by Keith Hamburger

Created on: June 13, 2008   Last Updated: February 13, 2009

Belgian lambic beers are brewed through a process of spontaneous, or natural, fermentation. Instead of using carefully cultivated varieties of yeast as is done with most varieties of beer, lambics are allowed to ferment using wild yeast and bacteria from the environment. This technique makes the resulting beverage less consistent than other beers but results in a unique flavor that can't be matched through more common processes.

Fermentation through exposure to wild yeast is probably the closest to the ancient processes of beer production. While many of the flavorings used in modern lambics were not used until relatively recently, this beer is likely to be the closest you will find to that of centuries past.

Like all beers, lambics are started with a mash of barley malt which is heated to varying temperatures allowing the enzymes in the malt to convert grain starches into sugars. Often additional grain adjuncts, mainly wheat, are used to create different flavors and textures in the beer. Hops are also used to provide bittering and other flavors.

After the mash is sparged, or the liquid separated from the spent solids, the resulting wort is cooled in the open air where yeast and other microbes are allowed to settle into the wort. Wide, shallow containers are used to provide a greater surface area to collect the microbes needed for the fermentation process. These yeast and microbes, along with others remaining in the fermentation vessels following the previous production run, are what ferment the wort into beer.

Since lambics are exposed to a wide variety of microbes that can produce strong and distinct flavors, they generally use a large amount of dry, or finishing, hops. The flower of the hops plant has anti-bacterial properties, which discourage spoilage and encourage yeast production to outnumber bacterial growth. The large amounts of hops used results in a strongly flavored beer.

Even using large quantities of hops, however, doesn't reduce the amount of bacteria to the level of those found in beer using carefully cultured yeast. These bacteria contribute to other unusual flavors in lambics. Lambics are particularly tart or sour due to chemicals produced by the unusual microbial populations in the beer. There is no concern about the safety of these brews as no one has ever found any microbes that are harmful to humans that can survive in the alcohol content found in beer.

Because of the slow process of spontaneous fermentation, lambics are allowed to ferment for a long time. Often using old wine barrels, which themselves impart a particular flavor to the beer, lambics are commonly fermented for a year or more. Many styles of lambics are aged a minimum of three years and some aren't even considered ready to drink until they are six years old. And, after fermentation is complete, a good gueuze (a particluar style of lambic) will be aged in the bottle for a minimum of a year, and often kept for up to twenty years.

To offset the unusual tartness in lambics they are often flavored with fruit juices or other sweeteners. The best of these use whole fruit for flavoring while those using syrups are generally considered to be of inferior quality.

Traditionally brewed only in one particular region of Belgium, lambic beers can have the variety of most all other styles of beers. But the spontaneous fermentation process gives lambics flavors that are unique to the particular style.

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