I’ve recently noticed that it’s becoming more and more der rigueur to ferment a beer with a single or multiple strains of Brettanomyces without the help of any other yeast.
That sounds interesting I thought, I’ll give that a crack, first things first though, research!
Brettanomyces does not in itself produce a traditional sour beer, brettanomyces is more often associated with funk more than sourness although Brettanomyces will produce both lactic and acetic acid, acetic acid production is relatively low and will only occur under aerobic conditions.
Brettanomyces fermentations will show a pellicle, a coarse white matt that floats on the beer protecting it.
Brettanomyces produces three compounds that have high sensory profiles: 4-ethyl phenol (band aid and barnyard), 4-ethyl guaiacol (wet burnt wood, spicy) and Isovaleric acid (fruity esters and rancid characters)
Research indicates that Brett has nutritional requirements similar to brewer’s yeast, doesn’t grow well at low temperatures or at pH values lower than 3.4. Brett works well between 13-30 degrees with less pleasing organoleptic results in the upper end.
To use Brett as a primary fermenter a very large cell count is required, proper pitching rates are not well defined but indications are to pitch at least 1.25 x 106 cells/mL per °P or as much as a lager fermentation. Brettanomyces fermentations properly pitched will take as long as a lager fermentation.
Although when thinking about a 100% Brettanomyces beer the natural assumption is that the beer will be crazy with a lot of wild Brettanomyces character, this however paradoxically is often not the case. Without the competition of a mixed strain fermentation Brettanomyces does not tend to ferment as many of the complex carbohydrates that are present, this coupled with the lack of by products supplied by Saccharomyces that serve as substrates for flavour development means that the crazy flavours and aromas that are the signature of Brettanomyces are often at lower levels.
So, what strain to use? Brettanomyces bruxellensis and B. clausennii are easy to come by from Whitelabs so I used them. What beer to ferment them in? I thought I’d go with a mid strength beer first off, I was brewing a New Zealand pale ale at the time so hijacked some wort and fermented some with B. bruxellensis and some with B. clausennii
Brettanomyces bruxellensis took 16 days to ferment wort from 1.055 down to 1.009
Brettanomyces clausennii took 16 days to ferment down 1.055 to 1.018 and then stuck there
Both beers were bottled without sugar and then refermented.
Tasting brux bottled 28/3 tasted 9/5 Bottling grav 1.009 down to 1.006
Pours a lovely gold with a big white fluffy head, looks great.
Aroma is a cacophony of sweet sweaty NZ hops and a horse blanket funk from the Brett
Flavour is moderately dry with a tart and slightly acetic flavour, bitterness and the flavour of the hops work well together
Finish is acidic and dry and long, a delicious beer that begs for a sunny day
Tasting claus bottled 27/3 tasted 9/5 Bottling gravity 1.018 no change
No Carbonation and no change in gravity.
Overly sweet and unfinished, some light funk and slight acetic character, overall disappointing.
The fermentation is unfinished with no carbonation in the bottle, although the pitching rate was the same as bruxellensis it seems that clausennii requires a higher pitching rate to complete fermentation.
A fascinating experiment, further brewing experiments are need to correctly determine the pitching rates required for different Brett strains. What’s your favoured brett strain to use? and how do my results compare to your own? Let us know in the comments below.