All About Beer Magazine - Volume 31, Issue 1
March 1, 2010 By K. Florian Klemp

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 Land

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.

At about three months, lactic acid-producing bacteria, Pediococcus and Lactobacillus, take their turn. Around eight months, Brettanomyces yeast species (bruxellensis and lambicus) grab the reins, and work for another year and a half to give the musty, barnyard character so craved by lambic devotees. Finally, oxidative species take over the final stages of fermentation/maturation, often alongside the Brett. Lambic may ferment and condition for several years, but one to three is the norm, with the youngest often used for further stylistic application.

A well-aged lambic serves up a multitude of distinct notes. They are vinous, fruity, musty, acetic and lactic all at once, with other minor constituents mingling about. Straight, traditionally brewed lambic is served uncarbonated from a cask in its most pristine form, ideally in greater Brussels. All things considered, it is truly an acquired taste, and a written column does little justice to the profile and experience. Lambic has two other incarnations that are more than worthy of mention. They are the rowdy and spirited gueuze, and fruit lambic, formulations of straight lambic that offer something a little more familiar and tame to those who can’t wrap their palate around the unaltered, purist originals.


Gueuze is a blend of old and young lambic, usually a mixture of one-, two- and three-year-old . After blending, the mixture is roughly filtered, but not entirely, to leave some of the vital bugs, and then bottled. The youngest (fox lambic) offers some unfermentables to the old lambic (vieux lambic), which in turn gives the product a rambunctious effervescence during bottle conditioning not unlike champagne. In fact, gueuze was initially inspired by the méthode Champenoise in the nineteenth century to make lambic more appealing to the masses.

Blenders are skilled artisans as lambic varies from batch to batch and even among casks within a batch. The blend and refermentation initiates yet another cascade of events within the bottle, initiated by the arousal of the different lambics. It is aged for three to nine months, and at least one summer, with the temperature swings being paramount to microbial activation. Gueuze is more than just a blend of lambic, but yet another distinct form of it.

Fruit Lambic

As the name so simply implies, this is lambic laced with fruit. The most common are, in order, kriek (cherry), framboise (raspberry) and cassis (black currant). For kriek, local sour cherries, known as Shaarbeek, are preferred and most traditional. Their contrasting sour-sweet character meshes perfectly in lambic. The habit of fruiting may come from the ubiquitous agrarian practice of frugality and using every single morsel of labor. Fruit is nutritionally and calorically preserved in beer. Even dried fruit on the branch was used, and often preferred for its concentrated condition. The fruit is put into casks and fox lambic racked over, kick-starting another fermentation. The bung is stuffed with twigs to act as an airlock. After a few months, it is bottled with more fox lambic for carbonation.

If you haven’t already, explore these beguiling brews, for to appreciate lambic, is to appreciate the wild and genuine side of brewing.

Cantillon Bruocsella 1900 Grand Cru

ABV: 5.0
Tasting Notes: Brewed in Brussels at the Cantillon Brouwerij (also home to the Brussels Museum of the Gueuze), Bruocsella is rare, unblended lambic, beer as nature intended. The bright, flat pour is deep gold. As expected, the aroma is huge. There are vinous, apple cider notes, and a stiff dose of Brettanomyces’ sweet musty wood. The sour lemon, vinegar tartness gives it a very dry palate, and the stillness allows oak and Brett character to wash unabated. The distinct flavors offer an oddly clean impression with a tight, quenching finish. Aged for three years before release, it will keep well beyond that.

Oud Beersel Oude Gueuze Vieille

ABV: 6.0
Tasting Notes: The name says it all. This traditional gueuze is brewed in the town of Beersel and proudly proclaims its rustic heritage. The color is bright gold with tints of pink, the thin rim of foam fed with fine streams of carbonation. There is a fresh herbal hay quality to the aroma, reminiscent of Saaz hops, a stiff dose of leathery Brett and apricot. The oaky, vinous flavor is full of must, with grapefruit and lemon citrus notes, and a jagged lactic, vinegar edge. The earthy finish is dry and lingers sharply.

Lindemans Cassis

ABV: 4.0
Tasting Notes: The 200-year-old Lindemans Farm Brewery in Vlezenbeek is renowned for its fruited lambics. Cassis is reddish violet with an inviting, lingering lavender head, the effusive aroma has a dominant summer berry vinaigrette nose, with earthy Brett in the background and a hint of cedar. Lactic tartness is balanced by juicy sweetness in the flavor and firm body; the currant taste is fresh and bright. Any of their fruited offerings and would be perfectly at home with creamy desserts, but the cassis is otherworldly.

Brouwerij Frank Boon Oude Kriek

ABV: 6.5
Tasting Notes: Brewed by traditional methods in Lembeek, Oude Kriek pours deep and hazy pink. The reserved effervescence emits an aroma that oozes musty Brett character laced with oak and cherry. The mouthfeel is somewhat creamy and dextrinous. The flavor is impossibly complex. Notes of sour cherry sit atop a woody, cider vinegar and lactic backdrop. The finish is dry, with a hint of sweetness, and cidery sour. This gem is quite balanced, with no facet fighting for supremacy; a masterpiece by any measure.

K. Florian Klemp
K. Florian Klemp is an award-winning homebrewer and general hobbyist who thinks there is no more sublime marriage than that of art and science.