Ambivalence of the influence of nitrogen supply on o-aminoacetophenone in 'Riesling' wine

AAP (o-aminoacetophenone) is the aroma substance responsible for the untypical ageing off-flavour (UTA). The impact of nitrogen supply on the formation of AAP was investigated between 1994 and 1999. The experiment was carried out in the Rheingau (Germany) with six fertigation treatments of annual quantities of N (0, 30, 60, 90, 150 kg center dot N center dot ha(-1)). Results indicated that the long-term varied N fertilization affected AAP concentration in wine as much as the year. Whereas a better N supply of the grapes due to effects of the year coincided with lower AAP values, the fertilization effect was reversal: higher N fertilization increased the concentrations of AAP. AAP did not correlate with its precursor IAA and only slightly with antioxidative capacity. Neither varying yield nor soluble solids could explain the high variance of AAP. An indicator for potential AAP formation could not be found, neither in must nor in wine.