Brettanomyces (AKA Brett), often mistaken as bacteria, is in fact a species of yeast. It can also called Dekkera which is the sexual reproductive stage of the organism.

It is a wild yeast, often found on the skin of fruit and naturally airbourne in most environments. Brettanomyces would have been a common contributor to the flavour and character of English beers until the 17th Century when pure cultures of  Saccharomyces cerevisiae and S. pastorianus took favour. Since then Brettanomyces has largely been regarded as unwelcome and treated as wild contaminate.

Brettanomyces has always been only used in the production of Belgium Lambic and spontaneous beers. In recent years though, especially in the United States, brewers have been embracing Brettanomyces once again. Highly respected brewers like Vinnie Cilurzo from Russian River Brewing and Chad Jacobson from Crooked Stave have been using Brettanomyces to give amazing character and complexity something not achieved using Saccharomyces alone. There are also now a growing number of breweries producing only beers made with Brettanomyces and bacteria.

Species of Brett

There are two main species of Brettanomyces commonly used in brewin.  B.anomalus (b.claussennii) and B.bruxellensis (b.lambicus). Much like strains of regular yeast species, These have many strains giving a wide variety of flavours. Think of the differences between lager and Belgian yeasts and multiply by 1000. Brettanomyces can offer a huge spectrum of chracters.

Brettanomyces is renowned for what is referred to as “Funk”. Hard to describe but when you have had a Brettanomyces beer you will immediately recognise its traits. Brettanomyces will create esters producing fruity notes of pineapple, hay, pear and applies. It may produce less obviously desirable characters barnyard, mousey and sweaty horse aromas but these can also add depth and complexity. Obviously if not handled correctly these can make from some pretty unpleasant traits can be unwelcome in most beers. They can also lift a normal beer into something quite amazing when paired with the correct sugars, hops and environment.


Funk not sour!

Although Brettanomyces can produce high levels of acetic acid lowering the pH and producing a sour tasting beer, this is only usually in the presence of plenty of oxygen.  There is a distinct difference between Brettanomyces only beers and what most people would call a sour beer. The majority of sours beers are produced using Lactobacillus and/or pediococcus bacteria producing high amounts of acids under the right conditions. Beers brewed using Brettanomyces only should not be classed as sour beers unless the conditions have led to high levels of acid.

One of the most interesting things about Brettanomyces is it’s ability to convert alcohols and compounds produced by Saccharomyces into new flavours and aromas. Immense fruit esters can develop when Brettanomyces is added after primary fermentation using standard Saccharomyces strains. Brettanomyces can also protect hop character as it reduces the effects of oxidation and therefore can be really helpful for hoppy IPA's and DIPA's.

Using Brettanomyces as a secondary strain.

Brettanomyces grows at a much slower rate then Saccharomyces. Therefore it can take a lot longer to develop full character. When using as a secondary strain, it can take many months for the full flavour and aroma to shine.  Brettanomyces also has the ability to ferment complex dextrins which are left by the primary fermentation and can easily ferment most beers to a final gravity of 1.003 or even lower. The more sugars the Brettanomyces is able to utilise, the more character will be added so creating a less fermentable wort via a warmer mash or even stopping the primary fermentation early by cooling can be advantagous. Brettanomyces will also process acids created when the Saccharomyces dies  through autolysis. The Brettanomyces breaks these down creating complex fruit esters. Therefore there is no need to rack the beer off the primary yeast once fermentaion is complete and in fact not racking will be beneficial.

When using Brettanomyces as a secondary strain, care must be taken to ensure the beer has reached a steady final gravity, otherwise you risk over carbonation and possibly even exploding bottles. Gravity must be stable over at least 4 weeks before you can confidently package, especially if you are using glass.

Pitching rates for Brettanomyces in secondary are relatively low. As little as 50,000 cells/ml will give significant Brettanomyces character although you can go up to 2 million cells/ml. Whitelabs Brettanomyces vials contain 17.5 billion which would provide around 875,000 cells/ml in a 20L batch and is an ideal starting point for experimentation. Often the more stressed the Brettanomyces is the more character it will add although this will take more time.

Pellicles can form when brewing with Brettanomyces. Although these look disturbing to the uninitiated these in fact protect the beer from oxygen. Care should be taken not be disturb them.

Fermentations using 100% Brettanomyces.

Brettanomyces is capable of producing beers without using Saccharomyces and therefore can be used on it’s own. Without the by products of the Saccharomyces, the Brettanomyces can be more restained but the fermentation will be quicker and similar to a saccharomcyes fermentation. Extended ageing is not required as terminal gravity will be reached reasonable quickly (around 3 weeks) and the Brettanomyces will usually leave more residual sugars then when used as a secondary strain. Again this should be monitored before bottling but a couple of weeks should be ample.  Unlike Saccharomyces, Brettanomyces does not produce the chemical glycerol which contributes to mouthfeel and body in the finished beer. It’s therefore advisable to add a good proportion of oats or wheat malt to the malt bill to ensure the final beer doesn’t taste too thin.

When using Brettanomyces as the primary fermentor higher pitch rates are required to avoid an extended lag time and possible exposure to unwanted spoilige organisms. Generally a pitch rate similar to a lager would be required, ie around 1.5 Million cells/ML or 2 whitelabs vials in a 20L wort. Starters can be made but this can produce large amounts of acetic acid as oxygen is present.

Commercial strains and working with Brettanomyces

There is a ever growing range of pure Brettanomyces and blends of Brettanomyces, Saccharomyces and bacterias available from wyeast, whitelabs, Yeastbay, Gigayeast and Omega Labs. Of course you can also resuse dregs from your favourite commerical beers.

Brettanomyces can also be very easy to store and it will remain active at room temperature so no need to keep refrigerated.

Although Brettanomyces is a yeast and therefore will be killed off by high temperature or drastic changes in pH, it can also bury itself into soft surfaces like plastic and wood. If you are brewing clean beers using just Saccharomyces as well as beers using Brettanomyces you will need some separate equipment. Stainless steel is fine but any plastic equipment including tubing and seals will need to be separate to avoid cross contamination. With careful sanitation both types of beers can brewed side by side without too much worry of spoilage.

Brett can be used in most styles of beers including Saisons, IPA’s, Porters and Belgium Style beers so experimentation is highly advised. Once you get the bug for alternative fermentations there will be no going back as it will open up a whole new world of flavour combinations. Next time you brew a batch of clean beer, perhaps split a batch or two off and age with Brettanomyces.

If you want to try some brett brewing then we have put some recipes over on our recipe generator or please share your own!