You’ll have noticed it with cheese, milk, matured cuts of beef… Mildew and rot aren’t always bad things, and they can even be beneficial for certain products, particularly in terms of their organoleptic qualities.

For grapes and wine, today we’ll be tackling noble rot, a fungus called Botrytis cinerea that develops on grapes from certain grape varieties under certain conditions of humidity and sunshine, and is highly sought-after for producing certain wines.

How does noble rot develop?

Botrytis cinerea is a fungus that can appear on grapes as soon as they flower. It feeds on the water present in the grapes and concentrates the berries in sugar. Botrytis cinerea thrives in regions with optimal morning humidity in October and November (when the bunches are forming). Then, if the weather is dry during the following months, water evaporation is encouraged and the fungus can take full effect on the grapes.

Once present on the grapes, the fungus must be monitored and its growth controlled, otherwise it will jeopardize the formation of the grapes and prevent them from “rotting” too much.

Where and why do we look for it?

As a result, noble rot is primarily sought after in regions close to a river, and in a terroir that combines humidity and heat, such as Sauternes. We can also mention the vineyards of Monbazillac, Jurançon, Coteaux-du-Layon, Tokaji (Hungary) and Trockenbeerenauslese (Germany).

In these regions, sweet white wines are produced that are particularly sweet and alcoholic, reaching much higher levels of sweetness than other wines (over 45 grams per liter versus less than 4 grams per liter for dry wines).

As we have already seen, these wines are obtained mainly thanks to the presence of noble rot on the grapes, which gives them all their sweetness, but also their highly concentrated aromas of candied fruit, exotic fruit and honey.

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