Flanders red + ??? = Sour Stout (Developing a recipe for blending)

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Brew-Mastress in training
HBT Supporter
Sep 2, 2020
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Hear me out....Next on my “Brewbucket List” is a sour stout, but looking at the threads and recipes on the topic, I don’t want to wait for Roeselare or bottle dregs to bring the funk and complexity when I do have a gallon of Dr. Lambic’s Flanders Red (Dr. Lambic’s Homebrewed Sour Red Ale), a mixed fermentation of Lactobacillus delbruckii (WLP6770), S-04, and Brett lambicus that’s been aging for over a year. It definitely has the funk factor and a light touch of astringency but it has never gotten more than vaguely sour. A few months ago, I kettle-soured half a gallon of amber extract, fermented with S-04, blended it with blackberry juice, and then blended *that* with my second-to-last gallon of the sour red and it made a really nice fruited “pseudo-lambic”.

I was thinking I could do something similar with a stout recipe. I could brew 1-2 gallons of a “stout base,” quick-sour it with lacto down to the 3.6-3.8 pH range, and lightly hop to stabilize the pH when I think it’s at a good level of sourness. Once fermented out, I would blend it and bottle it with the red ale to create a final beer that works as a tasty, complex sour stout that hopefully won’t need to age as long before drinking because half of it is already 1+ years old. However, I only have one shot at this because I’m down to my last gallon of the red ale, and typically don’t create recipes from scratch like this, so calling in the brain trust for feedback to see if this is the best or worst idea I've ever had.

Taste and composition considerations:
  • Because of the brett, if I want the blend to age in the bottle without overcarbing, the stout base will need to end up being really, really dry. I was playing around with the blending calculator and if the red got to 1.0 or thereabouts, I could blend in 1 gallon of stout base at 1.008, 1.25 at 1.007, etc. So flaked oats are probably out of the question, even though that’s a common ingredient in sour stouts and ToD clones. I’m open to blending and aging for a few months if needed to avoid risk of shrapnel.
  • I want the final blend to taste roasty enough to be a stout without the roastiness and sourness clashing. So I think I need to up the level of roasted grains above what I would do if not blending, without overdoing it. I was thinking to rely on chocolate rye and a touch of Carafa Special III to get there but not sure if that will be stout-like enough without including roasted barley. If it needs to be roast barley, how much or how little if I can get away with?
  • Bonus if the stout base is drinkable on its own after souring for any left over after blending. Extra bonus if the blended final beer would also work well with cherries or blackberries.
Current working malt bill (2 gallons)
  • 3 # 2-row (67%)
  • 8 oz rye malt (11%)
  • 6 oz Crystal 60 (8%)
  • 6oz chocolate rye (8%)
  • 4oz Carafa special III (6%)

Lactobacillus plantarum (source TBd)

Yeast – some highly attenuative Belgian or British yeast, maybe Safale-BE256

Saaz (or similar) hop tea (added after souring with lacto), aim for <10 IBUs
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Sounds like a fun project!

I’d shy away from the roasted barley. My suggestion is to make the stout about a medium for the roast level that you usually like in a stout and the sourness a little less sour than you’d usually like. I bet blending that beer with the Flanders would be nicely balanced. I’d suggest cherries over blackberries.

I currently have a dark, clean sour with cherries on tap. It is too sour, too roasty, and not cherry enough. I was just cleaning out the grain bins from fall and shooting from the hip. It’s still ok but it’s more of a novelty.

It was
64% Pilsner
18% F Oats
7% Midnight Wheat
5% Chocolate Rye
5% Amber Malt
2% Brown Malt
3# Cherries
Soured to pH 3.3
Thanks, this is helpful and encouraging! My non-sour stouts in the past have been 13-16% roast, so my current recipe has 13%, with a greater emphasis on the milder chocolate and huskless roast grains (now debating between midnight wheat and Carafa II). The final blend then would be in the range of 7% roast which is in line with ToD clone recipes.

@Funky Frank How did you hop your version, and what with?
I did a little hop tea/dry hop just to stop the souring. I used my bin of not quite aged hops so it could be anything but most likely it’s a high percent Tettnanger.
That sounds interesting! On Monday, I bottled 40 litres of almost two years old Flemish Red. I did perceive a very slight chocolate note far in the background and also thought about mixing with a porter-esque beer - but honestly I'd rather just mix in the glass to avoid the whole final-gravity-guessing-game. Even just minor deviations of the blend's FG from your prediction can make the difference between a flat beer and an overcarbonated beer. Imho it's not worth risking the long-aged beer.

If you do go down that road, I'd cut out the crystal malt entirely: your Red Ale surely already contains quite a bit of it, so it's not contributing any new flavours, but delays attenuation and stability of the blend. (I know we're losing the bonus points for the plain Stout's taste herr, but eh, gotta focus on one thing at a time - can always brew up another stout.)

I'm not sure if I agree that flaked oats increase the FG... (if that is the reasoning in your post) Chocolate rye and carafa spezial are great choices here imo, they give a pleasant, softer roastiness that should go well with acidity (I've also read that Brett+Carafa=<3).

Blackberries have a harsh acidity that I'd rather avoid here... Cherries could be nice, but it might also be too much at some point, don't know.
So I brewed this yesterday. Unfortunately saw the latest comment after I'd already bought my grains altogether, so did end up with some crystal. The final grain bill was approximately:
60% 2-row
20% rye malt
8% crystal 60
8% chocolate rye
4% Carafa Special 2

I am also going with US-05 to keep the flavor cleaner. The points about stability and uncertainty around FG are well-taken; and expecially since US-05 isn't quite so attenuative, I'd already abandoned the idea of blending in the bottle

It soured quickly to 3.6, at which point it was tasting really, really good (if the pH meter sample was any indication of things to come, I think the sour stout without the red might be pretty close to greatness on its own and worthy of a re-brew). I added hop tea earlier today to stabilize the acidity. Once the stout finishes primary, I'll split the batch, blend then let the blends sit for a few months before bottling. Since I can't resist the urge to experiment further, I'll probably end up bottling 3-4 different iterations, including "clean" sour, stout-red 2:1 blend with bourbon-soaked oak a la ToD, stout-red blend with cherry juice. Will try to report back.
...although I just realized that the airlock on the red has gone dry, likely recently judging by the pellicle and fill level. It tastes OK, just super-astringent (but not in a vinegary way), which tracks with its trajectory thus far. So this blending, when it occurs may be even more of a lark than anticipated, but I'm willing to go for it since the red is even less of a risk to lose and the stout will be happening again anyway.
How is your project evolving? I would like to see more embrace the sour stout. I find that many can't wrap their head around it, the complexity confuses and overwhelms them.
I made a sour stout and what put me off was the roast barley flavour. Just did not sit right with the acidity to me despite a lot of dark crystal. perhaps its to do with the low FG. I do like a 50/50 blend of stout and flanders red though. Makes a good beer cocktail.
Project is ongoing! I ended up with 3 gallons of roughly 2/3 stout base (see above) - 1/3 flanders with tart cherry concentrate and oak. It's been aging for about a month and starting to develop a pellicle. I will wait another month or so to check the gravity and hopefully bottle at least one of the gallons. I also submitted the "clean" lactic stout to a contest on a whim to figure out how to improve it for the next time, and got some helpful feedback. It got an OK score in light of the fact that it was still pretty green and at least one of the judges did not sound like a fan of sour stouts.
I bottled 2 gallons last night. From the samples I tried, one of the gallons (the one in the jug that originally held the brown ale) carried over some of the astringency from the long-aged brown, but is still quite good.

But the other, oh my goodness, was so much greater than the some of its parts - it made the entire kitchen smell like chocolate, and tasted oh so smooth, milk chocolatey, complex with just a hint of tartness and cherry. I bottled a few in such a way that I could submit it to a local comp, but I might have to think about the base category a bit. I'm thinking more of a less boozy Baltic porter than a stout, especially with the hint of cherry that comes through.