An Environmentally Benign Method for Reducing Off-Flavor Terpenoids in Aquaculture: Initial Laboratory Studies

Aquaculture products can develop an undesirable (i.e., off-flavor) taste. The majority of off-flavor is caused by two terpenoids, geosmin and 2-methylisoborneol (MIB), which are produced by cyanobacteria. Off-flavor is usually controlled by the regular application of copper sulfate or other herbicides. However, environmental concerns about copper in aquatic systems have recently been raised, and there is a growing public debate on the use of chemicals in food production. We report on an alternative, environmentally benign, nonherbicidal method for reducing off-flavor terpenoids in aquaculture products. We found that a hydrophobic material placed in aquaculture water will absorb the off-flavor hydrophobic terpenoids and lower the concentration in the water, thereby lowering the level in the aquaculture product. Reductions in off-flavor terpenoid concentrations of up to 85% were achieved in 48 h when various hydrophobic solids and liquids were added to terpenoid-spiked water. In live-fish experiments, channel catfish Ictalturus punctatus were placed in aquaria containing water spiked with both MIB and geosmin. In aquaria with a co-added hydrophobic compound (e.g., polystyrene or paraffin), the fish were rated as on-flavor by a taste panel. Conversely, fish exposed to the same level of terpenoids but without a co-added hydrophobic compound were rated as off-flavor.