Lager fermentation temperatures

[squirt in the turns]

I've got a Bohemian Pilsner and a Munich Dunkel fermenting with WY2124 (Bohemian Lager) in my brew box (cooled by ethylene glycol pumped from the freezer section of the keg/cold conditioning fridge). I was aiming to ferment at 9 or 10c, but the glycol cooling system is untested at those temps and it turns out it can only manage 12c, with the pump running constantly

According to the Wyeast website, 2124 "is great to use with lagers or Pilsners for fermentations in the 45-55°F (8-12°C) range", so I guess they'll turn out ok. I'm wondering if anyone has any experience with this yeast, and what difference a few degrees in the fermentation temperature will make?

[warra48]

I used this yeast about a year ago for a Pils.
Turned out quite a malty brew, very nice drinking, but was lacking a little in crispness.
I fermented mine with the TempMate set at 9.5ºC.
Don't know what it would be like at 12º. but you should be fine.
I didn't really lager mine long enough, so that probably contributed to the lack of crispness.

In your case, I think your temperature should be OK for the BoPils, just leave it long enough to ferment out. After all, it is within the recommended range.
It will certainly be fine for the Munich Dunkel. The inherent maltiness of the style and the lower IBU will help.

[squirt in the turns]

Thanks Warra. I'm a bit less concerned about the pils, as it started out fermenting in the fridge at 9-10ºC for 10 days, and moved to the brewbox when I needed the fridge space, and only has a few points to go. The dunkel started out in the bre box on Sunday, at 12ºC.

Is the most noticable effect likely to be a slight lack of crispness? Maybe a little more fruitness or diacetyl?

Both beers will definitely get a nice long secondary at 0-1ºC

Warra, I'm curious about your last comment about the dunkel - assuming you mean that the maltiness will overpower (or compliment) any by-products of a slightly warmer ferment? What do you mean regarding the lower IBUs?

[warra48]

BeerSmith gives these descriptions of the 2 beers:

Bohemian Pils:
Crisp, complex and well-rounded yet refreshing. First brewed in 1842, this style was the original clear, light-colored beer. Uses Moravian malted barley and a decoction mash for rich, malt character. Saaz hops and low sulfate, low carbonate water provide a distinctively soft, rounded hop profile. Traditional yeast sometimes can provide a background diacetyl note. Dextrins provide additional body, and diacetyl enhances the perception of a fuller palate. Bitterness from 35 to 45 IBU.

Munich Dunkel:
Characterized by depth and complexity of Munich malt and the accompanying melanoidins. Rich Munich flavors, but not as intense as a bock or as roasted as a schwarzbier. The classic brown lager style of Munich which developed as a darker, malt-accented beer in part because of the moderately carbonate water. While originating in Munich, the style has become very popular throughout Bavaria (especially Franconia). Unfiltered versions from Germany can taste like liquid bread, with a yeasty, earthy richness not found in exported filtered dunkels. Bitterness 18 to 28 IBU.

From that you will see the BoPils is a much crisper clean style, whereas the Munich Dunkel is much more malt driven.
The BoPils is bittered to a higher level, accenting the crispness with the hop bitterness. The Dunkel is less bittered, so as not to override the malt accent of the beer.

I wouldn't worry about the 12ºC fermentation. It will suit the Dunkel, and it's within the recommended range. A slightly higher temperature will allow more rounded malt character to shine through. I'm sure you'll be fine. If you pitched sufficient yeast, and at fermentation temperature, then you shouldn't have a diacetyl issue with your beers. The extended lagering at 0-1ºC will be great for the beers.