I recently purchased a bag of clams, though I realized my knowledge about the shellfish was limited. I decided to do a bit of research on storing, preparing and cooking them, and I'd like to share my findings.
I'll only cover clams sold in stores here. It's possible to harvest your own, but that's an entirely different matter (along with warnings of poisoning and biotoxins). Clams can be purchased year-round, but are usually cheaper during summer months, as they're easier to harvest. Although they can be kept for a few days, clams should be cooked or eaten as soon as possible after purchase.
There are two basic types of clams: soft-shell and hard-shell. Soft-shell clams live with their shells partially open, so they must be rinsed well before cooking. Soak them in salted water for at least two hours before cooking and rinse well with fresh water. Soft-shell clams are never eaten raw.
Hard-shell clams come in a variety of types with their names referring to the size of the clams, and they can be eaten raw (though care should be taken in eating any raw shellfish).
Clams in their shells must be sold live, and kept alive until time to cook or eat them. Keep clams in a breathable, non-sealed bag. If a bag isn't available, store them in an open bowl covered with a wet cloth in your refrigerator. (Never store them sealed or submerged because they'll die and spoil) It's best to consume clams within 24 hours of purchasing, though they should last a few days if stored properly.
It is alright for clams to open while you're storing them, but throw out any clams that don't close when tapped. Also discard any clams with broken shells or shells that can be easily pried apart. Another test is to place clams in a pot of water. Any that float must be discarded.
To prepare clams for cooking, first scrub their shells with a stiff brush to remove dirt, sand and debris. You can also submerge clams in salt water for a few hours before cooking.
To shuck clams, you can freeze them for up to twenty minutes to ease the opening of the clams. Remove them from the freezer and wait a few minutes. The shells will be easier to open.
Clams can be cooked in a number of ways, including steaming, boiling and frying. They don't take very long to cook, usually only a few minutes. When the shells open on their own, they're done. If any clams do not open, they must be discarded as they were not alive and may be contaminated with bacteria. For best results, cook at low heat settings.
