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Industrial processing and heat treatment of fish muscle generally lead to losses of water-soluble components, some of which may have beneficial health effects. The aim of this work was to determine the retention of taurine, selenium and n-3 polyunsaturated fatty acids when preparing African catfish by three traditional household techniques: boiling in pouches, deep-frying and baking. Cooking did not significantly reduce the content of selenium, having retention between 91and 104%. Deepfrying resulted in a taurine loss of 40%, which was significantly higher than in baking where losses were 25% The fatty acid profiles were similar for baked and boiled fillets, but were significantly different from deep-fried fillets, due to absorption of vegetable frying oil. Baking was the best preparation technique with regard to retention of 20:5n-3 (eicosapentaenoic acid; EPA) and 22:6n-3 (docosahexaenoic acid, DHA), retaining above 80% for both fatty acids, whereas boiling and deep-frying were able to retain only approximately 54 and 65% of each, respectively.

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In many fields the concept and measurement of quality is of prime importance. The fish industry is no exception to this and many sensory approaches have been devised to quantify this rather intangible property. The EU 5th framework project ‘SEQUID’ has concentrated on the measurement of the dielectric properties of fish tissue as a function of time both in frozen and chilled storage. The many deteriorative biochemical and microbiological processes that take place during the gradual spoilage of such materials have a subtle influence on the dielectric properties across the spectrum but notably in the microwave frequency region. In this region the complex interactions of water, solutes and structure-forming proteins are systematically changed by death and decay. Chilling or freezing may slow these processes but such preservation techniques do not halt them entirely. The SEQUID project has shown that it is possible, using a combination of time domain reflectometry and multivariate analysis, to predict certain quality-related variables, both sensory and biochemical, with comparable accuracy to existing methods. These results are presented in this paper.

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