Developing a robust and sensitive analytical method to detect off-flavor compounds in fish

Abstract

In recirculating aquaculture systems (RAS), off-flavors that accumulate in fish muscle tissue can be problematic in terms of consumer acceptance and the reputation of farmed fish products. Although off-flavors are not toxic at low concentrations, they often give fish muscle earthy, muddy, or other unwanted flavors. Traditionally, muddy off-flavors caused by geosmin (GSM) and 2-methylisoborneol (MIB) have been detected, but a variety of other compounds and flavors have also been identified. In this study, a method based on solid phase micro extraction (SPME) coupled with gas chromatography and mass spectroscopy was developed to identify and quantify 14 off-flavor–inducing compounds in RAS–farmed fish. The selected off-flavors were quantified in circulating water and in fish from a pilot-scale RAS rearing rainbow trout (Oncorhynchus mykiss). The method showed high accuracy and precision with limits of detection and quantification at a low ng L−1 level. In this study, 13 compounds were found in the fish muscle which decreased in concentrations during the 15-day depuration period. This study showed that off-flavors in fish can also be induced by other compounds besides GSM and MIB. This emphasizes the need for sufficient off-flavor control in the RAS, but also the importance of an accurate and reliable analytical quantitation method.

Comparative Evaluation of Wild and Farmed Rainbow Trout Fish Based on Representative Chemosensory and Microbial Indicators of Their Habitats

“…In our opinion, this was mostly true in the case of the fishy attribute, which increased from 1.6 in B-I to 4.41 points in B-P. Furthermore, fishy together with the musty and mushroom-like attributes might potentially mask the perception of attributes like sweet and green/grassy. , …”

“…The universal earthy/musty off-flavors geosmin and 2-methylisoborneol (MIB) were also detected. Additionally, other nine compounds with earthy and/or musty off-notes were detected, suggesting that earthy and musty malodors are not solely caused by geosmin and MIB. ,,,,− …”

“…Furthermore, fishy together with the musty and mushroom-like attributes might potentially mask the perception of attributes like sweet and green/ grassy. 31,32 Among the fish samples, wild fish was significantly different from farmed fish samples and presented higher ratings of sweet, fruity, and citrus-like aroma impressions compared to farmed fish. On the other hand, there was a lower rating of metallic, musty, earthy, and muddy off-flavor notes.…”

Water quality monitoring in recirculating aquaculture systems

“…Compound can be analysed with techniques based on liquid (LC) or gas chromatography (GC) based on its properties. Additionally, for the detection of low concentrations of analytes in complex RAS water matrix, a variety of pretreatment methods is required, including solid phase extraction (Gorito et al., 2022; Höglund et al., 2022), solid phase micro extraction (Lindholm‐Lehto, 2022) and dynamic headspace (HS) (Podduturi et al., 2017), to name a few (Table 3). In the case of volatile and semi‐volatile compounds, GC‐based methods are preferred (Lindholm‐Lehto et al., 2019; Lindholm‐Lehto, 2022), while LC with tandem mass spectrometry (MS/MS) detection is more suitable for antibiotics (Freitas et al., 2014).…”

Improved Quantification of Geosmin and 2-Methylisoborneol in Farmed Fish Using Stable Isotope Dilution Gas Chromatography–Mass Spectrometry

“…15,16 Research of off-flavor prevention techniques is limited by the ability to accurately quantify these compounds in fish flesh. 17 Although trained taste testers possess the ability to detect these undesirable flavors in fish, often, they are not able to provide identification or accurate concentration values. 18 MIB and GSM are easily quantified in aqueous matrices, 19 but as a result of the variable presence of matrix-interfering compounds, reliable measurement of off-flavor levels in fish is more difficult to accomplish.…”