386 5 Aroma Compounds
Table 5.34.Sensory properties of some terpenes
Compounda Aroma quality Odor threshold
(μg/kg, water)
Myrcene (I) Herbaceous, 14
metallic
Linalool (IV) Flowery 6
cis-Furanlinalool Sweet-woody 6000
oxide (IVb)
Geraniol (V) Rose-like 7. 5
Geranial (Va) Citrus-like 32
Nerol (VI) 300
Citronellol (VII) Rose-like 10
cis-Rose oxide (VIIa) Geranium-like 0. 1
R(+)-Limonene (IX) Citrus-like 200
R(–)-α-Phellandrene Terpene-like, 500
(XI) medicinal
S(–)-α-Phellandrene Dill-like, 200
(XI) herbaceous
α-Terpineol (XVII) Lilac-like, 330
peach-like
(R)-Carvone (XXI) 50
1,8-Cineol (XXIII) Spicy, 12
camphor-like
(all-E)-α-Sinensal Orange-like 0. 05
(XXXIX)
(–)-β-Caryophyllene Spicy, dry 64
(XLIX)
(–)-Rotundone (L) Peppery 0. 008
aThe numbering of the compounds refers to Table 5.33.
(5.28)(5.29)Most terpenes contain one or more chiral centers.
Of several terpenes, the optically inactive form
and the l- and d-form occur in different plants.
The enantiomers and diastereoisomers differ
regularly in their odor characteristics. For exam-
ple, menthol (XIV in Table 5.33) in the l-form
Fig. 5.31.Formation of R-δ-decalactone from linoleic
acid (according toTressl et al., 1996)(1R, 3R, 4S) which occurs in peppermint oil, has
a clean sweet, cooling and refreshing peppermint
aroma, while in the d-form (1S, 3S, 4R) it has
remarkable, disagreeable notes such as phenolic,
medicated, camphor and musty. Carvone (XXI
in Table 5.33) in the R(−)-form has a pepper-
mint odor. In the S(+)-form it has an aroma
similar to caraway. Other examples that show
the influence of stereochemistry on the odor
threshold of terpenes are 3a,4,5,7a-tetrahydro-
3,6-dimethyl-2(3H)-benzofuranone (cf. 5.2.5)
and 1-p-menthene-8-thiol (cf. 5.3.2.5).