Sour beers can be challenging. They’re usually complex. They rely on methods that most homebrewers don’t use all that often. They sometimes depend on driving a lot of flavor with relatively few ingredients and/or very low alcohol levels (I’m looking at you, Berliner Weisse). One of the most user-friendly sours, though, is also one that I don’t see homebrewers producing all that often, which is unfortunate because it can be one the easiest to get right! I’m talking about the Oud Bruin, or, because I find that awkward to write, read, and say, the Flanders Brown Ale. It’s a sour, for sure, but it doesn’t need to be in-your-face sour, so even if you undershoot you’re still in good shape. It’s also more malt-driven than any other sour style (though my sour Belgian Stout would give it a run), which means that even if you do over-yield on your perceivable acidity there’s a backstop of darker malt flavor to check it. Finally, one step in the process that can trip up those making the Flanders Red (oaking) is optional.
This can be a good “starter” sour for those looking to move away from beginner styles but don’t yet have a lot of confidence or experience, while also being a style that advanced brewers can have a lot of fun with and really dial in to their personal preferences.
Flanders Brown shares a lot of similarities with its cousin Flanders Red, but the small-ish differences that exist have larger effects on the overall flavor profile of the style. Both exhibit fruit flavors, both are sours, both can benefit from some “aged” sherry-like flavor – in this case, though, the details matter. Flanders Red is fruity, but in a berry-and-cherry way; Flanders Brown relies on the darker pit fruit flavors of fig and raisin. Red is brightly sour, sometimes with a characteristic acetic flavor; Brown is subtly sour and should avoid acetic flavors. Red certainly can be aged, but can also be consumed relatively young; Brown is designed, as the guidelines and historical sources note, to “lay down,” and aged examples are generally considered superior to younger examples.
Overall, this is a malty sour, emphasis on the malty. The finish should be sweet, and balanced much more by the acidic bite than any bitterness. Flavor complexity is added through aging, but the base recipe and flavor profile is itself layered and nuanced. Once you have a solid base in the fermenter, the yeast and bugs will do the rest!
This recipe is on the high side, both in ABV and color, but it’s a lesson learned from drinking a lot of lighter Oud Bruins and finding them to be a little underwhelming, but by all means, experiment with more table-strength versions if you like.
Begin with seven pounds of Pilsner malt and five pounds of Munich malt. To that base we can add half a pound each of wheat malt, British 65L crystal, Special B, and Biscuit Malt: that swirling mix of delicious character malts should give you all of the malt flavors you could ask for (toast, toffee, shortbread, dark fruit, burnt sugars…), and plenty of complex sugars for the bugs to chew on. Finally, 3-4 ounces of Carafa Special III will add a deeper color and some deep toast to the flavor, but the dehusked malt won’t add “roast,” which is a fault here.
Hops are easy enough: 20 IBUs of anything, added at the top of the boil. If you want to keep it “Belgian,” Styrian Goldings are a solid choice, but very, very little of any hops flavor will persist.
Finally, we’ll use the same yeast/bug pairing that I use on my Flanders Red (Wyeast 1007 and 3763, German Ale and Roeselare, respectively) and trust the recipe to balance out the sourness for us.
Mash and boil and fermentation are “as usual” here. Brew and chill and pitch the German Ale yeast first, and start relatively cool in fermentation, about 65F. Increase that to the high 60s, and on completion of primary fermentation, go ahead and rack into a second glass or steel vessel. Minimizing oxygen is more important here than in the Flanders Red, since oxygen makes it more likely that acetic acid develops. That tart, vinegar-y flavor can be excellent in the Flanders Red (as all the Duchesse fans can attest), but it should be minimal-to-nonexistent in the Flanders Brown.
Pitch the bug blend into your new vessel, and then tuck it away for a while. You’ll want to taste-test the sourness as it ages, but to minimize oxygen pickup I’d shoot for just once! A long three months should get you close, and if you’ve guessed right then go ahead and package it up and store it cold to slow down any further sour development.
If you’re into oak-aging, go ahead and do it here, but it’s a bit unusual within the style. It can add some fantastic flavors, though, and I recommend chips (rather than cubes), just for a week or so, medium-plus toast, just before packaging!
Flanders Brown comes with some built-in guardrails in the recipe, and I should point out that even if you blow past them and get a brightly acidic (or even acetic) beer with lots of oak character and a dry finish with lots of malt flavor, you’ll still have a beer that’s a ton of fun to serve and drink and talk about. Don’t think about it – just brew it!