Determination of geosmin and 2-methylisoborneol in fish muscle by gas chromatography-mass spectrometry

Abstract:

Geosmin and 2-methylisoborneol are semi-volatile, off-flavor compounds with similar chemical structures that are produced by certain species of actinomycetes, fungi, and blue-green algae. These off-flavor compounds tend to bio-accumulate within fish, depending on the concentrations in the water, the water temperature, the fat content and mass of the fish, and other abiotic and biotic factors. It is necessary to develop an accurate test of geosmin and 2-methylisoborneol in fish muscle to improve the quality of aquaculture products. A novel qualitative and quantitative determination method for geosmin and 2-methylisoborneol in fish meat was established, using cis-decahydro-1-naphthol as an internal standard and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. The method of geosmin and 2-methylisoborneol extraction and quantification in fish meat was investigated, the conditions of headspace solid phase microextraction were optimized, and the adaptability of the method was examined through the measurement of actual samples. In the range of 0.1~10.0 μg/L, the ratio of the peak area of geosmin and 2-methylisoborneol to the peak area of the internal standard was linearly related to the ratio of the mass concentration. The correlation coefficient (r2) was > 0.999, the detection limits were 0.018 μg/kg and 0.023 μg/kg, respectively, the limits of quantification were 0.059 μg/kg and 0.076 μg/kg, the average recovery of the three concentration gradients was 68.67%~80.30% and 62.67%~83.40%, and the relative standard deviations were between 2.35%~6.53% and 3.16%~6.80%. This method is highly sensitive, has good repeatability, and can be used to determine the geosmin and 2-methylisoborneol contents of fish.