Subscribe for 33¢ / day

One of the most widely acclaimed wines in the world is Chateau Mouton-Rothschild. Some people say this red Bordeaux is about as good a wine as you can buy.

Other people say various vintages of this wine are spoiled by an infection that leaves it with a horsey, leathery, barnyard-y quality.

The fact is, both arguments are right. This only proves that defining just exactly what a “fine wine” is sometimes is extremely difficult and calls for more precise definitions.

In this case, the element I have found, and dislike, in various vintages of many Bordeaux is the same thing some people really like. It is an aroma caused by an organism called brettanomyces, or more commonly “brett” by those in the industry.

Brett is a wild yeast that has long been known as hard to control and which ferments in a different way than the yeast saccharomyces that converts sugars to alcohol and carbon dioxide. Brett can leave a wine with an odd aroma, not to mention a harsher tannin structure.

Some people love the aroma characteristic associated with it, which they refer to as cedary, earthy, or mushroomy. Occasionally I hear the term “gamey” in reference to it.

Less politely, those who don’t like the aroma call it wet wool, sweaty horse blanket, mousey, wet dog, and chicken droppings.

The brett aroma isn’t uncommon to Bordeaux, though it flourishes in many areas of the wine world, and is a problem most California wineries want to stamp out.

It once was rare in California wines because wine makers fought its development by adding sulfur dioxide to wines and using prepared yeast strains instead of wild yeasts, which can be a little trickier to control.

To reduce brett populations, wineries also filter their wines before bottling. These procedures generally keep brett aromas from developing too strongly.

However, controversy has arisen. Some U.S. wine makers, in an effort to make more “complex” wines, suggest they do not mind a bit of this element in their red wines.

Such a tactic is considered by the academic community to be not only risky, but absurd.

Scientists say tinkering with fermentations to encourage a trace of brett is dangerous because there are several strains of brettanomyces, some of which may produce really strange flavors over time.

Also, the organism develops erratically, so although a young wine may well be a bit more complex, the end result of 10 years of aging the wine in a cellar could result in a truly objectionable smell and taste.

I once asked a UC Davis enology department researcher if those who like “a trace of” brett weren’t playing with fire. He said they were.

“We [at UC Davis] don’t praise those kinds of wines. [Bordeaux has] a history and tradition, but part of that tradition is natural flora, which we call microbial spoilage.”

“The problem is that [brett aroma] comes and goes. You can’t control it. As a consumer, you want to know what sort of wine you’re going to get. We don’t think some wine makers know what they’re doing. They cannot reproduce it from year to year, yet they will defend a wine that has it.

“But they won’t then realize that the next year, when they don’t have it, why they don’t have it.”

Some wine reviewers like this aroma, which they say can be intriguing when found in small amounts. But often they will praise a wine as having a “trace” of brett even though others find the level massive.

Obviously, this is a controversial subject and one most wine makers would rather not discuss, especially with a wine columnist!

But when bottles of wine are selling for $200 a bottle, the subject is germane. Consumers should be warned about buying expensive wines that are technically spoiled.

A decade after buying a wine, do you want to try getting your money back for a bottle you deem to be spoiled?

The problem is, the subject of brett is taboo with most wine makers. No one likes talking about it, and even fewer are willing to admit their wines have this problem.

Subscribe to Breaking News

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.

Dan Berger lives in Sonoma County, where he publishes “Vintage Experiences,” a weekly wine newsletter. Write to him at He is also co-host of California Wine Country with Steve Jaxon on KSRO Radio, 1350 AM.