Wine is an infection.

A fungus living on the grape skins (yeast, or, more precisely, saccharomyces) infects the grape, eating its sugars, and producing alcohol.

But not all infections are created equal.

TCA – the dreaded infection responsible for “cork taint” – produces a mildewy, wet cardboard taste. TCA infection is less prevalent these days as cork and bottling technology is far ahead of where it was a couple decades ago. Still, it renders any bottle undrinkable (you’ll know it when you smell it).

An infection from the yeast known as brettanomyces, on the other hand, can improve a vintage. Or destroy it. Really, it depends on who you ask. We’ve long been fans of “brett” around here. With its barnyard funk, a bretty wine can make you feel as if you were right there in the vineyard, walking the rows on a fall day right after harvest. As we wrote in this letter back in 2019: “as winemakers insist on clogging the market with ultra-fruity, even syrupy vintages (Exhibit A: Jam Jar), brett brings the wine world back down to earth.”

Certainly an out of control brett growth can overwhelm a wine – think gym socks (though we’ve been known to ask sommeliers for exactly that just to see what they come up with from the cellar). Yet, for many traditional winemakers – especially those of Bordeaux, Southern Rhône, and Southern Italy – brett is simply a part of the terroir.

The same is true of a fungus from the same phylum called Botrytis cinerea. Also known as “gray mold,” this fungus is responsible for one of France’s most famous (and expensive) wines.

More on that in a moment. But first… why are so many wineries called “Chateau”?

This week, resident wine expert Julien Miquel explains why certain wineries use “Chateau” in their name... How the French revolution changed the wine landscape & popularized this (formerly) aristocratic term… And why you’ll see the word pop up in the US & other places (but never Italy or Spain)...

On the banks of the Garonne River, south of Bordeaux by the villages of Sauternes, Barsac, and Cadillac, the vineyards, prone to excess moisture, are afflicted with Botrytis rot.

In other microclimates, the rot, a gray mold, might overtake the grape bunches and destroy them – la mauvaise pourriture as they call it (the bad rot).

Around Sauternes, and across the river in Cadillac, however, the vineyards get zapped by broiling hot days just in time to prevent the Botrytis from becoming full blown. The Botrytis remains, but rather than consume the grape with fuzzy gray mold, it begins to soak up the grape’s moisture. The grape begins to shrivel, which, to the untrained eye, doesn’t look great. But fear not, for this is la pourriture noble (noble rot). As the grape shrivels from the loss of moisture, the cells in the berry break down, liberating stored sugars which concentrate into the little moisture that remains. The acids and minerals concentrate likewise.

When the grape is finally hand harvested (it is too fragile for machine harvesting) and ever-so-gently pressed, it contains but a few drops of golden, ultra-concentrated liquid – high in sugar, high in acidity, high in sweet, pungent flavor.

Botrytized sweet whites are finicky in the winery. They require a slow fermentation of around two months, during which the winemaker must hope that other bacteria doesn’t invade the must and ruin the vintage (botrytis, a cousin of the antibiotic penicillin, has natural antibacterial qualities; but high sugar content nevertheless makes the must hard to resist for foreign invaders).

Get the fermentation right, though, and you wind up with deep notes of honeysuckle, ginger, and caramel. A botrytized sweet white can age for decades. A single bottle of 1969 Château d’Yquem – the foremost of Sauternes wineries – goes for around $2,000.

A noble rot indeed...

Until next time,

The Wine Explorer

Bonner Private Wine Partnership