The application of advanced oxidation processes including photocatalysis-based ones for the off-flavours removal (GSM and MIB) in recirculating aquaculture systems

Recirculating aquaculture system (RAS) popularity is threatened by the accumulation of off-flavour compounds such as geosmin (GSM) and 2-methylisoborneol (MIB) in the rearing water. Due to their lipophilic nature and the high bio-accumulation rate, they can be detected at very low concentrations in fish flesh, thus reducing product quality and marketability. The removal of these compounds often requires fish to be purged using high amounts of fresh and/or highly treated water before harvesting. A promising alternative is controlling the off-flavours throughout the production cycle by means of advanced oxidation processes (AOPs). In this review, the current state of the art of AOPs application to GSM and MIB degradation is reviewed under the perspective of their applicability to RASs. In particular the advantages of promising coupled processes such as photocatalytic ozonation have been highlighted. Finally, we critically reviewed the existing detection methods of off-flavour compounds in the rearing water, emphasising those allowing rapid and cheap measurements, in order to enable RAS plant managers to make real-time informed decisions, when off-flavours concentration increases above a certain threshold.