By K. L. Turner April 11, 2015

http://blog.quiniwine.com/wine-articles/brett-and-the-barnyard/ – more-1394

What’s that smell? You’ve likely heard some describe the nose of a wine as barnyard, sweaty saddle, or wet dog, none of which, in my humble opinion, seem particularly desirable. Others might list bacon, spice, cloves, or smoke, all of which prove palatable by comparison. Where do these wine aromas come from, and do they spoil the tasting experience for you? Or do those aromas make the wine more complex and interesting? If so, either way, blame Brett.

On the Wild Side

Brettanomyces is a family of yeasts that live in the wild, quite naturally, on the skins of fruit. Brett, as it is often called, is also found on the inside of barrels, both old and new, loving the crevices between staves as a comfy hangout with lots of cellulose fibers to feed on. It can also be delivered by fruit flies, but skins and staves are really where it’s at.

Brett causes compounds to form during wine production. These compounds often take over the show, reducing the fruity aromas on the nose of a wine, robbing it of its more pleasant scents. If allowed to run wild through the fermentation process, Brett also affects the taste, replacing varietal characteristics, even affecting colour.

The Fault Line

Are these aromas on the nose of a wine considered a fault? Some winemakers, mainly European, believe Brett is a naturally occurring yeast that gives their wines deeper character, capitalizing on the customer that finds such aromas a preference. Others, without a doubt consider Bretty wines a fault, especially new world winemakers, doing everything in their power to eliminate the yeast throughout the winery. Some simply think evidence of Brett in a wine means sloppy winemaking and poor sanitation, so there you go, you either love it or hate it.

The Brett compounds come primarily in groups of three, and in varying ratios. One, called 4-ethyl-phenol, is often the most prolific compound, bringing on the band aid, barnyard, or antiseptic sniffs. The second, 4-ethyl-guaiacol, inspires the more pleasurable scents of bacon, spice, cloves, or smoke. A third, isovaleric acid, does the sweaty, rancid thing.

Depending on the ratios of the compounds between themselves and to the wine, Brett makes wine smell like those different things, sometimes good, sometimes bad. The 4-ethyl-phenol is the most offending of the compounds. At a very small colony of 420 micrograms per litre, a wine will be labeled as Bretty.

Persistence

Once Brett moves into the winery, it is a very difficult tenant to remove. Some try to control it by adding sulfur dioxide (SO2) or dimethyl dicarbonate to the wine. Others run the wine through sterile filtration, physically removing the Brett, but also stealing away with some of the other yeasts, flavours, and aromas that are part of a wine’s profile.

Unfortunately, somewhat like humans and antibiotics, overuse of SO2 raises resistant strains of Brett that become truly difficult to manage, while exposing the bones of the wine, further stripping away the varietal character.

Prevention

All of the winemaking techniques that currently produce wines in alignment with consumer preferences, including longer hang times that let the fruit ripen on the vines, extended barrel aging, and use of fewer chemicals, contribute to the proliferation of Brett. Cool cellaring, low pH, thorough cleaning, and use of eggs or stainless steel tanks instead of wooden barrels all work against Brett’s invasion.

A Preference for Red

About 90 percent of spoilage of premium red wines points to Brett as the culprit. That’s no surprise since most red wines are crushed and fermented with skins on, while whites have them removed. Skins are not only where the yeasts prefer to live, fermenting with the skins on also raises the pH of reds wines in production, making them even more attractive targets for this bothersome lodger.

Living with Brett

We eat moldy cheese, salivate over aged steaks, and introduce cultures into pickles, sauerkraut, and other culinary adventures. Along those lines,