Belgium is synonymous with brewing eccentricity and whimsy―its brewers’ penchant for unusual ingredients, methods and historical usage is still very much alive. To them though, it is business as usual. Their most distinctive beer is lambic, which relies on the ancient method of spontaneous fermentation, a natural microbiological ambush for inoculation, fermentation and maturation. The outcome is a marriage between beer and wine, a product of process and local conditions as much as ingredient. It is the indigenous beer of Brussels and the rural Senne River Valley to the west, having survived unscathed through many recent brewing revolutions and innovations, including the doctrine of one Louis Pasteur. Lambic is without peer in complexity, a brew that is years in the making, and centuries old in design―beer in its most natural state.
Lambic is a vestige of a time when all beer was fermented at the behest of nature. This method endures because the unique population of microorganisms around Brussels infuses the wort with flattering characteristics over time. According to brewing documents, lambics are essentially unchanged in the past 500 years. They are brewed from roughly one-third unmalted wheat and two-thirds very pale malted barley, use aged hops and, of course, employ wild fermentation.
True lambic is intimately brewed in Brussels, and the Pajottenland-Zennevallei to the west. This largely rural area is still home to many modest traditional breweries. Farmhouse brewers relied on farmers for wheat, barley and often labor. Lambic was, and still is, only brewed between October and May to optimize desired, and minimize undesirable, conditions and organisms. The seasonal tempering ensures that fermentation will progress at a subdued, steady rate. During this period farmers were less busy and more able to assist in the brewery, and compensated with beer. The fallow summer brewing season was actually part of the maturation cycle of the beer.
Etymologically, the word “lambic” itself is either a corruption of Lembeek (Flemish) or Lembecq (French), the lambic-brewing town located on the Senne river; alambic, an old type of distilling apparatus; or lambere, the Latin word meaning “to sip.” At any rate, this uncertainty would be in keeping with the somewhat mysterious and charming nature of Belgian brewing itself―part legend and part indisputable.
The Méthode Lambic
It would be easy to assume that a spontaneously fermented beer requires little shepherding, but lambic production requires as much skill and attention as beers made under the most tidy and modern conditions. Each step is somewhat unusual, entirely adherent to old methods, and rather involved.
Though the appellation for lambic has been somewhat loosely protected over the years, the past 45 years have seen a winnowing of the guidelines through periodic legislation. The salient criteria for lambics are that they must be made with at least 30 percent unmalted wheat, undergo spontaneous fermentation, have an original density of 11° Plato and be cooled naturally. To further protect those produced by traditional methods, the words Oude, Vieille or Vieux must be found on the label.
Lambic wort is produced from pale malted barley and locally sourced unmalted wheat. Wheat chaff, or kaf, may be used in the mash tun to aid in filtration. Both infusion and decoction are used to take the mash through its three-step schedule. The mash is quite turbid, due to the unmalted wheat, and the liquid portion is known as milk or slime. Some of this is pulled off, boiled and returned to the mash tun (decoction) to aid in conversion.
The wort is then drained into the kettle as usual, and aged hops (one to three years), known as surannés, are added when the boil commences. These hops have lost their bittering properties, but not the antiseptic potency. Hops from the Alost and Poperinghe regions of Belgium have largely been replaced by Kent Golding from England. The boil lasts from three to six hours, an eternity by usual brewing standards.
After boiling, the wort is not flash cooled, but instead embarks on the adventurous journey that sets lambic apart. The hot wort is pumped into shallow vats, known as coolships, in the highest part of the brewery, where it is allowed to cool naturally overnight and into the next morning. During this period the magical inoculation takes root. The windows are opened to the wafting air of the surrounding countryside and the native microscopic residents enter the wort.
Once cooled, the wort is drained into wooden casks to start fermentation, where yet another populace of inoculants awaits. The wood casks are oak or chestnut from the Porto, Sherry, Madeira or Cognac regions. Old casks are preferred because detrimental tannins have leached out. The casks are left open; the oozing foam forming a barrier to excessive oxidation and warding off additional micro-invasions.
The organisms responsible for fermentation and maturation are staggering, numbering between 80 and 100, with five main groups. The process is a multi-phase, months-long trip where different groups of yeast and bacteria take turns preying on the wort and microbiological residue. The first seven days are dominated by acetic acid-producing strains. They relinquish duties at one to two weeks to Saccharomyces types, fermenting the wort in normal fashion for the majority of wort attenuation.