Choosing and Handling Crustaceans Because their flesh is so easily damaged by their own enzymes once they're dead, crustaceans are generally sold to consumers either frozen, cooked, or alive. Most "fresh" raw shrimp have been obtained frozen and thawed by the store. Ask for a sniff of one, and don't buy if you smell ammonia or other off-odors. Cook them the same day. Because their flesh is so easily damaged by their own enzymes once they're dead, crustaceans are generally sold to consumers either frozen, cooked, or alive. Most "fresh" raw shrimp have been obtained frozen and thawed by the store. Ask for a sniff of one, and don't buy if you smell ammonia or other off-odors. Cook them the same day.

The larger crustaceans, lobsters and crabs, are generally sold either precooked or alive. Live crustaceans should come from a clean-looking tank, and should be active. They can be kept alive in a moist wrapping in the refrigerator for a day or two. Relatively small lobsters and crabs will have finer muscle fibers and so a finer texture.

Traditional recipes often treat lobsters, crayfish, and crabs as if they were insensible to pain, calling for the cook either to cut them up or drop them in boiling water while they're still alive. These creatures don't really have a central nervous system. The "brain" in the head region receives input only from the antennae and eyes, and each body segment has its own nerve cl.u.s.ter, so it's hard to know whether or how pain can be minimized. The most sensible-sounding advice comes from marine biologists: anaesthetize the animal in iced salt water for 30 minutes just before cutting up or boiling.

Shrimps and Prawns Shrimp and prawns are the most commonly available sh.e.l.lfish in the world. Their predominance stems from their delicious flavor, conveniently small size, rapid reproduction in the wild and in aquaculture, and the tolerance of their flesh to freezing. The two terms are often used for the very same animals; in the United States, "prawn" usually means a larger variety of shrimp. There are some 300 species of shrimp and close relatives exploited for food around the world, but the most common belong to one semitropical and tropical genus, Shrimp and prawns are the most commonly available sh.e.l.lfish in the world. Their predominance stems from their delicious flavor, conveniently small size, rapid reproduction in the wild and in aquaculture, and the tolerance of their flesh to freezing. The two terms are often used for the very same animals; in the United States, "prawn" usually means a larger variety of shrimp. There are some 300 species of shrimp and close relatives exploited for food around the world, but the most common belong to one semitropical and tropical genus, Penaeus. Penaeus. Species of Species of Penaeus Penaeus can mature in a year or less and grow as long as 9 in/24 cm. Temperate-water shrimp belong to a slower-growing group and are usually smaller (a maximum of 6 in/15 cm). Today about a third of world production is cultivated, mainly in Asia. can mature in a year or less and grow as long as 9 in/24 cm. Temperate-water shrimp belong to a slower-growing group and are usually smaller (a maximum of 6 in/15 cm). Today about a third of world production is cultivated, mainly in Asia.

Shrimp Quality Shrimp flavor declines in just a few days on ice due to the slow loss of amino acids and other tasty small molecules. But thanks to their protective cuticle, shrimp can remain edible for as much as 14 days. Shrimpers often treat them with a bleaching solution of bisulfite to prevent discoloration, and like scallops, with a sodium polyphosphate solution to keep them moist; these practices can cause off-flavors. Shrimp flavor declines in just a few days on ice due to the slow loss of amino acids and other tasty small molecules. But thanks to their protective cuticle, shrimp can remain edible for as much as 14 days. Shrimpers often treat them with a bleaching solution of bisulfite to prevent discoloration, and like scallops, with a sodium polyphosphate solution to keep them moist; these practices can cause off-flavors.

The mainly muscular "tail" of the shrimp amounts to about two-thirds of its body weight, so producers often separate it from the flavorful "head" and its midgut enzymes, which can accelerate spoilage. The dark "vein" along the outside curve of the abdomen is the end of the digestive tube, and can be gritty with the sand from which the animals glean bacteria and debris; it's easily pulled away from the surrounding muscle. Though peeled, cooked shrimp are widely available and convenient, serious shrimp lovers seek out fresh whole shrimp and cook them in the sh.e.l.l, rapidly and briefly.

Lobsters and Crayfish Salt.w.a.ter lobsters (species of Salt.w.a.ter lobsters (species of Homarus Homarus and and Nephrops Nephrops) and freshwater crayfish (Astacus, Procambarus, and others) are generally the largest crustaceans in their neighborhood. The American lobster once weighed as much as 40 lb/19 kg, while today it's typically 13 lb/4501,350 gm. And more than 500 species of crayfish have evolved in the fresh waters of isolated rivers and streams, especially in North America and Australia. Most are relatively small, but the Australian marrons and "Murray lobsters" can exceed 10 lb/4.5 kg. Crayfish are the most easily cultured of the crustaceans, and have been raised in natural ponds in the Atchafalaya Basin of Louisiana for better than two centuries. They're also prized in Sweden. and others) are generally the largest crustaceans in their neighborhood. The American lobster once weighed as much as 40 lb/19 kg, while today it's typically 13 lb/4501,350 gm. And more than 500 species of crayfish have evolved in the fresh waters of isolated rivers and streams, especially in North America and Australia. Most are relatively small, but the Australian marrons and "Murray lobsters" can exceed 10 lb/4.5 kg. Crayfish are the most easily cultured of the crustaceans, and have been raised in natural ponds in the Atchafalaya Basin of Louisiana for better than two centuries. They're also prized in Sweden.

The main attraction of all these creatures is their white "tail" meat. Three European and American lobster species and their crayfish cousins have large claws, which in the American lobster can amount to half the total body weight. A larger group of more distant relatives, the spiny and rock lobsters (Palinurus, Panuliris, Jasus and others), are less impressively endowed, and are called "clawless"; they supply much frozen lobster tail, because their meat freezes better than clawed lobster meat. The claw meat is noticeably different from the main body and tail meats. Because they require more stamina, claw muscles include a substantial proportion of slow red fibers (p. 132), and have a distinctive, richer flavor. and others), are less impressively endowed, and are called "clawless"; they supply much frozen lobster tail, because their meat freezes better than clawed lobster meat. The claw meat is noticeably different from the main body and tail meats. Because they require more stamina, claw muscles include a substantial proportion of slow red fibers (p. 132), and have a distinctive, richer flavor.

Lobsters and crayfish are often sold live to consumers. The prime season for Louisiana crayfish is generally local winter through spring, when the animals are heaviest and firm-fleshed. The lobster body contains the flavorful digestive gland known as the liver or tomalley, a pale ma.s.s that turns green when cooked. Females may also contain an ovary, a ma.s.s containing thousands of 12 mm eggs, which turns red-pink when cooked; hence its name "coral." Lobster liver and coral are sometimes removed before cooking, and then crushed to a paste and added to hot sauces at the last minute to contribute their color and flavor.

Crustacean innards. The cephalothorax of crustaceans contains a large, flavorful digestive gland, the hepatopancreas, whose enzymes can also damage the surrounding muscle. The dark, sometimes gritty "vein" along the tail muscle is actually the end of the digestive tube.

Crabs Crabs are tailless. Instead they have a ma.s.sive cephalothorax, whose musculature enables these creatures to live in the deepest sea, burrow on land, and climb trees. Most crabs have one or two powerful claws for holding, cutting, and crushing their prey. Crab claw meat is flavorful but coa.r.s.er and harder to get at than the body meat, and generally not as prized. Exceptions are the ma.s.sive and flavorsome single claws of the Florida stone crab and European fiddler crab. The legs of the north Pacific king crabs, which can span 46 ft/1.21.8 m, provide large cylinders of meat that are often sold frozen. Crabs are tailless. Instead they have a ma.s.sive cephalothorax, whose musculature enables these creatures to live in the deepest sea, burrow on land, and climb trees. Most crabs have one or two powerful claws for holding, cutting, and crushing their prey. Crab claw meat is flavorful but coa.r.s.er and harder to get at than the body meat, and generally not as prized. Exceptions are the ma.s.sive and flavorsome single claws of the Florida stone crab and European fiddler crab. The legs of the north Pacific king crabs, which can span 46 ft/1.21.8 m, provide large cylinders of meat that are often sold frozen.

Most commercial crabs (species of Callinectes, Carcinus, Cancer, Callinectes, Carcinus, Cancer, and others) are still caught alive in baited traps or dredges. They may be sold live, or cooked and whole, or cooked and processed into sh.e.l.l-less meat. This meat is then sold fresh, or pasteurized, or frozen for longer keeping. In addition to the muscle tissue, the crab's large digestive gland, its "mustard" or "b.u.t.ter," is prized for a rich, intense flavor and creamy texture, which it lends to sauces or to crab pastes. Crab liver can acc.u.mulate the toxins from algae that cause sh.e.l.lfish poisoning (p. 186), so state regulators monitor toxin levels and restrict crabbing when they become significant. and others) are still caught alive in baited traps or dredges. They may be sold live, or cooked and whole, or cooked and processed into sh.e.l.l-less meat. This meat is then sold fresh, or pasteurized, or frozen for longer keeping. In addition to the muscle tissue, the crab's large digestive gland, its "mustard" or "b.u.t.ter," is prized for a rich, intense flavor and creamy texture, which it lends to sauces or to crab pastes. Crab liver can acc.u.mulate the toxins from algae that cause sh.e.l.lfish poisoning (p. 186), so state regulators monitor toxin levels and restrict crabbing when they become significant.

Soft-sh.e.l.l crabs Because freshly molted crustaceans have just spent much of their protein and fat reserves and are absorbing water to fill out their new sh.e.l.l, eaters generally disdain them. The major exceptions to this rule are the soft-sh.e.l.l sh.o.r.e crab of Venice, and the soft-sh.e.l.l blue crab of the U.S. Atlantic coast, which is fried and eaten whole. Animals that are about to molt are watched carefully and removed from salt water as soon as they shed their old sh.e.l.l, since their new cuticle would otherwise become leathery within hours and calcified hard in two or three days. Because freshly molted crustaceans have just spent much of their protein and fat reserves and are absorbing water to fill out their new sh.e.l.l, eaters generally disdain them. The major exceptions to this rule are the soft-sh.e.l.l sh.o.r.e crab of Venice, and the soft-sh.e.l.l blue crab of the U.S. Atlantic coast, which is fried and eaten whole. Animals that are about to molt are watched carefully and removed from salt water as soon as they shed their old sh.e.l.l, since their new cuticle would otherwise become leathery within hours and calcified hard in two or three days.

Molluscs: Clams, Mussels, Oysters, Scallops, Squid, and Relatives Molluscs are the strangest creatures we eat. Take a close look sometime at an intact abalone or oyster or squid! But strange or not, molluscs are plentiful and delicious. Judging by the ma.s.sive prehistoric piles of oyster, clam, and mussel sh.e.l.ls that dot the planet's seacoasts, humans have feasted on these conveniently sluggish creatures from the earliest days. This highly successful and diverse branch of the animal kingdom got its start half a billion years ago and currently includes 100,000 species, double the number of fish and animal species with backbones, from snails just a millimeter across to giant clams and squids.

The secret to the molluscs' success - and their strangeness - is their adaptable body plan. It includes three major parts: a muscular "foot" for moving; an intricate a.s.sembly that includes the circulatory, digestive, and s.e.xual organs; and enveloping this a.s.sembly, a versatile sheet-like "mantle" that takes on such jobs as secreting materials for a sh.e.l.l, supporting eyes and small tentacles that detect food or danger, and contracting and relaxing to control water flow into the interior. The molluscan sh.e.l.lfish that we eat have combined these parts in very different ways.

Abalones, the most primitive, have one cup-like sh.e.l.l for protection, and a ma.s.sive, tough muscular foot for moving along and clinging to the seaweed on which their rasping mouths feed.

Clams are enclosed in two sh.e.l.ls, and burrow into the sand with their foot. Modifications of the mantle have provided them with two pegs of muscle for closing the sh.e.l.ls, and with the muscular tube - the siphon or "neck" - that they extend to the sand surface and use to draw in pa.s.sing food particles. All the bivalves - clams, mussels, oysters - have comb-like gills for filtering food particles from the water that the mantle draws in and expels.

Mussels are also two-sh.e.l.led filter feeders, but they attach their foot permanently to intertidal and subtidal rocks. They have no need for a siphon, and one of their tough sh.e.l.l-closing muscles is much reduced.

Oysters cement themselves to inter- and sub-tidal rocks. Their two heavy sh.e.l.ls are closed by a single large muscle at their center, around which the mantle and other organs are organized. The bulk of their body is the tender mantle and food-trapping gills.

Scallops neither attach nor bury themselves. They lie free on the ocean floor, and escape predators by swimming. Their ma.s.sive central muscle claps their sh.e.l.ls shut and forces water out one end, thus propelling them in the other direction.

Squids and octopuses are molluscs turned inside out and transformed into highly mobile, streamlined carnivores with large eyes and arms. The remnants of a sh.e.l.l provide an internal support, and the mantle is now a specialized muscular sheet that expands and contracts to provide jet propulsion through a small funnel derived from the foot muscle.

The immobile molluscs do very well in aquaculture. They can be raised in large numbers in the water's three dimensions, suspended in nets or on ropes, and grow rapidly thanks to the good circulation of oxygen and nutrients.

Bivalve Adductor Muscles The two-sh.e.l.led or "bivalve" molluscs must spread their sh.e.l.ls apart to allow water and food particles in, and pull their sh.e.l.ls together to protect their soft innards against predators or - in the case of intertidal mussels and oysters - the drying air. To do this work they have evolved a special muscle system, one that poses some challenges to the cook but is mostly a boon, since these prepackaged animals can survive for many days in the refrigerator covered only with a moist towel. The two-sh.e.l.led or "bivalve" molluscs must spread their sh.e.l.ls apart to allow water and food particles in, and pull their sh.e.l.ls together to protect their soft innards against predators or - in the case of intertidal mussels and oysters - the drying air. To do this work they have evolved a special muscle system, one that poses some challenges to the cook but is mostly a boon, since these prepackaged animals can survive for many days in the refrigerator covered only with a moist towel.

Bivalve sh.e.l.ls are normally held open mechanically, by means of a spring-like ligament that connects and pulls them together at the hinge end, and thus pulls the opposite wide ends apart. To close the sh.e.l.ls, the animal must power a muscle, called an "adductor" (from the Latin adducere, adducere, "to bring together"), which extends between the broad ends of the sh.e.l.l and contracts to overcome the spring force of the ligament. "to bring together"), which extends between the broad ends of the sh.e.l.l and contracts to overcome the spring force of the ligament.

Tender Quick, Tough Catch The adductor muscle has to perform two very different kinds of work. One is to close the sh.e.l.l quickly to expel sediment, acc.u.mulated wastes, or eggs, or to slam the door on predators. The other is to keep the sh.e.l.l tightly closed for hours, sometimes even days, until the danger pa.s.ses. These two jobs are performed by adjoining parts of the muscle. The fast-contracting "quick" portion is quite similar to the fast muscles of fish and crustaceans; it's white, translucent, and relatively tender. But the slow, tension-maintaining "catch" portion is among the strongest muscles known, and can maintain its contraction with very little expenditure of energy, thanks to biochemical tricks that lock the muscle fibers in place once they've shortened, and reinforcement with large amounts of connective-tissue collagen. Catch muscles have an opalescent appearance, much like the tough tendons in a chicken leg or leg of lamb, and they are tough to eat as well unless cooked for a long time. In the scallop, the small catch portion would detract from the large quick portion's tenderness, and so is usually cut away. The adductor muscle has to perform two very different kinds of work. One is to close the sh.e.l.l quickly to expel sediment, acc.u.mulated wastes, or eggs, or to slam the door on predators. The other is to keep the sh.e.l.l tightly closed for hours, sometimes even days, until the danger pa.s.ses. These two jobs are performed by adjoining parts of the muscle. The fast-contracting "quick" portion is quite similar to the fast muscles of fish and crustaceans; it's white, translucent, and relatively tender. But the slow, tension-maintaining "catch" portion is among the strongest muscles known, and can maintain its contraction with very little expenditure of energy, thanks to biochemical tricks that lock the muscle fibers in place once they've shortened, and reinforcement with large amounts of connective-tissue collagen. Catch muscles have an opalescent appearance, much like the tough tendons in a chicken leg or leg of lamb, and they are tough to eat as well unless cooked for a long time. In the scallop, the small catch portion would detract from the large quick portion's tenderness, and so is usually cut away.

Mollusc Texture The adductor muscles largely determine the texture of several bivalves - especially the scallop, whose large and tender "swimming" muscle is often the only portion served. The other bivalve bodies are eaten whole, and include one or two adductors together with miscellaneous innards; small tubes and thin sheets of muscle and connective tissue; soft ma.s.ses of eggs, sperm, and food particles; and a general proteinaceous mucus that lubricates and binds food particles. Clams, mussels, and oysters are thus slick and both crunchy and tender when raw, chewy when cooked. The greater the proportion of muscle tissue, the chewier the mollusc. The adductor muscles largely determine the texture of several bivalves - especially the scallop, whose large and tender "swimming" muscle is often the only portion served. The other bivalve bodies are eaten whole, and include one or two adductors together with miscellaneous innards; small tubes and thin sheets of muscle and connective tissue; soft ma.s.ses of eggs, sperm, and food particles; and a general proteinaceous mucus that lubricates and binds food particles. Clams, mussels, and oysters are thus slick and both crunchy and tender when raw, chewy when cooked. The greater the proportion of muscle tissue, the chewier the mollusc.

Mollusc texture is also strongly affected by the animals' reproductive stage. And as they approach sp.a.w.ning and their bodies fill with eggs and/or sperm, the bivalves develop a soft creaminess that cooking sets to a custard-like texture. Immediately after sp.a.w.ning, the depleted tissues are thin and flabby.

Abalone, octopus, and squid meats are mainly muscle tissue with a lot of connective-tissue collagen and a complex fiber arrangement. They're chewy when lightly cooked, tough when cooked to the denaturation temperature of their collagen, around 120130F/5055C, and become tender with long cooking.

Mollusc Flavor Oysters, clams, and mussels are prized for their rich, mouth-filling taste, especially when eaten raw. We owe this savoriness to their acc.u.mulation of internal taste-active substances as an energy reserve and to balance the external salinity of their home waters. For osmotic balance, marine fish (and squid and octopus) use tasteless TMAO and relatively small amounts of amino acids, while most molluscs rely almost entirely on amino acids: in the bivalves, especially brothy glutamic acid. And instead of storing energy in the form of fat, molluscs acc.u.mulate other amino acids - proline, arginine, alanine, and some combined forms - as well as glycogen, the animal version of starch, which is itself tasteless, though it probably provides a sense of viscosity and substance, and is slowly transformed to sweet molecules (sugar phosphates). Oysters, clams, and mussels are prized for their rich, mouth-filling taste, especially when eaten raw. We owe this savoriness to their acc.u.mulation of internal taste-active substances as an energy reserve and to balance the external salinity of their home waters. For osmotic balance, marine fish (and squid and octopus) use tasteless TMAO and relatively small amounts of amino acids, while most molluscs rely almost entirely on amino acids: in the bivalves, especially brothy glutamic acid. And instead of storing energy in the form of fat, molluscs acc.u.mulate other amino acids - proline, arginine, alanine, and some combined forms - as well as glycogen, the animal version of starch, which is itself tasteless, though it probably provides a sense of viscosity and substance, and is slowly transformed to sweet molecules (sugar phosphates).

Because sh.e.l.lfish use amino acids to counteract salt concentration, the saltier the water, the more savory the sh.e.l.lfish. This fact accounts for at least some of the flavor differences among sh.e.l.lfish from different waters, and it is part of the rationale for "finishing" oysters for a few weeks or months in particular locations. Because sh.e.l.lfish use up their energy stores as they prepare for sp.a.w.ning, they become noticeably less tasty as sp.a.w.ning approaches.

When molluscs are cooked, their savoriness is somewhat diminished because heat traps some of the amino acids in the web of coagulated protein and so withholds them from the tongue. However, heating alters and intensifies the aroma, which is generally dominated by dimethyl sulfide, a compound formed from an odd sulfur-containing substance (dimethyl-[image]-propiothetin) that molluscs acc.u.mulate from the algae on which they feed. DMS is also a prominent aroma in canned corn and in heated milk: one reason that oysters and clams go so well with these ingredients in seafood soups and stews.

Choosing and Handling Molluscs Unless they've already been removed from their sh.e.l.l, fresh bivalves should be alive and healthy: otherwise they are likely to have begun spoiling. A healthy bivalve has an intact sh.e.l.l, and its adductor muscle is active and holds the sh.e.l.ls tightly together, especially when sharply tapped. Molluscs keep best on ice covered with a damp cloth, and should not be allowed to sit in a puddle of melt.w.a.ter, which is saltless and therefore fatal to sea creatures. Clams and relatives often benefit from several hours' immersion in a bucket of cold salt water ( Unless they've already been removed from their sh.e.l.l, fresh bivalves should be alive and healthy: otherwise they are likely to have begun spoiling. A healthy bivalve has an intact sh.e.l.l, and its adductor muscle is active and holds the sh.e.l.ls tightly together, especially when sharply tapped. Molluscs keep best on ice covered with a damp cloth, and should not be allowed to sit in a puddle of melt.w.a.ter, which is saltless and therefore fatal to sea creatures. Clams and relatives often benefit from several hours' immersion in a bucket of cold salt water (1/3 cup salt per gallon, or 20 gm/l) to clean themselves of residual sand and grit. cup salt per gallon, or 20 gm/l) to clean themselves of residual sand and grit.

When the cook wants to "shuck" an oyster or clam, or open the sh.e.l.l and remove the raw meat, it's the hinge ligament and adductor muscles that must be dealt with. The usual technique is to wedge the blade of a small, strong knife between the sh.e.l.ls near the hinge, then cut through the elastic ligament. Then run the knife along the inner surface of one sh.e.l.l to sever the adductor muscle(s) (clams and mussels have two, oysters and scallops one). Remove the loose sh.e.l.l, and cut the other end of the adductor(s) to free the body from the remaining sh.e.l.l.

Heat causes the adductor muscle to relax, which is why mollusc sh.e.l.ls open during cooking. Sh.e.l.ls that don't open may not contain a live animal and should be discarded.

Abalone There are about 100 species in the abalone genus There are about 100 species in the abalone genus Haliotis Haliotis; they have a single low-slung sh.e.l.l, and the largest grow to 12 in/30 cm and 8 lb/4 kg. In the United States, the red abalone, Haliotis rufescens Haliotis rufescens, is now farmed in offsh.o.r.e cages and onsh.o.r.e tanks, reaching 3.5 in/9 cm across and yielding 0.25 lb/100g meat in about three years. Abalone meat can be quite tough, in part because they apparently acc.u.mulate connective-tissue collagen as an energy reserve! Either very gentle or prolonged heating is essential; the meat toughens badly when it exceeds 120F/50C, and the collagen shrinks and compacts the tissue. Once this happens, continued simmering will eventually dissolve the collagen into gelatin and make the meat densely silken. j.a.panese cooks simmer abalone for several hours to obtain a more savory flavor (free amino acids apparently react to form taste-active peptides).

Clams Clams are the burrowing bivalves. They dig themselves into ocean or river sediments by extending a foot muscle downward, expanding its end into an anchor, and then contracting the foot while squirting water and rocking the sh.e.l.l. In order to reach the water from their burrow to breathe and feed, they have a pair of muscular tubes or "siphons," one for inhaling and the other for exhaling, which may be separate or else joined together into a single "neck." Clams are the burrowing bivalves. They dig themselves into ocean or river sediments by extending a foot muscle downward, expanding its end into an anchor, and then contracting the foot while squirting water and rocking the sh.e.l.l. In order to reach the water from their burrow to breathe and feed, they have a pair of muscular tubes or "siphons," one for inhaling and the other for exhaling, which may be separate or else joined together into a single "neck."

The U.S. term "hard sh.e.l.l" is applied to st.u.r.dy clams that close completely (little-neck, quahog), while "soft sh.e.l.l" clams have siphons much longer than the sh.e.l.l, which is thin and always gapes (steamer, longneck). The j.a.panese or Manila hard-sh.e.l.l clam (Ruditapes philippinarum) is the only one to be cultivated on a large scale worldwide, thanks to its robustness and preference for shallow burial. The other dozen or so common clam species are mainly regional products. Some species of the large surf clam (Mactromeris species) absorb plankton pigments and have a striking red layer on several muscles. The largest and most grotesque of the temperate commercial clams is the deep-burrowing geoduck of the Pacific Northwest subtidal mudflats ( species) absorb plankton pigments and have a striking red layer on several muscles. The largest and most grotesque of the temperate commercial clams is the deep-burrowing geoduck of the Pacific Northwest subtidal mudflats (Panope generosa), whose neck looks like a small elephant's trunk. Though most are 3 lb/1.5 kg, geoducks can reach 15 lb/8 kg with a neck 3 ft/1 m long!

Food Words: Mollusc, Abalone, Clam, Oyster, Scallop, Squid Mollusc, Abalone, Clam, Oyster, Scallop, SquidThe general term for these hard-sh.e.l.led creatures, mollusc, mollusc, comes from the Indo-European root comes from the Indo-European root mel, mel, meaning "soft," which the inner body parts indeed are. meaning "soft," which the inner body parts indeed are. Abalone Abalone entered English via Spanish from the Monterey Indian word for this streamlined snail, entered English via Spanish from the Monterey Indian word for this streamlined snail, aulun. Clam aulun. Clam began in the Indo-European began in the Indo-European gel, gel, a compact ma.s.s: a compact ma.s.s: cloud, cling, cloud, cling, and and clamp clamp are its linguistic relatives. are its linguistic relatives. Mussel Mussel derives from the Indo-European derives from the Indo-European mus, mus, meaning both "mouse" and "muscle," which moves quickly like a mouse under the skin. Since mussels hardly move at all, their dark, oblong shapes must have suggested the comparison. meaning both "mouse" and "muscle," which moves quickly like a mouse under the skin. Since mussels hardly move at all, their dark, oblong shapes must have suggested the comparison. Oyster, Oyster, from the Indo-European from the Indo-European ost, ost, "bone," names the mollusc with the heavy and bone-colored sh.e.l.l. "bone," names the mollusc with the heavy and bone-colored sh.e.l.l. Scallop, Scallop, with its unusually symmetrical and patterned valves, comes via the Middle French with its unusually symmetrical and patterned valves, comes via the Middle French escalope escalope, from a Germanic word for "sh.e.l.l." And squid squid? To date, the linguists are stumped. It appeared out of nowhere in the 17th century.

Their burrowing and siphoning musculature makes clams fairly chewy creatures. The tenderer portions of large clams (mantle, quick muscle) may be cut out and prepared separately. The large geoduck neck is usually scalded and the tough protective skin removed before the meat is sliced and/or pounded very thin for eating raw or either gentle or prolonged cooking.

Mussels The handful of mussel species we usually eat have become cosmopolitan: they have hitched rides or been intentionally introduced to various parts of the world, where they both grow naturally and are farmed and marketed at 2.5 in/6 cm in less than two years. The Mediterranean and Atlantic species of The handful of mussel species we usually eat have become cosmopolitan: they have hitched rides or been intentionally introduced to various parts of the world, where they both grow naturally and are farmed and marketed at 2.5 in/6 cm in less than two years. The Mediterranean and Atlantic species of Mytilus Mytilus have complementary habits; the Atlantic is in its prime in the spring and sp.a.w.ns in the summer; the Mediterranean is best in summer and sp.a.w.ns in winter. have complementary habits; the Atlantic is in its prime in the spring and sp.a.w.ns in the summer; the Mediterranean is best in summer and sp.a.w.ns in winter.

Mussels anchor themselves in the intertidal zone by means of a thatch of tough proteinaceous fibers called the byssus, byssus, or "beard." Where the clams have two similar adductor muscles to close and hold the sh.e.l.ls tightly shut, the mussel has one large adductor at the wide end and a small one at the narrow end. The rest of the mussel body comprises the respiratory and digestive systems and the mantle. s.e.xual tissues develop throughout these systems. Coloration depends on s.e.x, diet, and species; orange pigments from algae and crustaceans acc.u.mulate more in female and Atlantic mussels. or "beard." Where the clams have two similar adductor muscles to close and hold the sh.e.l.ls tightly shut, the mussel has one large adductor at the wide end and a small one at the narrow end. The rest of the mussel body comprises the respiratory and digestive systems and the mantle. s.e.xual tissues develop throughout these systems. Coloration depends on s.e.x, diet, and species; orange pigments from algae and crustaceans acc.u.mulate more in female and Atlantic mussels.

Mussels are the easiest molluscs to prepare; they tolerate some overcooking and readily come off the sh.e.l.l. Both characteristics reflect the relatively small amount of muscle tissue. Because the beard is attached to the body inside, tugging on it can injure the animal. Beard removal should be put off until just before cooking. To avoid toughening mussels, it's best to cook them in a broad, shallow pan in essentially a single layer: this allows the cook to remove the early openers so that they don't overcook while the others finish.

Oysters Oysters are the most prized of the bivalves. They are the sea's tenderest morsels, the marine equivalent of penned veal or the fattened chicken, which just sit and eat. Their sh.e.l.l-closing adductor amounts to just a tenth of the body weight, the thin, delicate sheets of all-enclosing mantle and gills account for more than half, and the visceral ma.s.s for a third. The oyster is a special delicacy when cut from the sh.e.l.l and eaten raw. It's big enough to make a generous morsel, has a full, complex flavor and suggestively slippery moistness; and its delicacy is a striking contrast to the encrusted, rocky sh.e.l.l. Oysters are the most prized of the bivalves. They are the sea's tenderest morsels, the marine equivalent of penned veal or the fattened chicken, which just sit and eat. Their sh.e.l.l-closing adductor amounts to just a tenth of the body weight, the thin, delicate sheets of all-enclosing mantle and gills account for more than half, and the visceral ma.s.s for a third. The oyster is a special delicacy when cut from the sh.e.l.l and eaten raw. It's big enough to make a generous morsel, has a full, complex flavor and suggestively slippery moistness; and its delicacy is a striking contrast to the encrusted, rocky sh.e.l.l.

Clam and mussel anatomy. The bulk of the clam body (left) (left) is the muscular foot, while the mussel body is the muscular foot, while the mussel body (right) (right) is mainly a nonmuscular mantle and the digestive and reproductive organs it encloses. The sh.e.l.l-closing adductor muscles are relatively minor parts. The mussel's "beard" is a thatch of tough protein fibers that anchor it to a rock or other support. is mainly a nonmuscular mantle and the digestive and reproductive organs it encloses. The sh.e.l.l-closing adductor muscles are relatively minor parts. The mussel's "beard" is a thatch of tough protein fibers that anchor it to a rock or other support.

Oyster Types Oysters became scarce as early as the 17th century, and are now largely farmed. A handful of the two dozen oyster species are commercially important; they have different shapes and subtly different flavors. European flat oysters ( Oysters became scarce as early as the 17th century, and are now largely farmed. A handful of the two dozen oyster species are commercially important; they have different shapes and subtly different flavors. European flat oysters (Ostrea edulis) are relatively mild with a metallic taste; Asian cupped oysters (Cra.s.sostrea gigas) have melon and cuc.u.mber aromas; and Virginia cupped oysters (Cra.s.sostrea virginica) smell like green leaves. Though there are exceptions, most oysters produced in Europe are the native flat, "Portuguese," and Asian; on the east and Gulf coasts of North America, the Virginia; and on the west coast, the Asian and the Pacific (Ostrea lurida). The "Portuguese" oyster is almost certainly a race of the Asian oyster that hitched a ride from China or Taiwan to the Iberian peninsula in the ships of early explorers, four or five centuries ago.

Oyster Waters The flavor of an oyster also depends on its home waters, which is why it makes sense to give geographical designations to oysters. The greater the salinity of the water, the more taste-active amino acids the oyster's cells must contain to balance the dissolved salt outside, and so the more savory its flavor. The local plankton and dissolved minerals will leave distinctive traces in the animal; and predators, currents, and exposure in the tidal zone will exercise and enlarge its adductor muscle. Water temperature determines how rapidly the oyster grows, and even its s.e.x: warmth and plentiful food usually mean fast growth and development into a plump female creamy with millions of tiny eggs; cold water means slow growth, an indefinitely postponed s.e.xual maturity, and a leaner, crisper texture. The flavor of an oyster also depends on its home waters, which is why it makes sense to give geographical designations to oysters. The greater the salinity of the water, the more taste-active amino acids the oyster's cells must contain to balance the dissolved salt outside, and so the more savory its flavor. The local plankton and dissolved minerals will leave distinctive traces in the animal; and predators, currents, and exposure in the tidal zone will exercise and enlarge its adductor muscle. Water temperature determines how rapidly the oyster grows, and even its s.e.x: warmth and plentiful food usually mean fast growth and development into a plump female creamy with millions of tiny eggs; cold water means slow growth, an indefinitely postponed s.e.xual maturity, and a leaner, crisper texture.

Handling and Preparing Oysters Live oysters can survive for a week or more under moist wraps in the refrigerator, cupped sh.e.l.l down. Up to a point, this holding period can heighten their flavor, since metabolism without oxygen causes savory succinic acid to acc.u.mulate in their tissues. Preshucked oysters are rinsed with cold fresh water and then bottled in their subsequent secretions, which should be mostly clear; p.r.o.nounced cloudiness indicates that the oyster tissues are breaking. Bottled oysters are often subpasteurized (heated to around 120F/50C) to delay spoilage while mostly retaining the fresh texture and flavor. Live oysters can survive for a week or more under moist wraps in the refrigerator, cupped sh.e.l.l down. Up to a point, this holding period can heighten their flavor, since metabolism without oxygen causes savory succinic acid to acc.u.mulate in their tissues. Preshucked oysters are rinsed with cold fresh water and then bottled in their subsequent secretions, which should be mostly clear; p.r.o.nounced cloudiness indicates that the oyster tissues are breaking. Bottled oysters are often subpasteurized (heated to around 120F/50C) to delay spoilage while mostly retaining the fresh texture and flavor.

Scallop and oyster anatomy. The prized portion of the scallop (left) (left) is the large main adductor muscle, a tender bundle of fast muscle fibers that claps the sh.e.l.ls together to propel the scallop away from danger. The crescent of "catch" muscle alongside it holds the sh.e.l.l closed. It is rich in connective tissue and tough, and is usually cut away from the adductor. The pink and tan reproductive tissues are prized in Europe but not in the United States. The oyster body is the large main adductor muscle, a tender bundle of fast muscle fibers that claps the sh.e.l.ls together to propel the scallop away from danger. The crescent of "catch" muscle alongside it holds the sh.e.l.l closed. It is rich in connective tissue and tough, and is usually cut away from the adductor. The pink and tan reproductive tissues are prized in Europe but not in the United States. The oyster body (right) (right) is mainly digestive and reproductive organs enclosed in a fleshy mantle; it's usually eaten whole, the adductor and catch muscles providing a crunchy chewiness. is mainly digestive and reproductive organs enclosed in a fleshy mantle; it's usually eaten whole, the adductor and catch muscles providing a crunchy chewiness.

Scallops The scallop family includes about 400 species that range from a few millimeters to a yard across. Most food scallops are still harvested from the ocean floor. Large "sea scallops" (species of The scallop family includes about 400 species that range from a few millimeters to a yard across. Most food scallops are still harvested from the ocean floor. Large "sea scallops" (species of Pecten Pecten and and Placopecten Placopecten) are dredged from deep, cold waters year-round on trips that may last weeks, while smaller "bay" and "calico" scallops (Argopecten) are either dredged or hand-gathered by divers closer to sh.o.r.e during a defined season.

Unlike all the other molluscs, the scallop is mostly delectably tender, sweet muscle! This is because it's the only bivalve that swims. It defends itself from predators by clapping its sh.e.l.ls together and forcing water out the hinge end, using a central striated muscle that can be an inch/2 cm or more across and long. This adductor muscle makes up such a large portion of the scallop's body that it also serves as protein and energy storage. Its sweet taste comes from large amounts of the amino acid glycine and of glycogen, a portion of which is gradually converted by enzymes into glucose and a related molecule (glucose 6 phosphate) when the animal is killed.

Because their sh.e.l.ls don't close tightly, scallops are usually shucked soon after harvest, with only the adductor muscle kept for the U.S. market, the adductor and yellow and pink reproductive organs for Europe. This means that meat quality usually begins to deteriorate long before it gets to market. On boats that go out for more than a day, the catch may therefore be frozen and/or dipped in a solution of polyphosphates, which the adductors absorb and retain, becoming plump and glossy white. However, such scallops have less flavor and lose large amounts of liquid when heated. Untreated scallops have a duller, off-white appearance with pink or orange tones.

In the kitchen, the cook sometimes needs to separate the large, tender swimming muscle from the adjoining, smaller, tough catch muscle that holds the two sh.e.l.ls shut. When sauteed, scallops quickly develop a rich brown crust thanks to their combination of free amino acids and sugars, which undergo Maillard reactions.

Squid, Cuttlefish, Octopus The The cephalopod cephalopod group are the most advanced of the molluscs, with their mantle turned into a muscular body wall and the remnants of their sh.e.l.l within (the term means "head-foot": the foot muscle is near the head). The octopus, species of group are the most advanced of the molluscs, with their mantle turned into a muscular body wall and the remnants of their sh.e.l.l within (the term means "head-foot": the foot muscle is near the head). The octopus, species of Octopus Octopus and and Cistopus, Cistopus, has eight arms cl.u.s.tered around its mouth with which it clambers along the bottom and seizes prey; the coastal-bottom cuttlefish (species of has eight arms cl.u.s.tered around its mouth with which it clambers along the bottom and seizes prey; the coastal-bottom cuttlefish (species of Sepia Sepia) and open-ocean squid (species of Loligo, Todarodes, Ilex Loligo, Todarodes, Ilex) have short arms and two long tentacles.

The anatomy of the squid mantle. This main portion of the squid body consists of an envelope of muscle that propels the animal by contracting and squeezing water through a small opening. The mantle muscle is built up from tough connective tissue and alternating rings of muscle fibers, some oriented across the mantle wall and some along it.

Cephalopod Texture The muscle fibers of squid and octopus are extremely thin - less than a tenth the diameter of a typical fiber in a fish or steer (0.004 mm, vs. 0.050.1 mm) - which makes the flesh dense and fine-textured. They're arrayed in multiple layers, and greatly reinforced with strengthening and toughening connective-tissue collagen, some three to five times more than fish muscle has. Unlike the fragile collagen of fish, squid and octopus collagen is extensively cross-linked and behaves more like the collagen of meat animals. The muscle fibers of squid and octopus are extremely thin - less than a tenth the diameter of a typical fiber in a fish or steer (0.004 mm, vs. 0.050.1 mm) - which makes the flesh dense and fine-textured. They're arrayed in multiple layers, and greatly reinforced with strengthening and toughening connective-tissue collagen, some three to five times more than fish muscle has. Unlike the fragile collagen of fish, squid and octopus collagen is extensively cross-linked and behaves more like the collagen of meat animals.

Like the abalone and clam, squid and octopus must be cooked either barely and briefly to prevent the muscle fibers from toughening, or for a long time to break down the collagen. Cooked quickly to 130135F/5557C, their flesh is moist and almost crisp. At 140F/60C it curls and shrinks as the collagen layers contract and squeeze moisture from the muscle fibers. Continued gentle simmering for an hour or more will dissolve the tough, contracted collagen into gelatin and give the flesh a silken succulence. Pounding can also help disorganize and thus tenderize mantles and arms.

Cephalopod Flavor and Ink Like finfish, squid and octopus maintain their osmotic balance largely with the tasteless TMAO (p. 188) rather than with free amino acids. Their flesh is therefore less sweet and savory than that of the other molluscs, and can turn fishy when bacteria convert TMAO to TMA. Like finfish, squid and octopus maintain their osmotic balance largely with the tasteless TMAO (p. 188) rather than with free amino acids. Their flesh is therefore less sweet and savory than that of the other molluscs, and can turn fishy when bacteria convert TMAO to TMA.

Cephalopod ink is a bag of pigment that the animal can squirt into the water when endangered. It's a heat-stable mix of phenolic compounds (animal cousins of the phenolic complexes that discolor cut fruits and vegetables; p. 269), and cooks use it to color stews and pastas a dark brown.

Other Invertebrates: Sea Urchins Spiny sea urchins are members of the animal group called echinoderms echinoderms (Greek for "p.r.i.c.kly skin"), which may account for 90% of the bioma.s.s on deep-sea floors. There are about a half dozen commercial species of sea urchins with average diameters of 2.55 in/612 cm. They're almost entirely enclosed in a sphere of mineralized plates covered with protective spines, and are collected mainly for their golden, creamy, richly flavored reproductive tissues, which can account for up to two-thirds of the internal tissues. Both testes and ovaries are prized, and are hard to tell apart. Sea-urchin gonads average 1525% fat and 23% savory amino acids, peptides, and IMP. In j.a.pan, sea urchins are eaten raw in sushi or salted and fermented into a savory paste; in France they're added to scrambled eggs, souffles, fish soups and sauces, and sometimes poached whole. (Greek for "p.r.i.c.kly skin"), which may account for 90% of the bioma.s.s on deep-sea floors. There are about a half dozen commercial species of sea urchins with average diameters of 2.55 in/612 cm. They're almost entirely enclosed in a sphere of mineralized plates covered with protective spines, and are collected mainly for their golden, creamy, richly flavored reproductive tissues, which can account for up to two-thirds of the internal tissues. Both testes and ovaries are prized, and are hard to tell apart. Sea-urchin gonads average 1525% fat and 23% savory amino acids, peptides, and IMP. In j.a.pan, sea urchins are eaten raw in sushi or salted and fermented into a savory paste; in France they're added to scrambled eggs, souffles, fish soups and sauces, and sometimes poached whole.

Preserved Fish and Sh.e.l.lfish Few foods go bad faster than fish. And until recently, few people in the world had the chance to eat fresh fish. Before refrigeration and motorized transportation became common, fish were harvested in such numbers and spoiled so rapidly that most had to be preserved by drying, salting, smoking, fermenting, or some combination of these antimicrobial treatments. Preserved forms of fish are still important and appreciated in most parts of the world, especially in Europe and Asia. It's true that their flavor is much more a.s.sertive than the mild fresh fish that are now the U.S. standard. But preserved fish aren't just an inferior relic of preindustrial necessity. They can be a delicious alternative, and they offer a taste of history.

Dried Fish Drying foods in the sun and wind is an ancient method of preservation. Fresh fish is about 80% water; below 25%, bacteria have trouble growing, and below 15% molds do too. Happily, dehydration also intensifies and alters flavor by disrupting cellular structure and so promoting enzyme action, and by concentrating flavorsome molecules to the point that they begin to react with each other to form additional layers of flavor. Very lean fish and sh.e.l.lfish are the usual choice, since air-drying will inevitably cause fat oxidation and some development of rancid flavors. Fatty fish are usually smoked, or salt-cured in closed containers to minimize rancidity. Often drying is preceded by salting and/or cooking, which draw moisture from the fish and make their surfaces less hospitable to spoilage microbes during the drying proper.

China and Southeast Asia are the largest producers and consumers of dried fish and sh.e.l.lfish. Cooks there use dried shrimp as is, either whole or ground, to season various dishes; they steam and shred dried scallops before adding them to soups; they reconst.i.tute tough abalone, octopus, squid, jellyfish, and sea cuc.u.mber by soaking in water, then simmer them until tender. They do the same with shark fins, which give a gelatinous thickness to soups.

Stockfish Perhaps the best known dried fish in the West is the Scandinavian stockfish, which traditionally has been cod, ling, or their relatives, freeze-dried for several weeks on rocky beaches along the cold, windy coasts of Norway, Iceland, and Sweden. The result is a hard, light slab that's nearly all protein and has a p.r.o.nounced, almost gamy flavor when cooked. Today, stockfish is mechanically air-dried for two to three months at 4050F/510C. Stockfish fanciers in Scandinavia and the Mediterranean region reconst.i.tute the woody ma.s.s in water for from one to several days, with frequent changes to prevent bacterial growth. The skin is then removed and the fish gently simmered, then served in pieces, in boneless flakes, or else pounded into a paste, and with a variety of enrichments and flavorings: in the north, often b.u.t.ter and mustard; in the Mediterranean, olive oil and garlic. Perhaps the best known dried fish in the West is the Scandinavian stockfish, which traditionally has been cod, ling, or their relatives, freeze-dried for several weeks on rocky beaches along the cold, windy coasts of Norway, Iceland, and Sweden. The result is a hard, light slab that's nearly all protein and has a p.r.o.nounced, almost gamy flavor when cooked. Today, stockfish is mechanically air-dried for two to three months at 4050F/510C. Stockfish fanciers in Scandinavia and the Mediterranean region reconst.i.tute the woody ma.s.s in water for from one to several days, with frequent changes to prevent bacterial growth. The skin is then removed and the fish gently simmered, then served in pieces, in boneless flakes, or else pounded into a paste, and with a variety of enrichments and flavorings: in the north, often b.u.t.ter and mustard; in the Mediterranean, olive oil and garlic.

Salted Fish Preservation by natural drying works well in cold and hot climates. Temperate Europe, where fish generally spoil before they can dry sufficiently, developed the habit of salting fish first, or instead. A day's salting would preserve many fish for several days more, long enough to be carried inland, while saturating the fish with around 25% salt keeps it stable for a year. Lean cod and relatives were salted and then air-dried, while fatty herring and their ilk were guarded from air-induced rancidity by immersing them in barrels of brine, or by subsequent smoking. The best of these are the piscatory equivalent of salt-cured hams. In both, salt buys time for transformation: it preserves them long and gently enough for enzymes of both fish and harmless salt-tolerant bacteria to break down flavorless proteins and fats into savory fragments, which then react further to create flavors of great complexity.

Alkaline Fish: Lutefisk LutefiskDistinctly alkaline foods are rare and have a slippery, soapy quality that takes getting used to. (Alkalinity is the chemical opposite of acidity.) Egg white is one such food, and another is lutefisk lutefisk, a peculiar Norwegian and Swedish way of preparing stockfish that probably began in late medieval times, and that gives it a jiggly, jelly-like consistency. Lutefisk Lutefisk is made by soaking the partly reconst.i.tuted dry cod for a day or more in a water solution that is strongly alkaline, originally from the addition of potash (the carbonate- and mineral-rich ashes from a wood fire), sometimes lime (calcium carbonate), and later lye (pure sodium hydroxide, at the rate of about 5 grams per liter water). These strong alkaline substances cause the proteins in the muscle fibers to acc.u.mulate a positive electrical charge and repel each other. When the fish is then simmered in the usual way (after several days of rinsing to remove excess lye), the fiber proteins bind to each other only weakly. is made by soaking the partly reconst.i.tuted dry cod for a day or more in a water solution that is strongly alkaline, originally from the addition of potash (the carbonate- and mineral-rich ashes from a wood fire), sometimes lime (calcium carbonate), and later lye (pure sodium hydroxide, at the rate of about 5 grams per liter water). These strong alkaline substances cause the proteins in the muscle fibers to acc.u.mulate a positive electrical charge and repel each other. When the fish is then simmered in the usual way (after several days of rinsing to remove excess lye), the fiber proteins bind to each other only weakly.

It's hard to draw a clear distinction between salted and fermented fish. Bacteria play some role even in hard-cured cod; and most fish fermentations start with a salting to control the bacterial population and activity. Most salted cod, herring, and anchovy products are not generally thought of as fermented, so I'll describe them in this section.

Salt Cod Bountiful cod was one resource that attracted Europeans to the New World, where the standard treatment was to split and salt the fish, and lay them out on rocks or racks to dry for several weeks. Nowadays cod may be hard-cured for 15 days to saturate the flesh with salt (25%), then held without drying for months. During that time, Bountiful cod was one resource that attracted Europeans to the New World, where the standard treatment was to split and salt the fish, and lay them out on rocks or racks to dry for several weeks. Nowadays cod may be hard-cured for 15 days to saturate the flesh with salt (25%), then held without drying for months. During that time, Micrococcus Micrococcus bacteria generate flavor by producing free amino acids and TMA; and oxygen breaks up to half the very small amount of fatty substances into free fatty acids and then into a range of smaller molecules that also contribute to aroma. The final artificial drying takes less than three days. bacteria generate flavor by producing free amino acids and TMA; and oxygen breaks up to half the very small amount of fatty substances into free fatty acids and then into a range of smaller molecules that also contribute to aroma. The final artificial drying takes less than three days.

Salt cod remains a popular food around the Mediterranean as well as in the Caribbean and Africa, where it was introduced during the slave trade. Scandinavia and Canada are still the largest producers. White pieces are preferred to yellowish or reddish ones, the colors being indicators of oxidized or microbial off-flavors. Cooks first reconst.i.tute and desalt it by soaking it for hours to days in several changes of water. Perhaps the best-known preparation is the Provencal brandade, brandade, a paste made by pounding the shredded poached fish along with olive oil, milk, garlic, and sometimes potato. a paste made by pounding the shredded poached fish along with olive oil, milk, garlic, and sometimes potato.

Salt Herring Herring and their relatives may be up to 20% fat by weight, and are therefore susceptible to becoming rancid when exposed to the air. Medieval fishermen solved this problem by barreling the fish in brine, where they would keep for as much as a year. Then sometime around 1300, the Dutch and northern Germans developed a quick gutting technique that left in place a portion of the intestine rich in digestive enzymes (the pyloric caec.u.m). During one to four months of curing in a moderate brine (1620% salt), these enzymes circulate and supplement the activity of both muscle and skin enzymes, breaking down proteins to create a tender, luscious texture and a wonderfully complex flavor, at once fishy, meaty, and cheesy. Such herring are eaten as is, without desalting or cooking. Herring and their relatives may be up to 20% fat by weight, and are therefore susceptible to becoming rancid when exposed to the air. Medieval fishermen solved this problem by barreling the fish in brine, where they would keep for as much as a year. Then sometime around 1300, the Dutch and northern Germans developed a quick gutting technique that left in place a portion of the intestine rich in digestive enzymes (the pyloric caec.u.m). During one to four months of curing in a moderate brine (1620% salt), these enzymes circulate and supplement the activity of both muscle and skin enzymes, breaking down proteins to create a tender, luscious texture and a wonderfully complex flavor, at once fishy, meaty, and cheesy. Such herring are eaten as is, without desalting or cooking.

Two particularly prized types of cured herring are the lightly salted Dutch groen groen and and maatjes, maatjes, or "green" and "maiden" herring, which traditionally broke the winter-long diet of hard-cured beef and fish. Because all lightly cured fish must now be prefrozen to rid them of parasites (p. 186), these formerly seasonal delicacies are now made and enjoyed year-round. or "green" and "maiden" herring, which traditionally broke the winter-long diet of hard-cured beef and fish. Because all lightly cured fish must now be prefrozen to rid them of parasites (p. 186), these formerly seasonal delicacies are now made and enjoyed year-round.

Cured Anchovies Anchovies, smaller and more southerly relatives of the herring, are cured in and around the Mediterranean to make that region's version of flavor-enhancing fish sauce (see box, p. 235). The fish are headed and gutted, then layered with enough salt to saturate their tissue. This ma.s.s is then weighted down and held for six to ten months at a relatively high temperature, between 60 and 86F/1530C. The fish can then be sold as is, or the fillets repacked in cans or bottles, or ground and mixed with oil or b.u.t.ter into a paste. Enzymes from the muscle, skin, blood cells, and bacteria generate many flavor components; and their concentration, together with the warm curing temperature, encourages early stages of the browning reactions, which generate another range of aromatic molecules. The result is a remarkably full flavor that includes fruity, fatty, fried, cuc.u.mbery, floral, sweet, b.u.t.tery, meaty, popcorn, mushroom, and malty notes. This concentrated complexity, together with the way that the cured flesh readily disintegrates in a dish, has led cooks from the 16th century on to use anchovies as a general flavor enhancer in sauces and other dishes. Anchovies, smaller and more southerly relatives of the herring, are cured in and around the Mediterranean to make that region's version of flavor-enhancing fish sauce (see box, p. 235). The fish are headed and gutted, then layered with enough salt to saturate their tissue. This ma.s.s is then weighted down and held for six to ten months at a relatively high temperature, between 60 and 86F/1530C. The fish can then be sold as is, or the fillets repacked in cans or bottles, or ground and mixed with oil or b.u.t.ter into a paste. Enzymes from the muscle, skin, blood cells, and bacteria generate many flavor components; and their concentration, together with the warm curing temperature, encourages early stages of the browning reactions, which generate another range of aromatic molecules. The result is a remarkably full flavor that includes fruity, fatty, fried, cuc.u.mbery, floral, sweet, b.u.t.tery, meaty, popcorn, mushroom, and malty notes. This concentrated complexity, together with the way that the cured flesh readily disintegrates in a dish, has led cooks from the 16th century on to use anchovies as a general flavor enhancer in sauces and other dishes.

Gravlax and Lox Gravlax originated in medieval Scandinavia as a lightly salted, pressed form of salmon that was preserved by fermentation (p. 235) and had a strong smell. By the 18th century, it had evolved into a lightly salted and pressed but unfermented dish. This new gravlax had a subtle flavor, a dense, silken texture that makes it possible to cut very thin slices, and a glistening, translucent appearance. This refined version of gravlax has become popular in many countries. Gravlax originated in medieval Scandinavia as a lightly salted, pressed form of salmon that was preserved by fermentation (p. 235) and had a strong smell. By the 18th century, it had evolved into a lightly salted and pressed but unfermented dish. This new gravlax had a subtle flavor, a dense, silken texture that makes it possible to cut very thin slices, and a glistening, translucent appearance. This refined version of gravlax has become popular in many countries.

Modern recipes for gravlax call for widely varying amounts of salt, sugar, and time. Fresh dill is now the standard flavoring, probably a domestic replacement for the original pine needles, which are a delightful alternative. The salt, sugar, and flavoring are sprinkled evenly over all surfaces of salmon fillets, the fillets are weighted down, and the container refrigerated for one to four days. The weighting provides intimate contact between flesh and flavorings, presses excess fluid from the fish, and compacts the flesh. Salt dissolves the major contracting protein myosin in the muscle fibers, and thus gives the flesh its compact tenderness.

Lox, most familiar as a delicatessen accompaniment to the bagel, is a heavily brined form of salmon. It's usually soaked to remove some salt before being sliced for sale.

Fermented Fish Many cultures from the Arctic to the tropics have recruited microbes to grow on fish and transform their texture and flavor. But the world center of fish fermentation is eastern Asia, where it has served two important purposes: to preserve and put to use the large numbers of small fish that inhabit the coastal and inland waters; and to provide a concentrated source of appet.i.te-stimulating flavors - above all the savory monosodium glutamate and other amino acids - for a diet dominated by bland rice.

Fish fermentation apparently arose several thousand years ago in the freshwaters of southwest China and the Mekong River region. It then spread to the coastal deltas and was applied to ocean fish. Two broadly different techniques evolved: simply salting a ma.s.s of small fish or fish parts and allowing it to ferment; and salting larger fish lightly, then embedding them in a fermenting ma.s.s of rice or other grains, vegetables, or fruits. In the simple fermentation, the proportion of salt is usually enough by itself to preserve the fish from spoilage, and bacteria are important mainly as flavor modifiers. But in the mixed fermentation, a smaller dose of salt preserves the fish for just a few weeks while the plant-based ingredients feed the same microbes that sour milk or turn grape juice into wine. The fish is then preserved by the microbes' acids or alcohol, and flavored by the many by-products of their growth.

From these simple principles, Asian peoples have developed dozens of distinctive fermented fish products, and Europeans a handful. These include the original sushi, which was not a pristinely fresh piece of fish on mildly vinegared rice! Here I'll describe some of the more common ones.

Asian Fish Pastes and Sauces Asian fermented fish pastes and sauces are vital manifestations of a preparation that has mostly disappeared in Europe b