Impact of depuration of earthy-musty off-flavors on fillet quality of Atlantic salmon, Salmo salar, cultured in a recirculating aquaculture system

Over the past decade in the United States, there has been increased interest in the establishment and use of land-based, closed-containment systems [e.g., recirculating aquaculture system (RAS)] for salmonid culture. These culture systems have unique challenges compared to net pen culture of salmonids, including maintenance of pumps and filters as well as the potential growth of certain bacteria within the systems that can render fish off-flavored. The purpose of this study was to determine the impact of implementing a deputation process to purge the earthy and musty off-flavor compounds geosmin and 2-methylisoborneol (MIB) from Atlantic salmon fillets on fillet quality characteristics (e.g., lipid content, color). During two depuration trials, salmon were depurated without feed in a flow-through tank, a recently cleaned RAS system or the originally stocked grow-out tank for up to 20 days. Results from both trials determined that the salmon required deputation in odor-free water for 10-15 days in either a flow-through system or a recently cleaned RAS to obtain the lowest residual levels of geosmin and MIB in the fish flesh. In trial 1, after 20 days, fish had lost significantly more weight (5.8%) compared to day 5 (3.8%). In the second trial, lipid content of the fillet also significantly dropped from 8.2% to 5.1% and moisture content increased from 69.3% to 71.1%. Fillet color quality was not compromised during the 20-day depuration periods. In trial I, MIB was the main off-flavor compound present in salmon fillets while geosmin was at higher levels than MIB in fish flesh in trial 2. During the second depuration study, three geosmin-producing species of actinomycetes were isolated from the recirculating system and were attributed as the likely sources of geosmin in the salmon fillets. Because fillet color quality was not compromised during the deputation periods used in these studies, the main fillet quality concerns for producers of RAS-cultured salmon are flavor, texture and lipid levels during the pre-harvest purging process. Published by Elsevier B.V.