Not all yeasts are good guys

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.

August in the Winery...

Vintage 2008 saw approximately 50 tonnes of Pinot Noir harvested from our vineyards in Waipara and Central Otago. This has translated into 140 barrels of wine. At this stage of the year the wine is in maturation mode and is awaiting warmer temperatures in the winery so that the secondary fermentation, the Malolactic ferment, can begin. Ideally the temperature for Malo needs to be in the 18-22C range but below this barrels do tend to kick off on their own. MLF can be innoculated with commercial bacteria but traditionally was left to start under its own steam in the spring following vintage. This is the approach we are using.

In the middle of the above photo you just might be able to make out my temp/humidity gauge sitting on top of a barrel. One reason I need to monitor these levels is to make sure the evaporation from the barrels doesnt get too high. Over the course of a year you might expect to lose around 2-5% to the 'angels share'.

As a result of this loss I need to top-up all the barrels on a regular basis. At this stage of its like each barrel of wine, whilst waiting for MLF to complete, is not protected from oxidation and bacteria by sulphur dioxide so they need to be kept as full as possible to elimate any ullage.

Roll out the Barrel...

Every year at Sandihurst we order a number of new French oak barrels from a variety of cooperages for our Pinot Noir. The amount is usually around 25-35% new oak in each wine (about 40 barrels), depending on the blend. Barrels from any one cooper differ in the forest the wood comes from (all forests are on a strict 160 year rotation), their control over the wood selection process, the grain of the wood, the method of drying the oak, the level and length of toasting and most importantly the style of each cooper in respect putting all these components toegther.

One cooperage we use here at Sandihurst is Claude Gillet. The small Gillet cooperage is in the village of Saint Romain, in Burgundy. They produce around 9000 barrels per year. Gillet barrels are very good for showing sweet pure fruit. They dont dominate the wine and help create a fuller mouth feel while staying elegant and balanced.

Heres a short video showing how Gillet barrels are made.