Bivalve molluscs that thrive in marine coastal waters, mussels attach themselves in clusters to sandbanks, rocks, and other objects by secreting a mass of strong silky threads known as a "byssus" or "beard."

Although they are found all over the world, mussels prefer colder waters. Particularly vulnerable to pollution (because they filter up to 81 litres of water per day), they are often bred in controlled environments.

Cultivated mussels are pollution-free and contain no sand or parasites (the source of the small grey pearls often found inside mussel shells). Their flesh is more tender, more abundant, and paler than the flesh of natural mussels, which are rarely sold to consumers. Mussels are reared in a variety of ways. The bouchot method is named for the wooden hurdles on which the mussels cluster. An Irishman named Patrick Walton is thought to have stumbled upon this method after being shipwrecked off the coast of France at the end of the 13th century. In an attempt to catch birds for food, he strung nets from posts he set up in the water; after a while, he noticed that the posts were covered with mussels.

The mussel is comprised of two thin oblong valves of equal size. The shell of the most common species, the blue mussel, is usually smooth but is sometimes covered with concentric ridges; blackish blue in colour, it is frequently dotted with eroded crimson patches. The valves of the shell can be concave, convex, or straight, and the shiny, polished, iridescent interior is white or pale grey with darker, sometimes crimson edges. The blue mussel is between 2½ - 10 centimetres in diameter, and the elastic ligament that connects its twin valves protrudes from the shell. The flesh of female mussels is orange, while that of males is a whitish colour. There are a great many species of mussels and the amount and firmness of their flesh varies from one species to another.

Nutritional Value

Blue mussels are rich in B-complex vitamins such as riboflavin, niacin, folic acid, and vitamin B. They are also rich in phosphorus, iron, and zinc.

Buying

Mussels are sold fresh (either shelled or unshelled) or canned. Never buy unshelled mussels unless they are still alive. The shells of live mussels are usually closed, and those that are open should close slowly when tapped. Canned mussels are packed in a variety of substances, including water, oil, tomatoes, and white wine, and are sometimes smoked.

Storage

Fresh unshelled mussels will keep for up to 3 days in the refrigerator when stored in a container and covered with a damp cloth. Shelled mussels stored in liquid in a tightly sealed container can be refrigerated for 24 - 48 hours. Mussels should always be eaten as soon as possible after they are purchased. Raw shelled mussels can be frozen in their own juices in a freezer container for up to 3 months.

Preparing

Wash and scrub the mussels. It is not necessary to remove all the filaments attached to the outside of the shells if you like the flavour they add to the stock. Mussels that are open and will not close when tapped, as well as those with damaged shells, are inedible and should be discarded.

Mussels that are unusually heavy may be filled with mud or sand. Either throw them out or soak them for an hour or more in salted fresh water (4 - 5 tablespoons of salt per litre of water).

After mussels are soaked or scraped, the adductor sometimes protrudes from their shells, which suggests that they may no longer be alive. To determine if a mussel is dead or alive, try sliding the two valves of the shell back and forth; if you succeed in moving them, the mussel is in fact dead and should be discarded.

Cooking

Poach or steam mussels until their shells open (2 - 5 minutes). If the recipe calls for unshelled mussels, remove them from their shells as soon as this can be done with ease, then continue to cook them as directed. Discard mussels that do not open when cooked.

Using

Mussels are rarely eaten raw, except when they have been freshly caught on the open sea and are thus unlikely to have been exposed to pollution. Cultivated mussels containing domoic acid, a toxic substance found in seaweed, have been known to cause food poisoning. As a result of such incidents, strict controls have been put in place to ensure that mussels are free of contaminants.

Of the many ways in which mussels can be prepared, the most famous is perhaps mussels a la mariniere: cooked in their shells with white wine, butter, onions or shallots, parsley, and pepper. Use approximately 1 kilogram of mussels per person when serving this dish as a main course.

Mussels can also be grilled, sauteed, fried, marinated, stuffed, or cooked au gratin or on brochettes. They are also a common ingredient in soups, sauces, hors d'oeuvres, salads, paellas, stews, and omelettes.
Canned mussels can be eaten "as is," either hot or cold.