GC-FTIR as a powerful tool for the characterization of flavor components in Kiwi

Extracts from deep-frozen Kiwi puree were investigated by an integrated method consisting of GC-FTIR and GC-MS for a reliable identification of the peaks detected and GC-sniffing to correlate this chemical information to sensory impression. Beneath trans-2-hexenal, that is responsible for the fresh, green scent, cyclohexarione was identified among a number of substances. By comparison of the FTIR-spectra to a specific vapor-phase-IR-library, that is presently accumulated in our group, most of the components could be identified. In particular 3 terpene-esters, linalyl-acetate, isobornylacetate anda-terpinyl-acetate were identified and found to be responsible for an overripe, terpene-like-off-flavor in stored Kiwi puree. In this field of unsaturated terpenes, esters and aldehydes the identification-capability of FTIR together with appropriate library-spectra exceeds that of mass-fragmentograms, especially for isomeric compounds, whereas the combined information of both techniques is needed for a reliable characterization of complex flavor-mixtures because of its complementary nature.