Beer - The Unique Oud Bruin - Part 2
Most brewers of the unique Oud Bruin style rely on pale malts, such as Belgian pilsner, for the bulk of the grist. Small percentages of the more highly colored Munich and Vienna are sometimes used. However, dark roasted malts, which can contribute bitterness and burnt, roasted flavors and aromas, are never used. Belgian specialty malts often used include caramel, aromatic, cara- Munich, cara-Vienne, Special B, and wheat. These add a little color, but their primary function is their contribution to malt complexity, flavor, and aroma.
A small amount of low alpha acid British or German hops is generally added early in the boil to achieve a bitterness level of around 20 IBU's. The goal is to balance some of the malty sweetness with a small amount of hop bitterness. Too much bitterness would not mix well with the acidic nature of the beer. Hop flavor and aroma are not typically present in Oud Bruin, however, some brewers do add small amounts of Czech or German aroma hop varieties later in the boil.
Starting gravities for Oud Bruin typically range from 1.048 to 1.053. The degree of attenuation is usually around 75 to 80% which results in beers with 5 to 6% alcohol by volume. However, as with most Belgian styles, these figures are not hard and fast. Thus, there is much variation among current examples. Beers with higher starting gravities and those with fruit are obviously higher in alcohol.
In addition to acidity and color from long boil times, two other hallmarks of the style are aging and blending. Aging contributes vinous flavors and aromas reminiscent of port and sherry. It also increases the tart, acidic characters due to prolonged contact with wooden casks. Today, the beer is aged for up to eight months before it is blended with a younger beer. The ratio of young to aged beer varies among different brewers. In general, as the proportion of aged beer increases, so does the tartness. When lesser amounts of aged beer are used, more malty sweetness comes through. Since aging and blending have such a dramatic impact on the overall character of the beer, there is much variability among commercial examples of the style. Developing a beer with just the right blend requires lots of trial and error and this is where the art of brewing comes to play. Oud Bruin brewers are very secretive about the specific aging and blending practices that contribute so much to the character of their beer.
Another factor in the individuality of these beers is fermentation practices. Many brewers ferment with proprietary yeast strains. In addition, the exact mix of wild yeast and bacteria present during fermentation is largely a function of the brewery environment. These organisms are present in the breweries themselves and in the wooden casks used for aging. Most of them are vulnerable to environmental changes and very difficult to culture. Brewers of Oud Bruin have been able to maintain a favorable environment for these finicky organisms by holding fast to tradition. Their breweries are largely as they were centuries ago. Most use outdated equipment and practice techniques long since forgotten.