Food Technology GCSE AQA 2010

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Fish Classification

  • Fish are generally classified according to their physical structure and composition
  • Oily fish-Herring, mackerel, trout, salmon, tuna, sardine.
  • The fat is in the flesh and so its usually darker in colour.
  • Most of these fish swim near the surface. Salmon and Trout live most of their lives at sea but return to freshwater to spawn
  • White fish-cod , haddock, coley and whiting-also known as round fish and plaice, trout, halibut, sole –also known as flat fish
  • Most white fish are sea fish


  • Shellfish-Crab, lobster, prawns and shrimps-also known as crustaceans-have legs with partly joined outer shells.
  • The meat from these is less easily digested.
  • Most are sold ready cooked.


  • Oysters, scallops, cockles and mussels are known as molluscs
  • They have harder outer shells and no legs
  • Some have hinged shells and are known as bi-valves e.g. oysters, scallops, and mussels
  • Others have shells in one piece e.g. cockles and winkles.
  • Some are traditionally eaten raw e.g. Oysters
  • Shellfish supply nutrients but they deteriorate quickly and are often expensive to buy.
  • Shellfish are highly perishable


  • Fish is a valuable source of protein which is of a high biological value
  • In white fish the oil is stored in the liver-the flesh is therefore white and very low in fat, its very easy to digest.
  • In white fish the oil is stored in the liver-the flesh is therefore white and very low in fat, its very easy to digest.
  • The liver oils are often sold as capsules e.g. cod liver oil
  • In oily fish the oil is distributed throughout the flesh making it darker in colour, more nutritious but harder to digest.
  • The fat found in oily fish is safe fat and contributes to the omega 3 & 6 fat
  • There is no carbohydrate in fish
  • Fish is a good source of vitamin A & D. It contributes iodine to the diet

An alternative classification

  • An alternative classification used sometimes is-Freshwater eg salmon and trout and Salt water
  • Demersal- is the term used for fish that live at the bottom of the ocean and are caught by trawlers e.g. cod, haddock, plaice, whiting and sole
  • Palagic- this type swim near the surface and are caught by drifters e.g. herring, mackerel, sprats, pilchards, mullet


  • Great care must be taken in the storage and preparation of fish, as it is a moist, protein rich food and therefore ‘HIGH RISK’
  • Fish rapidly loses its freshness
  • A lot of fish is prepared and frozen on trawlers whilst at sea, so it will remain in peak condition until it reaches the processing plan
  • The proportion of fish which is frozen is high

Frozen fish

  • It can be made available in a number of ways:-
  • As fillets, steaks etc and ready to prepare in the home
  • Ready coated-e.g. fish fingers
  • In a sauce e.g. Fish in parsley sauce
  • Frozen fish is popular as it is very fresh and


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