Traditionally, the yeast used in beer is yeast that is intentionally added and often referred to as domesticated yeast. But all kinds of wild yeast occur naturally! In fact, there is probably one or two hanging out in your back yard right now. Most brewers make conscious efforts to keep any unwanted yeast out of their brew because the flavors they create are more often than not, undesirable (or at least unintended). This is why hombrewers and commercial brewers are always so freaked out about keeping everything so damn clean.
But recently, there has been a growing movement back towards the roots of beer brewing and the use of so-called wild yeasts.
Historically, the use of wild yeast was common, as modern sanitation did not exist, and brewers did not have the option of keeping wild bacteria out of their beer. In fact, in Sweden they used to have a family “brewer's paddle” that was passed down from generation to generation. Imagine all the yeasties that would collect over the decades! Wild yeast has the advantage of adding complexity to beer and creating unique flavors and nuances that is not found in other brewing approaches, but they are often unpredictable and can product a variety of outcomes.
If you haven't used a strain before, be prepared for a wild ride!
So, how do you use wild yeast in beer?
Table of Contents
Manual Addition
Some wild yeasts can be manually added into brewing in the same way that domesticated yeasts can be. One of these yeasts is Brettanomyces, often known simply as Brett. A number of commercial beers and homebrewers have begun to take advantage of this yeast. The flavors it imparts on beer are sometimes called “funky” or “horseblanket” (yeah, that's a weird one, but it's true).
Brett can be used in all types of beer but you'll see it in a lot of aged beers and Belgian styles beers in my opinion. Belgians naturally have a dry mouthfeel and tart flavor to them (also because of yeast and attenuation {a60bef903c54612bed20edb95d22500dcc3da56ac2b90be5eb4391998d03cdd5}), while aged beers simply sit longer. Brettanoymces takes a while to fully attenuate, so adding some brett to a bigger beer can help dry it out a bit, and the aging process gives this style of yeast time to do its job. Of course, anything ‘sour' or ‘wild' is likely to have brett in it as well.
Another popular one is Lactobacillus. This is actually a common cause of spoilage of beers. Your sour stout or IPA that seems a bit tart may have got infection from this strain of yeast. But some styles require it! Berliner Weisse from Germany, as well as Flanders styles and lambics all use this souring strain of yeast.
More recently however, with the burgeoning interest in all things local, yeast wrangling kits have appeared, and it's actually possible to harness, isolate, and grow yeast from your area.
Open Fermentation
The second approach to brewing with wild yeast is simply to leave the batch open to the elements. This is a more random approach and it means your results will be much more unpredictable. This approach can certainly be more challenging, and it does involve an element of luck. This method works because leaving the fermenting beer open allows for wild yeasts and bacteria to find their way in there and begin a natural fermentation process. It's sometimes called spontaneous fermentation.
You do not know precisely what bacteria are in your brew or what the outcomes on the final flavor is likely to be, but that's the fun part! If you choose your grain bill wisely you may be able to pass it off as a decent sour beer.
Not all open fermentations are sour though, and traditional breweries like Sierra Nevada and Anchor Brewing still use open fermentation tanks even though they brew with domesticated yeast strains.
Sour Beers
The first time you try a sour beer it will be a very strange experience. They are unlike anything you've ever tried, especially if you are just getting into craft beer. The flavor is definitely NOT you would consider “beer”. It's only you are introduced to this new world of and discover how many styles are out there that you view of what beer is starts to broaden.
My first sour was a Berliner Weisse, and from that day on, I was hooked. If you are just getting started, lambic and some blended Flanders styles are very accessible both in availability and in taste.
Two awesome books exist on the topic of brewing sour beers: American Sour Beers and Wild Brews. The writer of American Sour Beers is also the owner and writer for the Mad Fermentaionalist, a blog that discusses the topic in length, including many experiments and recipes.
photo credit: Adam Barhan
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