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1992. [nfluence of fat content on uptake and depuration sf the sff-flavor 2-methylisobsrneol by channel catfish (bctalurus punctatus). Can. J. Fish. Aquat. Sci. 49: 2486-241 1.Channel catfish (Icealurus punstatus) sf different tissue fat contents (0.5-1 1 .O%) were held in water containing approximately 0.5 pg/L of the sff-flavor compound 2-methylissborneol (MlB) for various times. A new analytical method was developed to quantify tissue burdens of MlB. Fish showed significant bioeoncentration of MIB after 2 k and equilibrium by 24 h. The fatter fish (>2.5% muscle fat) accumulated nearly three times more MlB than lean fish (<2%j. Purging fish in MlB-free water indicated that leaner fish depurate faster (8 h) than fatter fish (48 h). Fat content had more influence in determining the time for return ts acceptable flavor than initial MIB concentration. Managing catfish production ts harvest leaner fish could minimize the impact of off-flavor on fish producers.Des barksues de riviPre (Ictalerrus punctatus) presentant diffbrentes teneurs tissulaires en graisses (de 0,s 2 11,0%) snt ete detenues dans de l'eau contentant environ 0,s pglL du compose 2-m6thylssborn&1I (MlB) generant une saveur desagreable pendant differentes pkrisdes. Une nouvelle methsde analytique a 6t6 mise au point pour quantifier la charge tissulaire en MIB. On a not6 chez les psisssns une biocowcentratisn significative de MIB aprPs 2 k et un kquilibre 21 24 h. Les p~issons plus gras (graisse musculaire > 2'5%) ont accumul6 pr6s de trois fois plus de MIB que les poissons maigres (< 2%). La purge des poissons dans de l'eau ne contenant pas de MIB a Indiquk que les poissons plus maigres detoxifient plus rapidement (8 k) que les psisssns plus gras (48 h). La teneur en graisses a eu plus d'influence pour detern-liner le temps requis jusqu'au retsur 2 une saveur acceptable que la concentration de MIB initiale. La gestisn de la production de Ia barbue de riviere avec capture des poissons plus maigres seulement pourrait minimiser I'impact de la saveur di2sagr6able sur les prsducteurs de poisssn.

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Oil was extracted from catfish viscera and purified (degummed, neutralized, bleached, and deodorized). The yield of catfish oil after purification was 65.7%. The major yield loss took place during the degumming process. The FA found in crude catfish visceral oil were 14:0, 16:0, 16:1

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The semivolatile cyclic alcohols 2-methylisoborneol (MIB) and geosmin (GSM) impart muddy or musty flavors to water and food products. A rapid quantitative analytical technique has been developed whereby microwave distillation is used to remove the volatile organic compounds from a lipophilic matrix into an aqueous matrix. Solid-phase microextraction (MD-SPME) is then used to extract and concentrate the analytes, which are then desorbed in the injection port of a gas chromatograph/mass spectrometer (GC/MS) for analysis. Limits of detection are 0.01 microg/kg and limits of quantification are 0.1 microg/kg. MD-SPME is comparable in precision, requires no solvents, and is faster than current methods of analysis. This methodology allows detection of MIB and GSM at concentrations below human sensory thresholds in fish tissue.

The microbial metabolite 2‐methylisoborneol (MIB) imparts a muddy off‐flavor to channel catfish Ictalurus punctatus. Uptake and depuration of MIB from fish are important considerations in the design and implementation of systems to remove off‐flavors from fish prior to processing. The kinetics of MIB uptake by channel catfish were determined by placing fish in 6.5, 14.0, 25.0, and 34.0 C water containing approximately 1.0 μg/L chemically‐synthesized MIB. Fish were sacrificed following 0, 2, 4, 8, and 24 h exposure to MIB. Fillet tissue samples were subjected to gas chromatographic and fat content analysis. The model for MIB uptake was: MIB in fillet tissue (μg/kg) =−0.61 ± 4.2 [log(h± 1)] ± 0.0076(T) (h) ± 0.089(T), where h is the duration of exposure to MIB in hours and T is the water temperature in degrees C. The model accounted for 74% of the total variation observed in the tissue MIB concentrations and indicated that the fillet fat content was not strongly correlated with MIB uptake. To investigate the depuration of off‐flavors, exposure to MIB was halted. Tissue samples were obtained 4, 8, 24, 48, and 72 h from fish held at 6.5, 14.0, 25.0, and 34.0 C. These data yielded the model: MIB in fillet tissue (μg/kg) = 3.6 ± 0.176(T) – 2.06 [log(h± 1)] – 0.00296(T) (h) ± 0.197 (% fat), where h is the duration of exposure to MIB in hours, T is the water temperature in degrees C, and % fat is the % fat in the fillet tissue. The model accounted for 67% of the total observed variation in tissue MIB concentrations. Reducing the fat content of fish and optimizing water temperatures may augment MIB removal from fish tissues prior to processing.