What is Brettanomyces ?
Its a yeast, in short. Actually we can say its a a spoilage organism that can in fact, in small doses, be a complexing element in wine. Problem is we cant control the amount. Its more prominent in red wines due to their high polyphenol content and higher pH levels. And it loves wood, lees, tolerates alcohol and doesnt need too many nutrients. It grows slowly just feeding on the little bits of O2 that barrel ageing gives it. Its tough.
There are a number of compounds responsible for the aromatic identification of Brett. The most common are 4-ethylphenol, 4-ethylguaiacol and isovaleric acid. Among the aromas we associate with Brett are medicinal, mousy, smoky, barnyard, bandaid and cheesy. And all these come at the cost of fruit and oak. Basically it all makes for unpleasant drinking and can ruin a wine although as I said earlier in small doses it can be aromatically enhancing for some wines.
Im thinking about this because in our cellar Ive got a bretty barrel. Its at the smoky stage (4-ethylguaiacol) which isnt too bad yet. And out of 140 barrels it isnt going to ruin the blend if it stays like that. But I have to be careful. Firstly when tasting never to transfer any wine from this barrel to others. I'll probably rack this wine off its lees, make sure MLF has finished, adjust the free SO2, clean the barrel, keep it topped and monitor regularly from there. That wont stop it but I can try to make its life harder. At blending time I will need to make some careful decisions because the last thing I want is Brett developing in bottle. One option would be sterile filtration of this barrel and that will stop this portion ruining the final blend. Those decisions will come later.
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