How to Choose a Brett Strain

Remember Brett? In a world of rampant pastry seltzers and fruit purée "berliners", it has felt a little like our funky friend has fallen by the wayside. But we're soldiering on here at Escarpment Labs, where we are devoted to showing all the potential of our funky friend Brett.

In this post I will cover:

  1. The history of Brett any why it's the original hype yeast
  2. Different species of Brett and what they do
  3. How the Escarpment Labs Brett collection compares
  4. Best practices and pitching rates for Brett primary and secondary fermentation

Brett: the original hype yeast

A hundred and twenty-ish years ago, Brett beers were the hyped beers. More specifically, a bunch of European brewers were trying to replicate the character of aged English porters, which had a complexity that was hard to replicate. Some smart early brewing scientists in Russia (Kalinkin), Ireland (Guinness), and Denmark (Carlsberg) figured out that reproducing the English character depended on a slow-growing yeast found in the beers, which was dubbed Brettanomyces (British fungus; Brett for short).

The lab at Carlsberg even patented Brett, which is notable for being the first patent on a microorganism! Since then, awareness of Brett improved and it became known for providing critical flavours to beers including Belgian Lambic, Flemish ales and Berliner Weisse. Interestingly, Carlsberg is still leading the charge in researching Brett. 

Different types of Brett

Since then, a number of Brettanomyces species have been classified including Brettanomyces bruxellensis ("British yeast from Brussels" - weird), Brettanomyces anomalus ("weird British yeast"), Brettanomyces custersianus (named after Custers, who did a bunch of early research on Brett). There are a few other species but they don't show up in beer very often.

In general, B. bruxellensis is the most aggressive fermenter of the family, with some strains capable of fully attenuating wort. Some strains are incredibly aromatic, producing up to forty times the concentration of certain esters when compared to their Saccharomyces cousins. They also tend to produce a higher quantity of funky phenols than other species, so B. bruxellensis tends to be your go-to for funk bombs. B. anomalus and B. custersianus are often more subtle and may lend citrus, peach, white wine, and lighter funk to a beer.

That Custers fellow is important. He found the Custers Effect, which is the odd trait of Brett to stall between aerobic and anaerobic fermentation. In practice, the Custers effect often leads to extremely long lag phases for Brett growth. This in turn means that Brett solo fermentations can be painfully slow to take off and complete fermentation.

Escarpment Labs Brett Catalog

Product Species Flavours Suitable Styles Primary Ferment

Brett B

B. bruxellensis Pear, Tropical Fruit Pale ales, sours, Orval clones
Brett D
B. bruxellensis
Pineapple, Hay Hoppy beers, pale sours Yes
Brussels Brett
B. bruxellensis
Fruit Salad, Candy, Lambic Pale sours, "Lambic"
Brett C
B. anomalus
Citrus, Mango Hoppy beers, anything barrel aged
Brett L
B. bruxellensis
Cherry, pleasant acetic Flanders Red, Oud Bruin, barrel aged sours Yes but slow
Brett M
B. bruxellensis
Balanced fruit and funk pretty much anything
Brett Q
B. bruxellensis
Strawberry, Red Wine Saison, barrel aged sours Yes
Berliner Brett I
B. anomalus
Citrus, White Wine Berliner Weisse, Saison, pale sours
Berliner Brett II
B. bruxellensis
Peach, White Wine
Berliner Weisse, Saison, pale sours 
MOTHERSHIP Brett Blend both A bit of everything mixed ferm Saisons, barrel aged sours


Brettanomyces flavours

Brettanomyces is a very special yeast, known for its delightful range of flavours which include both candied-fruit esters and bombastic funky barnyard phenols. Brett can produce a dizzying range of esters, which can make different strains taste like plum, pineapple, strawberry, cherry, and all sorts of hypothetical fruit in between. Those phenols are also important, giving Brett a potent complexity from their barnyard, hay, and campfire qualities. Those phenols are also why Brett has such a bad rep, especially in the wine world. In some environments like barrel aging red wines, Brett can run amok and produce excessive phenols and steamroll more delicate flavours.

But we're focused on beer. And in beer, we believe in the dizzying array of flavours and potential outcomes using our Brett strains.

Brett fermentation strategies

Brett is a survivalist. It's kind of like a microbial cockroach. It's able to survive in places where other microbes wouldn't bother. This is why it is so feared in the wine industry - and also in the beer industry, but I will say that accidental Brett contaminations are rarer than diastaticus or lactic acid bacteria.

This informs how we choose to ferment with Brett. It's used to finding itself in a beer with all the easily accessible sugars and nutrients gone, and it has adapted to scavenging what's left (longer chain sugars from malt and wood, polysaccharides and proteins released from dying Sacc, and so on). The funky flavours of Brett are a result of this activity. Brett is able to use some of the phenolic precursors as electron acceptors, helping it survive in a low-oxygen environment.

That's right - Brett doesn't do so well under anaerobic conditions. In fact, it really struggles (remember the Custers effect). While we long for the day that we get to title a scientific paper "Custers Last Stand: Improving Anaerobic Fermentation in Brettanomyces", we're not there yet.

In general, due to the Custers effect, Brett is much easier to work within secondary or co-fermentation where it is inoculated after or alongside a stronger-fermenting primary yeast. This ensures the beer gets through lag phase and is protected by alcohol faster, while still leaving plenty for Brett to work with in creating its magical fruity and funky flavours.

Brett primary fermentation

Brett primary fermentation is certainly a challenge, but not impossible. It's important to pick the right strain (some ferment maltose faster than others). From our stable, we've found Brett D to be the most reliable, but it's still Brett. Other strains capable of primary fermentation include Brett Q and Brett L. 

If you're taking on a primary fermentation with Brett, we strongly recommend making a vitality starter of the yeast 1-2 days prior to pitching into your ferment, even if it's a fresh lab culture - even cold storage and shipping can be enough to slow down a Brett culture since Brett doesn't seem to accumulate storage carbohydrates in cold conditions like Sacc does (e.g. glycogen and trehalose).

it's important to know that it will lag for a while (2-4 days is not uncommon) and then proceed through a linear fermentation (as opposed to the sigmoidal curve that most Sacc ferments follow. Typically this means it will drop 0.5-1ºP per day (0.002-0.004 SG points per day) before levelling off.

Oxygen and Brett primary ferments

Don't be afraid of oxygenating repeatedly (eg daily) while Brett is in lag phase. Most brewers are afraid of Brett plus oxygen, fearing acetic acid. The production of acetic acid by Brett requires ethanol being present first, and if the yeast has not produced ethanol yet, you're in the clear, and the Brett will be much happier getting some extra oxygen to get moving on fermentation. If you're afraid of THP, know that Brett can also reduce the most flavour-active form of THP. We'd rather you have a beer that requires a bit of time to clean up THP than a beer you have to dump because fermentation never started.

Those with the patience for the Brett primary ferment will be rewarded with exceptionally fruity aromas. We have observed Brett primary ferments to produce significantly higher concentrations of esters like ethyl hexanoate (pineapple) and ethyl octanoate (red apple) as well as esters fairly unique to Brett like ethyl isovalerate (tutti frutti).

Extra links:

Our 2019 publication on Brett primary ferments

Milk the Funk Wiki

Demystifying Brett with Caroline Tyrawa

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