2009_Book_FoodChemistry

358 5 Aroma Compounds
Fig. 5.15. Isotopic dilution analysis of 2-furfurylthiol (FFT), 2-methy1-3-furanthiol (MFT) and 3-mercapto-2-
pentanone (3M2P).
(a) Gas chromatogram, (b–g) mass chromatograms of the analytes and the deuterated (d) internal standards; traces
of the ions shown in brackets were monitored: d-MFT (m/z 118), MFT (m/z 115), d-3M2P (m/z 121), 3M2P
and 2M3P (m/z 119), d-FFT (m/z 83), FFT (m/Z 81) (according to Kerscher and Grosch, 1998)
this question, one or several aroma substances are
omitted in the model and a triangle test is used to
examine which of three samples (two complete
and one reduced aroma model) offered to the
testers in random order differs in aroma from the
others. If a significant number of testers determine
a difference in the reduced model, it can be
assumed that the odorants lacking in the reduced
model contribute to the aroma and, consequently,
belong to the key odorants of the food.
Some omission experiments, e. g., conducted
with the aroma model for French fries, are shown
in Table 5.15.
If methanethiol and the two decadienal isomers
are missing in Experiments 1 and 2, the aroma
has no similarity to that of French fries. All five
testers were in agreement. The Strecker aldehydes
with the malt odor (Exp. 3), 4,5-epoxydecenal
(Exp. 4) and both pyrazines (Exp. 5) are also important
for the aroma because their absence was
noticed by four of the five testers. 1-Octen-3-one,
(Z)-2- and (E)-2-nonenal are of no importance for
the aroma (Exp. 6). Surprisingly, this also applies
to methional (Exp. 7) although it has the second
highest aroma value (cf. Table 5.14) and smells
of boiled potatoes. It is obvious that methional is
masked by other odorants occurring in the aroma
model. In French fries, the odor note “like boiled
potatoes” is probably produced by methanethiol
in combination with pyrazines.