Unveiled the solution to off-flavour in fish and presence of water mould in RAS

Off-flavours in salmonids and water mould in recirculating aquaculture systems (RAS) pose a persistent challenge for both producers and researchers. These issues not only deter consumers but also result in significant economic losses. The problems are closely interconnected, primarily arising from the accumulation of organic matter, high humidity, and insufficient water circulation within these systems.

Off-flavours in fish are mainly caused by the presence of geosmin and 2-methylisoborneol, compounds produced through the metabolic activity of actinobacteria and cyanobacteria. Water mould, on the other hand, is triggered by the proliferation of the Saprolegnia genus, which thrives in the controlled conditions of closed aquaculture systems.

The Finnish Institute for Natural Resources (Luke) and the VTT Technical Research Centre of Finland have unveiled an innovative solution to tackle these issues. By employing chemically treated cellulose-based fibre materials, the researchers have developed effective methods to capture the compounds responsible for off-flavours and the spores of water mould within aquaculture systems.

“Off-flavours can significantly lower the market value of fish, reducing consumer appeal. Addressing this issue is essential for ensuring the profitability of sustainable aquaculture,” explained Jani Lehto, Director of Luke’s Bioeconomy and Environment Unit.

Water mould, meanwhile, remains a frequent concern in the farming of salmonids within RAS. It is estimated to cause up to 10% of annual production losses and poses a serious threat to endangered fish species maintained in aquaculture facilities.

Promising Experimental Results

Trials conducted at Luke’s experimental facilities have delivered highly promising outcomes. Chemically treated fibre materials were able to trap off-flavour compounds at concentrations up to 1,000 times higher than those found in untreated water, effectively reducing these compounds to levels undetectable by human senses.

“This is a significant breakthrough, particularly as no new solutions have emerged in recent years to address off-flavours in recirculating aquaculture systems,” said Petra Lindholm-Lehto, Research Manager at Luke.

Additionally, tests carried out at Luke’s Enonkoski facilities demonstrated that the same fibre materials substantially reduced the presence of water mould spores in fish tanks. This innovation offers a safer and more effective alternative to previous methods, many of which have proven either ineffective or harmful.

“Our approach uses harmless capture materials, making these results particularly encouraging,” Lindholm-Lehto added.

The Next Step: Commercialisation

With a patent application already filed, Luke and VTT are now preparing for the next phase of development: scaling up these solutions for implementation in commercial aquaculture farms.

As the aquaculture industry continues to expand, addressing challenges such as off-flavours and water mould is critical to ensuring its long-term sustainability. Through practical and environmentally friendly solutions, Luke and VTT are paving the way for a more profitable and resilient aquaculture sector.