Brewing
Today the beer is generally brewed from a grist containing approximately 70% barley malt and 30% unmalted wheat. When the wort has cooled, it is left exposed to the open air so that fermentation may occur spontaneously. While this exposure is a critical feature of the style, many of the key yeasts and bacteria are now understood to reside within the brewery and its (usually timber) fermenting vessels in numbers far greater than any delivered by the breeze. Over eighty microorganisms have been identified in lambic beer, the most significant being Brettanomyces bruxellensis and B. lambicus. The process is generally only possible between October and May as in the summer months there are too many unfavourable organisms in the air that could spoil the beer.
Since at least the 11th century and probably earlier, hops have been used in beer for their natural preservative qualities as well as for the pleasant bitterness, flavor, and aroma they impart. Today it is the latter that is the reason for their inclusion in almost all beer styles other than lambic. Since the method of inoculation and long fermentation time of lambic beers increases the risk of spoilage, lambic brewers still use large amounts of hops for their antibacterial properties. To avoid making the beer extremely bitter, however, aged, dry hops (which have lost much of their bitterness) are used. Consequently, lambics often have a strong, cheese-like, "old hop" aroma, in contrast to the resiny, herbal, earthy hop bitterness found in other styles.
After the fermentation process starts, the lambic is siphoned into old port or sherry barrels (of chestnut or oak) from Portugal or Spain (some of the brewers prefer used wine barrels.) The lambic is left to ferment and mature for one to two or even three years. It forms a "velo de flor" of yeast that gives some protection from oxidation, in a similar way to vin jaune and sherry; the barrels are not topped up.
Another important feature of lambic is that it is usually a blend of at least two different beers; many "producers" are in fact blenders who buy beers from other brewers, and blend two or more together to create the desired result. A good gueuze, for example, may have occupied space in several different cellars over 6 years or more. The locals are justifiably proud of their unique beer, and recent years have seen an explosion of interest around the world for this unusual beverage despite — or perhaps because of — its complex process of production. While those outside of the area are most likely to find the bottled gueuze and fruit versions, there are a wide variety of styles available to the local drinker, and they are often blended again or sweetened with sugar or flavored syrups before drinking, as some examples can be extremely tart.
Lambic beer is widely consumed in Brussels and environs, and frequently featured as an ingredient in Belgian cuisine.
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