Given their off-putting taste, the removal of taste and odor molecules from RAS is of substantial economical concern. The current best practice in RAS for filet depuration is by starving the fish while purging their tanks with clean water before harvest. The fish will only slowly excrete off-flavour compounds to the clean water and purging may therefore last up to two weeks. The starving fish may lose up to 20 % of marketable bodyweight during the depuration period reducing the economic viability of RAS. The practice of purging also leads to environmental concerns as it increases the outlet of wastewater.
The results of our project will be relevant to the RAS industry and may improve farming efficiency and sustainability.
Off-flavour occurs as Geosmin or MIB accumulate in the recirculating water where these molecules will enter the fish tissues untill an equilibrium is reached (denoted by equal size arrows). In this state the concentration of Geosmin and MIB remains constant in the fish and the issue with off-flavour peaks.
Depuration is achieved by placing the fish in a clean water flow-through system. Here the concentration of off-flavour molecuels will be higher in the fish than in the water. This will shift the equilibrium between the fish and water causing a net diffusive loss of off-flavour molecules from the fish into the water (denoted by unequal size arrows). Ultimately, the fish will lose their off-flavour as a new equilibrium is reached between the fish and the clean flow-through water.
