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Title: Geosmin causes off-flavours in artic char raised in recirculating aquaculture systems

item Schrader, Kevin

Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2006
Publication Date: 7/21/2006
Citation: Houle, S., Schrader, K., Vandenberg, G. 2006. Geosmin causes off-flavours in artic char raised in recirculating aquaculture systems. International Conference on Recirculating Aquaculture. July 21-23, 2006, Roanoke, Virginia.pp. 419.

Interpretive Summary:

Technical Abstract: The “earthy” and “muddy” off-flavour taste in pond-reared fish is due to the presence of geosmin and 2-methylisoborneol (MIB) in the flesh of the fish. Planktonic and benthic cyanobacteria and actinomycetes are known sources of MIB and geosmin. When these compounds are absorbed into the flesh of the fish, they are unmarketable until they undergo a period of depuration in freshwater to lose the earthy/muddy taint. Similar off-flavours have been documented in fish raised in RAS, however little information is available regarding the cause of these off-flavours. Our hypothesis was that earthy and muddy off-flavour compounds found in pond-raised fish are responsible for off-flavours in fish raised in RAS. In this preliminary study, we examined water, biofilms in RAS and fillets from cultured arctic char known to have off-flavours and requiring depuration. We used instrumental (solid-phase micro extraction procedure and GCMS) and human sensory analyses to determine the cause and the source of off- flavours in the fillets. Geosmin was present in the samples taken from the biofilter and on the side-walls of the tanks. MIB was only found in low levels in the samples. The GCMS results indicated the presence of geosmin in the fillets (1,095 ng/kg), but lower levels were observed in the water (56.3 ng/L). Sensory analyses also detected an earthy flavour (i.e., geosmin presence) in the fillets, and, therefore, we concluded that geosmin was responsible for the off-flavour. The cyanobacteria responsible for the earthy/musty flavour in commercial catfish pond are Oscillatoria perornata and Anabaena species. Neither one of these types of cyanobacteria were found in the water and biofilm samples taken from the recirculating system. Cyanobacteria that might be responsible for the geosmin in the water have not yet been identified, but further studies are being performed.