Product quality

In cultured fish, particularly freshwater species, there is often the risk of off-flavour. In general, this reduction in flesh quality is due to the presence of specific compounds, the most common of which are geosmin and 2-methylisoborneol. These secondary metabolites, which accumulate in the lipid tissue of fish, are produced by the blue- green algae (cyanobacteria) or by the bacteria of the genus Streptomyces, actinomycetes and myxobacteria. Geosmin gives a clear muddy flavour, while 2-methylisoborneol gives a mildewed taste that can severely affect consumer acceptance and disrupt the marketability of the product. Off-flavour occurs in both earthen ponds and RASs.

A common remedy for off-flavours consists of purging the fish for 3-5 days in clean water before sale or consumption. Fish must starve and be kept in a separated and aerated tank. In aquaponics, this process can be easily integrated in the ordinary management as the water used for the purging can be eventually used to refill the system.

Source: Food and Agriculture Organization of the United Nations, 2014, Christopher Somerville, Moti Cohen, Edoardo Pantanella, Austin Stankus and Alessandro Lovatelli, Small-scale aquaponic food production, http://www.fao.org/3/a-i4021e.pdf. Reproduced with permission.