December 11, 2012

Carburetor -- Stout/Sour Blend

About a year ago I was fortunate enough to sample what I think is one of New Belgium's best beers: Clutch. Clutch is a blend of an imperial stout and the dark sour beer used in other New Belgium sours like La Folie. Clutch is 80% stout, 20% sour. I visited Fort Collins last December and on the New Belgium tour I pestered the tour guide to give me a sample out of the Clutch tap hidden away in the barrel room. It's a delicious blend of flavors. The only time I found it locally in the Dallas/Fort Worth area was on New Years Eve last year at Meddlesome Moth, a gastropub in Dallas owned by the same folks who own the Flying Saucer chain.

Building the Concept

Ever since I tasted those delicious beers I set out to create a beer of my own in the same idea of blending sour and stout. Rather than brew a big 9% version like Clutch I decided I would take it to a more sessionable place, so I opted for a lighter 5.5% Belgian stout and an intensely dark sour beer. The biggest contributor to the decision to create an easier drinking version was at the time I started working on the plan, about a year ago, most of the homebrew in the house was high ABV and I wanted to work on more beers in the 5% and lower range. I wanted something that had the traditional stout flavors with the complex sour flavors and just a hint of Belgian yeast character.

Carburetor...makes you thirsty?
New Belgium named Clutch after a Maryland band and although they are very big into biking I thought if you're going to make a Texan version of the beer you have to look around at our community full of big pick up trucks guzzling down gas like there is no tomorrow. So I gave the beer all auto part names. So the Belgian stout is Motor Oil -- because it's dark and thick -- and the sour portion Battery Acid -- because it's acidic -- to come together as Carburetor. There's no relationship between the beer and carburetor. I just think it's a funny word.

I decided to work off a Belgian stout, rather than something more neutral because I wanted the yeast character to add some flavor complexity to make up for what might be missed not using a bigger stout that would carry more character than your standard Irish or English stout. Sour beers are very thin, which meant the stout needed lots of body so plenty of adjunct and mashing high would help keep some mouthfeel. Having never built a stout recipe, I started looking at a lot of Belgian stout recipes, particularly Boulevard's Dark Truth (which is actually more of an imperial Belgian stout, but I enjoy the flavor enough to use it as a starting point). The end result is Motor Oil. Based on the recipes I looked at I decided to make the grain bill more reliant on an American or British version of a stout than load it up with the typical Belgian specialty grains like caramunich and special B. I didn't want it to taste like a heavy oud bruin by the time it was all blended together.

The sour beer I decided I wanted to sort of go all over the map to put together the flavors I wanted instead of trying to tie it down to a particular style. So Battery Acid ended up with a German Pilsner base, C120, caramunich, carafa III and chocolate wheat. I wanted a grainy base with some raisin and caramel notes but I wanted it really dark without contributing more acrid malt flavors so I opted for carafa III and chocolate wheat for color. That chocolate wheat is good stuff. Very tasty and very smooth. I fermented it with a Belgian strain to get the esters available for brett to work into more complex flavors. I then racked out of primary and pitched the dregs of a bottle of my lambic solera to sour it. I didn't want a funky, lambic-like sourness in the beer but it's the only sour beer I had on hand that I knew would be viable. By racking off the trub I expected more sourness and less funk.

Putting the Pieces Together

I brewed a test run of the stout in early 2012 and although I really liked the flavor I wasn't in love with the mouthfeel. It wasn't thick enough and ultimately it led me to realize I had some temperature control issues with my one gallon system that I have since fixed. I brewed Battery Acid back in February 2012 and pitched the lambic dregs in March. It developed a nice pellicle after a couple weeks and sat quietly getting acidic. I tasted it a couple months ago and it was a fantastic blend of sour, cherry, raisin, caramel and a hint of carafa flavor. It's so good I'm half disappointed I'm going to blend some of it. I rebrewed the stout at the end of November with the plan to complete blending mid-December.

My initial plan had been to blend the entire gallon of stout with half a gallon of sour, so it would be 33% sour to 67% stout. Over the past year I went as far as wanting to blend all of it 50%/50% to as little as 20% sour. Ultimately I decided to go with my initial plan. It will be easiest to divide a gallon of sour beer into two halves. Ideally I would rather be able to take samples of the two beers and make different blends and see which I like but only having a gallon of each means I don't have a lot to lose. So the final plan is blend a gallon of stout with a half gallon of sour and bottle half of Battery Acid straight. It's the best of both worlds.

I will rack out Battery Acid to my bottling bucket and add priming sugar and champagne yeast for carbonation and bottle half straight. Then I will add more priming sugar and Motor Oil, give it a gentle stir and bottle the blended Carburetor. Wait. I know. You're wondering how I will blend live sour beer and unsour beer in a bottle and not create a cataclysmic explosion. I skipped over that part.

When blending a sour beer into a clean beer you have a couple options. You can bottle in really thick bottles and hope you drink your beer fast enough that it doesn't explode on you first. If your clean beer is fairly dry, like a saison, there's not as much leftover sugar or starch to consume but a stout is full of starches and unfermentable sugars so that's not an option here. The other option is to stabilize the sour beer before blending. If you have a fancy set up you can filter the beer and/or pasteurize. That's what New Belgium and many other commercial brewers do. Since I can't flash pasteurize my beers I have to go with more rudimentary methods.

I borrowed a method from Michael Tonsmeire, who writes and appears online frequently under the name Oldsock. He is a brewing genius, especially when it comes to sour beers. It works like this: you take your sour beer, add finings and cold crash. This process tries to knock out as much of the brett as possible. Finings will attract the yeast, making them larger chunks of matter and more likely to fall to the bottom of the fermenter. Once the beer clears at cold temperatures for a few days, rack out to another fermentor and add campden. Let it sit for twenty-four hours, then blend and bottle. The campden will do two things. First, campden does a neat thing to yeast where it prevents them from reproducing. That means any brett coming through won't be able to reproduce and any eating it does will be a very slow process. Second, campden kills bacteria. So all the souring bacteria will die off and leave a more stable beer. I tried this process once before except I didn't have any finings to add. As a result, a bit of brett got into the final beer and has made some very well carbonated but after 18 months, incredibly delicious beer. Fortunately I bottled it in champagne bottles. The finings, it seems, are really important and cannot be skipped.

The easiest way to use finings is gelatin. I've never used post-boil finings before so this was a new one for me. I followed the advice of Greg Noonan in New Brewing Lager Beer to add one gram of gelatin to two ounces of water. Let bloom at room temperature for one hour and then heat to 150-160 and add to beer. Swirl gently for a couple minutes and then cold crash. I followed this process and shoved my sour beer into a fermentation chamber at 42F. I left it there for three days. It's hard to tell on a beer that is midnight black whether it is clear or not. I had to judge based on the increasing thickness of the trub.

Next I racked off the trub into a fresh fermentor and bombed it with campden. Since I only had a gallon of beer and a whole tablet of campden is good for five gallons, I only added a quarter of a tablet I crushed and added to the fermentor. I let the campden sit for another three days even though you really only need one to let the campden dissolve and then degas the sulfur. I let it sit so long just because I had my last final coming up and didn't have time to bottle beforehand. I'm glad I let it wait the extra couple days because there was still a bit of sulfur in the beer I gently stirred to degas. Seemed to work ok.

Bottling was tricky because I wanted to bottle both the sour straight and the blend. I had to reyeast the sour portion and make sure I primed for both bottling runs. I added 1.3oz of priming sugar for the gallon of sour beer. That will carbonate to about three volumes with some extra sugar to make up for the CO2 lost during aging and with all the racking and stirring to get to bottling. I added a slug of champagne yeast from the fridge. Both priming sugar and yeast were added at the beginning of racking out so it would mix well. I ran off five bottles of the sour beer and then stopped. Oddly enough the sour portion seemed really dark in the fermentor during aging but after cold crashing it turned a dark brown and by the time I bottled it was about the color of an oud bruin. I then added another ounce of priming sugar (in boiled water) and racked the stout into the bucket and once it was all in the bucket together I gave it a couple swirls just to be sure it got mixed. I then bottled another fourteen bottles.The stout portion came out of the fermentor a strange purple color but once mixed turned out a nice black color.

The sour portion tasted pretty much the same as it did last week. I'm pretty happy with it. The blend seems right around where I wanted it to be. The coffee and chocolate flavors come through. There's a good hit of acidity on the back -- a little more than Clutch -- and there's a bit of a smack in the face of roast that Clutch doesn't have but I think it very intriguing. I'm excited to see how this beer develops in the bottle after carbonation. I'll update with a tasting on both after each conditions in the bottle for a few weeks.


  1. Wouldn't kegging the beer be a fourth option in addition to exploding bottles, pasteurizing, and campden tablets?

    1. In general, yes but I don't have a kegging system yet.