Catfish geosmin

Fig. 1. Structures of geosmin and 2-methylisoborneol, the two most common causes of off-flavor in farm-raised channel catfish.

For example, in channel catfish Ictalurus punctatus) aquaculture ponds in the southeastern USA, some species of cyanobacteria produce earthy and musty metabolites such as geosmin and 2-methylisoborneol (MIB) (Fig. 1). These compounds are rapidly absorbed across the gills of the catfish and accumulate in the flesh of the catfish, thereby rendering them unpalatable and unmarketable. 

Physiological Strategies To Control Geosmin Synthesis in Channel Catfish Aquaculture Systems... 

Economic impacts associated with "off-fiavors" have encouraged research into the bioregulation of geosmin and MIB synthesis. Although this chapter focuses primarily upon controlling geosmin production in the context of the channel catfish aquacultiue industry, the approaches discussed may have relevance in the control of undesirable metabolites in other systems. 

Geosmin synthesis in channel catfish aquaculture systems, 322-333 biosynthesis, 328-329 occurrence in organisms, 324,325r odor quality, 13 synthesis, 322,323/ synthetic mutant selection, 330-333 Glucosyloxyethyl methacrylate polymerization, 224,225/ synthesis and toxicity, 222,224 Glucosyloxyethyl methacrylate polymers potential applications, 226r properties, 224-227... 

The microwave distillation SPE apparatus is shown in Figure 9.12. A filet of catfish is placed in the microwave oven and heated, which drives the geosmin out of the tissue and is swept through the solid-phase extraction sorbent with argon gas. The condenser unit cools the gas, which increases the retention of geosmin, onto the 500 mg of C-18 in Figure 9.12. The sorbent is present in the bottom of the condenser unit. Charcoal, XAD-2, and C-18 were all tried for recovery of geosmin, and C-18 had the best recovery. 

Conte, E. D., Shen, C. Y., Perschbacher, P. W., and Miller, D. W. 1996. Determination of geosmin and methylisoborneol in catfish tissue (Ictalurus punctatus) by microwave-assisted distillation—solid phase adsorbent trapping, J. Agricul. Food Chem., 44 829-835. 

In catfish aquaculture, offensive odors can be rapidly absorbed in the flesh of the fish. The major uptake route for geosmin and MIB is across the gills [18], and these compounds are primarily stored in the adipose tissue [29]. Elimination of these odorous compounds is much slower than the uptake rate, and elimination rate decreases as water temperature decreases and adipose tissue content of the catfish increases [30]. 

Brewer, R, Catfish experiments in Kansas, Kansas Fish and Game, 29, p. 5, 1972. Yurkowski, M., J.A.L. Tabachek, Identification, analysis and removal of geosmin from muddy flavored trout, J. Fish Res. Board Can., 31, p. 1851, 1974. 

SW Lloyd, CC Grimm. Analysis of 2-methylisoborneol and geosmin in catfish by microwave distillation-solid-phase microextraction. J Agric Food Chem 47 164-169, 1999. 

Geosmin [19700-21-1] Musty, earthy Catfish, wheat, water 107,110... 

S. W. Lloyd and C. C. Grimm, Analysis of 2-methyhsobomeol and geosmin in catfish by microwave distillation—solid phase microexiraction, J. Agric. Food Chem. 47 164 (1999). 

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