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[ FISHERIES ] to protein rich animal feed via biological fermentation are usually less expensive than elaborately produced isolates such as collagen, keratin or chitosan that serve as functional components in numerous products. Although research and development in this field only really got underway just a few years ago it is already revealing that a lot of useful substances are to be gained from fish and seafood waste and that some of them probably have antimicrobial properties and can also be effective against tumours. Fish waste has to be processed quickly, however, for the organic material has a low biological stability (short shelf life) due to its high water content, its oxidation susceptibility and high enzyme activity.

Chitosan and dried cod heads One of the most popular by-products from seafood processing is chitosan which is produced from the shells of shrimps and other crustaceans. Chitosan is used in the production of cosmetics and pharmaceutical products but also in other fields. Due to its positive charge and coagulating properties chitosan has chelate-building

properties. It binds and flocculates the protein-containing residues found in waste water from the food industry. Apart from that, chitosan has germ-killing effects on bacteria, yeasts and fungi and also film-forming properties. The packaging industry is trying to coat film with chitosan to make packaging materials antimicrobially “active�. An elegant possibility to make use of fish oil and fat from slaughter waste is also to process it to biodiesel which can be used in its pure form or as an additive in crude oil-based diesel fuels. Slaughter waste is also very suited to the production of biogas. A much more effective usage area for the remnants from fish processing, however, is for human consumption. The best known example of this is unsalted airdried cod heads and backbones that are left over in large quantities during production of stockfish and klippfish in Norway and Iceland. The most important market for this by-product is Nigeria where “okporoko� serves as an aromatic stock for soups and stews: an inexpensive and nutritious food that contains a lot of protein with a long shelf-life plus other nutrients. In Norway alone

Fish leather and gelatine are typical by-products from fish skin. Recently the collagen rich skin has also been used in medical products.

The liver of cobia (Rachycentron canadum) is comparatively large and extremely tasty, particularly when fried.

about 50 to 60 million US dollars revenue is generated with the export of dried Gadidae heads.

Leather and gelatine from fish skin A raw material that arises during processing and which is often underestimated is fish skins. Part of the skins, particularly of salmon, tilapia, cod and catfish but recently also skate, shark and sturgeon is already processed to very elaborate, resilient and optically attractive leather but, with that, the full potential is by no means exhausted. One reason for this is presumably the small size of the individual fish skins which forces users to intricate patchwork creations. Usage areas are thus mostly limited to handbags, purses, shoes, jewellery and similar decorative fashion accessories. Fish gelatine is also of great significance. It is produced using hydrolysis of the collagen in fish skin, mostly the skin of cod, haddock and pollock. One advantage of fish gelatine is its chemical composition. Although it contains the same amino acids as other animal gelatines it has a relatively low share of proline and hydroxyproline. This reduces the number of hydrogen bridges between the molecules and lowers gelling temperature. Fish 


gelatine is a thermo-reversible hydrocolloid with high gelling stability and a good viscosity. In numerous foods it serves as a gelling and thickening agent, emulsifier and stabiliser but it is also used in cosmetics, pharmaceuticals and film material. Because, in contrast to mammalian gelatines, religious Jews and Moslems hardly have any reservations against fish gelatines these are preferably used in kosher and halal products. The skins of some fish species can also be prepared like “chicharron�, the crisply fried pork skin that is found in Mexican cuisine. For this product the scales and any remaining pieces of meat are removed from the fish skins which are then boiled in salt water, dried and subsequently fried crisp in vegetable oil. Finely seasoned, for example with herbes de Provence, smoked pepper or lemon pepper the fish chicharrones are eaten like crisps. An original but very promising new usage of tilapia skins can currently be seen on Youtube which shows Brazilian doctors using sterilised fish skins as bandages when treating severe burns. They cover the burn completely with the tilapia skin which contains a particularly large quantity of collagen type 1 which accelerates the healing process and reduces scar formation. &VSPlTI .BHB[JOF 


Profile for Eurofish

Eurofish Magazine 5 2017  

Featuring Albania's fisheries and aquaculture sector, this issue also looks at EU and Japan's trade agreement while the fisheries section co...

Eurofish Magazine 5 2017  

Featuring Albania's fisheries and aquaculture sector, this issue also looks at EU and Japan's trade agreement while the fisheries section co...

Profile for eurofish