Oud Bruin: The Dark Sour of Flanders
Oud Bruin: The Dark Sour of Flanders
While the “Flanders Red” is often called the “Burgundy of Belgium,” its cousin to the East—the Oud Bruin (Old Brown)—is a more mysterious and malt-driven creature. Born in the breweries of East Flanders (specifically around Oudenaarde), the Oud Bruin is a dark, sour ale that celebrates the marriage of roasted malt sweetness and lactic acidity.
Unlike its “Red” cousin, which is typically aged in large wooden “foeders,” the traditional Oud Bruin is primarily aged in stainless steel or glass, resulting in a cleaner, maltier profile that lacks the intense “oak” and “balsamic” tannins of the Flanders Red.
To understand Oud Bruin with authority is to understand the technical balance of a “Sour Stout”—where the dark, cocoa-like flavors of the malt must live in harmony with the sharp, refreshing snap of a wild fermentation.
1. The Fermentation: Long vs. Fast
There are two primary ways that authority-level Oud Bruins are created.
The “Long” Traditional Method
In breweries like Liefmans, the beer is fermented in open vats with a “house” mixed-culture (yeast and bacteria). It is then aged for 4 to 8 months. Historically, a “young” (freshly fermented) beer was blended with an “old” (sour and aged) beer to create a consistent, balanced profile. This is very similar to the “Gueuzesteker” art of Lambic.
The “Fast” Kettle Method (Modern Hack)
Some modern craft brewers use a “Kettle Sour” method, where the wort is soured with Lactobacillus first, boiled to kill the bacteria, and then fermented with a clean ale yeast.
- The Authority Opinion: While this produces a “sour brown” beer, it lacks the depth of the traditional method. The complex byproduct of a long, secondary fermentation with Brettanomyces and Pediococcus provides the “leather” and “raisin” depth that a quick kettle sour cannot replicate.
2. Technical Profile: BJCP 2021 Standards (Category 23C)
Oud Bruin is a substantial beer, often feeling more like a “Sour Scotch Ale” than a typical suröl.
| Parameter | Targeted Range |
|---|---|
| Original Gravity (OG) | 1.040 – 1.074 |
| Final Gravity (FG) | 1.008 – 1.012 |
| ABV | 4.0% – 8.0% |
| Bitterness (IBU) | 20 – 25 |
| Color (SRM) | 15 – 22 |
Sensory Breakdown
- Aroma: A complex mix of malt sweetness (caramel, toffee, chocolate) and dark fruit (prunes, plums, raisins). The acidity should be “cleanly lactic,” smelling more like yogurt than vinegar.
- Flavor: A bold, malty start followed by a sharp, sour finish. The roast should be “smooth” (dark chocolate) rather than “burnt” (coffee). There is often a subtle “sweet-and-sour” interplay that is the hallmark of a great Oud Bruin.
- Mouthfeel: Medium to full-bodied. It has a “velvety” texture that is much fuller than a Flanders Red or a Gueuze.
3. The Malt Bill: Designing the “Chocolate Snap”
To brew an authoritative Oud Bruin, your malt bill must provide the body that the acidity will eventually “thin out.”
- The Base: Use a high-quality Munich Malt or Vienna Malt. This provides the “bready” core and the melanoidins needed for the deep brown color.
- Specialty Grains: Use 10% Crystal 120 or Special B to provide the dark fruit and raisin flavors.
- The Roast: Use a small amount (2-3%) of De-husked Chocolate Malt (like Carafa Special III). This provides the cocoa color and flavor without adding harsh tannins that would clash with the acidity.
4. Acidity Management: Lactobacillus vs. Pediococcus
In an Oud Bruin, the goal is Lactic Acidity.
- Lactobacillus: Provides a “sharp” and “bright” acidity. Usually found in kettle sours.
- Pediococcus: Provides a “deeper” and more “complex” acidity. It takes longer (months) to work, but it creates a more integrated finish that works better with the heavy malt bill of a Brown Ale.
Authority Tip: To prevent the beer from becoming too sour, brewers often “blend back” the aged beer with 10-20% fresh, un-soured beer before bottling. This “buffers” the acidity and ensures a pleasant mouthfeel.
5. Distinction: Oud Bruin vs. Flanders Red
| Feature | Oud Bruin | Flanders Red |
|---|---|---|
| Acidity Type | Purely Lactic (Clean) | Lactic + Acetic (Vinegar/Tart) |
| Malt Profile | Dark, Chocolate, Nutty | Red, Biscuit, Toast |
| Aging | Stainless / Glass (Closed) | Oak Foeder (Open/Oxygen) |
| Texture | Full and Velvety | Thin and Crisp |
6. Style FAQ: Professional Insight
Q: Can I use “Balsamic Vinegar” to mimic the sourness? A: Never. Acetic acid (vinegar) is generally considered a flaw in a traditional Oud Bruin. While it is a key component of a Flanders Red, the Oud Bruin should be “cleanly sour.” Adding vinegar will ruin the delicate balance of the dark malts.
Q: Why is “Liefmans Goudenband” the standard? A: Because it is the last remaining “masterclass” of the style. It is fermented in open vats and then aged in the cellar for almost a year. It showcases the perfect “iron” and “raisin” complexity that defines the Oudenaarde tradition.
7. Blending Math: The Secret of Consistency
Like the Gueuzesteker, the Oud Bruin brewer must be a master of the blend.
- The Ratio: Traditionally, a blend of 20% Aged Beer (sour) and 80% Young Beer (sweet) provides the optimal balance.
- Secondary Fermentation: When you mix young and old beer, the yeast in the young beer will continue to work on the complex sugars in the old beer. This creates a fine, natural carbonation that is much more integrated than forced carbonation.
8. Food Pairing: The Sweet-and-Sour Table
- Main: Carbonnade Flamande (Belgian Beef Stew)
- This is the “ultimate” pairing. The beer is actually used as an ingredient in the stew. The acidity of the Oud Bruin tenderizes the beef, while the malt echoes the caramelized onions.
- Side: Roasted Beets with Goat Cheese
- The earthiness of the beets and the “funk” of the goat cheese are a perfect match for the dark fruit and lactic acidity of the beer.
- Dessert: Warm Apple Tart with Caramel
- The “sweet-and-sour” profile of the Oud Bruin reflects the flavors of a baked apple, while the malt depth supports the rich caramel sauce.
9. Expert Tip: The Steel Paradox
While most famous sour beers are aged in oak, the Oud Bruin remains unique for its use of stainless steel.
- The Advantage: Steel allows for a “clean” sourness. You get 100% of the malt and 100% of the bacteria, without any of the “woodiness” or “tannins” of oak. This is why Oud Bruin tastes “plush” while Flanders Red tastes “sharp.” If you are brewing this at home, a standard glass carboy or stainless conical fermenter is the perfect aging vessel—avoid the barrel!
10. Technical Case Study: The “Long vs. Fast” Fermentation
In a study of traditional Oud Bruin, researchers found that the “Old” component of the blend often contains over 50 different strains of microflora.
- The Complexity: A “Quick Sour” Brown ale made with a single lab-strain of Lactobacillus has a very narrow flavor window. It tastes “lemony” and that’s it.
- The Authority Blend: A traditional Oud Bruin from Oudenaarde contains a “biological backlog” of years of fermentation. This creates an “Iron” and “Vinous” note that acts as a structural foundation for the acidity. When you drink a Goudenband, you aren’t just drinking a beer; you are drinking a 10-year biological history of the brewery.
11. Advanced Oud Bruin FAQ
Q: Can I age Oud Bruin in plastic buckets? A: No. Plastic (HDPE) is oxygen-permeable. Over a 12-month aging period, too much oxygen will enter the beer, causing the Acetobacter to produce vinegar (acetic acid). For an authoritative Oud Bruin, you must use glass, stainless steel, or PET carboys that have a high oxygen-barrier rating.
Q: Why does my Oud Bruin have a “Metallic” taste? A: This is often an issue with the dark malt husks reacting with the lactic acid. Lactic acid is a powerful solvent. If you use a lot of “bitter” dark malts, the acid will pull those metallic compounds out of the grain. Using de-husked malts (Carafa Special) is the best way to prevent this.
Q: Is it okay to use “Brettanomyces” in Oud Bruin? A: Yes, in moderation. Traditional Oudenaarde brewers have a small amount of Brett in their house cultures. It provides a “leather” and “earthy” finish that supports the malt. However, it should never be as “funky” as a Lambic. The malt should always lead.
Conclusion
Oud Bruin is the connoisseur’s suröl. It is a beer that requires the brewer to be both a chemist (managing acidity) and a chef (layering malts).
It is a deeply satisfying style that bridges the gap between the dark beer lover and the sour beer enthusiast. By mastering the Oud Bruin, you are demonstrating your understanding of one of Belgium’s oldest and most rewarding brewing secrets.
Next time you want a suröl with “teeth” and “soul,” reach for the Old Brown. It is a beer that is as deep as the history of East Flanders itself.