The Hungarian word Aszú was originally “dried”, but the term has now come to be associated with the type of wine made from shrivelled, botrytis-affected grapes. Aszú berries are picked individually, collected in huge vats and trampled into a paste (known as Aszú dough).
Unfermented grape must or light wine is poured onto the Aszú dough and is left for 24–48 hours before being racked off into wooden casks or vats where fermentation is completed and the Aszú wine matures. Casks are stored in a cool environment and are not tightly closed so that a slow fermentation process can continue in cask, often for several years.
The concentration of Aszú wine was traditionally defined by the number of puttony (25kg baskets or hods) of dough added to a gönc (136 litre barrel) of must.
Nowadays, the puttony number is based upon the content of residual sugar and sugar-free extract in the mature wine. Aszú wines range from 1 puttonyos to 6 puttonyos in sweetness, with a further category called Aszú-Eszencia which is the undiluted free-run juice of the Aszú grapes.