Characterization of Aroma-Active Compounds in Italian Tomatoes with Emphasis on New Odorants.

Abstract

An aroma distillate was prepared by solvent extraction and subsequent SAFE distillation from Italian vine-ripe tomatoes eliciting an intense overall aroma. Application of gc/olfactometry and the aroma extract dilution analysis revealed 44 odor-active compounds, 42 of which could be identified. The highest odor activity value of 2048 was established for the green, grassy (Z)-3-hexenal, the metallic smelling trans-4,5-epoxy-(E)-2-decenal, the potato-like 3-(methylthio)propanal, and the caramel-like 4-hydroxy-2,5-dimethyl-3(2H)-furanone. Of the further odorants, 13 compounds have previously not been reported as tomato odorants. Although most of these showed lower FD-factors, in particular, the coconut/dill-like smelling wine lactone ((3S,3aS,7aR)-3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one) appeared with a quite high FD factor. In addition, a fruity, almond-like odorant (6) with an FD factor of 1024 was detected. By application of high resolution mass spectrometry and polarity considerations, the structure of a methyl-2-ethoxytetrahydropyran isomer was suggested for 6. Four of the five possible isomers, the 3-methyl-, 4-methyl-, 5-methyl-, and 6-methyl-2-ethoxytetrahydropyran were synthesized and showed similar mass spectrometric patterns. However, these were excluded by their different retention indices. Although the synthesis of the remaining 2-methyl-2-ethoxytetrahydropyran resulted in only small yields, which were not sufficient for NMR measurements, this structure is very likely for 6. This compound was never reported as a food constituent before. Finally, quantitation of 23 odorants by stable isotope dilution assays allowed for the preparation of an aroma recombinate resembling the overall aroma of the tomatoes.