Food Technology GCSE AQA 2010

Fish

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-crustaceans

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.

Molluscs

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

Nutrition

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

Storing

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

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