Food Chemistry

5.2 Aroma Analysis 347

Fig. 5.4.Headspace analysis of aroma substances of white-bread crust.aCapillary gas chromatogram (the
arrowsmark the positions of the odorants),bFD chromatogram. Odorants: 1 methylpropanal, 2 diacetyl,
3 3-methylbutanal, 4 2,3-pentanedione, 5 butyric acid, 6 2-acetyl-1-pyrroline, 7 1-octen-3-one, 8 2-ethyl-3,5-
dimethylpyrazine, 9 (E)-2-nonenal (according toSchieberleandGrosch, 1992)

Table 5.7.Yields of aroma substances on distillation
under vacuuma

Aroma substance (amount)a Yieldb (%)

Model I Model II

3-Methylbutyric acid 91 31
(1.9 μg)
Phenylacetaldehyde 84 21
(4.2 μg)
3-Hydroxy-4,5-dimethyl- 100 3. 3
2(5H)-furanone (2.2μg)
2-Phenylethanol (3.7 μg) 100 10. 7
(E,E)-2,4-Decadienal 100 3. 4
(1.4 μg)
(E)-β-Damascenone 100 2. 8
(0.9 μg)
Vanillin (3.7 μg) 100 0. 4
aAmount in the model solution: I in diethylether

(50 ml), II in a mixture of diethylether (50 ml) and
triglycerides (50 ml)
bDistillation in the apparatus shown in Fig. 5.5 at 35◦C

liquid food or the extract from the funnel ( 1 in
Fig. 5.5) into the distillation flask which is heated
to 35–40◦Cinawaterbath( 2 ). The volatiles in-
cluding the solvent vapor are transferred into the
distillation head ( 3 ). The distillate is condensed
by liquid nitrogen in the receiver ( 4 ). TheDewar
flask ( 5 ) protects the vacuum pump (reduced pres-
sure 10−^3 Pa).

Fig. 5.5.Apparatus for the distillation of aroma sub-

stances from foods (for explanation, see text. Accord-

ing toEngelet al., 1999)