AGEN2002 Lecture Notes - Lecture 7: Oily Fish, Omega-3 Fatty Acid, Collagen
15 May 2018
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7. Biochemistry of fish & seafood
Three types of seafood
1. White fish
• < 5% fat, delicate flesh
• E.g. whiting, john dory, flathead
2. Oily fish
• 10-25% fat, darker flesh colour
• Good source of Omega 3
• E.g. salmon, sardines, tuna
3. Shellfish
• Has an outer shell
• Crustaceans: hard outer shell, turns orange when cooked e.g. crab
• Molluscs: shell that opens when cooked e.g. oysters
Anatomical differences between white & oily fish
White fish
Oily fish
• Large proportion of white fibres
(fast-twitch collagen fibres)
• Low blood supply
• Anaerobic energy (burst swimming)
• Fatigue quickly
• Large proportion of red fibres
(slow-twitch)
• High blood supply
• Aerobic (mitochondria)
• Ability to swim long distances
• Fat reserves used for energy
sources
Nutritional benefits of seafood
• Contains all essential aa
• Good source of omega3, vit B (important for cell metabolism), A & D (only oily fish),
minerals (P, Ca, I)
Properties of fish
Composition
• 70% water, 20% protein, 10% other (connective tissue, fat, vit & minerals)
Muscle arrangement
• Layers of short fibres surrounded by very thin sheets of delicate connective tissue
o They don’t require strong connective tissue to support limbs as aquatic
o Only 3% of body weight is connective tissue (mammals has 5x)
Visually
• Raw: translucent, firm to touch, clear & watery juices
• Cooked: opaque, flakes begin to separate, milky white juices
