Lambic

Lambic is brewed from malted barley with a high share of unmalted wheat, sometimes 30 to 40 %. The hops are aged for several years before use, so they preserve more than they bitter. After boiling, the wort is pumped into a coolship, a wide shallow vessel, and left overnight; the air inoculates it with local wild yeasts and bacteria. Brewing traditionally runs from October to April, when temperatures stay below about 15 °C.

Fermentation takes place in wooden casks left open to the air. A first stage of three to six months makes mostly alcohol; a second of one to two years makes mostly acids. Late in the sequence come Brettanomyces yeasts, which give lambic its "Brett" aroma. Unblended lambic is sour, without foam or sparkle, and served on draught in only a few places.

The Confederation of Belgian Breweries applied in 1996 to register traditional lambic beers as EU "certificates of specific character". The registration file defines them as acid beers from spontaneous fermentation, "a boiled wort after natural inoculation from the ambient air during cooling", with Brettanomyces as a determining microbe. Today "Oude Lambiek" is protected with Oude Geuze as a Traditional Speciality Guaranteed.