How a fish is built
THE CUTS, THE FLAKES AND WHY SOME FISH FALL APART.
Muscle and collagen
Why does fish flake?
Fish muscle is built as short blocks separated by thin sheets of collagen. Those sheets are what you see as flakes. Fish collagen dissolves at a much lower temperature than the collagen in meat, so the sheets melt early in cooking and the blocks slide apart. The flake is a seam, and heat dissolves the seam.
The cuts
Where does a fillet come from?
A fillet runs parallel to the spine. A round fish gives two, a flat fish gives four. The loin is the thick even section and the cut to ask for when nothing may overcook. The tail is thinner and cooks in half the time, so we separate the two.
Bone and skin
Why does a steak hold together?
Bone and skin are structure. A steak is a cross-section through a round fish with the bone left in, and it holds where a bare fillet falls open. A tronçon is the same cut through a flat fish. Skin-on keeps a thin fillet in one piece in the pan.
Texture by species
Which fish holds together?
Firm and dense
Halibut, monkfish, turbot, John Dory, tuna and swordfish. Tight muscle that holds its shape in a pan.
The reference flake
Cod is the flake everyone pictures, large and soft. Pollack is close to it and softer again.
The oily ones
Salmon and sea trout stay moist through big flakes. Mackerel and sardine collapse if you cook them a minute too long.
Fine and delicate
Haddock flakes tighter than cod. Hake is finer again and breaks if you move it about.
Thin and quick
Lemon sole and plaice cook in about two minutes a side. Dover sole is firmer and grills whole.
No flake at all
Skate wing cooks into long parallel strands that lift off the cartilage in ribbons.
Worth asking
What should you ask for?
Not every fish eats well on day one. Dense fish stiffen and then relax, and many improve over a few days. Ask what is eating well, and we will fillet, pin-bone and skin it while you wait.
