What is the difference between cod and haddock?

Cod and haddock are close relatives and they look similar on ice, but they eat differently. Cod has a large, loose flake and a mild, sweet flavour. Haddock has a finer, softer flake and a slightly more savoury one. Both are white round fish, both cook by the same methods and both are sold here filleted, pin-boned and skinned free by hand.

What is the difference between cod and haddock in texture?

Cod breaks into large, thick flakes that come away in sheets, because the muscle blocks in a cod are big and the fillet is deep at the shoulder. Haddock breaks into smaller, finer flakes and feels softer on the fork, because the fish is slimmer and the muscle blocks are narrower. Cod holds its shape better in a pie or a stew. Haddock falls apart more readily, which is why it suits gentle poaching and creamed dishes.

What is the difference between cod and haddock in flavour?

Cod, Gadus morhua, tastes mild and slightly sweet, and it takes on whatever you cook it with. Haddock, Melanogrammus aeglefinus, tastes a shade more savoury and has more of its own character, which is why it is the fish traditionally used for smoking. Smoked haddock is a different proposition again, cured and cold-smoked, and the flavour is not comparable to fresh.

How do you tell cod and haddock apart on the slab?

Look at the line along the flank. Haddock has a dark, almost black lateral line and a dark thumbprint-shaped mark just behind the gill, and the skin is grey with a purple sheen over the back. Cod has a pale, curved lateral line and mottled olive-brown or greenish skin covered in small spots. On a skinned fillet the tell is thickness. A cod fillet is deep and blocky at the shoulder, a haddock fillet is thinner and more even along its length.

Which holds a batter better, cod or haddock?

Cod holds a batter more reliably. The fillet is thicker, the flakes are larger and the piece stays in one block while the batter sets around it, so it comes out of the pan intact. Haddock in batter gives a softer, finer interior and a lighter mouthful, and it is the traditional choice in Scotland and the north of England. Neither is wrong. Ask for a shoulder cut of either, since the thin tail end overcooks before the batter is ready.

Which is better for a fish pie?

Cod is the safer choice for a fish pie because the large flakes survive being folded through a sauce. Haddock works too and gives a finer texture, and a mix of the two with a piece of smoked haddock is a common way to build the flavour. Cut either into pieces about the size of a walnut and add them to the dish raw, since they finish cooking in the oven.

Can you swap cod for haddock in a recipe?

Yes. They cook at the same temperatures and in roughly the same times, so any recipe for one works for the other. Haddock is thinner, so take two or three minutes off an oven time and check earlier. Both are done when the flesh at the thickest point turns opaque and the flakes separate under gentle pressure from a knife tip.

Why does fish flake?

Fish muscle is not one long grain like beef. It is built from short blocks of muscle stacked along the body, and between each block sits a thin sheet of connective tissue made of collagen. Heat dissolves that collagen into gelatine, the sheets give way and the blocks separate. That is a flake. Fish collagen dissolves at a far lower temperature than the collagen in meat, which is why fish cooks in minutes rather than hours, and why a fish left too long in the pan collapses instead of resting.

How do you stop cod falling apart in the pan?

Salt the fillet lightly and leave it for twenty minutes before cooking. The salt firms the outer flesh and draws off surface water, so the fillet browns instead of steaming and holds together when you turn it. Turn it once only, and lift it with a wide fish slice rather than tongs.

Cod and haddock are both cut to order at 18 Barnes High Street. Filleting, pin-boning and skinning are free and done by hand. Order by 1pm for next-day delivery across London and the UK, or collect in Barnes in about two hours.

Featured photograph by Wilhelm Thomas Fiege, licensed CC BY-SA 4.0, via Wikimedia Commons.

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