Instrumental versus sensory detection of off-flavors in farm-raised channel catfish

Abstract

Results from an instrumental method for determining the presence of the earthy, muddy or blue-green off-flavor in catfish were compared with those of four professional flavor checkers. Solid phase microextraction and gas chromatography/mass spectrometry were used to detect the off-flavor compounds, 2-methylisoborneol and geosmin. The odor threshold for an average flavor checker was determined to lie between 0.1 and 0.2 μg/kg for 2-methylisoborneol and estimated at 0.25 to 0.5 μg/kg for geosmin. The odor threshold for geosmin in channel catfish appears to be only slightly greater than that of MIB. The lower end of the sensory limits served as the instrumental cutoffs for grading fish off-flavor. Comparison of the instrumental method versus the flavor checkers resulted in a high correlation ( R=0.9).