Simultaneous determination of ketoacids and dicarbonyl compounds, key Maillard intermediates on the generation of aged wine aroma

The am of this work was the simultaneous determination of both ketoacids and dicarbonyl compounds in wine. To detect ketoacid, compounds in wine, a method based on the quinoxaline derivatives by the reaction with diaminebenzene, currently employed to detect a-dicarbonyl compounds, was developed. The quinoxaline derivatives were detected by RP-HPLC with UV detection, which allows the determination of the major dicarbonyl compounds In wine: glyoxal, methylglyoxal, diacetyl and pentane-2,6-dione, and the quinoxaline/quinoxalinol derivatives of alpha keto-gamma-(methylthio)butiric acid and ss-phenylpyruvic acid (intermediate ketoacid compounds of methional and phonylacetaldehyde) were simultaneously detected by a fluorescence detector. The identification was performed by comparison with standards and also by using LC-MSMS. The levels found in 15 wines analyzed (white wines, Madeira wines, and Port wines) diverge according to the type and the age of the wine. The ketoacid compounds ranged from 0.2 to 5.7 mg/L for alpha-keto-gamma- (methylthio)butyric acid and 0.1 to 9.6 mg/L for ss-phenylpyruvic acid. The quantities observed for dicarbonyl compounds were similar to those already reported.