No less a leading light than Voltaire once commented, apparently favourably, that Burgundy smells like ‘merde’.

He may have been a great author, but he was evidently not the ideal person to describe the individual flavours of the great Burgundies.

And then again, wine vocabulary features dozens of everyday words in special senses. But, in the sometimes wacky world of wine evaluation, some descriptions are nevertheless straightforward and can be justified by scientific analysis.

Brettanomyces, often referred to as just Brett, are wild yeasts which are sometimes found on grape skins and in wine barrels, where they dwell and multiply.

Nearly all of the Brettanomyces species are very sensitive to sulphur dioxide, so their presence in a winery may indicate a low-sulphur winemaking regime or less than perfect hygiene.

While winemakers do everything in their power to avoid Brett, Belgian brewers rely on it for their Lambic style of beer and dare not sweep cobwebs from the brewery.

Once Brett is embedded in cooperage, or obvious in a wine, it can be difficult to eliminate. As a wine fault, it’s not always immediately apparent though.

When a wine is clearly affected by these spoilage yeasts, it will (slightly) offend with organic aromas and flavours that aren’t particular appetising.

Brett-affected wines may smell off-puttingly mousey or even like chicken manure.

Although scientifically detectable, Brett is controversial. While most wine lovers consider any trace of it as significant flaw, some consumers will tolerate a low level of Brettanomyces, some might even enjoy a touch of it thinking it adds complexity.

Just to make things a little more complicated, wines from certain grapes such as Mouvèdre may demonstrate a similar earthiness that’s easy to mistake for Brett.

In the U.S.A. it’s almost fashionable and associated with, for example, the super-expensive concentrated claret-like Dominusb made by Frenchman Christian Moueix of Château Pétrus.

In Southern France, Château Beaucastel and Domaine Tempier’s top red wines with a high percentage of Mouvèdre also almost habitually show signs of Brett.

Be that as it may, the question is whether you should send a spoiled uncorked bottle back?

As long as that barnyard quality forms an elusive overtone that evokes country lanes on a damp summer evening, probably not. However, have no second thoughts when that dirt track swerves into a chicken farm!