All Brett Porter

It’s a cold day to be brewing in the garage!

Just a forewarning – this is going to be a long post. This weeks brew is an all-Brettanomyces Brown Porter.  As readers of my blog know, I’m interested in wild brewing – I’m also a huge porter fan.  Today’s brew is a fusion of these two loves, forming what I hope will be a fantastic brew.  I find it odd that today’s wild beers are largely based on lighter beer styles, as wild yeasts such as Brettanomyces have a long and close relationship with darker beers.  Indeed, in its heyday (1800’s) Porter was one of the most widely brewed styles of beer.  Aged porters (often labelled as ‘Stock’ or ‘Stale’ porter) usually had gone through a secondary ferment with Brettanomyces that was resident in the ageing barrels. This flavour was reputedly a cherished and desired for characteristic by many beer consumers.

Todays brew is a modern twist on this old tradition – instead of secondarying with Brett I am instead using it as the sole yeast in the beer.  This is not as simple a task as one might expect – brewing all-Brett dark beers is a challenge for a range of reasons. One issue is that Brett has a tendency to accentuate the astringent aspects of dark malts.  Meaning the normal mild astringency in porter, provided by chocolate & other dark malts, can be converted by Brett into an unpalatable mouth-drying astringency.  Moreover, the polyphenols found in the hulls of darker malts can act as substrates for the enzymes in Brett which create unpleasant mousy and plastic flavours (e.g. 4-ethyphenol). As such, careful planning of the recipe and brewing methods are required to minimize the formation of these unwanted flavours.  Lastly, bretts digest a lot of the dextrins that provide body, meaning we have to provide body through other mechanisms.

But the use of Brett offers a number of interesting possibilities – most notably, the unique impact Brett  has on flavour.  Brett produces a rage of unique flavours through two mechanisms. The first of these are fermentation products, both phenols and esters. While the phenols can be desired (leather & earthy flavours/aromas) they can also be undesired (burnt plastic, mousy, old socks). The esters, however, are a unique canvass for us to work with – citrus & tropical fruits, cherries, stone fruits, etc, are all part of Bretts flavour/aroma palate. In addition, Brett expresses β‐glucosidase, an enzyme which allows Brett to degrade unique carbohydrates such as cellulose (wood) and some hop compounds. The later hop derivatives can also create some unique flavours/aromas, especially those of tropical fruits like papaya & mango.

Like I said, this is going to be a long post, so more details, the recipe & brewday notes are below the fold.

Choosing a Strain:

Formulating a Recipe:
To reduce the likelihood of producing undesired off flavours it is necessary to modify the typical porter recipe and brewing process to prevent the extraction of the undesired flavour precursors that brett can convert into downright nasty flavours. Mainly, we are targeting polyphenols, which are found in the husk of the grain – especially in the roast malts. My base grain bill is a classic porter bill:

• 3.85 kg Marris Otter
• 0.5 kg Crystal 60L
• 0.4 kg Chocolate Malt

Brewed with conventional English ale yeasts and some fuggels hops this recipe makes a nice brown porter.  With brett this brew has the potential to be both highly astringent (due to the chocolate malt) and very thin bodied due to the consumption of dextrins.  So we need to make a few small changes. Three-quarters of the chocolate malt will be replaced with a dehusked dark malt – balckprinz (AKA Carafa Special III).  This will provide the flavour of chocolate malts without astringency from the roasted husks.  One quarter of the chocolate malt remains to provide a better flavour profile.  A handful of oats are added to provide body, in the form of the glucans (carbohydrate-coated proteins that are resistant to degradation by brettanomyces).  So the grain bill now becomes:

• 3.85 kg Marris Otter
• 0.5 kg Crystal 60L
• 0.3 kg Blackprinz Malt
• 0.1 kg Chocolate Malt
• 0.2 kg Rolled oats

Despite our recipe modifications we still need to make extra efforts to avoid polyphenol extractions and thus the formation of harsh phenolic flavours like burned plastic. This is rather simple – we ensure our mash and sparge never gets over 75C (167F) and if fly-sparging, that we keep our sparge water at proper pH (5.2 – 5.6) and run-off gravity above 1.010. I’m batch sparging, so this is easy – no mash-out, and sparge water heated to 75C.  Efficiency will be hurt slightly, but a few cents extra malt is a better option than an undrinkable beer.

The Recipe:

A new pot & warm boots make a cold brew-day bearable!

Brew-day:
Once again I find myself shivering in the garage while brewing; while happy wife = happy life, sometimes keeping her happy (by not brewing in the house) has some real drawbacks! But warm boots, a jacket and a toque make it bearable.  Because its cold (about -7C) and extremely windy I mashed-in a few degrees warmer (77C instead of 75C) to account for the heat-loss during mash-in. I hit mash temp dead-on, and by wrapping a sleeping bag around my mash tun I managed to keep the temperature within a degree of where it should be. I’m starting to think some sort of recirculating system may be in order.

My efficiency was higher than normal 83%, up from 75%; I think this is a good sign that I’m dialing in my new grain mill to an ideal (and hopefully consistent) setting.  I had to slightly modify the hop schedule as the alpha-acid content was lower (4.3%) than modelled in beersmith (4.75g); I kept the bittering addition the same and upped the flavour addition by 10g, restoring my planned 30IBU while adding a bit more hop character to the brew.  The rest of the brew-day was uneventful; during the boil I built a door for the pantry I just built in the basement and started work on a deadman for my tablesaw (you know you’re having a slow brew-day when other chores can get done).

Resources:
Obviously, a lot of research went into preparing this recipe & post – I hope the beer works out after all that work!  My main resources for this was:

• Chad Yakobson thesis work on Brettanomyces in beer fermentation.
• Youtube videos of a lecture by Chad Yakobson
  • Video 1 – bulk of lecture
  • Video 2 – last 10 min of lecture + questions
  • Video 3 – questions
  • Slide handout
• Lucy Josheph’s Lecture Slides (Powerpoint)