Friday, February 5, 2010

Composition and nutritional quality of fish from fisheries and farming

INRA, UMR1067, Nutrition, Aquaculture and G
PHydrobiologie INRA
F-64310 St PFrance Fish market is supplied from both fisheries capture and aquaculture. The part of products from fish farming is growing, accompanied by an increased consumers concern about the quality of such products compared to that of wild catch. Nutritional and healthy value of fish is based on the characteristics of the flesh components. Fish flesh is the primary source of n-3 long chain highly unsaturated fatty acids (HUFA) in human food, has a high protein content with a well balanced amino acid profile and supplies many minerals and vitamins. There is a wide variety of fish species with different geographic habitats and different feeding habits, which results in differences in body composition.

Even though amino acid profile is nearly constant, protein content varies from 14 g/100g (pangasius catfish) to 27 g/100g (tuna), as a special feature of each species irrespective it is from fisheries or from farming. There are huge differences in lipid content among fish species resulting in large variation in the levels of n-3 HUFA typical of fish (EPA: eicosapentanoic acid and DHA: docosahexaenoic acid). Some species such as sole, haddock and cod, are classified as "lean" species because of a limited capacity to store fat in the muscle (less than 2g/100g), some others such as herring, sardine and Atlantic salmon contain more than 12 g/100g and are classified as "fatty" species. Rainbow trout is considered as intermediate with a muscle lipid level between 5 and 10 g/100g. In fatty species from fisheries, fat content varies dramatically with season, depending on food availability, water temperature and sexual status of fish (for instance from 1g/100g in March, after spawning, up to 18.4 g/100g in September in sardine muscle). The content in EPA and DHA generally increases with the lipid content of fish muscle so that EPA and DHA content of sardine muscle varies from 275 mg to 5 g/100 g wet weight depending on the season. Fish from farming can be tailored through feeding and rearing practices. Muscle fatty acid profile reflects that of the diet. Feeding fish with diets containing fish oil, some months before slaughter, improves EPA and DHA content of fish flesh.

In addition to species special feature, physiological factors such as age and sexual maturity and feed composition are the main factors affecting the flesh content in vitamins such as the vitamins A, D, E and PP, B6 and B12. Concentration in minerals such as potassium and phosphorus and trace elements such as selenium and iodine depends upon both water quality and dietary supply.

The origin of products, from aquaculture or fisheries, is not strong determinant of the differences in flesh components that give to fish its healthy value. It should be recommended to consume products from both aquaculture and fisheries to get benefits from the different fish species since they are complementary from a nutritional standpoint.

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