In the first of this mini-series on the subject of wine faults, we looked at cork taint (corked wines) and oxidation. In this feature we have a quick run through of a more recent and sometimes controversial fault, caused by a rogue yeast that is colloquially known as Brett.
Brett, the Bad Boy of Yeasts
‘Brett’ is short for Brettanomyces, which is a type of yeast that lives on the skins of fruit, but also for winemakers can hang around in the winery, in particular in barrels. It changes the character of wine, in most cases for the worse. The conditions that allow it to develop are varied; poorly cleaned harvest and winery equipment, problems with fermentations, low acidity in wines, and less than perfectly cleaned tanks and barrels being the most common.
Once the winery is ‘infected’ with Brett, it is a devil to get rid of, which is why many wine traders who buy in bulk (ie from the tank) will not touch any wines from a property where they have detected even a small hint of Brett, for fear of contaminating their (usually very large) wine blending facility.
Having said that, it has long been argued that ‘a bit of Brett’ makes a wine more interesting. Well, it can do but only in specific circumstances; the Brett compound has to be the right type (see below), be only in small quantities – itself reliant on people’s sensitivity to it which varies a lot, and also the wine must be stable – that is to say, a bit of Brett today can soon become a lot tomorrow.
Btrett produces three phenolic compounds which give different characteristics to the wine, namely;
4-ethylguaiacol – typical aromas and tastes include smoky bacon, spice, and cloves
4-ethylphenol – band-aids and antiseptic, acetic acid
isovaleric acid – sweaty socks, cheese, horse, mouse droppings
The first one, 4-ethylguaiacol, can be pleasant in a wine – the others not so much!
To combat the threat of Brett, winemakers need a healthy crop of grapes, careful hygiene all stages of the harvest and winemaking process, diligence during fermentations, and good control of temperature and levels of sulphur (the all-purpose preservative and antioxidant used in winemaking) are also important. In organic winemaking, given we use much less sulphur, the other factors become even more important.
2018 is a vintage marked by low acidity in Bordeaux (high pH) which has set the alarm bells ringing, due to the relative inability of sulphur to protect wine with low acidity, so extra care (and even, in some case, acidification of wine), is needed.
Incidentally, there are winemakers who take the opposite view and let Brett do its thing (along with all the other volatile compounds), most notably Chateau Musar, the famous Lebanese wine. However, they are the exception and most people in the industry nowadays view Brett as a fault to be avoided.
Fun fact; Brettanomyces actually comes from the Greek for ‘British Fungus’, as it was first discovered when chemists investigated spoilage of British beer over a century ago.
Chateaux Musar (Lebanon) and Beaucastel (Chateauneuf-du-Pape), two famous wines who, it is said, have had a strong presence of Brett over the years.
A few of the aromas caused by Brett…