EFFECTS OF TEMPERATURE ON THE UPTAKE AND DEPURATION OF 2-METHYLISOBORNEOL (MIB) IN CHANNEL CATFISH ICTALURUS-PUNCTATUS

The microbial metabolite 2-methylisoborneol (MIB) imparts a muddy off- flavor to channel catfish Ictalurus punctatus, Uptake and depuration o f MIB from fish are important considerations in the design and impleme ntation of systems to remove off-flavors from fish prior to processing . The kinetics of MIB uptake by channel catfish were determined by pla cing fish in 6.5, 14.0, 25.0, and 34.0 C water containing approximatel y 1.0 mu g/L chemically-synthesized MIB. Fish were sacrificed followin g 0, 2, 4, 8, and 24 h exposure to MIB. Fillet tissue samples were sub jected to gas chromatographic and fat content analysis, The model for MIB uptake was: MIB in fillet tissue (mu g/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 a ccounted for 74% of the total variation observed in the tissue MIB con centrations and indicated that the fillet fat content was not strongly correlated with MIB uptake, To investigate the depuration of off-flav ors, 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 da ta yielded the model: MIB in fillet tissue (mu g/kg) = 3.6 + 0.176(T) - 2.06 [log(h + 1)] - 0.00296(T) (h) + 0.197 (% fat), where h is the d uration of exposure to MIB in hours, T is the water temperature in deg rees C, and % fat is the % fat in the fillet tissue. The model account ed for 67% of the total observed variation in tissue MIB concentration s. Reducing the fat content of fish and optimizing water temperatures may augment MIB removal from fish tissues prior to processing.