What Is Noble Rot?
August 10, 2016

What Is Noble Rot?

“Noble Rot” is associated with a process that happens to grapes creating a distinctive, concentrated, exotic, honey flavored wine with a crisp, acidic finish. Through the magic of nature, this royal rot is what we have to thank for Bordeaux’s signature sweet white wines, most often referred to as Sauternes.
Botrytis Cinerea

Noble Rot, officially known as Botrytis Cinerea, is a good fungus, which in the right climatic conditions attacks very ripe, thin-skinned grapes. As a result of this benevolent attack, grapes start to shrivel like raisins. Grape flavors and sugars become more concentrated. This good fungus actually changes the entire metabolism of the grape, and the resulting flavors are quite unique.

“Grey Rot” or “Bunch Rot” is the evil counterpart to Noble Rot. These are destructive fungal diseases caused by excessive moisture throughout the day in the vineyard and can cause severe crop losses.

The Ideal Merger

In order for Noble Rot to occur, an ideal merger of climate and grape variety must happen. Early morning mists from nearby bodies of water must be followed by warm, sunny afternoons. Humidity is generated by these early morning mists, and, as a result of that humidity, the Noble Rot fungus attacks the grapes by penetrating the skins. The spores in the fungus germinate resulting in grape water evaporation. The warm, sunny afternoons assure that the grapes dry off to prevent malevolent Grey Rot. During the autumn, this entire process repeats itself on a daily basis and occurs naturally in specific wine regions. The Sauternes region of Bordeaux is one of the most famous of these ‘noble rot’ regions.

The Ideal Grapes

The ideal grapes to be affected by Noble Rot are thin-skinned varieties with tight grape clusters. The fungus can more easily penetrate the thin skin. Tight clusters result in a faster spread of Noble Rot throughout the cluster. The most ideal variety in Bordeaux is Semillon.

Making Botrytized Wines

Why are botrytized wines so expensive? The Noble Rot does not spread through the grape cluster in a uniform fashion. Therefore, harvesting is labor- intensive and costly, requiring hand-harvesting and several passes through the vineyard over a two month period. The pressed juice is extremely rich and concentrated and requires a long, slow fermentations. One entire vine makes only one glass of botrytized wine. These wines are naturally sweet because the fermentation finishes well before all the fermentable sugars have been converted into alcohol. The level of residual sugar in a Sauternes wine will vary form year to year depending on the level of noble rot – but it is usually between 130g/l and 150g/l – though it can go much higher.

Bordeaux’s Sweet Wine Miracle

The region 40 km (25 mi) southeast of Bordeaux city is where the ideal merger of climate and grape variety reaches an apex, where the cooler water of the Ciron tributary flow into the larger warmer watered Garonne River, creating these morning mists that are followed by sunny afternoon. Semillon grapes planted in this area are prime targets. Perfect conditions exist in Sauternes and surrounding areas of Barsac, Cérons, Cadillac, Loupiac, and Sainte-Croix-du-Mont for the formation of Noble Rot and the world renowned Botrytized Sweet Wines of Bordeaux.

Enjoying Wines With Noble Rot

Having these unctuous, delectable wines only for dessert is a mistake, according to many Bordelais. In fact, sweet wines from Bordeaux appear in the Aperitif section of a wine menu. Even though the usual pairings are blue-veined cheeses and Foie Gras, other savory treats provide wonderful pairing opportunities. For example, Neal Rosenthal, wine importer, suggests sautéing lobster tail meat in butter, deglazing the pan with Bordeaux Sweet Wine, and pouring that on top of the lobster. What a blessing in disguise!

Three Sauternes To Try

Château Grillon, Sauternes, 2013

Intense aromas and lovely flavors of grapefruit, honey, apricot and smoky noble rot.

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Château Doisy-Védrines, Sauternes, 2009

Rich nose with floral, honeyed accents, and a medium power, melted character, and freshness.

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Château Sigalas Rabaud, Sauternes, 2011

Full body with an amazing intensity of dried pineapple, mango, and spicy aromas of noble rot.

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Guest blog by Jo-Ann Ross, DWS, a Boston-based accredited CIVB Wine Tutor. 


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