# New Insight on the Formation of 2-Aminoacetophenone in White Wines
## 3 Results  
### Surveys of 2-Aminoacetophenone in Commercial Wines  
The first survey aimed to measure 2-AAP concentrations in 86 Austrian white wines from the 2021 vintage prior to and after ageing for 4 days at 40 \({}^{\circ}\)C in order to assess the potential of the same wines to produce 2-AAP after prolonged ageing. Results show that the level of 2-AAP concentrations were clearly influenced by the variety (Figure 1).  
The lowest 2-AAP concentrations before artificial ageing were measured in Gruner Veltliner and Chardonnay wines with average values at 0.17 ug/L and 0.27 ug/L, respectively. The highest average concentrations were obtained in Riesling and Muscat wines (2.3 and 4.3 ug/L, respectively). The maximum 2-AAP concentrations were reached in Muscat wines with some values up to 10 \(\upmu\)g/L. The same varietal effect was observed after artificial ageing, which increased 2-AAP concentrations as expected. The highest gains of concentration were observed in Riesling and Muscat wines, with average gains of 1.1 ug/L and 3.5 ug/L, respectively. The final 2-AAP concentration after ageing increased  
Figure 1: Box plot of 2-AAP concentration measured in 86 fresh and aged Austrian wines from four different varieties: GV—Grüner Veltliner (20), CH—Chardonnay (16), RI—Riesling (25) and MU—Muscat Ottonel (25) (blue color = wine before artificial ageing, orange color = aged wine). The crosses indicate the average concentrations.  
up to 20 \(\upmu\)g/L in one Muscat wine. The lowest average increase in 2-AAP concentration after ageing was measured in Chardonnay wines (0.17 \(\upmu\)g/L). On the other hand, the relative gain in concentration was the highest in Gruner Veltliner wines, with average concentrations 3.6-fold higher after than before ageing. Finally, the range of 2-AAP concentrations measured in the different samples were generally wider after ageing than in fresh wine. This was particularly the case for Gruner Veltliner, and, to a lesser extent, Chardonnay and Riesling wines.  
The second survey aimed to measure 2-AAP and tryptophan metabolites considered as potential 2-AAP precursors in 53 Slovenian and Croatian white wines. For each variety, 2-AAP average concentrations were overall higher in this set of wines in comparison to the first survey (Table 3). Similar trends were observed, with 2-AAP contents substantially higher in Muscat and Riesling in comparison to Chardonnay wines. The lowest 2-AAP contents were measured in Zelen and Welschriesling wines. In contrast, Zelen wines show the highest average concentration in 3-indoleacetic acid (18.8 \(\upmu\)g/L), which is known to be the main precursor to 2-AAP formation in wine. There was generally no correlation between 2-AAP concentration and the content of tryptophan metabolites. However, it can be noticed that ILA and anthranilic acids were significantly higher in Riesling wines, which often displayed a high level of 2-AAP. Finally, indole-3-lactic acid was by far the most abundant tryptophan metabolite, ranging from 50 \(\upmu\)g/L to 350 \(\upmu\)g/L, whereas 3-indoleacetic acid content ranged from 0.2 \(\upmu\)g/L to 60 \(\upmu\)g/L. ANOVA analysis a showed statistically significant difference in concentrations of anthranilic acid, 3-IAA, kynureine and 2-AAP between five varietal wines.