The historic kingdom of Flanders encompasses much of the northern part of Belgium. For centuries, the traditional beer of Flanders was a dark, sourish ale aged in oak casks at the brewery. Made from predominantly Pilsner or moderately kilned malts and some form of corn, with low hopping levels, many of the current examples exhibit a reddish hue. The name Flanders red ale or, more descriptively, Flanders acid ale denotes a beer that ferments with many more microorganisms than traditional brewers yeast. The most widely recognised example of the style is made by Brouwerij Rodenbach, in the town of Roeselare.
Unlike most other beers, the byproducts of microorganisms that many brewers scrupulously avoid — including Lactobacillus, Pediococcus, Brettanomyces and Acetobacter — define the flavour and aroma of Flanders acid ales. Aged for up to three years in oak barrels, resident microorganisms produce acids and esters far different than traditional brewer’s yeast. Alone or in large concentration, these byproducts are not terribly appealing, but in the correct blend, they can compose a truly sublime beer.
Often called the “Burgundies of Belgium,” largely due to the deep reddish-brown to burgundy colour resembling a red wine, some of the typical, traditional flavours and aromas are reminiscent more of the grape than of the grain. A fruitiness resembling the flavours of black cherries, plums and red currants are typical, sometimes complemented by the spicy, vanilla character associated with oak. Tannins from the wood add a crisp, tart astringency and full mouthfeel. A characteristic tartness in both the flavour and aroma, due to both lactic and acetic acid, defines Flanders acid ales as reminiscent of red wine.
Long ageing with “wild” microorganisms leads to a beer of considerable acidity and attenuation. While not traditional, many of today’s Flanders style beers are pasteurised and blended with sugar or aspartame to restore sweetness and body. Alcohol levels hover around 6–6.5% alcohol by volume (ABV). Consistency in both alcohol, body and character is achieved by blending batches aged in multiple barrels