Mussels and clams

Why

Mussels and clams are live bivalves that spoil quickly after death, and because they filter seawater they can carry bacteria, viruses such as norovirus and, at some times of year, toxins from plankton. A live bivalve keeps its shells shut with a muscle or closes them when tapped, while a dead one leaves them open, which is why open ones that do not close and broken ones are thrown away before cooking. Heat relaxes the muscle and the shells open, which also shows that the meat is done; further minutes only tighten the proteins, and the meat shrinks and turns rubbery much as with shrimp (Shrimp, squid and octopus card). Plankton toxins are destroyed neither by cooking nor by freezing, so safety comes from official monitoring of harvesting areas and buying from a reliable seller, not from the calendar: the rule of eating mussels only in months with an r does not guarantee safety, and flavour depends more on the spawning season, when they tend to be thinner. In the EU, molluscs are one of the 14 allergens that must be labelled, listed separately from crustaceans.

How to do it

• Buy mussels and clams from a reliable seller with the origin labelled; do not gather them yourself on the coast unless the area is officially open for harvesting.
• Keep live ones in the fridge in an open bowl covered with a damp cloth, not in water or a sealed bag, and cook them as soon as possible.
• Sort them before cooking: throw away broken ones, tap open ones on the worktop and leave them for a moment, and throw away those that do not close as well.
• Leave gritty clams for about 2 hours somewhere cool in cold water with 20–30 g salt per litre and lift them out by hand; just scrub mussels and pull off the beards right before cooking.
• Cook covered in a little wine or stock over high heat until they open, usually a few minutes, and discard any still closed; for children, pregnant women, older or ill people cook 3–5 minutes more.
• Cook shelled raw or frozen mussels and clams only until firm and opaque, to 63 °C in the centre to be safe (Fish: when is it done card).

If it goes wrong

Overcooked rubbery mussels will not become tender again; shell them, chop them and stir them into a sauce or soup just to warm through. If sand crunches, let the cooking liquid settle for a moment, pour it carefully through a fine sieve or cloth and leave the sediment behind. If the pot smells putrid or of ammonia, eat nothing from it, not even the liquid. Tingling or numbness of the lips and fingers, paralysis or difficulty breathing after eating shellfish are a reason to call emergency services at once.