Determination of off-flavor compounds, 2-methylisoborneol and geosmin, in salmon fillets using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry

Abstract

A sensitive and solvent-less method for the determination of musty and earthy off-flavor compounds, 2-methylisoborneol (MIB) and geosmin (GSM), in salmon tissue was developed using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry (SBSE-TD-GCMS). MIB and GSM were solid phase extracted using polydimethylsiloxane (PDMS) coated stir bars, analyzed by gas chromatography, and detected in full scan mode of mass selective detector (MSD). Using this method, the calibration curves of MIB and GSM were linear in the range of 0.3-100ng/L, with a correlation coefficient above 0.999 and RSDs less than 4% (n=4). The limit of detection (LOD, S/N=3, n=6) and limit of quantification (LOQ, S/N=10, n=6) of MIB and GSM were both ∼0.3 and 1ng/L, respectively. The recoveries of MIB and GSM were 22% and 29% by spike in 30ng/L standard compounds, 23% and 30% by spike-in 100ng/L standard compounds in salmon tissue samples with good precision (<8% of RSDs, n=6), respectively. The recoveries of MIB and GSM were better than reported methodologies using SPME fibres (<10%) in fish tissue samples. This method was successfully applied to monitor and characterize depurated salmon fillet samples (0, 3, 6 and 10 days).

Keywords: Geosmin and 2-methylisoborneol; Salmon fillets; Stir bar sorptive extraction; Thermal desorption coupled with gas chromatography–mass spectrometry.