II. HOW WINE IS MADE
As discussised in the prior section, the winemaker can choose from a number of yeasts when producing wine. Perhaps the winemaker will rely on "wild yeasts". But even when carefully choosing the yeast, a winemaker may find that "stray" yeasts may also affect the wine. One such yeast is called "Brett," also known as the Brettanomyces strain of yeast (which can be added or come from wild yeast fermentation). Found in some beers, it is considered by some (especially in California) to be almost completely undesirable in wine. (Some say it is linked to development of 4-ethylphenol.) Mostly this depends on your taste, it certainly is found in some French wine (but is never good in excess). Look for meaty/gamy/smoky/sweaty socks or perhaps metallic notes.
That's the short answer about Brett, but the fact is that this is one of the more controversial discussions for it brings into play several favorite areas of contention--The University of California and the idea of just what is winemaking, art, science or what?
A little (but not a lot) of Brett can let a wine become distinctly individual. Somehow, however, it seems that many California vintners consider any Brett at all a major flaw. Naysayers like to say that this is due to the influence of the University of California at Davis (UCD) which, they say, somehow causes their students to produce standardized "cookie-cutter" wine. Brett is definitely found is some French wines, especially Burgundies and some Rhone wines. Nevertheless, finding Brett for some is a major problem--even a defect making the wine unworthy of purchase.
For some reason whether or not Brett can be found in a wine has generated a huge amount of cyber-rattling. (Could I have just invented a phrase?) That finding Brett in a wine is a "problem" that taints a winery (and, I guess, for that reason only gives them something to talk about). The more down-to-earth wine enthusiasts merely say they don't care where the taste comes from: if they like it, fine, if not, don't drink it. Whether or not something is a "problem" is very much a matter of individual taste.
To eliminate Brett does mean that any of the characteristics it imparts will also not be present. Does this make the wine less interesting? Does it make the winemaker less individualistic? Since, in the end, you can find the wine of your choosing in all the varieties produced both in California and world-wide, why not just vote with taste buds and pocket book?
One more thing about "wild yeast fermentation." The process gives the "aura" of a hand-craft product. It is important to remember that not all hand-crafted products are quality products!