Editor's note: this blog post was written by our summer intern/resident expert in all things microbial, Mike Tonsmeire, AKA The Mad Fermentationist.
There is plenty of confusion about what role Brettanomyces (Brett) plays in the fermentation of beer. Many people incorrectly believe that it generates the acidity that makes sour beers sour, but this is actually the dominion of the lactic acid bacteria Lactobacillus and Pediococcus. Brett is a sugar-consuming alcohol-producing yeast, a cousin of Saccharomyces cerevisiae (ale yeast). While Brett is often referred to as “wild” it was first isolated over 100 years ago, and today is easily ordered from yeast labs.
Traditionally, Brett works in tandem with Saccharomyces. In these cases its role is to produce bright fruity and complex “funky” flavors, as it slowly reduces sweetness. A more phenolic (spicy) primary fermentation by a Belgian or hefe weizen yeast strain creates more precursors for Brett to pump out the classic “horse blanket” aromatics for which it is known. For Neverwhere we decided to forgo brewer’s yeast entirely, allowing the Brett to work alone. Counter-intuitively, the result is less aggressively funky flavors than a beer fermented with both Brett and ale yeast.
Just like clean American ale yeast and fruity/spicy Belgian ale yeast are both members of the same species, there is a wide range of Brett strains. For Neverwhere, we selected Brettanomyces bruxellensis var. Drie. This strain is known for bombastic fruitiness, imparting aromatics reminiscent of mangoes and pineapple. Rather than try to contrast the flavors provided by the Brett, we instead reinforced them by heaping in Citra, Centennial, and Chinook hops. On the nose you couldn’t be blamed for assuming that this is simply a righteous IPA. However, the flavor has a deeper and more complex pineapple flavor than hops are capable of instilling. The result is juicy, bright, but with some complex earthy undertones.
Unlike classic mixed fermentation Brett beers, Neverwhere is not intended for long-term aging! It will be at its peak for only a few months after its early July release, after which the hop character will fall off. Later this week, we’ll be brewing Modern Times’ second 100% Brett beer; an as-yet-unnamed pale ale flavored with a blend of hops from three continents: Motueka from New Zealand, Cascade from America, and Triskel from France. We expect to have it done in about a month.