Brettanomyces
Brettanomyces
Brettanomyces, usually shortened to "Brett," is a wild yeast that can survive in wineries and barrels and produce distinctly animal, medicinal aromas. It is unusual among wine faults in that opinion is genuinely divided a whisper of it is embraced as complexity in some traditional red wine styles, while more than a whisper is considered a serious flaw almost everywhere.
What does it smell like?
Barnyard, horse sweat, band-aid, or a medicinal, leathery edge that sits over the fruit rather than within it.
At very low levels it can read as savoury, earthy complexity; at higher levels it overwhelms the fruit and reads as a distinctly "dirty" character.
Aroma Classification
Brett falls outside the primary/secondary/tertiary framework it is a microbial spoilage character caused by wild Brettanomyces yeast metabolising compounds in the wine, most often during barrel ageing.
Nature's Influence
Climate
Brett is driven far more by winery hygiene and barrel age than by climate or vineyard conditions old, porous barrels are its most common hiding place.
Warmer, less hygienic cellars and wines with lower free sulphur and higher pH are generally more vulnerable to Brett taking hold.
Soil & Site
Not applicable, Brett is a cellar-borne organism, not a vineyard character.
Vintage
Not vintage-dependent in the way fruit aromas are; risk is driven by cellar practice year to year rather than the growing season itself.
The Winemaker's Hand
Harvest Timing
Not applicable.
Fermentation
Brett is rarely active during primary fermentation, when yeast populations and alcohol levels suppress it; it typically establishes afterward.
Extraction
Not directly linked to extraction technique.
Maturation
Old, porous oak barrels are Brettanomyces' preferred habitat, since the yeast can colonise the wood itself and re-infect every wine matured in that barrel afterward.
Old or poorly sanitised barrels are the single biggest source of ongoing Brett contamination in a cellar.
Sealed steel tanks offer Brett almost nowhere to hide, making them a much lower-risk environment.
Extended lees contact without adequate sulphur can give Brett more opportunity to establish.
Once bottled, Brett character is essentially locked in and does not diminish with further ageing.
Careful sulphur management, barrel hygiene and the eventual retirement of old barrels are the standard defences.
Blending
Brett-affected batches are sometimes blended down below detection threshold, though this only works when the overall level is low to begin with.
Where You'll Find It
Typical Wine Styles
Almost exclusively a red wine issue, and historically most discussed in relation to traditional, barrel-aged styles such as some Rhône reds and older-world Bordeaux.
Typical Regions
What Does It Tell You?
- Wild yeast contamination
- usually barrel-borne
- Cellar hygiene and barrel age
- A winemaking philosophy more or less tolerant of the character
Because tolerance for Brett varies so much by taster and by tradition, it is one of the few faults regularly debated as much as it is condemned.
Food Pairing
Similar Aromas
Is any "barnyard" or "earthy" character in a red wine automatically Brett?
No. Genuine earthiness, forest floor and savoury notes can come from terroir, tertiary bottle age or winemaking choices with no Brett involved at all. Brett specifically produces animal, medicinal, band-aid-like compounds (chiefly 4-ethylphenol and 4-ethylguaiacol) that a trained nose learns to distinguish from natural earthy complexity.
Learn to Recognise It
- Is there a distinctly animal, barnyard or band-aid smell sitting over the fruit?
- Does the wine smell more medicinal than earthy?
- Does the character increase noticeably with time in the glass?
- Is the fruit still identifiable underneath, or has it been replaced entirely?
A trace of Brett can add rustic complexity to a big, structured red; a strong, dominant dose replaces the fruit rather than complementing it.
Brettanomyces sits at the boundary between fault and character, which makes it one of the more philosophically interesting outcomes a wine can carry. It is a reminder that not every judgement in Aurenloch is simply right or wrong, some outcomes depend on context, tradition and the values of the person tasting them.
Brettanomyces was first identified in English beer, not wine, its name literally means "British fungus." It later became known as a persistent challenge in wine cellars around the world.