Fermentation stalled with Oktoberfest Lager WLP820

[mcgster]

I am brewing my 3rd Oktoberfest lager as i continually try and tweak my recipe and this is the first time i have had an issue with this yeast stalling mid fermentation. This was a killer batch to brew with a double decotation mash and i'm really debating what i should do with this batch. Originally brewed 14 days ago, i pitched 0.75 million cells / ml / plato into my 2.5 gal batch. OG was 1.057 now 14 days later it is stuck at 1.040. The brew was set in my fermentation chamber at 50F.

So now i'm debating raising the temp or pitching another starter of Oktoberfest yeast. Any suggestions would be really appreciated!


Thanks!

 

[mkeckjr]

In my experience with this yeast it is a notoriously slow starter, is prone to finish early/stall, and leaves lots of diacetyl if not treated really really well. Note some of the additional information on White Labs' site about this yeast strain. First, this strain performs terribly in the first generation as far as lag time. White Labs suggests pitching at even higher than normal lager pitch rates (which I think they suggest between 1.5 and 2 million cells / ml/ degree Plato for a standard lager, so your pitch rate is well below that). Second, note the optimal fermentation temperature for this yeast strain on their website (52 F - 58 F). As low as you are, I am not surprised the yeast stalled out. I think 55 F is pretty much the optimal temp for this yeast, so I wouldn't ferment quite as low as you are doing.

As far as "saving this batch", if it were me, I'd honestly do something like make a starter of WLP001, and when it's at high krausen, pitch that. It will ferment clean between 55 F and 60 F, and at least you'll get a beer that's close to the style you're aiming for. The longer you leave a slow moving yeast in that beer with a lot of residual gravity, the higher the probability gets that the beer will come out with off-flavors from other microorganisms that were able proliferate due to your monoculture not doing its job. Just my 2 cents, best of luck.

 

[mcgster]

The previous 2 batches have had sluggish starts as well but by day 14 were all below 1.020. i fermented the last batches around 55F so i thought i'd try dipping below a few degrees as i have a lite lager in the ferm chamber as well. I seeded a starter today of the same yeast so i'll probably wait until that kicks off, i'm not too worried about other microbes competing with the yeast at 50F, even at a sluggish rate the yeast population in there by now would be huge (just calculate the cell count of a 20L starter that went from 1.057 to 1.030). I'll bring the temp up by4F to 54 and seed it with a new starter and see how it turns out. I really hate the thought of pitching a yeast that isn't to style after going to great lengths to pull the double decotation off!