How are Scallops kept Fresh and What is the Difference between Diver, Dry, and Processed Scallops?

A scallop is a lump of white seafood shaped like a marshmallow, right? Wrong. We might as well say that a cow is a steak. “Scallop” is the name of a remarkable critter that we almost never see whole.

Fishermen shuck most of them at sea as soon as they’re dredged from the bottom, throwing away all but that big, pale muscle that ends up in our markets. That’s the scallop’s adductor muscle, which it uses to close its hinged pair of shells that are shaped like Shell Oil signs. Other bivalve (two-shell) mollusks, including clams, oysters, cockles, and most mussels, have pairs of adductor muscles, but scallops have only that single, huge Schwarzeneggish one.

Americans generally disdain the rest of the animal, but it is all edible (except for the shells, of course). Try it raw on the half shell if you ever get the chance. A whole, raw scallop is sweeter than a clam and without the oyster’s sulfurous tang. But be sure it’s absolutely fresh, no more than a day or so out of clean, certified waters. Scallops spoil quickly, even faster than most other kinds of shellfish because their shells don’t fit together tightly. Most other bivalves can be shipped around the country tightly “clammed up,” still alive and fresh. But scallops die soon after being taken out of the water, and, gaping as they do, they’re an open invitation to spoilage bacteria.

The two major species of scallops sold in the United States are loosely referred to as sea scallops and bay scallops. American sea scallops (mostly Placopecten magellanicus) are the bigger ones, averaging about 20 to 30 meats per pound. They’re about an inch or more high and taken from shells that may be 8 to 12 inches across. Bay scallops (Argopecten irradians) are smaller in both muscle (less than an inch high) and shell (2 to 3 inches); they average about 60 to 90 per pound and are found closer to shore. The really tiny scallops you occasionally see in the market, at more than about 7 0 per pound, are calico scallops (Argopecten gibbus). Many fishmongers ignore the niceties of biology and geography, applying the names sea or bay based on size, or whim, alone.

The very large so-called diver scallops (10 or fewer per pound) have supposedly been hand-harvested by scuba divers rather than dredged from the sea bottom. Because of their impressive size, relative scarcity, and consequent high price, you’ll find them only at expensive restaurants. But don’t swallow the scuba story hook, line, and sinker. There’s nothing to prevent a restaurant from calling any large scallop a diver, if it so chooses.

Using their big adductor muscles, scallops in the wild can clap their shells together forcefully, shooting themselves through the water by jet propulsion to escape a predatory fish or starfish. (It’s a jungle down there.) They can even aim their spurts of water to propel themselves in almost any direction, although most often “forward” by jetting water straight out the hinge end.

You think that’s wild? Wait’ll you hear this. Many scallops have blue eyes. No kidding. They’re the only bivalves that have eyes at all, much less baby blues. If you peek in between the shells of a scallop, you’ll see two rows of fifty or more tiny eye dots, staring back at you from the critter’s front edge, or mantle. While a scallop can’t exactly read the bottom line on an eye chart, it can distinguish changes in light intensity, and that’s a good enough warning that it’s time to scoot away from any stranger that darkens its door.

One of my most exciting experiences (I know: You’ll think I need to get a life) was wading among live scallops in the shallows off Cape Cod and watching each one jet away the instant my shadow fell upon him and her. (Note: That’s him and her. not him or her; most scallops are hermaphrodites.) In Europe, the female red roe is saved and served along with the adductor muscle, covered with a cream sauce, topped with browned bread crumbs, and called coquilles St. Jacques.

Scallop muscles have a tendency to dry out and lose weight, decreasing their per-pound value in the marketplace. So wholesalers, and even the fishing boat crews themselves during a long trip, may soak them in fresh water or in a solution of sodium tripolyphosphate (STP) to keep them hydrated. Because scallop meat is naturally saturated with salty seawater, osmosis will force water into it from the less salty soaking liquid. The STP helps the scallop to retain that water. Soaked scallop meats are called “wet”or processed scallops to distinguish them from unsoaked or “dry” scallops.

Processed scallops that have been loaded with water will be excessively heavy and should rightfully be sold at a lower price per pound. (Consumers, take note.) Processed or “wet” scallops will be almost pure white (the phosphate acts also as a bleach) rather than their natural ivory, creamy, or pinkish color, and they will be resting in a milky, sticky liquid that makes them tend to clump together. They’re a disaster to sauté, because they’ll release their excess water into the pan and steam instead of browning.

The role of the FDA? It monitors the water content of scallop products. Back home in the sea, scallops are 75 percent to 80 percent water. If a commercial product contains more than 80 percent water, the FDA requires that it be labeled an “x % Water-Added Scallop Product” and, if applicable, “Processed with Sodium Tripolyphosphate.” Scallops containing more than 84 percent water may not be sold at all. So much for that “The FDA made me do it” cop-out.

The problem is that these FDA-mandated labels are affixed to the wholesale buckets and you may never see them in the retail market. So buy your scallops only from a fishmonger whom you trust not to sell wet scallops at dry-scallop prices. Why pay $ 7 to $14 a pound, depending on size and season, for water?