Effect of different N fertilization of vine on the tryptophan, free and total indole-3-acetic acid concentrations

The compound responsible for UTA (untypical ageing off-flavour) in wines is o-AAP (o-amino acetophenone). It is formed from IAA (indole-3-acetic acid), triggered by sulfurylation. The aim of this study was to evaluate the effect of different N fertilizer supply on this precursor in must and wine, making use of a long-term nitrogen fertilization experiment. Trp (Tryptophan) as well as free and conjugated IAA were determined in musts and wines produced from grapevines supplied with 0, 30, 60, 90 or 150 kg N ha super(-1) year super(-1). IAA concentrations in musts and wines varied highly over years (1994-1999), wines containing about half of the total IAA of musts. The IAA concentration in must was positively correlated with the concentration of amino acids in must, however, nitrogen supply did not have any effect, neither on Trp nor on IAA concentrations.