Abstract
Geosmin (GSM) and 2-methylisoborneol (MIB)-induced off-flavors can cause serious problems in a recirculating aquaculture system (RAS), such as delayed harvest and increased production costs, but also damage producers’ reputation. Traditionally, off-flavors have been removed by depuration before harvesting. Rainbow trout (Oncorhynchus mykiss) and European whitefish (Coregonus lavaretus) are commercially valuable species produced for consumers, both being suitable for rearing in RAS. In this study, European whitefish and rainbow trout were raised from juvenile up to 240 g (European whitefish) and 660 g (rainbow trout) to monitor the long-term accumulation of off-flavors. The concentrations in fillet of rainbow trout reached 3.6 ng·g−1 (MIB) and 5.6 ng∙g−11 (GSM) with lipid content of 22.5%, while for European whitefish up to 3.2 ng·g−1 (MIB) and 3.9 ng·g−1 (GSM) were found with 14.8% in lipid content. Concentrations up to 58 ng·L−1 (MIB) and 49 ng·L−1 (GSM) were found in the circulating water. Based on the results, the accumulation of MIB proceeds at similar pace for both species. In the case of GSM, the accumulation started similarly for both species but proceeded more quickly for rainbow trout after 140 days of the experiment, with a statistically significant difference (p < 0.05).
Highlights
GSM and MIB are produced as metabolic by-products of several strains of bacteria, such as streptomyces, myxobacteria, actinomycetes, cyanobacteria, proteobacteria, and fungi [12,13,14] related to, for example, photosynthesis and pigment synthesis, but in recirculating aquaculture system (RAS) prone to grow in variety surfaces
The accumulation of off-flavors increased as the fish increased in weight and lipid content
It is known that even relatively small concentrations in circulating water can lead to an accumulation of off-flavors in fish fillet, emphasizing the importance of the good quality of the water used for depuration and the efforts made to reduce the levels of off-flavors in circulating water
Summary
Land-based intensive recirculating aquaculture systems (RAS)s allow stable rearing conditions, and enable a reduction in water consumption and nutrient discharge per kg of produced fish [1].off-flavors are often formed in RAS, which has been widely reported in fish of different species reared in RAS [2,3,4], in ponds [5,6,7], and in wild fish [8].Off-flavors are typically induced by two saturated bicyclic terpenoids, geosmin (GSM, trans-1,10dimethyl-trans-9-decalol) and 2-methylisoborneol (MIB, (1-R-exo)-1,2,7,7-tetramethylbicyclo-[2.2.1]heptan-2-ol), which produce an earthy and musty odor and taste [9,10]. Land-based intensive recirculating aquaculture systems (RAS)s allow stable rearing conditions, and enable a reduction in water consumption and nutrient discharge per kg of produced fish [1]. Off-flavors are often formed in RAS, which has been widely reported in fish of different species reared in RAS [2,3,4], in ponds [5,6,7], and in wild fish [8]. Off-flavors are typically induced by two saturated bicyclic terpenoids, geosmin (GSM, trans-1,10dimethyl-trans-9-decalol) and 2-methylisoborneol (MIB, (1-R-exo)-1,2,7,7-tetramethylbicyclo-[2.2.1]heptan. GSM and MIB are produced as metabolic by-products of several strains of bacteria, such as streptomyces, myxobacteria, actinomycetes, cyanobacteria, proteobacteria, and fungi [12,13,14] related to, for example, photosynthesis and pigment synthesis, but in RAS prone to grow in variety surfaces
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