Welcome to the first entry in what I hope to be a continuing series of empirical investigations into a variety of yeast strains commonly used in homebrewing, which I call The Yeast Bank. The goal of this series is to help my fellow homebrewers with a visual guide of how various strains look and act during their different stages. These aren’t reviews of the strains, per se, just an examination of their characteristics.
For no reason other than this yeast happens to be what I had on-hand when I thought of the idea, the first entry into this series is White Lab’s WLP540 Abbey IV Ale Yeast. This is actually my first foray into Belgian style beers (as long as you you don’t count Saison), so I’m curious to see how this yeast behaves as compared to the English and German strains that I typically use. I picked up the vial from Home Brew Mart and was pleased to discover it was only a few weeks old, so I’m confident that this vial of WLP540 will be representative of the strain. Belgian yeasts are renowned for their unique esters and phenols, but is their fermentation character equally unique as well? Let’s find out!
Via White Labs.
An authentic Trappist style yeast. Use for Belgian style ales, dubbels, tripples, and specialty beers. Fruit character is medium, in between WLP500 (high) and WLP530 (low).
Note: This strain benefits from extra oxygenation.
Optimum Ferm Temp: 66-72°F
Alcohol Tolerance: High
Starter: 1.5L ~1.037 OG
Est. cell count after harvesting: ~200 billion
Est. pitching rate: 0.81M cells / mL / °P
Destined for: Belgo Session IPA
Beer OG: 1.045
Beer FG: 1.010
Apparent Attenuation: 77%
Time to FG: Two(!) days.
Even though WLP540 is classified as medium flocculation, the yeast in the vial clumped to the bottom like many highly flocculant yeasts I’ve used. After the vial warmed up out of the fridge and I shook it out of its “wad” the yeast had a chunky, gravelly texture to it.
I left for the evening shortly after pitching the vial into the starter, so I wasn’t able to keep a close eye on it for the first few hours. However, roughly four hours later after I returned there was already a decent foamy cap of CO2. I typically use FermCap S on my starters, so I usually don’t get a krausen, but I could tell plenty of activity was going on.
The following morning the starter had taken on the cloudy, milky appearance of a well-growing yeast. I’d say the apperance is halfway between what I was expecting for a medium floc’ing yeast and the “egg drop soup” apperance of highly flocculant yeast. I took a sniff of the starter and I can only describe it as “really yeasty:” no sulphur, nothing funky or fruity, just the smell of yeast.
To get this party started I chilled the 1.045 OG wort down to 64ºF, blasted it with pure O2 for 90 seconds, then pitched my decanted starter into the wort. I usually like to pitch two or three degrees cooler than my target temp and let it free rise up over the next few hours, in this case to 66ºF. The following morning I did something I don’t usually do for beers this “small:” roughly 12 hours after pitching I blasted the beer again with 30 seconds of pure O2. If the experts are going to say this yeast loves oxygen, then by golly I was going to let it have some!
By the time I went to bed, ~6 hours after pitching, the top of the beer was a little bit hazy, but there otherwise wasn’t any external signs of fermentation. The next morning, however, the yeast was active and vigorous with about a half an inch of krausen on top. No doubt the krausen would be larger typically, but I used more FermCap since no one seems to have mentioned if this strain was especially vigorous or not (it doesn’t seem especially so). The wort was really cloudy and active, but no large flocs were present. ~24 hours after pitching the beer was at high krausen and the yeast was going full blast. As you can see in the images and video below large flocs were being thrown about and fermentation was very vigorous.
~48 hours after pitching a curious thing happened: almost all apparent activity had ceased and the beer had almost cleared. The haze was gone and a good portion of the yeast had flocculated. If I hadn’t been paying close attention I would’ve thought fermentation had never even started. WLP540 has all the properties this far of the highly flocculant English strains I’ve used in the past. I certainly wasn’t expecting that!
Chatter on homebrew forums as well as White Lab’s own page discuss WLP540 taking forrrrrrever to attenuate or finishing at a really high gravity compared to what was expected. Before I took a gravity reading I was really sweating it that only two days after pitching fermentation had mostly slowed to a crawl, but lo and behold I was sitting at my target gravity of 1.010; it seems rumors of WLP540 being finicky are unfounded when handled with proper care. My hunch is that the note at the top of White Lab’s page, “this strain benefits from extra oxygenation,” is the key to getting this strain to behave like you expect: juice this baby with as much pure O2 as you can handle.
What you can expect from this strain: despite indications to the contrary, this strain behaves a lot like a highly flocculant yeast, but without the huge krausen you might expect from crop-friendly English strains. Though I’d treat it much the same as an English strain: pitch cool and continuously raise the temp to ensure full attenuation and cleanup.