Wednesday, December 30, 2009

WLP925 - finally an evaluation


I finally have a beer tapped up that I fermented with the WLP925 High Pressure Lager Yeast. At least one that's worth drinking anyway. The first lesson I learned with this yeast is that it's seriously non-flocculent, so with the Dunkel that I first brewed to be fermented with this yeast I had to dump the entire four liter starter into it. It doesn't taste all that swell, so I figured I'd wait until this second pitch to pass judgment on the yeast.

The recipe was about 99% Weyermann Pale Ale malt with a dash of Carafoam. Bittering hops only, no flavor or aroma additions. Fermented with the second pitch of the WLP925 yeast at around 64F under about 15psi. OG 1.053, FG 1.012 after just under two weeks. Racked it to secondary for ten days at 35F. Fined with gelatin and racked to serving keg.

The beer is a deep gold with a thick, tight white head. Slight haze. Tough coaxing the aroma out of it. Some grain, some bread crust. Also some light esters of the ethyl hexanoate variety - apple, aniseed. Some alcohol showing even though it's only 5.4%. Malt sweetness with some definite bready notes in the flavor. Esters and alcohol don't show as they did in the nose. Bitterness is moderate. Mouthfeel is creamy in the middle and finishes dry. Carbonation is soft, though definitely high enough to be appropriate to style.

I've got a couple of other batches coming with re-pitches of this yeast, so I'll wait to see how those come out before a final verdict, but here are some early pros and cons:

Pros:
  1. This strain attenuates very nicely, which I think is important for a lager strain.
  2. Capturing carbonation during primary fermentation seems to have really created an interesting mouthfeel. This beer doesn't have that carbonic bite that may or may not happen in some beers that are force carbonated.
  3. Pretty clean lager beer in about three weeks.

Cons:
  1. The yeast doesn't flocculate at all. Even after fining with gelatin it's still a little hazy. Also, I basically wasted the first batch that was pitched with the entire starter since the starter yeast wouldn't flocculate. I think that the next time I would use this yeast I'd just get a few vials and pitch them all instead of making a starter.
  2. The beer isn't completely clean. The slight esters that it created bothered me. I had a problem with my spunding valve during primary fermentation that I corrected with a new pressure relief valve in the most recent batch. We'll see if that corrects it.
  3. This is nitpicking, but I don't think that the yeast performs as quickly as advertised. I think you need at least 10 days in primary to get complete attenuation, another week or so in the secondary and to condition and clarify, then another day to settle in the serving keg. So I'd be hesitant to call it a beer any sooner than two and a half weeks after brew day.
For those in the NYCHG I'll try to bring some samples to the January meeting.

3 comments:

thatguy314 said...

Given that this yeast is used by a number of professionals, but not much on the homebrew level, do you think that many of these breweries might simply be filtering to get the yeast out? Do you filter any of your beers?

Tom E said...

Oh, I'd be certain that any professional brewery using this yeast is filtering it. Unfortunately I don't have a filtration setup so I'm relying on clarifying agents, time, and temperature to get clear beer. Maybe one day down the road I'll invest in some kind of filtration, but it's definitely not a priority.

Thanks for reading!

Oliver said...

Hello,
First, excuse me for my bad English...
I would like to try this yeast but I don't find where I can buy it.
Can you help me?
Thanks

Oliver, Belgium