Abstract: An analytical method was established for determining geosmin (GEO) and 2-methylisoborneol (MIB) as off-odor compounds in freshwater fish using gas chromatography-mass spectrum (GC-MS) based on microwave assisted distillation followed by solid phase microextraction. Such sample preparation parameters as microwave power, distillation time and carrier gas flow rate were optimized to be 360 W (40% of the maximum power), 6 min, and 60 mL/min, respectively. Under the optimized conditions, the detection limits were 0.044 μg/kg for GEO and 0.095 μg/kg for MIB. A good linearity was observed for GEO and MIB over the concentration range of 0.5 to 20 μg/kg with r2 of 0.998 and 0.991, respectively. The recoveries were 42.7% for GEO and 61.9% for MIB. Using this method, the contents of GEO and MIB in a commercially available tilapia meat sample were determined to be 4.97 μg/kg and 1.21 μg/kg, respectively.

Key words: off-flavor compounds, microwave-assisted distillation, tilapia, geosmin, 2-methylisoborneol