Off-flavor in channel catfish is a serious problem in the commercial culture industry affecting 50-80% of growout ponds during the warmer months of the year. A microwave distillation technique has been developed to isolate volatile compounds from affected material. 2-Methylisoborneol (MIB) is the predominant compound isolated from off-flavored catfish during the growing season (April-October) in west Mississippi and is responsible for a musty type of flavor. Geosmin and other as yet unidentified compounds are also important causes of an earthy type off-flavor. 2-Methylenebornane and 2-methyl-2-bornene, dehydration products of MIB, were shown to contribute to the off-flavor problem. The absorption (2 hours) and depuration (48 hours) of MIB in catfish fingerlings were determined. MIB and its dehydration products are concentrated primarily in subepidermal and abdominal fat. Lesser concentration occurs in the liver and muscle tissue of off-flavored fish. Removing fish to clean, flowing water to purge MIB and geosmin could provide a partial means for off-flavor abatement.

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