Noble rot

Noble rot is a beneficial infection of ripe wine grapes by Botrytis cinerea. The fungus dehydrates berries and alters their chemistry, concentrating sugars and developing flavors used in certain dessert wines.

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Botrytis cinerea: A fungus that causes gray mold in plants and, under suitable conditions, noble rot in wine grapes. This fungus infects the berries and drives the dehydration and chemical changes that define noble rot.
Tokaji Aszú: A Hungarian sweet wine made from individually selected botrytized grapes and base wine. It is a renowned wine style built around grapes affected by noble rot.
Sémillon: A white wine grape variety widely grown in Bordeaux and valued for sweet wines. Its thin skin and ripening traits make it especially suited to botrytized sweet wines.
Dessert wine: A wine with substantial sweetness, produced by leaving or adding fermentable sugar or by concentrating grape sugars. Noble rot is one route to the concentrated must used for naturally sweet wines.
Late harvest wine: Wine made from grapes left on the vine beyond ordinary ripeness, with or without fungal infection. Late harvesting can concentrate grapes without requiring Botrytis infection.
Transpiration: The loss of water vapor from plant tissues, especially through leaves and fruit surfaces. Water loss from infected berries concentrates sugars and other dissolved compounds.
Sauternes: A French sweet white wine from Bordeaux, commonly made with botrytized Sémillon and Sauvignon Blanc grapes. Its vineyards’ autumn conditions can encourage noble rot in ripe grapes.
Sauvignon Blanc: A white wine grape variety originating in France and grown worldwide. It is often blended with botrytized Sémillon in Bordeaux sweet wines.
Volatile acidity: A measure of volatile acids in wine, chiefly acetic acid, which can contribute vinegar-like aromas. Botrytis-damaged fruit can increase microbial and chemical risks that raise volatile acidity.
Ice wine: A sweet wine made by pressing naturally frozen grapes, which concentrate sugars as water remains frozen. Freezing concentrates grape juice by a different process than noble rot’s dehydration.