Wild yeast and bacteria – Why is it in my beer?

Sour beers are starting to become a craze on the West Coast. Originating in Belgium with the sour ales, such as the Lambic, Gueuze, Flanders Red Ale, and Oud Bruin (which I wrote about previously, here), a lot of the local breweries have decided they want to make their own sour beers.

Let’s talk about first why we’re calling it wild in the first place. The origin of sour beers from Belgium would be produced in what’s called “open-air fermentation“. This means that rather than using a yeast where it is measured, carefully selected and used in a controlled environment, the tanks in this case were left open. This would allow yeast and bacteria to enter the tanks, leaving behind a sour flavour. While this type of fermentation can leave behind “off-flavours” in other types of beer, this type of fermentation is actively trying to re-produce these wild conditions to develop a unique flavour.

Next, let’s talk about what yeast and bacteria are considered among the wild class:

Four Winds Berliner Weisse

Only lacto. German style sour wheat beer.

– Brettanomyces (aka “Brett”) is a wild yeast that is used in fermentation of many sour beers. It can take weeks, months, or years before the yeast is finished fermenting. It can be a slow process and you won’t necessarily get the same results every time. This is why people may purchase the same beer from year to year and then cellar it (remind you of wine enthusiasts, doesn’t it?). Any time you think of a beer tasting funky, you have Brett to thank for that!

Driftwood Gose-uh label

Only lacto. Gose German style sour.

– Lactobacillus is a bacteria that will consume the sugar and impart lactic acid. This is where the sour of sour beers come from. Since this bacteria is going to be occupied making lactic acid however, the yeast has to be added at a different time so that the increasing acidity doesn’t kill all the conversion of sugar into alcohol. (Thanks again, Brett!If the lactobacillus is used without the Brett however, the flavour left behind is a clean sour taste. Nothing funky or barnyard-y about it!

– Pediococcus is another bacteria that functions similarly to lactobacillus except that it imparts sourness and funk into the mix. I personally haven’t seen it listed on any beer labels, but the Belgians tend not to label their beers, either.

Moon Under Water - Hip As Funk label

Only Brett. Farmhouse IPA.

Since the West Coast beers are relatively new to producing sours, they like to include what they used to make it sour. Which is great, if you know which of the sour flavours you like and don’t like. Sour beers are polarizing; just like IPAs, people either love them or hate them. Knowing what aspect of the sourness one likes or dislikes, they can choose more wisely. Perhaps you like the sour and not the funk? Or perhaps you like the funk or not the sour? Or perhaps you are a sour fiend such as myself and you love all of it!

 

Links for further reading:
The Brettanomyces Project – someone’s Masters dissertation on Brettanomyces, in addition to the beer they are producing
Pediococcus on Wikipedia
Lactobacillus on Wikipedia
Gose beer on Wikipedia
Four Winds Brewing Company – in Delta, BC
Driftwood Brewery – in Victoria, BC
Moon Under Water Brewery – in Victoria, BC

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