DETERMINATION OF GEOSMIN AND METHYLISOBORNEOL IN CATFISH TISSUE (ICTALURUS-PUNCTATUS) BY MICROWAVE-ASSISTED DISTILLATION-SOLID PHASE ADSORBENT TRAPPING

Methylisoborneol (MIB) and geosmin (GEO) are algal off-flavor compound s, which when present in catfish tissue create undesirable taste and o dors in the prepared products. These undesirable taste and odor proble ms are not limited to catfish aquaculture. A procedure was developed f or the determination of off-flavor compounds in channel catfish tissue that involves microwave radiation distillation with solid phase trapp ing. This is a modification of a microwave distillation-cold trapping procedure but without the need of a cryogen or a liquid-liquid extract ion step. A channel catfish fillet sample is placed in a container loc ated within a microwave oven. This container, which is directly connec ted to a thermostated condenser containing a solid phase adsorbent, is continually purged with argon gas. The trapped distillate components are eluted with ethyl acetate and then injected into a gas chromatogra ph-ion trap mass spectrometer for analysis. This technique offers a ra pid and sensitive means of off-flavor analysis in fish tissue and impr oved recovery for MIB from 73 +/- 3% (50 ppb) to 85 +/- 5% (10 ppm) co mpared to 62 +/- 6% for microwave-cold trap collection. The method det ection limits are 1.7 and 1.1 ppb for MIB and GEO, respectively.