As soon as Riesling grapes are affected with botrytis, the aforementioned fruit aromas are decomposed step by step, and the formation of raisin-like and caramel-like aromas then occurs.

The raisin tone comes about via the botrytis fungus which leads to loss of fluid and at the same time to a concentration of the aromas in the grape. With  Berenauslese, Trockenbeerenauslese and Eiswein, it is in fact difficult to recognize Riesling by its aroma.