Scallops represent one of the most sophisticated delicacies found in the world's oceans. While they are often lumped together with clams and oysters under the broad umbrella of "shellfish," scallops possess unique biological traits and culinary profiles that set them apart. In the culinary world, a scallop is primarily known as a succulent, sweet, and tender morsel of white meat, but in the wild, it is a complex marine animal with surprising capabilities. Understanding what is scallops involves looking beyond the dinner plate and exploring their biology, the different varieties available in the market, and the industry secrets that dictate their quality.

The Biology of the Scallop

Scallops are bivalve mollusks belonging to the family Pectinidae. Unlike their cousins—clams, mussels, and oysters—most scallops are not sedentary. While an oyster cements itself to a rock for life, a scallop is an active swimmer. This mobility is their most defining biological characteristic. By rapidly snapping their two shells together, scallops create a form of jet propulsion, allowing them to zip through the water to escape predators like sea stars.

This constant swimming requires a powerful muscle. The part of the scallop that humans consume is almost exclusively the adductor muscle. In most other bivalves, the adductor muscle is relatively small because it only needs to keep the shell closed. For the scallop, this muscle is oversized, strong, and highly developed, which gives it that distinctive marshmallow-like shape and meaty texture.

Another fascinating aspect of scallop biology is their vision. Around the edge of a scallop’s mantle—the soft tissue just inside the shell—are dozens of tiny, bright blue eyes. These eyes are remarkably complex, containing mirrors to focus light. While they may not see detailed images, they are highly sensitive to movement and light changes, providing the scallop with an early warning system against threats.

Varieties You Will Encounter

When people ask what is scallops in a commercial sense, they are usually referring to one of three main types found in fish markets and restaurants. Each has a specific size, flavor profile, and ideal cooking method.

Sea Scallops (Placopecten magellanicus)

Sea scallops are the heavyweights of the family. Harvested from the deep, cold waters of the North Atlantic, these are the large, fleshy discs often served as main courses. A single sea scallop can grow up to two inches in diameter. Because of their size, they are the preferred choice for pan-searing. Their flavor is a balance of intense sweetness and a briny ocean finish. In the market, they are often graded by size, such as "U-10," meaning there are fewer than ten scallops per pound.

Bay Scallops (Argopecten irradians)

Bay scallops are much smaller and are found in the shallow, grassy waters of estuaries and bays along the East Coast. They are prized for their exceptional sweetness—often described as candy-like—and their delicate, velvety texture. Because they are small (roughly the size of a dime or a nickel), they cook very quickly. They are typically used in pasta dishes, chowders, or quick sautés where their subtle flavor isn't overwhelmed by heavy sauces.

Calico Scallops

Often confused with bay scallops due to their small size, calico scallops are found in warmer waters, such as the Gulf of Mexico and near Florida. They have beautiful, mottled shells (hence the name "calico"). While they are edible and often affordable, they tend to be slightly firmer and less sweet than true bay scallops. They are a great choice for stews or ceviche where they can absorb the flavors of the surrounding ingredients.

The Critical Distinction: Wet vs. Dry Scallops

For anyone looking to master the art of choosing high-quality seafood, understanding the difference between "wet" and "dry" scallops is more important than knowing the species. This distinction refers to how the scallops are treated after they are harvested.

Dry Scallops

Dry scallops are the gold standard. They are shucked on the boat and packed on ice without any chemical additives. They have a natural, ivory or slightly pinkish hue and a firm texture. When you cook a dry scallop, it releases very little moisture. This allows the surface to reach the high temperatures necessary for the Maillard reaction—the chemical process that creates a caramelized, golden-brown crust. If you want a restaurant-quality sear, you must seek out dry scallops.

Wet Scallops

Wet scallops are treated with a solution of sodium tripolyphosphate (STP). This chemical serves two purposes for the distributor: it acts as a preservative and, more controversially, it causes the scallop to absorb water, increasing its weight by up to 30%. This water weight is then sold at the price of the scallop. From a culinary perspective, wet scallops are difficult to work with. When heated, they release all that extra water into the pan, effectively boiling the scallop instead of searing it. They often have a stark white, opaque appearance and can leave a slightly soapy aftertaste. While they are often cheaper, the loss of flavor and texture makes them a less desirable option for many home cooks.

What Do Scallops Taste Like?

The flavor of a scallop is unique in the seafood world. They lack the aggressive "fishiness" associated with some oily fish and the intense saltiness of an oyster. Instead, a fresh scallop is remarkably sweet. This sweetness comes from the high levels of glycogen stored in the adductor muscle to power its swimming.

The texture is equally important. A perfectly cooked scallop should be tender and almost buttery, offering very little resistance to the tooth. It is often described as a "steak of the sea" because of its meaty, substantial feel. When raw, as in crudo or sushi, they are soft and creamy with a clean, oceanic scent.

The Sizing System: Decoding the "U"

When buying scallops at a professional fishmonger, you will notice labels like U-10, U-15, or 20/30. This is the industry standard for sizing:

  • U-10: This stands for "Under 10." It means it takes fewer than 10 scallops to make one pound. These are the largest, premium sea scallops.
  • U-15: Between 10 and 15 scallops per pound. Still very large and excellent for searing.
  • 20/30: This means there are between 20 and 30 scallops per pound. These are smaller sea scallops, often used for skewers or smaller portions.
  • 80/120: This range is typical for bay scallops, indicating their much smaller size.

Choosing the right size depends on your recipe. For a standalone entrée, U-10 or U-12 are generally preferred. For a seafood risotto or pasta, the 20/30 range provides a better distribution of meat throughout the dish.

How to Select the Best Scallops

Quality is paramount when dealing with scallops, as they are highly perishable. Here are some observations to help you make the best choice at the market:

  1. Scent: Fresh scallops should smell like the ocean—clean, salty, and sweet. If there is any hint of ammonia or a pungent "fishy" odor, they are past their prime.
  2. Color: Look for a creamy white, pale beige, or even a light peach/pink color. Avoid scallops that are unnaturally bright white, as this is often a sign of chemical soaking (wet scallops).
  3. Appearance: The scallops should look relatively dry and matte. If they are sitting in a pool of milky white liquid, they are likely wet-processed.
  4. Firmness: If you are able to touch them (or observe through the glass), they should appear firm and plump, not shredded or falling apart.

Cooking Scallops: The Art of the Sear

Because scallops are low in fat and high in protein, they are notoriously easy to overcook. An overcooked scallop becomes rubbery, tough, and loses its sweetness. The most popular way to prepare sea scallops is pan-searing, which highlights the contrast between a crisp exterior and a tender interior.

The Preparation

The most important step in cooking scallops happens before they even touch the pan. You must pat them bone-dry with paper towels. Even if you bought "dry" scallops, there will be surface moisture. Any moisture on the surface will turn to steam in the pan, preventing the crust from forming.

Before seasoning, check for the "foot" or the side muscle. This is a small, tough strip of tissue on the side of the scallop that attaches it to the shell. It becomes very chewy when cooked, so it is best to simply pinch it and pull it off before cooking.

The Technique

Use a heavy-bottomed pan, such as cast iron or stainless steel, which can hold heat well. Add an oil with a high smoke point (like grapeseed or avocado oil). Wait until the oil is shimmering and just starting to smoke.

Place the scallops in the pan, making sure not to crowd them. If they are too close together, the temperature of the pan will drop, and they will steam. Once they are in the pan, do not move them. Resistance is the enemy of a good sear. Let them cook undisturbed for about 2 to 3 minutes.

When you see a golden-brown ring forming at the bottom, carefully flip them. At this point, many chefs add a pat of butter and some herbs (like thyme or garlic) to the pan, spooning the foaming butter over the scallops to finish them. The second side only needs about 30 to 60 seconds. The center should still be slightly translucent and the internal temperature should reach about 125°F to 130°F (52°C to 54°C) for a perfect medium-rare to medium finish.

Nutritional Profile

Scallops are an excellent choice for those seeking a nutrient-dense, low-calorie protein source. They are remarkably lean, containing less than one gram of fat per three-ounce serving. Despite being low in fat, they are rich in essential minerals:

  • Protein: High-quality protein that contains all essential amino acids.
  • Vitamin B12: Essential for brain function and the formation of red blood cells.
  • Phosphorus and Magnesium: Important for bone health and muscle function.
  • Selenium: A powerful antioxidant that supports heart health.
  • Omega-3 Fatty Acids: While lower in omega-3s than fatty fish like salmon, scallops still provide a modest amount of these heart-healthy fats.

Sustainability and Ethical Sourcing

In recent years, the sustainability of scallop harvesting has become a point of interest for many consumers. Most sea scallops are harvested using dredges—large metal frames dragged across the ocean floor. While efficient, this can be disruptive to the seabed.

As an alternative, "diver scallops" are highly sought after. These are scallops harvested by hand by commercial divers. This method is incredibly sustainable because it involves zero bycatch and no damage to the ocean floor. Because it is labor-intensive, diver scallops carry a significantly higher price tag, but they are often the freshest and highest quality available.

Furthermore, many bay scallops are now being farmed through aquaculture. Scallops are filter feeders, meaning they actually help clean the water around them as they grow. Farmed scallops are generally considered a very "green" seafood choice with a low environmental impact.

Cultural and Historical Significance

The scallop shell is perhaps the most iconic shell in the world. Its symmetrical, fan-like shape has been a symbol in art and religion for centuries. In ancient Rome, it was associated with Venus, the goddess of love, famously depicted in Botticelli’s "The Birth of Venus."

In the Middle Ages, the scallop shell became the emblem of the Camino de Santiago, the pilgrimage to the shrine of Saint James in Spain. Pilgrims would wear the shell on their hats or cloaks to signify their journey. Even today, the shell remains a symbol of travel and discovery.

In the kitchen, the term "scalloped" has moved beyond the animal itself. To "scallop" a dish, like scalloped potatoes, refers to the practice of slicing ingredients into rounds that resemble the shape of the scallop or baking them in a way that mimics the fluted edges of the shell.

Common Myths About Scallops

There are several misconceptions that often deter people from enjoying or cooking scallops at home. One common myth is that scallops are "fake" or made of shark meat. While there were rumors in the past of unscrupulous sellers using circular cutters to make "scallops" out of stingray or shark wings, this is virtually non-existent in modern, regulated markets. A real scallop has distinct muscle fibers running vertically through the meat, which is impossible to replicate with other fish.

Another myth is that scallops should be perfectly white. As mentioned earlier, a natural scallop often has variations in color. Some female sea scallops may even have a bright orange or coral tint. This is perfectly natural and does not affect the flavor or safety of the meat; in fact, some gourmets find the orange-tinted scallops to be slightly richer.

Summary

Understanding what is scallops reveals a fascinating intersection of marine biology and culinary excellence. Whether you are enjoying the diminutive sweetness of a bay scallop in a summer salad or the majestic, caramelized crust of a jumbo sea scallop, you are participating in a tradition that spans from ancient art to modern fine dining. By choosing dry-packed, sustainably sourced varieties and respecting the delicate nature of their protein during cooking, you can unlock the full potential of this oceanic treasure. Scallops are more than just a menu item; they are a testament to the rich, diverse flavors that the deep sea provides to those who know how to look for them.