What was a “look, cool: wild yeast-fermented beer!” afterthought to my post on sustainable brewing has met an indignant commenter crowd who found my two-sentence description rightfully vague and careless. And so, as penance suggested by commenter koelschip, here is a complete guide to making lambic beer. Whether you are an old Belgian couple who ferments outside or a homebrewing web user with closed wild yeast inoculations in your basement, I think we can all agree that sour beer is delicious. And the greenness isn’t so bad either: reclaimed oak barrels, energy-free inoculation and all natural ingredients (provided you don’t start with the sham fruit syrups and packaged yeast…) contribute to its carbon-reduced diet.
Step #1: Move to Belgium
For purists, this is a must. Only in the Senne valley of Belgium can the brewer encounter the true wild yeasts of lambic beers which contain the essential bacterias, Bretanomyces bruxellensis and B. lambicus. In fact, to move to Belgium is the only way to enjoy an authentic lambic experience without compromising the eco-friendliness of the endeavor with trans-Atlantic shipping.
Step #2: Mash Up
A lambic wort is traditionally comprised of 60-70% barley malt and 30-40% unmalted wheat. Mash at 45° C. After 10 minutes, warm the mash to 52° C until you obtain the milk (15 minutes). Warm the milk further to 65-75° C, which begins the conversion from starch to sugar (additional 20-40 minutes). Filter this solution (now called wort) and season it with dried hops that have been aged three years. The proportion here is 4 ounces per 5 gallons of wort. Boil for 3.5 hours.
Step #3: Treat the Wort
Once boiled, pour into a copper cooling tin in a well-ventilated room or covered outdoor area. Put it out in your field, if you happen to be my friend Jan’s grandparents. This cooling period (or “open coolship”) is also when the spontaneous fermentation or inoculation occurs thanks to the yeasty Belgian air. It must be noted that spontaneous fermentation should only be attempted in the winter, when less bacteria fills the air.
Step #4: Aging Process
Pour the inoculated wort into oak barrels. These barrels should be old, as new barrels will leach tannins into the beer, affecting its subtle flavor balance. An old wine cask is ideal. If you want to add fruit or fruit syrups, this is the stage to do so. Some modern brewers use steel tanks with wood chips in place of wooden casks, although the flavor is said to be inferior. You will know that the beer is fermenting properly when white foam bubbles up through the top hole in the barrel within a few days of casking. This foam turns brown and hardens, creating a porous cap that protects the brew from outside elements but still allows the fermenting-induced CO2 to exit. The beer should ferment for two to three years. Once bottled, the beer can undergo a second fermentation and is subsequently called Geuze.
Step #5: Be a Snob About It:
If you would like to make a Lambic-style beer in your basement or garage, there are many recipes in brewing magazines, although cross-contamination with other beers is a concern leading many homebrewers to do away with the open fermenting. You can purchase a prepackaged wild yeast blend to best approximate the real thing. However, be warned: several Belgian Royal Decrees and an EU regulation prevent brewers from calling their inauthentic brews “lambic.” The open cooling method and spontaneous fermentation are essential parts of the definition.
Image Credit: Joe M500 under Creative Commons License.