exBEERiment | Yeast Comparison: WLP940 Mexican Lager Yeast vs. WLP838 Southern German Lager Yeast In A Vienna Lager

Author: Marshall Schott

A couple months back, owner/brewer of House of Pendragon Brewing Co., Tommy, asked if I might consider whipping up a test batch using WLP838 Southern German Lager Yeast, as he was preparing to make numerous lager beers in time for Oktoberfest. I phoned the local homebrew shop and was informed they’d have to special order a vial and that it’d be on the truck a couple days later. It wasn’t. I waited another week, spent some time researching this strain, and discovered folks were generally very pleased with it, particularly the fact it seemed to drop clear a bit quicker than other traditional lager strains. The yeast was finally available by the middle of the following week, at which point I’d decided to split a batch of Helles wort and pitch another yeast I’d yet to use into half. I went with WLP940 Mexican Lager Yeast, apparently sourced from Grupo Modelo, as I’d read some very favorable reviews of this strain and have been meaning to try it for awhile.

Once home with my 2 vials, I made a couple starters with a plan to brew 3 days later. Given the larger starter size for lagers, I always crash and decant the spent beer, hence the reason these starters were made so far in advance.

Well, as shitty luck would have it, the starter pitched with “fresh” Southern German Lager yeast was showing absolutely no signs of fermentation activity 36 hours post-pitch. Unfortunately, this is the third time in the past few months a fresh vial of White Labs yeast hasn’t performed as expected, leading me to speculate about their quality control during this time of transition to a new way of packaging. I’m certainly not giving up on White Labs, I’m just hoping things turn around once the new PurePitch is up and running. Thankfully, I had a previously harvested pitch of WLP830 German Lager Yeast sitting in my yeast fridge, it was allowed to warm up for a couple hours before being added to the dead starter.

Signs of activity were visible within hours and things were ripping along nicely by the next morning. Unfortunately, I was forced to move my brew day ahead a couple days due to the yeast issue. The Mexican starter was about finished, but I let it sit out until the German starter finished up, at which point both were thrown into my cold ferm chamber to crash overnight. Brewing commenced the following morning. I batch sparged a 10 gallon batch of my Munich Helles recipe, as I wanted something light in order to emphasize any differences in yeast character.

I’m always pleased with the golden color of the first runnings of this wort, and that smell!

Since German Pils Malt made up the majority of this grist, a 90 minute boil was in order, meaning I collected nearly 3/4 gallon more wort than I do for a 10 gallon batch of ale… meaning my kettle was very full.

Thanks to FermCap-S, I didn’t even consider the possibility of a boilover. My badass Bayou KAB4 burner brought this massive volume of wort to a rolling boil in less than 15 minutes (note: this burner uses the same 10″ banjo as the much more expensive Blichmann burners, if you’re in the market). With 15 minutes left to flameout, I threw my new JaDeD Hydra into the boiling wort to sanitize it.

I’ve yet to be less than amazed with the quality and results I achieve using JaDeD Brewing’s immersion chillers, and this batch was certainly no exception– 11.5 gallons of wort from boiling to 6°F above groundwater temperature in just under 8 minutes. Damn!

For all of my split-batch exBEERiments, ingredient and process alike, I believe it’s fairly important to ensure equality between the batches, thus I usually give the wort a hearty stir prior to racking to each carboy in hopes of equalizing the amount of trub going into the fermentors.

Both carboys were placed in my 46°F fermentation chamber and allowed to finish chilling to my target pitching temp (46°F) overnight. The following morning, I removed the starters from the chamber to decant them.

As you can see, the German starter was considerably more hazy than the Mexican starter. The large cake at the bottom of the flask gave me enough confidence an adequate amount of yeast had fallen out of suspension that decanting wouldn’t be detrimental. The Mexican starter had performed as expected. I pitched.

At 12 hours, the Mexican beer was already developing a krausen while the German batch appeared still.

A full day post-pitch and the Mexican beer was clearly in the lead, though my worries did subside when I noticed some bubbles forming on the edge of the German carboy.

At 36 hours, the Cerveza de Mexicano was doing it’s thing while the German beer looked like a dud. I started wondering if my fermentation temperature of 48°F might be the cause of its sluggish start, but I’d fermented many lagers with WLP830 at that temp in the past, so that theory seemed suspect.

It took a full 4 days for the German beer to develop an even somewhat normal looking krausen.

I let them ride at 48°F another 24 hours before the temperature began automatically ramping up per my quick lager method profile in The Black Box controller.

Interestingly, a creamier kräusen began to form on the German batch once the temperature rose above 51°F, perhaps that was a factor.

I checked the evening before The Black Box was scheduled to start cold crashing, they both showed very little activity and fermentation appeared to be complete.

Hydrometer samples confirmed my target FG was hit for both beers. Ahhhhhh.

At this point, the Mexican half was observably clearer than its German counterpart. Would this carry through to the finished beer? I kegged the beers per my normal routine and let them sit in my keezer to condition and clear up a bit. They were ready for consumption a week later.

| IMPRESSIONS |

I shared both of these beers with friends and asked them to provide feedback without knowing what the difference was. They were only informed that different yeasts were used to ferment each beer after they evaluated the beers.

Appearance
No one disagreed that the batch fermented with Mexican Lager yeast was clearer than the German Lager fermented batch. Besides that, all concurred the color and head retention seemed to be very similar if not totally the same.

Aroma
The beer fermented with the blend of German yeasts was fairly easily identifiable by most tasters as being the more traditional Helles. It had a slightly more noticeable sulfur component when compared side-by-side to the beer fermented with Mexican Lager yeast, which had a decidedly cleaner and crisper aroma. The German beer also seemed to emphasize the breadiness of the Pils malt, while the Mexican Helles was just, well, clean. A couple tasters noted a very subtle apple character in the Mexican half, though not necessarily the green apple you might expect from acetaldehyde. My guess is they were picking up a whisper of the ester ethyl hexanoate.

Flavor
Again, the German beer was selected as being the most Helles-like to most tasters, many of whom have used this yeast in their own homebrewing and were familiar with its characteristics. For the most part, the flavor followed the aroma evaluations. Tasters described the Mexican beer as being crisper with a slight apple-tartness on the back of the palate and neither malt nor hops dominated. The German beer was described by most as being noticeably more malt forward with the hops not playing a significant role at all. In general , the German beer was experienced as having a smoother and fuller flavor profile, while the beer fermented with Mexican Lager yeast came across as almost lacking in any strong malt or hop flavors, with one person saying it “tastes like a what macro beer should be.”

Mouthfeel
The beer fermented with the German yeast was universally experienced as having more body than the Mexican lager, the latter of which people described using words like “light” and “crisp.” While carbonated the exact same way for the same exact amount of time to the same exact predicted volume of CO2, nearly everyone experienced the Mexican beer as being more highly carbonated, something I’m guessing is due to the perceived difference in body.

My Impressions: I recently read a BYO article where a dude compared a bunch of different yeasts blindly, scored each beer fermented with these different yeasts, then presented them in order of preference. Mexican Lager Yeast took the cake with both tasters in that experiment commenting on the clean lager character it imparts (among other things). Their comments seem to corroborate the experience of the tasters in the present comparison. For me, the Mexican Lager Yeast produced an incredibly clean and drinkable beer that was malt-hop balanced and super easy to drink. The German yeast produced something I was much more familiar with, that sort of sharper yeast character I expect from German-style beers with an emphasis on malt over hops. When I ask myself which I prefer more, I have a very hard time selecting one, as both beers possess characteristics I really enjoy. In fact, I found myself going back and forth between each keg in hopes of keeping the levels of each even. Now, one thing I do know is that I would not use the Mexican Lager strain for lighter German-style beers in the future, it really doesn’t seem to impart the character I believe to be so necessary in styles like Helles or Pils. I do believe, though, that the Mexican yeast would make a great Schwarzbier, Vienna Lager, Bock, or any of the American lager styles.

Ultimately, Tommy settled on using WLP830 German Lager Yeast for his beers, an old standby for him, and I’m glad he did. He’s currently serving Munich Helles, Oktoberfest, and Schwarzbier fermented with this yeast and they are truly delectable! If you’re in the Central Valley area, head over to the HoP tasting room for a couple pints, you won’t be disappointed.

If you have any questions, please don’t hesitate to ask. Also, if there’s an ingredient, yeast or otherwise, you’ve been curious about and you’d like to have me test it out, let me know. Cheers!

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