Beer - The Unique Oud Bruin - Part 4
Authentic Oud Bruin, like lambic, is one of the more difficult styles for home brewers and most professionals to reproduce. This is due to the use of traditional brewing practices, antiquated equipment, wooden casks, and various wild yeast and bacteria in its production. Because brewers of Oud Bruin are such traditionalists, the style is very hard to emulate using modern brewing procedures and techniques. The aging and blending practices so important to the character of Oud Bruin are other obstacles, since most brewers will not divulge the specific procedures they use.
Probably the biggest obstacle facing the brewer trying to emulate this style is managing the microorganisms which give it its characteristic sourness. Although the key organisms are the lactic acid bacteria, lactobacillus and pediococcus, various wild yeast may also play a role. For most professional brewers and home brewers, this presents many problems. First, modern commercial breweries expend lots of time and effort just to keep these organisms out of their facilities. For most brewers, these are some of the most feared organisms, notorious for causing good beer to go bad. Once they get into a brewery, it is very tough to get them out. Second, even if you don't have a problem with bringing these organisms into your brewery, it is very difficult to get them to do what you want. Lactic acid bacteria are particularly hard to culture and wild yeasts are unpredictable at best.
Another complication facing brewers of this style is the difficulty in controlling the level of acidity in the beer. Oud Bruin brewers achieve the proper balance of sweet and sour through aging and blending. Following a normal fermentation, the beer is matured in oak casks with the proper mix of microorganisms, during which it obtains acidity along with other characteristics of aged beers. A portion of this beer is then blended with a young beer to balance some of the acidity with sweetness. Aging and blending requires much trial and error and can only be perfected through experience. Most brewers of Oud Bruin have been doing this for hundreds of years.
If you are interested in experimenting with Oud Bruin, there are a few alternatives for achieving the acidity without resorting to lactic acid bacteria and wild yeast. You could let part or all of the mash stand overnight before continuing with lautering and boiling, to encourage the growth of lactic acid bacteria. This technique is known as a sour mash and could be used to impart some acidity to your beer. You can also add food grade lactic acid to beer before bottling. Start by adding very small amounts and taste the beer often until you achieve the desired level of acidity. Too much lactic acid can make the beer undrinkable and it's likely that even blending will not remedy it. Though these methods aren't authentic, they may work for those who would rather not mess with bacteria. If you're not worried about the microorganisms, and if you can find some bottle-conditioned Oud Bruin, you can try adding a few bottles to a younger beer and allowing it to ferment. If you have a wooden cask to put it in, all the better.
Thus, like lambic, Oud Bruin is one of the most difficult styles for home brewers. It is a style typically reserved for only the most experimental of brewers. It may take the typical home brewer a couple of batches to perfect a favorite pale ale recipe, but something like this could take years to get right. Nevertheless, for brewers willing to invest the time and effort, this is certainly a style worth experimenting with. Imagine presenting your very own version of Oud Bruin to members of your home brewing club. If you are able to perfect your own example of this rare, classic style, you will have done something few microbrewers outside of Flanders and home brewers have even tried.