Czech Dark Lager Brewday

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Tuesday's brewday included a number of firsts for me: my first lager and my first time utilising a decoction mash.

Recipe was influenced by the Mad Fermentationist's attempt at recreating the U Fleků beer (http://www.themadfermentationist.com/2015/12/tmave-pivo-czech-dark-lager.html). I've taken into account his recommendations, but swapped out Munich for Vienna so it's a bit lighter in flavour.

Recipe

Estimated Batch Size: 20l (In fermenter)
Estimated OG: 1.055
Estimated FG: 1.018
Estimated ABV: 4.9%
Estimated EBC: 51.9
Estimated IBU: 26.6

3.74kg Weyermann Premiere Pilsner (Ger) - 72.3%
750g Weyermann Vienna (Ger) - 14.5%
340g Weyermann CaraMunich II (Ger) - 6.5%
250g Weyermann Carafa Special II (Ger) - 4.8%
100g BestMälz Acidulated (Ger) - 1.9%

27g Northern Brewer 7.7% AA (Ger) - 60 mins - 24.2 IBU
25g Saaz 4.2%AA (Cze) - 5 mins - 2.4 IBU

2 packets Mangrove Jack's Bohemian Lager Yeast

As usual, I used The Malt Miller 'My Recipe Kits' creator for this, less the acidulated which I decided to use to lower the mash PH. As in The Mad Fermentationist's post, the dark malts are usually added just before sparging to ensure that colour but not too much roastiness is extracted. I hadn't taken this into account when making my recipe kit, but the guys at TMM obviously spotted it as the Carafa was is a separate bag to the main malts. Nice spot guys!

The mash schedule was intended to be a 15 minute protein rest @ 55°C, decoction to raise mash to first saccharification rest of 62°C for 30 mins, then a second decoction to raise mash to second rest of 68°C. The mash out would be done as part of the batch sparge.

In reality I couldn't do the protein rest for just 15 mins as I decided to hold the first decoction at 65°C for 15 minutes for some conversion. All in all the protein rest ended up being ~30 mins, which I've read can be a problem for modern, well-modified malts. We shall see. I used an 11l stockpot as my decoction pot, it has a nice thick base so didn't scorch the decoction.

Second decoction step coming up to boil

14bu6jb.jpg


Following sparging, the pre-boil gravity was 1.046 as predicted, but I had an extra 2l - so decoction does seem to increase efficiency. Unfortunately I'm going to have to tinker around with my Beersmith setting as post-boil I ended up with 19l @ 1.054 as opposed to 20l @ 1.055.

The decoction steps ended up slightly higher than anticipated, with 64°C on the first rest and 69°C on the second rest. I believe this was due to Beersmith taking the Carafa Special II into account for the mash, when it wasn't there.

I rehydrated the yeast and added to the fermenter, which was sealed and put into my keezer at 12°C. The plan is to let it sit here for 14 days, then I'll bring it up to 16°C for a couple of days as a diacetyl rest. I'll then lager this in the keg.

The double decoction went smoothly and I'd recommend anyone interested to give it a try and not be too awed by it.. I tried a step mash on a BIAB weizenbock on Saturday and that was more trouble than the decoction. I'll definitely give decoction another go when I next brew a wheat or German/Czech lager.
 
Fermentation was pretty much done as done in 9 days (down to 1.018), so brought up to 18°c for a diacetyl rest - finished at 1.017 which is fine.

It's now sitting in my keezer at 6°c - will reduce this to 1-2°c tomorrow to lager in the keg for at least 28 days.
 

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