How to choose shellfish

How to choose shellfish

The purchaser of shellfish is faced with a number of different forms from which to choose. The first decision is whether to buy them processed or alive. Lobsters, crabs. oysters, and clams all may be purchased alive and in their shells. Shellfish are highly perishable, and to maintain their quality, must be kept alive until they are cooked, or in the case of oysters, occasionally consumed raw. Crustaceans being normally active creatures, it is easy to tell whether or not they are alive, but determining the state of mollusks in their closed shells poses more of a puzzle. Tapping on the shell should cause it to close more tightly; the rule in most cases is that if the shell remains open, the mollusk is dead and should be discarded. The exceptions to this rule are mussels, which ordinarily gape, and longneck (steamer or soft-shell) clams, which normally have a gap in the shells where the "neck" protrudes. Any shells that are broken, have a decaying odor, or float should be discarded. An old rule of thumb held that shellfish should be eaten only during the months with the letter "r" in their names, because bacterial illnesses are more common in the warmer months of May through August.

This is still a valid guideline, although modern methods of harvesting and storage provide a safer supply of shellfish year round.

Shellfish can also be bought cooked in the shell and chilled or frozen. Alternatively, the meat can be removed from the shell and sold fresh, chilled, frozen, canned, salted, smoked, or dried. Uncooked shellfish can be sold headless, as in the case of shrimp or lobster tail, or they may be shucked, or removed from the shell, with a special knife. Shucked shrimp, scallops, oysters, and clams are often breaded and frozen. Shrimp may also be sold with the intestinal tract removed, a form known as "peeled and deveined."

Shucking bivalves such as clams and oysters is a somewhat dangerous process. The hand holding the bivalve should be protected with a towel or a metal-mesh glove. The hinge is severed as the shells are pried apart, and the empty half of the shell is discarded, while the muscle attachment to the other shell is spliced so the meat can be removed. An average worker can shuck almost 7 pounds in an hour, but automated shucking speeds up the process.


Oysters can be bought live in the shell, or shucked and then chilled, frozen, or canned. Live oysters should have tightly closed shells. Any gap between the shells means the oyster is dead and should be discarded. Select shucked oysters which are plump and full-bodied; about one cup is equal to one serving. If the oysters are in their shell, buy half a dozen per person. Three varieties of oyster are commonly available in the United States: Eastern oysters from the Atlantic coast, and Olympia (small) and Japanese (large) oysters from the Pacific coast. Oysters in the shell and well refrigerated have a longer shelf life than other mollusks because their shells remain very tightly closed, while other shellfish have a tendency to gape, making them more susceptible to drying out and dying.


Clams can be bought in the same forms as oysters, and, as with oysters, their shells should be closed tightly and there should be no decaying odor. About six to eight shelled clams are required per serving. Two major east coast types are hard-shell and soft-shell clams, with the meat of hard-shell clams being less tender. Hard-shell clams include cherrystones, which are the most common variety; littlenecks, which are the smallest and most tender; and chowders or quahogs, which are the largest. Soft-shell clams are also known as longnecks or steamers because of the long tube extending from the shell opening. Since soft-shell clams do not completely close, and are very susceptible to drying out and dying. A limp neck hanging out of the shell signals that the clam is dead and should be discarded. West coast varieties include razor and Pismo clams.


In North America, the only part of the scallop that is eaten is the creamy white or tan-colored abductor muscle responsible for opening and closing the shell to move it through the water. Scallops cannot close their shell tightly when taken from the water, so they are usually shucked and then sold fresh, frozen, or canned. This sweet-tasting mollusk varies in diameter from 1/2 to 2 inches, and about 1/4 to 1/3 pound is an adequate portion for one person. The three main varieties of scallops available are bay scallops, which are small, sweet, and delicate; sea scallops, which are larger and not as delicate; and calico scallops, the least expensive and tiniest of all and the blandest in flavor. Calico scallops are often sold cooked or frozen.


The black or dark-blue colored shells of common mussels should be scrubbed free of barnacles, but the "beards" or black threads used to attach the shells to solid foundations in the ocean should not be pulled out until the mussels are ready to be cooked, because removing them kills the mussel. Mussels are heated in their shells after being purchased live, or they are shucked and packed in brine. Extremely hollow or heavy-feeling mussels should be discarded, because they are either dead or filled with sand. Also available are the larger, green-lipped New Zealand mussels whose size makes them ideal for stuffing and baking.

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