Atypical aging (ATA), also known as untypical aging, is an off-flavor that can occur within a period of few weeks to one year after the first addition of sulfur dioxide postfermentation. It has been first reported in Germany, in the early 1980s. ATA can occur in wines made from Vitis vinifera L. vine varieties and from the interspecific vine varieties. It is generally accepted that the ultimate cause of ATA are stressful growth conditions in the vineyard, as well as stress reactions during alcoholic fermentation. White vine varieties, such as 'Welschriesling', 'Riesling', 'Istrska Malvazija' and 'Chardonnay' show a greater propensity to form ATA. Such wines show lack of varietal aroma compounds, while at the same time, aromas reminiscent of acacia flowers, naphthalene, dirty dish rag and wet wool develop. Wines seem meager and thin, with greater perception of bitterness and astringency. 2-aminoacetophenone (2-AAP) is one of the major odor-active compound responsible for the off-flavor. AAP is generated by degradation of indole-3-acetic acid (IAA). IAA originates both from the grapes and from the yeast. By the IAA content in the must given, we can not deduce the final content of 2-AAP in the wine. The sensory detection threshold of 2- APP in wine is between 0.5 and 1.5 μg/l. Faster sensory recognition and development of 2-AAP in bottled wine is also contributed by unfavorable conditions of maturing the wine. Addition of ascorbic acid to the wine is a temporary solution. Despite the stressful growing conditions that influence the formation of ATA in wine, the desire of every winegrower is to alleviate these factors by right viticultural and winemaking measures, thus preventing the wine's tendency to form ATA and prolong its quality.
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