atypical ageing (ATA) or untypical ageing (UTA), known as untypischer Alterungsnote in Germany, where it was first documented in the late 1980s, is a term used to identify a phenomenon found in white wine-growing regions worldwide, although varieties such as müller-thurgau, kerner, and bacchus seem to be particularly susceptible. Heat and dry conditions immediately before and after veraison resulting in extreme water stress can lead to the development of this aroma/flavour defect. Wines from hot, dry growing seasons and sites are more prone to developing ATA. Vine nitrogen deficiency may also be a contributing factor. Research suggests that the compound 2-aminoacetophenone (2-AAP) is primarily responsible and that indole-3-acetic acid (IAA) is its precursor. Affected wines lose varietal character very early, develop atypical aromas and flavours described as naphthalene (moth balls), wet towel, or old furniture varnish, and may show an increase in bitterness. These characteristics are not the same as those typical of wines suffering from premature oxidation, where some varietal qualities may remain. Methods to minimize the development of ATA include avoiding extreme moisture stress around veraison, ensuring adequate plant nitrogen, and avoiding overcropping, which could delay maturity. ascorbic acid additions (100–150 mg/l) in conjunction with proper sulfur dioxide levels in the wine may help to limit the extent of this phenomenon.
