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Wild, Sour & Mixed Fermentation

Posted: 2017-11-09 By yoke_admin

What gets me up in the morning is Brettanomyces, and to be more specific, the management of Brettanomyces in a mixed flora environment.


When I started at Marble Brewery at the very beginning of 2016, the was no barrel or mixed culture programme to work on, so I set about creating one. After finding and assessing four unused barrels that were previously hidden away in storage, I settled on exactly how we should kick our programme off. One of the first beers I brewed was an Old Ale, this type of beer is strong and relatively lacking in initial depth which makes it perfect for adding both interesting yeast strains and bacteria, and carefully selected adjuncts.


Brewing an Old Ale, for me, was a clear win given the aromas contained in the barrels we already had in reserve. What it also meant was that I could indulge my love for British Stock Ales, these to me are as complex and interesting as anything by Rodenbach or Duchesse de Bourgogne from Brouwerij Verhaeghe, but in comparison, Stock Ales just don’t get as much press. They’re not brewed too frequently either, except the few that still come out of Greene King, which is a shame as these vatted strong beers are completely crawling with fascinating microflora. Take a look at our Barrel Aging Program to see how our work with historical styles is cumulating.


My other great love is mixed fermentation wild/ sour beers, so my long-term plan was to get things rolling as soon as possible, as it usually takes between one to three years to achieve the required level of maturity. We’ve got a few barrels in the brewery at the moment, most of them bought as and when the opportunity arose, depending on how I was feeling at the time or precisely to fit in with my strong and bretty plans. The key thing I was looking for when buying was wood. Lots and lots of wood that I could age and ferment wild beer in. First things first though, I wanted to reduce the tannin load and the previous occupancy character, beer is a great solvent, so the best way to do this is to fill them, let the beer take up those qualities and then empty.


Once I’d done this with the barrels that I required to start the wild programme I went ahead and brewed four beers.



The first beer we brewed was a turbid mash.


  • Pilsner Malt
  • Oats
  • Rye
  • Wheat
  • Spelt
  • 1.044
  • 3ibu


Three Belgian strains went into the blend for primary fermentation; 20% Chimay, 30% Westmalle and 50% La Choufe. We first used this blend in Pugin Belgian Pale, brewed with Gorton Monastery, followed by Assisi Belgian Dubbel and so on the third pitch, I expected some blend drift. I wanted to create a sophisticated ester profile for the Brettanomyces to biotransform while targeting certain characteristics that each Belgian strain would bring to the blend.


Once primary fermentation was complete, I transferred to purged, second-fill Meursault, Pinot Noir and Rum barrels, and added differing proportions of  Brett, Lacto and Peddiococus yeast strains to maximise blending potential:

  • Brettanomyces bruxellensis
  • Brettanomyces lambicus
  • Brettanomyces claussenii
  • Brettanomyces anomalous
  • Brettanomyces trois
  • Lactobacillus brevis
  • Peddiococcus damasus



The second beer I brewed/ experimented on was the Madeira barrel refill.


  • Pilsner
  • Carapils
  • Caramalt
  • 1.047


For this beer, I took unbittered wort and filled the Madeira barrel after emptying them of Gales Prize Old Ale. I pitched no yeast into this, limited the oxygen in the wort and then pitched Lactobacillus and Pedioccocus – the plan with this beer was to target bacterial growth hoping to strengthen our cultures while using the Brettanomyces present in the barrel to slowly ferment the beer. By doing this, I could create both a strong culture going forward and more blending options.



The third beer I experimented with was a Flanders Red.


  • Pilsner
  • Oats
  • Munich
  • Vienna
  • Crystal
  • Special B
  • 1.065
  • 20ibu


With this beer we took an entirely different approach, I decided that I wanted to set the sour character first and then build the beer and complexity around it. To do this, I kettle soured it and then boiled. Post-boil I sent it to the fermenter and pitched our house Saccharomyces strain into it. I then immediately filled barrels (Pinot Noir, Rum and Bourbon) and pitched a further two different Brettanomyces blends. My goal and reason for a mixed yeast fermentation was to provide the Brettanomyces with flavour active compounds that it could work on to ensure compelling complexity in the finished beer.



  • Pilsner
  • Oats
  • Rye
  • Spelt
  • 1.047


Once again, I put unbittered wort in the barrels (Barbera and Pinot Noir). The goal for this beer was to test the strength of our Lacto strains while pairing them with Saison and Brettanomyces yeast strains. I intend to create a strong mixed culture that will develop and sour over a relatively short period of time (3-6 months).


These are our current wild fermentations, as time goes on we’ll be emptying barrels and refilling them with further sour projects to broaden our blending potential and to provide a constant supply of beer at different stages of complexity and maturity. You can watch these projects develop over on our Barrel Aging Programme Page.

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