Author: Marshall Schott
Brewer: Jake Freshour
To the delight of many, present company definitely included, lager beer appears to be gaining popularity among craft beer drinkers. The recent release of deliciously plain pale lager offerings from the likes of Firestone-Walker and Founders Brewing is evidence of this growing interest in a style with deep historical roots.
Noted as being the oldest independent brewery in Munich, Augustiner Brewery has been crafting deliciously crisp and quaffable lager beer since 1328. Those who have had the pleasure of drinking an Augustiner beer, especially their Helles or Pils, are likely familiar with the way the malt presents itself so beautifully, a characteristic many attribute to the particular strain of yeast they use. As a S. pastorianus variant, the Augustiner yeast performs well at cooler temperatures with manufacturers recommending to ferment with it between 50°F/10°C to 60°F/16°C, as anything warmer will lead to stylistically inappropriate ester development.
One such manufacturer is Imperial Yeast whose L17 Harvest is purportedly sourced from the Augustiner Brewery. After hearing good things about this yeast from others, most of whom used it as directed, I experienced the blasphemous urge to ferment with it a bit warmer. I fermented a couple non-comparative batches with L17 at ale temperatures and was quite pleased with the results, but that could easily be chalked up to my shitty palate, so we put it to the test!
| PURPOSE |
To evaluate the differences between beers fermented with a single pack of Imperial Yeast L17 Harvest at either 50°F/10°C or 66°F/19°C.
| METHODS |
When planning out the beers we wanted to serve at Homebrew Con 2018, a lager fermentation temperature xBmt was high on my list, and seeing as we had yet to test L17 Harvest, it was an easy choice. Huge thanks to Oregon homebrewer, Jake Freshour, who went through the trouble of brewing these beers for us to serve!
Nincompoop
Recipe Details
| Batch Size | Boil Time | IBU | SRM | Est. OG | Est. FG | ABV |
|---|---|---|---|---|---|---|
| 5.5 gal | 60 min | 37.8 IBUs | 3.9 SRM | 1.050 | 1.011 | 5.2 % |
| Actuals | 1.05 | 1.008 | 5.5 % | |||
Fermentables
| Name | Amount | % |
|---|---|---|
| Pelton (Mecca Grade) | 9.75 lbs | 95.12 |
| Metolius (Mecca Grade) | 8 oz | 4.88 |
Hops
| Name | Amount | Time | Use | Form | Alpha % |
|---|---|---|---|---|---|
| Magnum | 14 g | 60 min | First Wort | Pellet | 14.6 |
| Hallertauer Mittelfrueh | 14 g | 15 min | Boil | Pellet | 3.7 |
| Tettnanger | 14 g | 15 min | Boil | Pellet | 3.5 |
| Hallertauer Mittelfrueh | 14 g | 5 min | Boil | Pellet | 3.7 |
| Tettnanger | 14 g | 5 min | Boil | Pellet | 3.5 |
Yeast
| Name | Lab | Attenuation | Temperature |
|---|---|---|---|
| Harvest (L17) | Imperial | 72% | 50°F - 60°F |
Notes
| Water Profile: Ca 59 | Mg 8 | Na 0 | SO4 89 | 63 |
Download
| Download this recipe's BeerXML file |
Jake threw together a single large starter of Imperial Yeast L17 Harvest a couple days ahead of time that would later be split between 2 fermentors.
The night before brewing, Jake prepared by collecting and adjusting the full volume of brewing liquor then weighing out and milling the grain.
He then measured out the hops he’d be using.
Having set his heat stick on a timer, Jake was greeted by heated strike water when he started his brew day.
After mashing in with the full volume of liquor, Jake checked to ensure he hit the target mash temperature.
He then let the mash rest for 60 minutes.
At the end of the mash, Jake collected the pre-boil volume of wort in his kettle then boiled it for 60 minutes with hops added as stated in the recipe.
With the boil completed, Jake quickly chilled the wort with his immersion chiller.
A hydrometer measurement at this point revealed the wort was at the expected OG.
Equal amounts of wort were racked to identical fermentors.
The fermentors were placed in separate chambers, one controlled to 66˚F/19˚C and the other controlled to 50˚F/10˚C. After a few hours, both worts had reached their respective fermentation temperatures, at which point Jake pitched the yeast.
At 12 hours in, the warm fermented batch was visibly more active than the cool ferment beer.
A similar observation was made at 24 hours post-pitch.
The cool ferment batch developed a hearty kräusen around 36 hours post-pitch while the warm ferment beer was starting to die down a bit.
With both beers showing signs of halted fermentation activity after 3 weeks, Jake took hydrometer measurements showing they’d reached the same FG
The beers were kegged at their respective fermentation temperatures.
The filled kegs were allowed to lager in Jake’s cool keezer overnight before he fined with gelatin. About 3 weeks later, he pressure transferred the carbonated and clear beers to sanitized serving kegs that would be brought to Homebrew Con 2018. Unfortunately, in our conference haze, we forgot to get a picture of the finished beers, but we did snag a shot of Jake serving them behind the bar!
| RESULTS |
A total of 47 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the beer fermented cool and 1 sample of the beer fermented warm in different colored opaque cups then asked to identify the unique sample. At this sample size, 21 tasters (p<0.05) would have had to identify the unique sample in order to reach statistical significance, though 25 (p=0.004) made the accurate selection, indicating participants in this xBmt could reliably distinguish a pale lager fermented with Imperial Yeast L17 Harvest at 50°F/10°C from the same beer fermented at 66°F/19°C.
The 25 participants who made the accurate selection on the triangle test were instructed to complete a brief preference survey comparing only the beers that were different. A total of 14 tasters reported preferring the beer fermented warm, 8 said they liked the cool fermented beer more, and 3 people had no preference despite noticing a difference.
My Impressions: I attempted this triangle test 4 times while it was being served at Homebrew Con, the first two served to me by fellow crew members I got wrong, though I did pick the odd-beer-out on my following 2 attempts. Truthfully, I mostly resorted to guessing. Even knowing the variable and intensely focusing on ester presence, I thought the beers were far more similar than different.
Jake’s Impressions: As a huge fan of the crisp yet delicate nuances of a proper German Pilsner, I really anticipated the results of this xBmt with the L17 Harvest strain fermented 16°F/9˚C apart. I’ve also spent the majority of 2018 making multiple styles of traditionally fermented lagers. Upon tasting the beers individually, I noticed the cool fermented batch seemed to have a crisper and slightly more bitter finish that lingered just a touch. The warm fermented version tasted very similar upfront but finished with a slightly creamier and smoother mouthfeel with less overall perceived bitterness. In non-blind comparisons, I actually preferred the warm fermented version. I didn’t serve myself a proper triangle test at home, but when I did take the triangle test at Homebrew Con, I resorted to guessing… incorrectly. A humbling moment indeed. I don’t know that I would’ve been successful on subsequent attempts because the variances were so subtle, even with knowledge of the variable. I did not pick up any off-flavors in either, and the only differences I noticed were really in the hop finish and nothing major in the malt profile, aroma, etc. I am going to enter a few bottles of the warm fermented batch in a local competition next month to see how it fares. I am also going to make a few of my more recent award-winning lager recipes fermented warm with L13 Global and L17 Harvest to experiment a bit more. The part that excites me the most about these results and others previously isn’t trying to disprove someone/something, but rather opening up the ability to make lagers (at least with some tolerant yeast strains) at home fermented just like you would most ales and not be so intimidating to the beginner/novice homebrewer who thinks they need to buy a bunch of extra equipment to make their first lager.
| DISCUSSION |
As a traditional S. pastorianus lager strain that purportedly comes from the Augustiner Brewery, Imperial Yeast L17 Harvest and its counterparts from other labs is recommended to be fermented on the cooler end of the spectrum to ensure a clean fermentation profile. While other strains seem to be more robust than expected, blind tasters in this xBmt were indeed capable or reliably telling apart a German Pilsner fermented with L17 Harvest at 66˚F/19˚C from the same beer fermented at a more traditional 50˚F/10˚C.
On the surface, these results might seem obvious– tasters were able to distinguish beers because the one fermented warm clearly possessed more esters than the one fermented cool. Oddly enough, that wasn’t the consensus among those who were correct on the triangle test, and neither Jake nor I picked out any out-of-style fruitiness. I asked a few correct participants to describe what they perceived as being different and there was little in the way of consistency. A couple people noted the warm ferment sample having a slightly thinner mouthfeel, one person thought the cool fermented Pilsner had a little more sulfur on the nose, and a few responded honestly with, “They’re just a little different.”
Indeed, these findings suggest that fermenting warm with Imperial Yeast L17 Harvest may very well produce a beer that’s different than one fermented at a cooler temperature, but it says little about the impact on quality fermentation temperature has. In fact, a majority of correct tasters reported preferring the warm fermented sample, and given my personal experience fermenting warm with this particular strain, I certainly have no plans of stopping now!
If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!
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21 thoughts on “exBEERiment | Fermentation Temperature: Imperial Yeast L17 Harvest In A German Pils”
Another great exbeeriment as always! These ones have made me seriously consider trying a lager even with pretty shoddy temperature control. Small thing I noticed while reading over it is you forgot the “Cl” in your water profile although I’m assuming it’s the 63. Brew on!
I see an oxygen tank in one of the photos but didn’t see it mentioned in the write up. Did these batches also recieve pure O2 as part of their treatment?
Yes, both received approx. 45 seconds of O2
Interesting experiment…
I thought, and have always considered Pils and Helles to be similar but different beer styles. Seems like you are saying they are the same.
While I do like your experiments a lot, it’s not uncommon for the discussions to try and justify what you thought going in. This is an example of really strong significance, likely one of the strongest in the history of the site. Yet the discussion is partially about dismissing the result.
(quoting the article) “Indeed, these findings suggest that fermenting warm with Imperial Yeast L17 Harvest may very well produce a beer that’s different than one fermented at a cooler temperature, but it says little about the impact on quality fermentation temperature has.”
The point of experimentation is not subjective commentary about whether things are “good” or “bad”, just that they either “are” or “are not” significantly different. I’ve been brewing for 25+ years and I don’t recall anyone saying you can’t make a delicious beer fermenting a lager yeast at ale temperatures. They may have said that doing so makes it not a lager (somewhat true) or would give it different characteristics (which you’ve proven). What this experiment shows is that there are qualitative differences between the two. Preference is always personal.
I’m intrigued by your results with fermentation temperature using lager yeasts and it may indeed be strain dependent. What I think it suggests is that certain lager strains may, in fact, not be lager strains at all or that some ale strains might turn out to be more lager-ish. White Labs is genotyping many of its strains to get some more detail and I think we’ll figure out a lot of the strains are similar.
“This is an example of really strong significance”. No, it isn’t. The statistical significance may be strong, but that says very little. The interesting result here is that only slightly above 50 % could identify the unique beer, which really isn’t much. I have brew for 10 years and I have often run into claims (or myths rather) that fermenting S. pastorianus at higher temperature will get you a beer ripe with off flavours.
Further, almost all scientific papers have a discussion section where the authors present a more personal opinion of the results. Even though it is not the most central part of the paper, it is usually very interesting.
A p-value of 0.004 is, by definition of the experimental design, significant. We don’t get to choose what is or isn’t in science. The comment was a non-sequiter–the experiment wasn’t “can you make a good beer using lager yeasts at ale temperatures” it was “are these different?”…and they are. Part of what I enjoy about Brulosophy is the willingness to challenge long-held assumptions. I just don’t want them replaced with new assumptions that in time will be considered long-held. 🙂
A low p-value says that the result was *statistically* significant, which is not the same as significicant. I strongly recommend you to do some reading about null hypothesis testing and p-values, and its shortcomings. In particular you could google “sizeless science”.
The discussion was relevant in pointing out that the percieved difference was never described as fruity or estery, something which is claimed to be one of the main effect.
I had the Founder’s Solid Gold and thought it wasn’t very good–wasn’t a beer that made me want another. Kind of blah.
It would be important to test out chilling temperature and ferment temperature at the same time. As I understand the precursors for Diacetyl, VDK, are limited if the pitching and ferment temperature is below 48F. Why not split a batch into four fermenters? Two chilled to 44 and two chilled to 66F. Then ferment one each at 48 and one at 66F. No diacetyl rests. Also the OG looks more like 1.052 and FG 1.009. I would recommend a finishing hydrometer. Mis-read gravities seem to be a common error in these exbeeriments. Unless it is the picture angle the bottom of the meniscus is not being read. lastly why did more participants prefer the warm ferment temp versus the cold?
This was a very interesting experiment to taste, I had a very hard time picking one that was different. On aroma alone I was sure I had the odd one out but after sipping over and over I kept second guessing myself. My buddy that was tasting next to me mentioned that he was precivibg a temperature difference on one but I couldn’t see it.
Thanks for all your work, it is extremely helpful to set brewing anxiety at ease and relax, don’t worry…
I tend to agree with Marc that the effect of fermentation temp may be strain dependant. I think the traditional distinction between lager yeast and ale yeast is simplistic and there may well be a few surprises if the results of genetic strain tests are made public at some point.
I wouldn’t read too much into the preference results. For instance, in this case, perhaps most tasters prefer ale to lager, so ale-like characteristics in the warm fermented beer are preferred. Just supposition of course, but the important point is that the p test matters more than the preference survey.
I am continually intrigued by these results. The preference data in this case is particularly interesting. I understand the reluctance to ascribe much meaning to the preference data (especially, as Ben pointed out, since the tasters don’t know what style they’re tasting). Still, if we were asked beforehand to place $100 bets on how the significance and preference data associated with this XBMT would turn out, I don’t think many of us would have come out with more money in our pockets 🙂
So, we’ve seen at least a couple of these high temp experiments with at least as many lager yeasts. I wonder how confident we can be that this blasphemy applies to ALL lager yeasts?
Have you considered revealing the intended style to those who guess correctly and asking them which beer better represents the style? To me, that is more relevant data than just asking which beer is preferred.
Great timing for this one! I just brewed for the first time (~80 batches now over the years) with a lager yeast- this one! Bit in the middle here, pitch at 58, free rise to ferment at 62. My point is all these batches I’ve brewed, and never a lager as I wasn’t willing to go the traditional lager route. And you guys now convinced me with all these lager exbeeriments to go for it. Thanks to all at Brulosophy for that!
I doing a similar ferment on my first lager, a dry-hopped Pilsner using Harvest. But I’m also adding pressure. How did yours at those temps with L17 come out?
Very cool
I’m only want to know if you make a diasetyl rest the cool fermenting(12-14) ℃
Keep working
Thank you
Yes, a D-rest was done on the cool ferment
Interesting results. I have been using WLP 860 (which is supposed to be same stain as L17) as my main lager yeast for more than two years now. In my experience, the quality of the results were directly in line with temperatures – the colder the better. Summertime brewing at ambient cellar temperatures gave me unpleasant results, which I would not call “fruity” in a banana/pineapple/peach sense but ascribe to acetaldehyde.
One difference between my brewing and Brülosophy’s experiments is aeration: I always see pure O2 being used, where I’m using ambient air. Maybe the combination of low O2 and warm temperatures are what contributed to my off-flavours? I’m just wondering, there’s lots of anecdotal evidence from home brewers getting poor results at the wrong temperatures, but your experiments haven’t been able to replicate those.
Maybe it is not a single factor that causes this, but a combination of practices that a typical beginning home brewer would have? Typically, a beginner would not have pure O2, no temperature controlled fermentation (warm or cold), use bottles instead of kegs, not make a starter and chill in an ice bath. I’d find it interesting to see an A/B comparison of a recipe brewed the “just got the basic brewing kit”-way and using your standard process.
I don’t see why you’re pitching the same quantity of yeast in both batches. You actually need at least twice as much when fermenting at 10 C as at 19 C. But of course that’s one of those pieces of common wisdom that you might challenge in an exbeeriment :).
There’s something odd here. You should compare the best possible versions of these two beers in order to get interesting results – but then you you can’t have them differ only in fermentation temp. So in a way this is an impossible exbeeriment.