Tucked away in a small alley in Brussels, there’s a brewery that still practices open fermentation. Hundreds of yeast and bacteria in the air (the “open” part) are responsible for brewing (the “fermentation” part) a very special kind of beer called the lambic. Unlike other breweries you may have visited, this one has no sterile steel tanks, no shiny floors, and no smell of disinfecting compounds. Spiderwebs cover the barrels, the ceiling, and all the other nooks and crannies. The arachnids are well fed by gnats and fruit flies swarming around the barrels of fermenting beer. Bungholes ooze with fluid and the whole place is heavy with the smell of malted grain. Welcome to brasserie Cantillon.

Brussels, Belgium

Special Air Microbiota

Beer brewing is a delicate business. You don’t want to disturb the yeast lest your final product ends up being some funky, vinegary, feet-smelling liquid. Unless, of course, you happen to be at the right place at the right time. The right place being southwest Brussels (aka: the Senne valley) and the right time being October through May. Remember how your large intestine has its own unique group of bacteria living there? Well, the Senne valley has its own special air microbiota too. This is why lambics can only be made in this particular part of Belgium.

War in A Barrel

The biological warfare that takes place between the 120+ strains of yeast, and 60+ strains of bacteria gives lambics a unique flavor. First, oxygen is used up. Then, in the dark anaerobic environment, ethanol, carbon dioxide, acetic acid, and lactic acid are produced as by-products of fermentation. Hundreds and thousands of other reactions occur between the other metabolites of these microorganisms. Just like in a jar of pond protozoa, populations of certain species surge then die out. This war can rage for years. You can find remnants of these micro-soldiers at the bottom of your Cantillon beer bottles, still alive, still fighting.

the lambic
The Gueuze from Cantillon. Enjoyed at Moeder Lambic bar in Brussels.

Lambic and Gueuze

Probably one of the best jobs in the world is the Master Taster at Cantillon. Yes, that’s a real job. Lambics come out of their barrels after about 18 months, but in order to sell a consistent product, it needs tweaking. Gueuzes are a mix of young lambics with older lambics. In order to get the perfect concoction, the Master Taster mixes and matches different amounts and flavors every year so that the Cantillon Gueuze you buy in stores (very select stores) tastes the same every time. It’s a job for those gifted with extraordinary taste buds and olfactory bulbs.

Global Warming

One of the biggest concerns regarding the future of lambics is global warming. Delicate ecosystems change drastically with temperature fluctuations. What happens when temperatures remain high during brewing season? How will that affect the microorganisms? More importantly, how will this change the beer? Perhaps there will be a way to preserve the special air microbiota of this little corner of the world, but until then, I consider every bottle of lambic I can get my hands on a microbiological sample of the world before global warming.

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