New Thinking in the Brett Debate

UC Davis researchers create Brettanomyces aroma wheel

by Andrew Adams
brettanomyces uc davis
Savory, veggie, fruity and floral represent four spokes in the Brettanomyces Aroma Wheel created by Dr. Linda Bisson and Lucy Joseph at the University of California, Davis.
San Rafael, Calif.—As much as it’s reviled, Brettanomyces still has its supporters in those who think a little bit of barnyard or wet dog imparts a distinct identity to their wines.

The clean, modern winemaking practices of the sort espoused by the University of California, Davis, have put Brett squarely in the menace category. Dr. Linda Bisson, who studies the metabolic pathways of yeast at UC Davis, however, likened Brett to a color in an artist’s palette.

Granted, it might be a color similar to a brash, fluorescent green that is best used sparingly, she told Wines & Vines.

Bisson and UC Davis Viticulture & Enology Department staff member Lucy Joseph released a Brett aroma wheel around the start of the year. The wheel is the result of a study the two performed on a collection of 83 Brett strains, of which 17 were identified as positive and five as negative by a sensory panel.
Strains that garnered a negative reaction were those that generated more aromas in the rotten and putrid category, as opposed to positive characteristics such as floral and spicy. Some strains had no sensory impact even though the Brett population grew in the wine. Certain strains also exhibited a correlation of descriptors such as earthy and putrid or Band-Aid and soy.

The positive strains did add something good to the wine rather than just not befouling it, Bisson said. The finding would appear to underscore the essence of the Brett debate between those disgusted by its flaws versus others intrigued by its complexities.

Bisson said Brett’s effect on a wine is influenced by the strain found in the vineyard or winery as well as cultural and regional differences in taste. What may be considered a flaw in a Napa Valley Cabernet could be described as integral to the essence of a Burgundian Pinot. “Spoilage is in the eye of the beholder,” she said.

The wheel divides Brett aromas into main categories such as “animal,” which is further divided by wet dog, sweaty/sour, urine, fecal, barnyard and horse. The other categories are savory, woody, putrid, chemical/solvent, veggie, fruit, floral spice, fermentation, dairy and earthy.

Joseph has revised the wheel a few times since it was first released. Further refinements to the wheel will come with the results of future research.

Brett is still too unpredictable for Bisson to recommend winemakers begin flirting with it to try and hit some of those more pleasant sounding parts of the aroma wheel.

It’s far more adaptable to pH and temperature changes, can metabolize a host of other substances than just sugar and can adapt quickly to whatever conditions are found in a wine, essentially “living off the land.”

Therefore, placing a certain strain in two different wines could yield wildly different results. Winemakers, she said, should not try and “inoculate” their wines by using a Brett-infected barrel from a winery that makes wine with positive Brett characteristics. “A lot of people do that, and it just ends up in disasters,” she said.

Future research about Brett could lead to “neutral” strains that metabolize available nutrients but don’t produce the same aromatics, thereby denying resources to Brett that produces scents of something like rotten meat. Another possibility is to pin down those good strains and impart the exotic characteristics of “good” Brett. Bisson said, though, it may be more likely for scientists to determine if a wine is safe for Brett rather than creating a safe Brett.

Unless a winemaker already is producing wines that exhibit positive attributes from Brett, it’s just too risky to facilitate exposure to the spoilage yeast.

A “touch” of Brett can be dangerous, Bisson said, because a population could change or grow to overwhelm the wine. The first year could be nice and interesting, but by the second vintage the Brett population could have exploded and by the third “it’s going to be, ‘Oh my God! What happened?’”

Trying to designate a “Brett area” of a winery with separate hoses, barrels and sample thieves is also hard to maintain. The designations between Brett friendly and Brett free become especially difficult to maintain during harvest, when workers (often seasonal help) will grab any piece equipment just to get a job done.

In February, Bisson organized a seminar about Brett as part of UC Davis’ ongoing Flavor101 series. She said during a panel discussion of winemakers all agreed that while some wines without much varietal character could benefit from a dash of Brett, if it was gone tomorrow they wouldn’t miss it.

Posted on 05.06.2013 - 11:21:51 PST
As a consumer desiring those characteristics, I buy that wine from France. Having taken over so much else of their wine industry, we should leave them at least that.
Patrick Boyle

Posted on 04.05.2013 - 18:23:43 PST
Good article! One correction from one of the winemakers on the panel: I asked very simply, "If we all succeed in eradicating Brett from all our wines, would any of you miss it?" Everyone, even if they have had some positive experiences, replied, "No" -- except for one person, me. I would miss it.
Chris Howell

Posted on 04.06.2013 - 08:22:43 PST
Before coming to Sonoma County, I was chairman of a 120 person wine society and we did blind tastings on differing varietals each month. For the American born members, wines with even the slightest hint of Brett always came in last. European members, however, were much more favorable. The American palate just doesn't like Brett, which is a bit regrettable, but a fact of life.
William Hipp

Posted on 04.17.2013 - 12:58:29 PST
My wine making partner and I tried an experiment with a gallon of wine that we purposely infected with Brettanomyces ordered on the internet. It got pretty stinky. My intent was to blend it in with the rest of the wine before bottling. He got so scared due to rumors of people "burning down the winery" to get rid of Brett, that he pasturized it. Interestingly this removed the smell. I would conclude that the "bugs" need to be intact to have the smell. I would not exclude in the future a developed method for controlled addition of Brett.
John Wright