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United States Department of Agriculture

Agricultural Research Service

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

Location: Natural Products Utilization Research

Title: Off-flavors in salmonids raised in recirculating aquaculture systems

Author
item Schrader, Kevin

Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: May 17, 2013
Publication Date: July 1, 2013
Citation: Schrader, K. 2013. Off-flavors in salmonids raised in recirculating aquaculture systems. Global Aquaculture Advocate. 16(4):32,34-35.

Interpretive Summary: Producers of aquaculture products will typically verify the flavor quality of their product by sensory evaluation (flavor testing) before harvesting the crop for market. “Off-flavors” detected in the product may require holding the fish in a purging system containing fresh, clean water to depurate from the fish flesh the compounds causing the undesirable taints. Based on recent research, “earthy” and “musty” appear to be the most common off-flavors that occur in the flesh of certain salmonids, e.g., Arctic charr (Salvelinus alpinus), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss), raised in RAS. Geosmin and 2-methylisoborneol (MIB) are the most common off-flavors encountered in freshwater aquatic animals, and these compounds have been verified to be the cause of earthy and musty off-flavors in a wide variety of cultured products. Based upon recent studies, actinomycetes are considered to be the main contributors of geosmin and MIB in RAS. Most actinomycetes are aerobic, though some are facultative anaerobes and anaerobes, and they include odor-producing genera such as Micromonospora, Nocardia, and Streptomyces. The genus in which many odorous compounds have been identified is Streptomyces, and geosmin and MIB production is usually associated with streptomycetes. The sources of the some of the other less intense objectionable off-flavors, such as ammonia, bitter, and metallic, remain unknown at present.

Technical Abstract: Producers of aquaculture products will typically verify the flavor quality of their product by sensory evaluation (flavor testing) before harvesting the crop for market. “Off-flavors” detected in the product may require holding the fish in a purging system containing fresh, clean water to depurate from the fish flesh the compounds causing the undesirable taints. Based on recent research, “earthy” and “musty” appear to be the most common off-flavors that occur in the flesh of certain salmonids, e.g., Arctic charr (Salvelinus alpinus), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss), raised in RAS. Geosmin and 2-methylisoborneol (MIB) are the most common off-flavors encountered in freshwater aquatic animals, and these compounds have been verified to be the cause of earthy and musty off-flavors in a wide variety of cultured products. Based upon recent studies, actinomycetes are considered to be the main contributors of geosmin and MIB in RAS. Most actinomycetes are aerobic, though some are facultative anaerobes and anaerobes, and they include odor-producing genera such as Micromonospora, Nocardia, and Streptomyces. The genus in which many odorous compounds have been identified is Streptomyces, and geosmin and MIB production is usually associated with streptomycetes. The sources of the some of the other less intense objectionable off-flavors, such as ammonia, bitter, and metallic, remain unknown at present.

Last Modified: 8/30/2014
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