Characteristics of the flesh and quality of products of catfishes

Abstract

Specificities of the structural, chemical, physical and sensory characteristics of the flesh are reviewed and related to different aspects of flesh quality. Potential for processing of catfish is high in terms of mechanization but rather low in terms of processing yields. The variability observed in body conformation traits supports the possibility to improve processing yields by genetic selection. Little is known on the structure of catfish flesh but a higher cohesiveness due both to greater connective tissue strength and probably a greater homogeneity of muscle tissues is observed, compared to other freshwater species. Although the presence of adipose tissues has not been demonstrated, intermuscular adipose tissues contributes with red muscle to lipid deposits in commercial size. Lipid content in catfish flesh increases with age but even at commercial size it is still lower than what is reported in other cultured fish. There is however a tendency in recent years for an increase in lipid content in catfish flesh due to increasedlipid content in the diet. Thus, further information on the control of lipid deposits is required in future especially in a view to improve taste and processing yields. The lipid composition of neutral lipids reflects that of the diet with high levels of monounsaturated fatty acids and a low w3/w6 ratio.Flesh colour is very subtle but it could be controlled either by the use of pigment supplementation in the diet or by rearing non pigmented catfish. Other physical characteristics of the flesh are very stable during the cooking process. Cooked flesh has a relatively low water-holding capacity and a low resistance to mechanical stress (compression, extrusion) thus contributing to the juiciness and tenderness of the flesh. The sensory characteristics of the flesh are somewhat neutral but consumers are able to detect thespecific characteristics of different species such as Channel catfish, African catfish and European catfish. Significant efforts to standardize the sensory evaluation of Channel catfish have been made in the USA but flavor and aroma of catfish seem to be more related to the fish itself than to other factors such as the diet composition. New data is available on off-flavors related to geosmin and methyl-iso-borneol. Specific control of the phytoplankton species which produce these compounds appears to be possible.Storage on ice affects the flesh acceptability as it does for other fish species, but catfish flesh seems to be stable at least physically during freezing. Traditional processing is used for preservation of the flesh. New processing methods have been tested for the diversification of catfish products or to produce substitutes for other animal products. Catfishes are generally shown to be suitable for processing.