 3 days of fermentation, after which they were cold crashed to 36˚F/2˚C and left to lager for 1 week.

After transferring the beers to serving kegs, I degassed samples from each and took hydrometer measurements showing both hit a similar FG.

Once adequately carbonated, the beers were put in my keezer with the gas set to serving pressure for a few days before they were ready to serve to participants.

| RESULTS |

A total of 20 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 sample that was unique. While 11 tasters (p<0.05) would have had to correctly identify the unique sample in order to reach statistical significance, only 8 (p=0.34) picked the odd-beer-out, indicating participants in this xBmt were not able to reliably distinguish a lager fermented at 48˚F/9˚C from the same lager fermented at 72˚F/22˚C using Wyeast 2124 Bohemian Lager yeast.

For fun, I figured I’d share the preference data of the 8 tasters who got the triangle test correct, even though it means nothing. In all, 3 people said they preferred the cool ferment lager, 4 liked the warm ferment beer more, and 1 person noted having no preference despite noticing a difference.

My Impressions: I attempted 4 triangle tests with these beers and selected the unique sample only twice. While my palate can certainly be called into question, I honestly could not tell the beers apart, despite my confidence going into these tests that I’d be able to easily distinguish a difference. I fully expected the cool ferment beer to be more crisp than the warm ferment batch based on what I believed to be true about lager fermentation, but that wasn’t the case at all. The warm ferment batch, which was fermented far warmer than I’d ever intentionally ferment anything other than maybe a Saison, was equally as clean, crisp, and flavorful as its cool ferment counterpart, which was surprising as hell.

| DISCUSSION |

We’ve been taught that fermentation temperature is one of the most important factors when it comes to making good beer, particularly lager styles, which purportedly require cool temperatures to keep undesirable esters and other off-flavors at bay. I can’t really say how I’d feel about the results of this xBmt showing tasters were unable to reliably distinguish a lager fermented cool from one fermented warm if someone else had performed it, but after sampling these beers myself both side-by-side and in semi-blind triangles, I find myself questioning my preconceived convictions. The beers tasted exactly the same to me despite being fermented 24°F/13°C apart from each other, and having brewed the, I knew what to look for.

When viewed together with other surprising fermentation xBmt results, these findings suggest to me brewers who love lager styles may not have to avoid making them due to fermentation temperature limitations. As we say often, a single xBmt result does not a principle make, and while 3 non-significant fermentation temperature xBmts using traditional lager strains certainly isn’t conclusive, it’s enough to get me to open my eyes to the idea that maybe the processes we’ve adopted from historical methods isn’t necessarily required. Regardless, I’ll likely continue to ferment most of my lagers cool for the most part, but if I desire a quick turnaround Pilsner or Märzen, I won’t hesitate to ferment it like an ale.

If you have any thoughts about this xBmt, please share them in the comments section below!

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