Environmental Engineering Reference
In-Depth Information
Table 1
Physical and chemical characteristics of geosmin and 2-methylisoborneol (MIB)
Characteristics
Geosmin
2-Methyl isoborneol
Structure
CH
3
CH
3
OH
CH
3
CH
3
CH
3
OH
CH
3
Chemical name
trans
-1,10-Dimethyl-
trans
- 1,2,7,7-Tetramethyl-
9-decalol exo-bicyclo-heptan-2-ol
Molecular formula C
12
H
22
O C
11
H
20
O
Formula weight 182.31 168.28
Appearance Light yellow oil White solid
Boiling point 270°C —
Organoleptic properties Earthy-muddy Musty
Odor threshold concentration (ng/L) 10 29
Human olfactory sense (ng/L) 4 7-15
Toxicity to rainbow trout (mg/L) 0.45 10
LC
50
(sea urchin embryos) (mg/L) 17 69
Sources:
Cees et al. 1974; Gagne et al. 1999; Gerber 1968, 1969; Nakajima et al. 1996; Persson
1979; Watson et al. 2000.
structures and chemical and physical characteristics are shown in Table 1. Geosmin
and MIB implicated in muddy-musty flavors of water and fish are a problem in
the aquaculture, food, beverage, and potable water industries. These compounds
are reported as a source of musty-earthy flavor in grain caused by improper storage
(Wasowicz et al. 1988; Jelen et al. 2003). Geosmin is also known to contribute
to a characteristic earthy red beet flavor (Lu et al. 2003) and an earthy smell in
grapes (La Guerche et al. 2005). MIB was related to musty-earthy notes in Brie
and Camembert cheese flavor (Karahadian et al. 1985). Siegmund and Pollinger-
Zierler (2006) detected higher concentrations of 2-isopropyl-3-methoxypyra-
zine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 1-octen-3-ol, fenchyl
alcohol, geosmin, and guaiacol as well as 2,6-dibromophenol in apple juice samples.
Geosmin and MIB have been reported to be responsible for most source-water
odors (Persson 1979, 1981, 1983, 1988; Wnorowski 1992; Wnorowski and Scott
1992; Saxby 1993; Jüttner 1995). The FLAVOR Profile (FPA) method was adapted
to drinking water by Krasner et al. (1985). The FPA method was also employed by
Lin et al. (2002) to determine the odor groups in the source water of two water
treatment plants in Taiwan, and chemical analysis showed that MIB and geosmin
were present in the source water and were responsible for the musty odor.
MIB and geosmin are stereoisomeric and can be detected easily at low levels by
human olfactory senses because of their very low odor threshold concentration
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