Water with off-putting odors is a common nuisance in water treatment facilities and similarly presents challenges in aquaculture including Recirculating Aquaculture Systems (RAS). The primary reason for the odors is microbial activity which causes an aqueous accumulation of the metabolites Geosmin (GSM) and 2-Methylisoborneol (MIB) that are best described as carrying a musty or ‘earthy’ scent and taste.
When present in RAS these metabolites enter the fish where they rapidly accumulate at levels much higher than in the sorrounding water. This accumulation can impart the filets with a muddy off-taste, reducing their quality. The issue of off-flavour is exacerbated by the remarkable ability of humans in detecting GSM and MIB even at concentrations down to a few nanomolars (which far surpasses the ability of sharks to smell blood in water).