Fish Flashcards
Oily fish
High in unsaturated fat
Contains polyunsaturated fat
Eg: salmon,tuna and swordfish
Shellfish
Low in fat
Higher in cholesterol
Eg: lobster, prawns and mussels
Classification of fish
White fish
Oily fish
Shellfish
Protein
HBV
Contains proteins collagen,actin and myosin
Fat
Oily fish- polyunsaturated fats (PUFA)
Omega 3 fatty acids
Vitamins
B group
C in oysters
A and D in oily fish
Minerals
Iodine,phosphorus and zinc
Calcium in tinned fish
Iron in shellfish
White fish
Low in fat
Eg: cod,plaice and haddock
Oxidative rancidity
Fish flesh reacts with oxygen in air and becomes rancid
Enzyme action
Naturally occurring enzymes continue to work even at reduced temperature
Bacteria (spoilage)
When fish are caught, they struggle. This uses up glycogen in liver and muscles. As there is very little glycogen left to convert to lactic acid (preserves fish), when fish die they deteriorate very quickly due to action of bacteria on flesh.
This produces a nitrogen smelling compound called trimethylamine
Guidelines to follow when BUYING fish
Buy from clean shop
Fish in season are cheaper and taste better
Should be stored on ice
Choose medium sized pieces
Can be bought whole or as cutlets,steaks or fillets
Signs of freshness of fish
Bright bulging eyes Bring red gills Moist and unbroken skin No unpleasant smell Firm and elastic skin Tight scales Molluscs shells should be closed
Guidelines to follow when STORING fish
Refrigerate and use within 24 hours
Place on bed of ice
Freeze frozen fish
Check use by date
Effects of cooking/ heat on fish
Protein coagulates and sets Flesh changes from translucent to opaque Collagen converts to gelatine and flesh separates (flakes) Shrinks due to water loss Micro-organisms destroyed Vitamins and minerals are lost Cooked fish is easier to digest Overlooked fish is rubbery
