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Research Project: Management of Off-flavors and Undesirable Bacteria in Aquaculture

Location: Natural Products Utilization Research

Title: Evaluating standard operating procedures to mitigate off-flavor from Atlantic salmon Salmo salar cultured in a semi-commercial scale recirculating aquaculture system

Author
item Davidson, John - Freshwater Institute
item Schrader, Kevin
item Swift, Bruce - Tri-Gen Fish Improvement Ltd
item Ruan, Eric - Lacombe Research Centre
item Aalhus, Jennifer - Lacombe Research Centre
item Juarez, Mamual - Lacombe Research Centre
item Good, Christopher - Freshwater Institute
item Wolters, William - Bill
item Burr, Gary
item Summerfelt, Steven - Freshwater Institute

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/22/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Fish cultured within water recirculating aquaculture systems (RAS) can acquire “earthy” or “musty” off-flavors due to bioaccumulation of the compounds geosmin and 2-methylisoborneol (MIB), respectively, which are produced by certain bacterial species present in RAS biosolids and microbial biofilms. Fish cultured in RAS are generally transferred to separate depuration systems that that are flushed with water in a single pass or are operated with limited water recirculation (with no biofilter), in order to purge these unpalatable flavors. Technologies and standard operating practices that optimize purging kinetics for Atlantic salmon Salmo salar and other species cultured in RAS are needed to improve the consistency and efficacy of depuration. During Study 1, off-flavor concentrations in the salmon flesh increased for all treatments, emphasizing the need to begin with clean, biofilm-free depuration systems. Study 2 indicated that pre-treatment of systems with H2O2 combined with GAC filtration of the makeup water resulted in the greatest reduction of off-flavor levels in the culture water and salmon fillets. However, H2O2 disinfection alone appeared to be just as effective. Study 3 demonstrated that depuration systems that are disinfected with H2O2 and absent of aeration media were the most effective at purging off-flavor concentrations from salmon compared to control systems that were not disinfected and contained aeration media. In addition, the study found that off-flavor concentrations within the flesh of individual Atlantic salmon cultured in RAS can vary widely. These studies demonstrated that the depuration process for Atlantic salmon cultured to harvest size in RAS can be optimized when using standard operating procedures that provide clean and relatively biofilm-free depuration systems. Pre-disinfection of depuration systems using 250 mg/L hydrogen peroxide appears to enhance off-flavor removal. Aeration media should not be used within depuration systems because of the challenges posed for effective cleaning, disinfection, and inactivation of off-flavor producing bacteria. Unit processes and areas that are difficult to clean and disinfect should be avoided within depuration system designs. When establishing the optimal number of days for depuration, the range of off-flavor concentrations within individual salmon should be considered, and a purging period that effectively reduces off-flavor to acceptable low levels in all fish should be selected. The authors recommend inclusion of these techniques as standard operating procedures to optimize the depuration process for Atlantic salmon and other salmonids that are cultured to harvest size within recirculating aquaculture systems in order to provide an on-flavor product.