Mini-class No. 4 … Understanding Noble Rot

So, you’ve heard the term “Noble Rot,” but what is it? Bet you never thought a fungus could make such incredible wine. Read on to discover how.

Fungus … friend or foe?

Botrytis Cinera can either be a destructive pest or great friend to a wine maker, depending on weather and harvest conditions. This fungus, which attacks berry fruits such as grapes and strawberries and the flowers of apples, can have some delicious results under the right conditions for wine.

When Botrytis Cinera attacks unhealthy grapes or if constant wet conditions occur, it destroys the grapes. However, if the fungus attacks healthy, ripe grapes during a warm, sunny Autumn season, the result is a sweet, honeyed dessert wine that is very sought after. Known as “noble rot,” the Botrytis feeds on the juices in the grapes, causing them to become dehydrated like raisins and concentrating their sugars.

Controlled infections

Making great noble rot wines is not as easy as letting nature take her course, though. Unfortunately, the noble rot will often infect just certain grape bunches or even just a portion of one bunch. As a consequence, the grapes must be harvested individually, often in several passes (known as tris), in order to harvest the right grapes at the right time. The dried grapes produce considerably less juice than their healthy, ripe counterparts and they are also very difficult to press. The big effort involved in making this wine pays off, though, with a rich wine with honey, toast and apricot flavors.

The most well known noble rot wines are Aszu from Hungary, Sauternes from France, Beerenauslese and Trockbeerenauslese from Germany, Amazon from Italy, Ausbruch from Austria, and South African Noble Late Harvest.

Some Autumns in Northeastern U.S. areas such as the New York Finger Lakes have ideal conditions for noble rot, especially with tightly clustered sweet hybrids such as Vignoles. Cooler climates also have ideal conditions for creating a similar sweet wine known as Ice Wine, which uses the same method of making wine of dehydrated grapes. In the case of Ice Wine, the grapes are dehydrated due to the death and freezing of the grape vines.