Journal of Agricultural and Food Chemistry
Article
Table 7. Retention Indices, MS-EI Data, and Sensory Properties of 2-Ethyl-3-mercaptoalkan-1-ols
RI
odor
c
threshold
reported previouslyd
a
b
compound
FFAP
1798
DB-5
1047
MS-EI: m/z (intensity in %)
odor quality
(ng/L in air) as food constituent
2
-(mercaptomethyl)-
butan-1-ol
86 (100), 57 (89), 55 (86), 41 (52), 47 (52), 69 (40), onion, meat
56 (36), 68 (31), 60 (30), ..., 120 (19, M )
0.61
+
2
-ethyl-3-mercapto-
butan-1-ol
1780 (a)
810 (b)
1872 (a)
892 (b)
1945 (a)
966 (b)
2037 (a)
060 (b)
1102 (a) 61 (100), 60 (71), 100 (67), 55 (59), 71 (57), 41
onion, meat
onion, meat
onion, meat
0.0089 (a)
3.3 (b)
+
(56), 69 (27), 83 (25), 56 (22), ..., 134 (13, M )
1105 (b)
1
2
2
2
-ethyl-3-mercapto-
pentan-1-ol
1191 (a) 74 (100), 55 (93), 75 (63), 41 (58), 85 (45), 114+
0.0058 (a)
0.047 (b)
0.027 (a)
0.040 (b)
1.2 (a)
(44), 83 (21), 47 (21), 101 (20), ..., 148 (11, M )
1196 (b)
1
-ethyl-3-mercapto-
hexan-1-ol
1279 (a) 55 (100), 88 (48), 69 (33), 128 (30), 89 (29), 41
+
(27), 85 (22), 57 (19), 56 (16), ..., 162 (7, M )
1285 (b)
1
-ethyl-3-mercapto-
heptan-1-ol
1376 (a) 69 (100), 55 (49), 60 (41), 41 (40), 142 (25), 85
burned,
onion
+
(23), 87 (20), 57 (19), 67 (17), ..., 176 (7, M )
1384 (b)
2
1.8 (b)
a
b
For further spectroscopic data (MS-CI, NMR) see the Supporting Information. Odor quality as perceived at the sniffing port during GC-O at
c
8 d
threshold level. Odor thresholds in air were determined as previously reported. First report.
Table 8. Retention Indices, MS-EI Data, and Sensory Properties of 3-Mercapto-3-methylalkan-1-ols
RI
odor
c
threshold
reported previously as food
a
b
d
compound
FFAP DB-5
MS-EI: m/z (intensity in %)
odor quality
(ng/L in air)
constituent
1
5
2
16
3
3
3
-mercapto-3-methyl-
1658
1800
1879
975 69 (100), 41 (76), 86 (54), 71 (49), 75 (34), 87 sweat, onion
0.42
coffee, wine, passion fruit,
+
26 19 20
butan-1-ol
(25), 39 (18), 43 (15), 55 (15), ..., 120 (5, M )
blackcurrant, beer, hops
-mercapto-3-methyl-
pentan-1-ol
1093 55 (100), 83 (58), 41 (47), 71 (40), 100 (33), 67 sweat, onion
0.045
+
(20), 101 (18), 43 (17), 39 (16), ..., 134 (3, M )
-mercapto-3-methyl-
hexan-1-ol
1183 55 (100), 97 (53), 41 (48), 71 (48), 81 (44), 69 grapefruit
(42), 56 (26), 115 (25), 114 (24), ..., 148 (3,
0.0047
+
M )
3
3
3
3
-mercapto-3-methyl-
1973
2079
2185
2293
1281 69 (100), 55 (81), 41 (53), 71 (47), 56 (45), 81 grapefruit
0.0048
0.078
11
+
heptan-1-ol
(26), 129 (25), 87 (22), 43 (22), ..., 162 (2, M )
-mercapto-3-methyl-
octan-1-ol
1381 69 (100), 55 (73), 41 (55), 71 (46), 56 (35), 83 grapefruit
+
(29), 81 (21), 57 (21), 68 (16), ..., 176 (1, M )
-mercapto-3-methyl-
nonan-1-ol
1486 69 (100), 55 (91), 41 (72), 71 (68), 83 (64), 56 grapefruit,
+
(52), 81 (36), 43 (34), 68 (28), ..., 190 (1, M )
fatty
-mercapto-3-methyl-
decan-1-ol
1590 55 (100), 69 (83), 41 (80), 71 (67), 56 (67), 43 meat, fatty
62
+
a
b
For further spectroscopic data (MS-CI, NMR) see the Supporting Information. Odor quality as perceived at the sniffing port during GC-O at
c
8 d
threshold level. Odor thresholds in air were determined as previously reported. First report.
the alkyl chain to 1-mercapto-2-methylheptan-3-ol then
resulted in a 240-fold (diastereomer I) or even 480-fold
Odor thresholds for the diastereomers were determined
individually, except for the 3-mercapto-2-methylbutan-1ols,
which did not show a sufficient GC separation. Thereby,
odor thresholds of the first eluting diastereomer were
consistently lower than for the second eluting compound
(Table 6). The biggest differences in odor thresholds were
found for the diastereomers of 3-mercapto-2-methylpentan-1-ol
(factor 520). The other homologues showed only slight
differences in the range from factor 4 to factor 8. The first
eluting diastereomer revealed a distinct minimum in odor
thresholds at C /C with extremely low thresholds for 3-
(diastereomer I) increase in odor thresholds. In contrast to the
other homologous series, no significant differences in odor
thresholds between the respective diastereomers were observed.
The 3-mercapto-2-methylalkan-3-ols consistently exhibited
burned odor notes. In addition, 4-mercapto-3-methylbutan-2-
ol and 1-mercapto-2-methylpentan-3-ol also showed grapefruit-
like aroma qualities, whereas for 1-mercapto-2-methylhexan-3-
ol and 1-mercapto-2-methylheptan-3-ol rubber-like odors were
detected. As for the odor thresholds, also for the aroma
qualities no significant differences between the diastereomers
occurred. To the best of our knowledge, none of these
compounds has been identified in foods so far.
5
6
mercapto-2-methylpentan-1-ol and 3-mercapto-2-methylhexan-
1-ol (0.0014 and 0.0080 ng/L). With a higher number of
carbon atoms, the threshold values exponentially increased, for
example, by a factor of 6100 between C and C . In contrast to
3
-Mercapto-2-methylalkan-1-ols. The mass spectra of
the 3-mercapto-2-methylalkan-1-ols, as shown for 3-mercapto-
-methylhexan-1-ol (Figure 3B), revealed fragmentation
5
8
the differences in odor thresholds, no differences were detected
2
for the odor qualities of the diastereomers. At C /C
3
4
patterns very similar to those of the corresponding 3-
predominantly burned odors were detected; with increasing
mercaptoalkan-1-ols. Characteristic signals occurred at m/z
length of the alkyl chain (C −C ) onion-like, meaty aroma
5
7
+
+
1
48 (M ), m/z 130 ([M − H O] ), and m/z 114 ([M −
notes occurred, which finally changed to burned, grapefruit-like
2
+
H S] ). However, in contrast to the 3-mercaptoalkan-1-ols,
at C . Some of these 3-mercapto-2-methylalkan-1-ols have been
2
8
compounds of this series showed considerably higher signals for
shown to cause a major influence on food aromas; for example,
3-mercapto-2-methylpentan-1-ol is a key aroma compound of
+
[
M − CH O] (m/z 117).
3
G
J. Agric. Food Chem. XXXX, XXX, XXX−XXX