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

item Burr, Gary
item Wolters, William
item Schrader, Kevin
item SUMMERFELT, STEVEN - Freshwater Institute

Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2012
Publication Date: 3/17/2012
Citation: Burr, G.S., Wolters, W.R., Schrader, K., Summerfelt, S. 2012. Impact of depuration of earthy-musty off-flavors on fillet quality of Atlantic salmon, Salmo salar, cultured in a recirculating system. Aquacultural Engineering. 50:28-36.

Interpretive Summary: Atlantic salmon is an important culture species and interest in growing this species on land in tanks is increasing. However, flavor issues arise when salmon are grown in land based tanks if the fish have a muddy or dirty flavor. Before these fish can be sold to consumers, this muddy or dirty flavor must be eliminated. The purpose of this study was to determine the conditions needed to eliminate this off flavor. Salmon needed to be moved into clean tanks or placed into tanks in which the water passes through the tanks only once and not filtered. The fish need to be left in the clean tanks and not fed for at least 10 days but not more than 15 days to remove the off flavors. The quality of the fish fillets, color and oil content, are not affected during this period.

Technical Abstract: 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 depuration period required to adequately purge the earthy and musty off-flavor compounds geosmin and 2-methylisoborneol (MIB) from Atlantic salmon fillets in order to provide an on-flavor product and the impact of the depuration period 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 off-flavor salmon required depuration in odor-free water for 10-15 days in either a flow-through system or a recently cleaned RAS. 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%. Fillet color quality was not compromised during the 20-day depuration periods. In trial 1, MIB was the main contributor to off-flavor in salmon fillets while geosmin was the main contributor 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 depuration periods used in these studies, the main fillet quality concerns for producers of RAS-cultured salmon are flavor and lipid levels during the pre-harvest purging process.