Microbially Derived Off-Flavor from Geosmin and 2-Methylisoborneol: Sources and Remediation - Reviews of Environmental Contamination and Toxicology - page 2

Taiwan (Lin et al. 2002), and Spain (Sabater et al. 2003; Vilalta et al. 2003, 2004).
Food industries, including grapes (La Guerche et al. 2005), apples (Frank 1977;
Siegmund and Pollinger-Zierler 2006), pears (Nunes 2002), peaches (Mercier and
Jimenez 2004), and vegetables such as dried beans or beetroot (Maga 1987) have
also been affected with inconsistent flavor. Based on suspected origins, Tucker and
van der Ploeg (1999) and van der Ploeg (1991) categorized off-flavors as rotten,
decayed, cardboard, stale, petroleum, fishy, woody, earthy or muddy, and musty.
This chapter presents an extensive review of chemical causes of off-flavor problems,
especially with reference to muddy and musty flavor in aquatic organisms and pos-
sible remediation techniques.

II Chemical Causes of Off-Flavor

Problems of off-flavors caused by chemicals have been reported for fish (Whitfield
et al. 1994) and Crustacea (Whitfield et al. 1981, 1988). Petroleum off-flavors
occur mainly from accidental spills of diesel fuel when fish are exposed to persis-
tent petroleum products, causing long-lasting flavor problems (Tucker and van der
Ploeg 1999; Motohiro 1983). Rotten and sulfury off-flavors have been attributed to
polysulfides formed by decomposition of blooms in freshwater reservoirs in
Australia (Hayes and Burch 1989). Dimethyl trisulfide has been correlated with
off-flavor problems in cheese, prawns, and vegetables (Hayes and Burch 1989;
Whitfield et al. 1981).
Algal volatile organic compounds (AVOCs), mainly terpenoids, cause economic
losses to water, food, and aquaculture industries because of reported taste and odor
(Wnorowski and Scott 1992; Engle et al. 1995; McGuire 1995; Watson 1999,
2003), which establish chemical communication among organisms (Harborne and
Tmoas-Barberan 1989; Harrawijn et al. 2001). The role of natural biofilm inside
pipelines as a potential source and reservoir for odorous volatile organic com-
pounds has been well documented (Skjevrak et al. 2005). Watson and Ridal (2003)
found that periphyton is a major T/O source in the St. Lawrence River.
A large group of compounds such as 2-methoxy-3-isopropylpyrazine, di-, tri-,
tetra-, and pentachloro anisoles, octa-1,3-diene, 2-methylisoborneol, (MIB), and
geosmin are responsible for an earthy-musty off-flavor (Kilkast 1993). Schnurer et al.
(1999) characterized fungal volatiles from mainly Aspergillus , Fusarium , and
Penicillium with gas chromatography, mass spectrometry, and sensory analysis; common
volatiles found were 2-methyl-1-propanol, 3-methyl-1-butanol, 1-octen-3-ol,
3-octanone, 3-methylfuran, ethyl acetate, and the malodorous 2-methylisoborneol
and geosmin. Fravel et al. (2002) characterized volatile compounds emitted by
sclerotia of Sclerotinia minor and Sclerotinia sclerotiorum and identified as
2-methylenebornane and 2-methylisoborneol by solid-phase microextraction
followed by gas chromatography and mass spectrometry.
Because this review focuses mainly on geosmin ( trans -1,10-dimethyl- trans -
9-decalol) and 2-MIB (1,2,7,7 tetramethyl- exo -bicyclo heptan-2-ol), their chemical