Sunday, February 27, 2011

Diacetyl Precursors and Purging Secondary Carboys

This is actually the 3rd "official" beer in our Cry Havoc yeast series. First we did a Blonde Ale, then a Maibock (more on that later when we get some scoresheets back - good but probably not in style), and then we brewed Charlie Papazian's Contrarian Amber-Golden Lager, which is what this is about.

I had high hopes for this beer, as it was the only recipe we made that's actually designed by Charlie himself to go with this yeast. After fermentation and a diacetyl rest, and slowly brining it down to 40F, it was tasting really good. Bready malt flavors and nicely hoppy. The only thing left was to dry hop it. So, I transferred it to a carboy, and dry hopped away. Then I was like - hmmmm.... shoulda purged that carboy with CO2. Oh well, I don't always purge carboys and never had a problem. The CO2 coming out of the beer usually makes the carboy sorta purge itself. 

So after 10 days or so of dry hopping, I put it in the fridge to crash everything down. Then today before we went to keg it, we pulled a taste and wow, diacetyl - right in the nose and on the tongue. The bready, hoppy goodness was gone. What happened?

Well, after reviewing my process and going through Jamil and Chris' Yeast book, I think I figured it out. There are diacetyl precursors in beer, namely acetolactate, that can produce diacetyl when introduced to oxygen. These precursors must have been present, and when I racked to the non-CO2-purged carboy, they took up the oxygen and whammo - diacetyl. I racked too soon. Next time, I'll perform a simple diacetyl test, which goes a little something like this. Anyhoo - the beer was butter. Yes, homebrew mistakes can happen.

But Can't You Save It?
There are ways to get rid of the dreaded "D". Your best best is to let the beer rise back up to room temp so the that yeast can reabsorb the diacetyl. Diacetyl is actually a natural product of fermentation - the yeast just reabsorb it towards the end. In lagers, that's why you do a diacetyl rest, and maybe even a follow a diacetyl reduction scheme (cold pitching). But since I'd already removed the beer from the yeast, that wouldn't work so well here.

You can also "krausen" the beer, where you pitch some actively fermenting wort back into the beer, with the hope that the active, healthy yeast will reabsorb the diacetyl - but since I'd already dry hopped the beer (used 1oz), I wasn't 100% sure that would work as the hop gunk could get in the way of the yeast. I could have racked *again* but I also know from past experience that if there's too much diacetyl that even krausening won't work, and there was a lot here. So going off my past experience, I made the command decision to dump and move on, causing the entire bathroom to stink of butter. I generally find trying to "fix" D-bomb beers an aggravating, time-wasting experience that never lives up to my expectations. Would rather re-brew.

The good news is that we've made another, final beer with this yeast, a smoke beer, and no diacetyl (just a smokey nose without any slickness on the tongue). And if there is, well, the smoke covers it nicely! I think this is further evidence that the "D" developed in the secondary.

Anyways, if I make this again - I'd just skip the dry hopping or dry hop right in the fermentor - maybe just extending the diacetyl rest into a dry hopping period (any tips on dry-hopping lagers?). It's an interesting recipe, and if you'd like to try it out - here it is:

Recipe: Contrarian Amber-Golden Lager

Wort Volume Before Boil: 8.00 US gals
Wort Volume After Boil: 6.72 US gals
Volume Transferred: 5.50 US gals
Water Added: 0.00 US gals
Volume At Pitching: 5.50 US gals
Final Batch Volume: 5.00 US gals
Expected Pre-Boil Gravity: 1.047 SG
Expected OG: 1.056 SG
Expected FG: 1.016 SG
Expected ABV: 5.1 %
Expected ABW: 4.0 %
Expected IBU (using Tinseth): 56.0
Expected Color: 7.5 SRM
Apparent Attenuation: 68.0 %
Mash Efficiency: 80.0 %
Boil Duration: 90.0 mins
Fermentation Temperature: 52-55 degF

German Pilsner Malt 9lb 14oz (74.9 %) In Mash/Steeped
German Pilsner Malt 8.00 oz (3.8 %) In Mash/Steeped (for boiling - keep reading)
US Flaked Rice 1lb 5oz (10.0 %) In Mash/Steeped (for boiling - keep reading)
US Rice Hulls 8.00 oz (3.8 %) In Mash/Steeped
Canadian Honey Malt (Gambrinus) 4.00 oz (1.9 %) In Mash/Steeped
Belgian Aromatic Malt 4.00 oz (1.9 %) In Mash/Steeped
Belgian Special B 4.00 oz (1.9 %) In Mash/Steeped
German Sauer(Acid) Malt 4.00 oz (1.9 %) In Mash/Steeped

French Strisselspalter (1.8 % alpha) 1.50 oz Loose Pellet Hops used 60 Min From End
US Mount Hood (5.0 % alpha) 1.50 oz Loose Pellet Hops used 60 Min From End
US Liberty (4.5 % alpha) 1.00 oz Loose Pellet Hops used 60 Min From End
US Liberty (4.5 % alpha) 1.00 oz Loose Pellet Hops used 20 Min From End
US Mount Hood (5.0 % alpha) 1.00 oz Loose Pellet Hops used 10 Min From End
French Strisselspalter (1.8 % alpha) 0.50 oz Loose Pellet Hops used Dry-Hopped

Yeast: White Labs WLP862-Cry Havoc, lager-size starter or ready yeast cake

Mash Schedule
Mash Type: Full Mash
Schedule Name: Papazian 132 - 155F
Step: Rest at 132 degF for 30 mins
Step: Raise by infusion to 155 degF for 30 mins

Recipe Notes (from Zymurgy)
OG: 1.056
FG: 1.016
IBU: 55 or so
Color: 14 SRM

Special Instructions
  1. Add 9q (2.75 gal) 140F water to rice husks and crushed malt. (Do NOT add .5lb pils or flaked rice). Stir, stabilize at 132F for 30 minutes.
  2. Meanwhile, add leftover pils and flaked rice to 7 quarts (1.75 gal) cool water and bring to a boil (stir to prevent boil over/scortching). 
  3. After 30 minutes, add the boiling mixture to the mash, adding heat as needed to bring up to 155F and hold for 30 minutes.
  4. Raise/Sparge at 167.
I did this in my 10 gallon cooler, and the mash worked great. 


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