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{ SOMMjournal.com } 103 PHOTO COURTESY OF EUREKA BREWING OF ALL WINE FAULTS, BRETTANOMYCES IS ONE OF THE MOST COMPLEX— and also one of the most fascinating, partly because it is one of those "faults" that in some contexts can be regarded as a positive. Indeed, there are many sought-after, expensive wines that owe some of their character to Brettanomyces (usually referred to simply as "brett"). It's also a controversial topic, with some arguing that brett is to be avoided at all costs, while others think a less dogmatic approach is more in order. First, some basics. Brettanomyces is a genus of yeast, also known as Dekkera (the yeast can exist in two states, and this latter name is used for the sexual, spore-producing form). While several species names are commonly used, the current classification has the wine-relevant brett as just two species, B. bruxellensis and B. anomala, with the former by far the most important. Brett was first discovered by the brewing industry as an important component in British and Belgian beer styles in the early years of the 20th century. Indeed, when the first single-culture Saccharomyces cerevisiae yeasts (the species of yeast used for making wine) were used to make British beers, people noticed that something was missing: the imprint of brett, which in the context of a good bitter can add real interest. The reason brett is a problem in winemaking is that it is annoyingly resilient, sitting around, biding its time, and then growing in conditions in which virtually nothing else can. In practical terms, this means that it does its real damage after the regular alcoholic and malolactic fermentations are complete. Brett is slow-growing and tough, and doesn't need much to feed on. While it is seen in white wines (albeit very rarely), it's predominantly a red wine problem. And the reason it is such a problem is that it produces some distinctive flavours that, at higher levels, can ruin wines. Recognizing Brett What are the key characteristics of this wine fault as it might be encountered in wine? The first sign is reduced varietal character, followed by the degradation of certain fruity aromas by esterases present in this yeast. Esterases are enzymes that cause the breakdown of esters, important in conferring fruitiness. Pinot Noir, among other grape varieties, is particularly badly hit by brett, because it loses its bright cherry and violet characters. Then, hints of smoke and spice begin to appear, with the chief culprit here being a compound called 4-ethylguaiacol. As the infection progresses, the wine will begin to smell and taste medicinal (4-ethylphenol is largely responsible for this), and it will lose its fruity flesh, exposing the structural bones of the wine. Finally, the wine will begin to smell of barnyards, horses, animal sheds and Band-Aid. It's difficult to teach people how to spot brett, because the characteristics of bretty wines will vary depending on the substrates that were initially available to the brett cells as they multiplied, the precise strain of brett involved and also the context of the other flavors present in the wine. Depending on the combination of spoilage compounds produced and their relative concentrations, the overall effects of brett will differ. The Prevalence of Brett How common is it? It's hard to be sure, but at least we can say that it is far from rare in red wines. Wine scientist Pascal Chatonnet, who was responsible for much of the groundbreaking research on this sub- ject, surveyed the incidence of brett in a variety of red wines some years ago and found that just under a third had levels of 4-ethylphenol above 600 μg/litre (4-ethylphenol is used as a diagnostic indicator for the presence of brett; most people can spot it at around 420 μg/litre, but this will vary with the style of wine). He says that he thinks the incidence now will be higher. For his Master of Wine (MW) dissertation, consultant winemaker Sam Harrop did a study in which he presented 25 of the world's leading Syrah- based wines in a blind tasting, and asked those present to comment on whether they detected brett or not. He then sent samples of these same wines away for chemical analysis for 4-ethylphenol. A striking number of these wines showed above-threshold levels, including some famous names. { wine science } Somm Journal June/July.indd 103 5/9/14 12:13 PM