Off-flavor In Catfish Research Articles

Exploration of volatile compounds causing off-flavor in farm-raised channel catfish (Ictalurus punctatus) fillet

Off-flavor is a major challenge to the quality of farm-raised catfish fillet. In this work, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) was employed to analyze volatile compound profile of catfish fillet to find the volatiles which might be responsible for the off-flavor. Ten volatile compounds were identified, and their concentrations in on-flavor and musty off-flavor fillets were compared. The off-flavor fillet contained significant larger amount of geosmin (GSM), 2-methylisoborneol (MIB), hexanal, 1-octen-3-ol and nonanal, indicating they might be related to the musty off-flavor. Sensory evaluation of the five compounds and their combinations suggested that GSM and MIB might be mainly responsible for the musty off-flavor, while the presence of hexanal or 1-octen-3-ol might notably intensify the off-flavor. This research suggested that besides GSM and MIB, some small aldehydes and/or alcohols might also need to be considered for controlling off-flavor in catfish fillet. This work also provided a useful chemistry-based objective method to evaluate the effects of treatments and/or managements in reducing catfish off-flavor.

Chemical Treatments to Reduce Off-Flavor in Farm-Raised Channel Catfish (Ictalurus punctatus ) Fillet

The efficacy of chemical treatments on reducing musty off-flavor in catfish fillets was evaluated in this work. Two ingredients, tea polyphenols and acetic acid, were found effective on removing the off-flavor. Three treatments, i.e., 0.40 g/L tea polyphenols, 0.50% acetic acid and 0.40 g/L tea polyphenols + 0.50% acetic acid, presented significantly better results than water wash (the control). Mechanism study indicated that the three treatments were able to reduce the contents of geosmin and/or 2-methylisoborneol which are the two major off-flavor causing compounds in catfish fillet. The treatment with both of the ingredients showed slightly better results than the treatment with only one ingredient. Practical Applications Off-flavor is a major quality concern to farm-raised catfish fillet. Major revenue lose could be caused by delay of harvest and/or defective products due to off-flavor. This study offers a novel strategy to reduce the musty off-flavor by chemical treatment, which could help the catfish industry improve fillet quality and lower production cost. The research indicated that tea polyphenols and/or acetic acid were effective to reduce/remove musty off-flavor in farm-raised catfish after harvest. The two chemicals could reduce the contents of geosmin (GSM) and/or 2-methylisoborneol (MIB), which are the two major off-flavor causing compounds in various fish fillets. Therefore, the treatments developed in this work may also be effective for other seafood products.

Detection of Off-Flavor in Catfish Using a Conducting Polymer Electronic-Nose Technology

The Aromascan A32S conducting polymer electronic nose was evaluated for the capability of detecting the presence of off-flavor malodorous compounds in catfish meat fillets to assess meat quality for potential merchantability. Sensor array outputs indicated that the aroma profiles of good-flavor (on-flavor) and off-flavor fillets were strongly different as confirmed by a Principal Component Analysis (PCA) and a Quality Factor value (QF > 7.9) indicating a significant difference at (P < 0.05). The A32S e-nose effectively discriminated between good-flavor and off-flavor catfish at high levels of accuracy (>90%) and with relatively low rates (≤5%) of unknown or indecisive determinations in three trials. This A32S e-nose instrument also was capable of detecting the incidence of mild off-flavor in fillets at levels lower than the threshold of human olfactory detection. Potential applications of e-nose technologies for pre- and post-harvest management of production and meat-quality downgrade problems associated with catfish off-flavor are discussed.

Algicidal Activity of Stilbene Analogues

Continuing our search for natural product and natural product-based compounds for the control of off-flavor in catfish, 29 stilbene analogues were synthesized and evaluated for algicidal activity against the 2-methylisoborneol (MIB)-producing cyanobacterium Oscillatoria perornata. The cis and trans isomers of 4-(3,5-dimethoxystyryl)aniline showed moderate and selective algicidal activity toward O. perornata with the lowest observed inhibitory concentration and lowest complete inhibition concentrations of 10 muM. This is the first report on selective stilbene algicidal activity toward a MIB-producing cyanobacteria species.

Cyanobacteria and earthy/musty compounds found in commercial catfish ( Ictalurus punctatus) ponds in the Mississippi Delta and Mississippi–Alabama Blackland Prairie

The compounds responsible for earthy and musty “off-flavors” in farm-raised channel catfish ( Ictalurus punctatus) in the southeastern United States of America are geosmin and 2-methylisoborneol (MIB), respectively. These compounds are produced by certain species of cyanobacteria (blue-green algae) that grow in the aquaculture ponds. Previous research has focused on the species of cyanobacteria found in catfish ponds in west Mississippi (the leading region of catfish production in the USA), while the species responsible for earthy/musty off-flavors in catfish produced in the Mississippi–Alabama Blackland Prairie (MABP) region (second greatest region of catfish production) have not been described. We examined water samples from commercial catfish ponds in both regions to contrast the different types of cyanobacteria and assess the prevalence of geosmin and MIB. Results established that filamentous cyanobacteria are more common in west Mississippi compared to the MABP region. Also, the MIB-producing cyanobacterium Oscillatoria perornata is present in catfish ponds in both geographic locations, and geosmin is more prevalent in catfish ponds in the MABP region than in west Mississippi.

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

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).