Tokaj How is an aszúszem (botrytised grape berry) born?

The main character: Botrytis cinerea

Everything begins with a tiny fungus called Botrytis cinerea. In most wine regions, this fungus is an enemy (it causes grey rot), but in Tokaj, at the meeting point of humid rivers (the Tisza and Bodrog) and warm autumn sunshine, it becomes “noble.”

The “attack” and the defence

When morning mist settles over the vineyards, the fungus colonises the skins of ripe grapes. With its fine filaments, it pierces the grape skin, but instead of destroying the berry, the dry, sunny daytime weather stops the process. The grape begins to “defend itself”: through the tiny holes created by the fungus, it loses water, causing its internal components—sugars, acids, and aromas—to become extremely concentrated.

The transformation (shrivelling)

During noble rot, the fungus also alters the grape’s chemical structure. It creates unique aromas (honey, apricot, exotic spices) that are not present in normal grapes. The berry slowly shrinks, becoming dark brown, wrinkled, and eventually almost powder-dry—this is the true aszúszem.

Selection: only by hand!

Since not every grape on a bunch ripens into aszú at the same time, the aszú berries are still today selected individually by hand. This is one of the most labour-intensive harvest processes in the world: even an experienced picker can collect only 8–10 kilograms in a full day.