Ask the Master of Wine: Brett

Australian Wine Selector Winter 2006

Dear Nick,
I recently attended a wine tasting with a work colleague who is, I believe, quite knowledgeable about wine. Some of the reds that I liked, he said had Brett in them(?). Judging from his reaction I took this to be a fault. What, or who, is Brett and what is he doing in my wine? Am I wrong, (or worse, uncultured), for liking some of these wines?

A good question and a very timely one!

Brett is short for Brettanomyces, a yeast that is present on grapes and in many wineries. (Strictly, it should be referred to as Dekkera.)

We use yeasts to ferment our grapes into wine and produce the carbon dioxide to make our bread rise. In most cases we use yeast strains which have been selected as quick, strong fermenters, but there are many yeasts occurring naturally which have many different characteristics, not all of them desirable. Brett is one of these. It’s a weak fermenter, but is able to use the very low concentrations of sugar that sometimes remain in our wines – principally in reds. Brett produces a variety of by-products, the most widely recognised being a compound known as 4-EP, which has a smell described as horsy, Band Aid® or earthy. Another is 4-EG, which has a smoky, clove-like smell and is related to the compounds responsible for the charred oak smell in wine and for the smoky taint found in wines made from grapes affected by bush fires. Both compounds also give a gritty, dry, metallic edge to the tannins in red wines.

Almost all red wines contain these compounds, particularly those matured in oak barrels, but the concentrations are usually below our threshold of detection. However, we all vary in our sensitivity to various smells and tastes. In my classes with winemakers at Charles Sturt University, I have seen some people reel away from Brett-affected wines while other, equally experienced, tasters haven’t seen what the fuss was about.

I’m only moderately sensitive to Brett myself and quite like the complexity it brings to wine at very low levels although, equally, I’m disgusted by it when it’s more obvious. Red wines from Bordeaux, the Rhône Valley and, in the past, the Hunter Valley and Italy have tended to have more noticeable Brett, and one high-profile Californian winemaker deliberately used it for complexity, which I think too dangerous. Good cellar hygiene and sound winemaking usually keeps Brett taint to below the limits of detection, but occasionally any winemaker gets a surprise.

You may find that you recognise Brett more readily in future with more frequent exposure, but this isn’t necessarily the point. As consumers, we all differ in our likes, dislikes and sensitivities in our food and beverages and, provided the characteristic doesn’t injure us – which Brett won’t – it probably doesn’t matter.

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