5.2 Aroma Analysis 357Fig. 5.14.Odorants labelled with deuterium () or carbon-13 () as internal standard substances for isotopic
dilution analyses of the corresponding unlabelled odorants.
1 2-[α-^2 H 2 ]furfurylthiol, 2 2-[^2 H 3 ]methyl-3-furanthiol, 3 3-mercapto-2-[4,5-^2 H 2 ]pentanone, 4 [4-^2 H 3 ]methio-
nal, 5 2-[^2 H 3 ]ethyl-3,5-dimethylpyrazine, 6 (Z)-1,5-[5,6-^2 H 2 ]octadien-3-one, 7 trans-4,5-epoxy-(E)-2-[6,7^2 H 4 ]
decenal, 8 1-(2,6,6-[6,6-^2 H 6 ]trimethyl-1,3-cyclohexadienyl)-2-buten-1-one (β-damascenone), 9 3a,4,5,7atetra-
hydro-3,6-[3-^2 H 3 ]dimethyl-2(3H)-benzofuranone (wine lactone), 10 tetrahydro-4-methyl-2-(2-methylpropenyl)-
2H-[3,4-^2 H 3 ]pyran (sotolon), 11 4-hydroxy-2,5-[^13 C 2 ]dimethyl-3(2H)-furanone, 12 3-hydroxy-4,5-[4-^13 C]di-
methyl-2(5H)-[5-^13 C]furanone (rose oxide)
that the odorants showing higher AVs contribute
strongly to the aroma of the food. For this pur-
pose, the odor thresholds of the compounds dis-
solved in water, in oil or applied to starch are
used, depending on which of these materials dom-
inates in the food.
An example are the AVs of the odorants of French
fries based on their odor thresholds in an oil
(Table 5.14). Methanethiol, methional, methyl-
propanal and 2-methylbutanal exhibit the highest
aroma values. Consequently, they should belong
to the most important odorants of French fries.
5.2.7 AromaModel,OmissionExperiments
Finally, the identified odorants must actually pro-
duce the aroma in question. To test this, the de-
termined concentrations of the odorants are dis-
solved in a suitable medium, which is not difficult
in the case of liquid foods. The solvent for the re-
combination mixture called the aroma model can
be adapted to the food. An ethanol/water mixture,
for example, is suitable for wine. In the case of
solid foods, however, compromises have to be ac-
cepted.
The aroma profile of the model is then compared
to that of the food. In the example of French fries
discussed in detail here, a very good approxima-
tion of the original aroma was achieved.
The selection of odorants by dilution analyses
(cf. 5.2.2) does not take into account additive
(cf. 20.1.7.8) or antagonistic effects (example
in Fig. 5.2) because the aroma substances, after
separation by gas chromatography, are sniffed
individually. Therefore, in view of the last men-
tioned effect, the question arises whether all the
compounds occurring in the aroma model really
contribute to the aroma in question. To answer