Name for a wine defect derived from the unpleasant to disgusting sound of ammonia and the smell of mouse urine. It is also expressed by a dull, oxidative, musty and vinegary smell. Depending on the intensity, however, the off-flavour is often only noticeable in the finish (aftertaste), where it is expressed by a long-lasting, scratchy taste sensation that lingers unusually long on the palate.
It mainly occurs in young wines with residual sugar, especially also in fruit wines (strawberry and currant). Particularly at risk are low-acid (pH 3.5 to 4), warm-fermented wines that have been stored in a cloudy state for a long period of time or that have not been sufficiently sulphurised. Long periods of heat during the ripening period are favourable.