Chemical and Sensory Quantification of Geosmin and 2-Methylisoborneol in Rainbow Trout (Oncorhynchus mykiss) from Recirculated Aquacultures in Relation to Concentrations in Basin Water

Abstract

Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs.

Investigation of sensory profiles and hedonic drivers of emerging aquaculture fish species

“…Of the 70 consumers that participated, 45 (64.3%) were male and 25 (35.7%) were female. The age of participants ranged from 18 to 64 years with subgroup distribution: young adults: 30.8%; middle adults: 38.5%; senior adults (51–64): 30.8%.…”

“…This odor/flavor can be grouped under the earthy, muddy and musty off-flavors/odors that have been identified in farmed fish species such as catfish, rainbow trout and pikeperch. [32][33][34][35][36] These characteristics, which are considered as taints, have been connected to the existence of geosmin or 2-methylisoborneol, or a combination of both, in the fish tissue and attributed to the rearing origin of the fish. [32][33][34][35][36] Moreover, the existence of the compounds implicated for such off-odors/flavors has been found to result in reduced intensity of other odors/flavors existing in the same sample.…”

“…Participants were free to choose more than one answer for the respective question. young adults[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] : 30.8%; middle adults 36-50 : 38.5%; senior adults (51-64): 30.8%.…”

Impact of water quality on the bacterial populations and off-flavours in recirculating aquaculture systems

“…Sorangium are known to possess a putative geoA, and Nannocystis have been shown to produce geosmin (Dickschat et al, 2007;Schneiker et al, 2007). Moreover, higher concentrations are generally detected in trout fillets (Petersen et al, 2011) due to the accumulation of these compounds in the gills, skin or gastrointestinal tract by lipid-rich fish tissues (Klausen et al, 2005). A gap of 28 days between the detection of geoA in samples and the presence of geosmin in trout fillets could explain this observation.…”

“…It is highly probable that the detection of geoA preceded the production and/or release of geosmin in the RAS units. Moreover, higher concentrations are generally detected in trout fillets (Petersen et al, 2011) due to the accumulation of these compounds in the gills, skin or gastrointestinal tract by lipid-rich fish tissues (Klausen et al, 2005). Attempts to isolate geosmin producers, such as actinomycetes or cyanobacteria (Robin et al, 2006;Guttman & van Rijn, 2008;Schrader & Summerfelt, 2010), on different selective media or to detect them by Ion Torrent sequencing were unsuccessful (data not shown).…”