Unlike other mollusks, it is the adductor muscle of the scallop that is eaten. Because they perish so quickly once removed from seawater, scallops are almost always sold shucked. Purchase only those that are creamy in color with a slight pink tint; never purchase scallops that are pure white (they have been bleached or are not scallops at all), brownish, or of a dull sheen. Shucked scallops often still have the tough hinge clinging to them. If so, remove it by hand or with a knife.
If buying scallops in the shell, choose heavy specimens that are firmly closed. Rinse first under cold running water. Then hold the shell in the palm of your hand with the muscle facing away from you. As a safety measure, cover your hand with a thick towel. Carefully insert a rigid blade between the two shells. Cut or scrape off the white muscle from the top side of the shell. When the muscle is cut, the shell will open automatically. Remove the band of nerves surrounding the scallop, as it will retract when cooked. Rinse the scallop under cold running water to eliminate any sand. Cook as quickly as possible after purchasing.