Winemaking Flaws: Brett

Janet Fletcher's article, "Does this smell funny? A pesky yeast causes a stink" in SF Gate is an excellent article on Brettanomyces, the funky smelling yeast residue.

Overview of Brettanomyces

• A trade-off of California winemakers adopting a hands-off approach to winemaking is techniques for eliminating or controlling Brett.


• A little Brett is not a bad thing. Less of a problem in white wines and at low levels it can give some red wines cedar, tobacco or cigar-box aromas, scents frequently used to describe Cabernet Sauvignon. It also mutes some of the fruitiness of youth, making the wine seem more mature and complex, at least in the short term.

Desciptions include: leathery and animal-like, horsey, wet horse blanket or sweaty saddle. Although some people can enjoy these smells, many find them unattractive.

At their worst, Brett aromas turn medicinal, reminding many tasters of the inside of a metal Band-Aid box. The animal scents get funkier, more barnyard-y.

One common description likens the smell of a major Brett infection to a dirty mouse cage. The wine's fruitiness vanishes, and it loses any indication of varietal character.

• Winemakers can test their wines for Brett, but it's faster and easier to test for 4-ethylphenol (4-EP), one of the volatile compounds that active Brett yeasts produce and that are largely responsible for some of the off-aromas. If 4-EP concentrations are rising, Brett activity is on the rise. If a winemaker can catch the problem early enough, he or she can take action, like isolating the wine and treating it with sulfur dioxide to stop the Brett growth.

  A winemaker who doesn't recognize the source of the problem may try to dilute a stinky barrel of wine by spreading it around to all the other barrels.



• Sulfur dioxide will kill it or slow its growth, depending on the concentration used. Lowering the cellar temperature also makes the yeast sluggish, but that's expensive and it slows the wine's maturation, too. Keeping the wine's pH low -- typically by adding tartaric acid -- makes it less hospitable to Brett. Sterile filtration removes the troublesome yeast for good, but it also takes out many desirable flavor components, winemakers say