Author: Marshall Schott

Fermentation temperature interests me. For years, I was guided by the idea that cooler fermentations decreased the risk of off-flavor production and ultimately produced better beer. While the first ferm temp xBm using a hybrid strain seemed to discredit this idea, the second trial using an English ale yeast offered some confirmation. As a lover of lager beer, I was naturally curious how different a beer pitched with a traditional lager strain might taste when fermented at a temperature far outside the manufacturer’s recommendation. Naturally and with only slight trepidation, I designed an xBmt I felt would certainly would produce interesting results.

| PURPOSE |

To investigate the qualitative differences of 2 beers made from the same wort, pitched with the same amount of the same yeast, and fermented at temperatures 16°F apart from each other.

| METHOD |

I chose to brew a Bohemian Pilsner for this xBmt not only because it’s a delicious style, but I participate in a quarterly local competition and this was the prescribed style due at the time.

Bohemian Pilsner Recipe

Batch Size Boil Time IBU SRM OG FG ABV 11 gal 60 min 38.8 3.3 1.049 1.008 5.4 %

Fermentables

Name Amount % Belgian Pils Malt 17 lbs 92% CaraPils 1.5 lbs 8%

Hops

Name Amt/IBU Time Use Form Alpha % Magnum ~28 IBU 60 min Boil Pellet 12.2% Czech Saaz 60 g/7 IBU 30 min Boil Pellet 3% Czech Saaz 60 g/2.7 IBU 10 min Boil Pellet 3% Czech Saaz 60 g/1.1 IBU Flameout Boil Pellet 3%

Yeast

Name Lab Attenuation Ferm Temp WLP800 Pilsner Lager Yeast White Labs 84% 50°F & 66°F

I picked up a fresh vial of WLP800 Pilsner Lager Yeast and threw it into a large starter a few days ahead of time, which I would later split evenly between each batch.

The night prior to brew day, I milled the grains and collected all my water.

It’s always good to have a willing deckhand around.

The next morning, I awoke to Minus The Bear’s Listing, hit the flame on my strike water, started a pot of coffee, and was mashed in before 5AM.

Utilizing Martin Brungard’s fantastic Bru’n Water spreadsheet, I was able to reach my target pH of 5.3 using gypsum, calcium chloride, and a touch of lactic acid.

After a 1 hour mash, I collected the sweet wort, nearly filling my 15 gallon kettle, using FermCap-S to avoid one of the most annoying of brew day incidences– the boilover.

You’d probably never guess, but I question the necessity of boiling wort longer than 60 minutes, even when it’s made from mostly Pils malt (xBmt planned). After an hour of boiling, I chilled the entire volume of wort to 65°F (18°F) with my Hydra IC, racked equal amounts to separate 6 gallon PET carboys, then placed each in a different fermentation chamber, one set to 66°F (19°C) and the other set to 50°F (10°C). I had to wait 6 hours for the cool fermentation batch to chill completely before pitching the yeast into each batch.

At 6 hours post-pitch, the cool ferment beer looked predictably unchanged, while the warm ferment beer was starting to show signs of activity in the form of white frothy bubbles.

Indeed, I’m becoming a bigger fan of some dry yeasts lately, though something I appreciate about liquid yeasts propagated in starters is the reduced lag time. Just 24 hours in and both beers were chugging along nicely.

I used a modified version of the quick lager method for these beers, extending the time left at target fermentation temps by about 4 days. I took an initial hydrometer reading 8 days post-pitch and found the SG of the cool ferment beer was much higher than that of the warm ferment batch, which wasn’t unexpected.

At this point, I began gently ramping the temperature of the cool ferment batch. It took approximately 2.5 days for it to reach the same 66°F (19°C) as the warm ferment batch.

Another 4 days and both beers were sitting near the target finishing SG.

I waited another 4 days before confirming the FGs remained the same, after which I cold crashed, fined with gelatin, and kegged.

The beers were clear, carbonated, and, in my opinion, rather tasty by the following weekend.

| RESULTS |

I allowed these beers to sit in my cool keezer to lager for nearly 3 weeks before presenting them to participants, as my plan was to collect data for this xBmt during the 2015 National Homebrewers Conference. When it came time to prepare the beers for travel, I bottled from my tap using the now defunct (sadly) Bowie Bottler into 22 oz bottles and kept them chilled at all times. On the morning of the first day of the NHC, I sent out a message inviting interested folks to meet me in the lobby for some tasting… if you tweet it, they will come.

Later that day, a live tasting was performed for Basic Brewing Radio in my room where another 8 people completed the evaluation.

The next day, I setup tasting stations during the AHA Forum meet-up, which Malcolm helped manage, and another group of great people contributed their palates to the cause.

The response was overwhelmingly positive and the cast of participants was truly incredible. Thank you all so much for your help!

In all, a whopping 39 conference goers participated in this xBmt including certified BJCP judges, provisional judges, experienced craft beer drinkers, and homebrewers. Each participant was blindly presented 3 samples, 2 from the warm ferment batch and 1 from the cool ferment batch, then asked to select the one they experienced as being different. While 19 (p<0.05) accurate responses would be required to achieve statistical significance, only 13 tasters accurately selected the cool ferment beer as being different. These results suggest any impact a 66°F fermentation temperature had on the beer was difficult to distinguish for a rather hefty majority of participants.

Since I started doing these xBmts, more than a few people have suggested we might see more significant results if the participant pool consisted of only “trained tasters,” opining a panel of certified BJCP judges might produce more valid data. I typically respond that we’re not interested in what only trained tasters perceive, though even if we were, it would be logistically very difficult to get a large enough sample size to produce any meaningful information. Unless, of course, data is collected at an event chock-full of these masterful palates. For no other reason than to satiate curiosity, I decided to parse out the responses of the 19 certified BJCP judges who participated in the xBmt, a sample size similar to what we are usually able to achieve. In order to reach statistical significance, 11 judges (p<0.05) would have had to select the different beer. Only 7 were capable of doing so.



Just like with the non-judge tasters, the responses of the certified BJCP judges were consistent with chance. Certified BJCP judges were correct 36.8% of the time while non-judges were correct 30% of the time, a difference that may seem significant, but statistically it’s not. To me, this seems to suggest a similar capacity to distinguish differences regardless of whether one is a judge or not. But who am I to say?

Since significance was not reached in this xBmt, the comparative data from even the 13 correct participants is moot, so please take the following information with a gigantic grain of salt.

In regards to the aroma, flavor, and mouthfeel characteristics of the beers, opinions regarding similarity were hugely inconsistent, with most tasters endorsing each sample as being somewhat similar to the other. While an insignificant majority or those who were correct on the triangle test reported preferring the aroma of the cool ferment beer, preference for flavor and mouthfeel were evenly split. Overall, 9 of the 13 participants who were accurate on the triangle test endorsed the cool ferment beer as being the most preferred. The nature of the xBmt was then revealed and participants were asked to select the sample they believed was fermented at a traditional lager temperature– 6 chose the correct beer.

My Impressions: I’m not ashamed to admit I was rooting for the cool ferment beer to not only be noticeably different than the warm ferment batch, but better overall. I began sampling the beers a couple days after kegging and was utterly floored at how similar they were. Even with full awareness of the nature of the xBmt and knowing which beers were in the glasses, I could barely determine any differences. I didn’t even have to pretend to suspend bias, they were that fucking close.

| DISCUSSION |

This one got me, it got me real good. Of 3 fermentation temperature xBmts, the 1 furthest from statistical significance not only used a traditional lager strain but had the largest temperature differential (16°F/9°C). If you had told me last month that a Bohemian Pilsner could be fermented with a lager strain at 66°F and come out tasting at least nearly identical to a more conventionally fermented version, I would have arrogantly laughed in your face, accused you of being an annoying ass, then questioned the reason for your website… I mean… anyway, I wouldn’t have believed you. I’m primarily a lager beer brewer, I’ve read more about the methods and techniques for making lagers than pretty much anything else, and there’s no way a good Pils could be produced fermented at ale temps. Uh-uh!

Yet here I sit today, data in front me be, jaw slightly agape. What the hell are we to make of this? Should I start fermenting all of my traditional lager beers at ale temps? I don’t think so. After all, as we rarely fail to point out, this is but a single point of data involving a beer produced under relatively well controlled conditions using a particular list of ingredients. It’s totally possible a different strain used in a different wort would produce more noticeable differences.

I’ve never claimed to be an expert on anything, I’m just annoyingly curious and like to test shit out. While I’ve no good answer for why these beers were so similar, I couldn’t help but ponder some potential explanations. I’ve heard/read higher pitch rates tend to suppress ester and phenol production thereby producing a cleaner beer; maybe the lager pitch rate for the warm ferment batch had something to do with its clean character. Another idea has to do with a concept I think about often, that commercial brewing practices don’t always apply to homebrewing. As homebrewers, we ferment relatively small volumes of beer under significantly less pressure than the pros, it’s possible these conditions simply require less attention to temperature. Then again, this goes against information I recently read about some commercial breweries turning around huge batches of lager in 10 days when fermented under 1-2 bars of pressure (14-30 psi).

I’m not ready to recommend people start fermenting their traditional lager beers any warmer than they currently do… unless you’ve an experimental bent and don’t mind risking a lost batch, then be my guest! While I certainly don’t plan to adopt this approach (yet), I look forward to continuing this exploration of fermentation temperature using different lager and ale strains.

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