Explainer Science

Understanding Brett and Its Divisive Impact on Wine

Some say this yeast adds complexity while others loathe it at any concentration — here's what to know

David W. Brown By October 18, 2021
Illustration by Meredith Lynne.

There are some words that no wine producer would ever put on a label: barnyard smell, Band-Aid, sweaty saddle. And yet, on the nose and palate, the scent of stable is sometimes unmistakable. It is caused by a stray yeast called Brettanomyces, or colloquially, “Brett.” Depending on the drinker, Brett can bring even the best wine to its knees, or imbue a wine with regional character at the microbial scale. 

Brett produces a number of volatile compounds that can affect wine, the most common one adding the barnyard notes; others can add a Band-Aid smell, or even an attractive smokiness. At low levels, it may be undetectable, or add a pleasant clove note, but at high levels, the wine may taste metallic and stripped of fruit. Most commonly associated with the wines from the Rhône Valley in France, its presence can be felt the world over.

Beloved by beer brewers for the flavors it adds, it’s much more controversial in wine. People have opinions about Brett, and they tend to be expressed as fact, ex cathedra, in a way that you don’t see with p-Mentha-8-thiol-3-one, which makes some bottles of Sauvignon Blanc smell like cat urine. Brett, perhaps, rolls easier off the tongue. Some people loathe Brett, while others consider it part of a region or vineyard’s signature.

The people who hate Brett, though — they really hate it. Many of them are New World winemakers from countries where learning about wine faults is a strict, integral part of wine education, in a way that is rarer elsewhere. What is a flaw, and what is terroir? Brett is part of nature, but does that make it natural in wine?

“Can I think of a wine that’s actually made better, elevated beyond what it might otherwise be, by the presence of Brett?” asks Nick Ryan, wine critic for The Australian newspaper. “The answer is unequivocally, no. Brett is a diminishing force, a smudger of a wine’s true nature.”

A deep divide

But can Ryan tolerate, say, a touch of Brettanomyces in his wine? “This is murkier area,” he says. “We’re stumbling around the tightropes of tolerance here. We often hear the Brett advocates and apologists say it adds complexity. That’s a point immune to rebuttal.” If, he explains, complexity is the multi-layering of many elements, the presence of yet another element can always be said to increase it. 

“But does it make it better? You draw a moustache on the Mona Lisa,” says Ryan. “Have you made it a more complex painting? You could argue, yes. Have you made it a better one? That’s a far harder case to prosecute.”

Brett doesn’t come in a bottle that you pour into barrels. Rather, it is a ubiquitous, microscopic presence in vineyards, from grapes to countertops, and once it flexes its little fungus muscles, is nearly impossible to eradicate. 

That is a good thing, says Pascaline Lepeltier, Master Sommelier and managing partner of Racines NY. The notion of a Brett-free wine world would be “maybe more spotless, but also would deny the importance of spontaneous fermentation and the complexity of yeast activities, which makes wine, wine,” she says. Wine would lose its transcendence, and become simply a processed food made with grapes. 

The issue becomes one of winemaking itself. She explains, “For some, it is the absolutely clean expression that contemporary oenology allows. For others, it is the do-nothing. Behind that, there are standards of taste and quality that are deeply linked to an economy and a culture, thus evolving in time and space.”

Nature versus culture, she says, is “a problematic, false, modern occidental dichotomy,” and suggestive of a much older debate: the definition of terroir.

“I find myself, more and more, leaning toward an idea of bringing microbial life into the idea of terroir, balanced with the physical environment, the climatic environment, the vegetal environment, and, of course, the cultural environment,” she says. The debate over Brett reveals “our disinterest in the complexity and importance of microbiomes, and a divide in perceptions of the world.”

As for the polarizing distinctiveness of Brettanomyces, says Lepeltier, the reactions they trigger might say as much about the drinker as they do about the aromatic compounds themselves. Some notes “are very primal and trigger something very primal in the brain. So maybe there are aromas that make people overreact. There is something very Freudian about what certain smells can remind you of.”

Keeping it in check

Regardless of region, however, Old World or New, what might be taken as complexity at a low level can become ruinous at a higher level. It is the fine winemaker’s goal to keep Brettanomyces from exerting undue influence.

“From a winemaking point of view, in terms of hygiene, we do all sorts of things to try to limit its infection. We are incredibly careful about hygiene in barrels and hygiene in tanks,” says Steve Webber, chief winemaker for the Yarra Valley winery, De Bortoli. They also take steps during the actual winemaking process to protect the wine from microorganisms. “If you haven’t got your hygiene right, it can genuinely get out of control.”

As an experienced chief wine judge, his opinions are more subdued when he encounters the divisive yeast in bottles from other winemakers.

“I don’t mind it as long as it doesn’t overpower the wine, I suppose,” he says. “In the early days, I did a lot of judging, and one of the things that we often spoke about was the level of Brett that was acceptable, just as the level of oak that was acceptable, and just as the level of some other characteristics that are a bit more obvious. We always used to say that, you know, over-oaked wine is just as bad as Brettanomyces.”

For some, including Webber, grape variety can play a role in whether Brett is especially offensive. “There are some varieties, I think it’s probably a little more suited to. I don’t mind it in some of the more rustic varieties and wine styles,” whether that’s a Tempranillo or Sangiovese or Grenache, Syrah, and Mourvèdre blend. “I think at lower levels, it can make wine look quite complex and interesting.”

Cabernet, not so much. “I think it’s terrible in Cabernet, which has certain characteristics that are compromised by Brett.” Likewise, when he finds Brett in Beaujolais, he says, “I do genuinely get disappointed.”

Still, he is circumspect on the subject. “With wine,” he says, “it is the imperfections in one that make it so compelling.”

And, indeed, perhaps Brett can also be considered part of the place it came from — part of the terroir.

Rob Geddes, an Australian Master of Wine, who is both an experienced judge and wine commentator, says it is impossible to make a declaration either way, that Brett is good or bad.

“My view is that Brett is tolerable to some people but intolerable to others,” he explains. “You can’t rule on something where perception is so varied, as it all depends on the person’s sensitivities. This allows for terroir-specific Brett to exist. The aim should be for this to be minimized.”

That said, he believes that “wine should taste like the grapes, soils, and climate of the place it comes from — not the result of random microbiological events.”

 

This article has been updated to reflect the fact that Brettanomyces produces volatile compounds that are responsible for different odors; the article originally mistakenly attributed the odors to different species of the fungus.