Tuna. Six species of tuna are canned and sold in the United States: yellowfish, skipjack, bluefin, Oriental tuna, little tuna, and albacore. “White” canned tuna comes from albacore and is the most expensive. All other tuna is labeled “light meat tuna,” although some of it can be quite dark. Canned tuna comes in three different styles: fancy or solid pack (a filet or whole piece), chunk (large pieces), and flake (fine pieces or grated). Solid pack has the best appearance and is also the most expensive. Tuna may be canned in either water or oil, so buyers should examine labels for nutrition information. The total calories (kcal) can vary drastically, depending on the canning medium. Each tablespoon of vegetable oil added to a can of tuna contains about 100 calories (kcal) and 15 grams of fat.

Salmon. Chinook or King salmon is the most expensive of the canned salmons. In the less expensive ranges are Sockeye (red salmon), Coho (medium red), pink, and chum. Salmon is often packed with the bones, which increases the calcium content, but only if consumed.

Sardines. Sardines are always packed with their bones unless otherwise noted on the label. They come packed in tomato or mustard sauces or in oil. It is even possible presently to find them on the shelves packed in jalapeno sauce or plain water.

Caviar, which has a mystique surrounding it as a food of the very rich, is really just fish eggs. Its official definition will vary according to the country in which it is sold. In the United States and many other countries, caviar is the clean, salted fish eggs of any fish species. The label is required to list the particular type of fish serving as the caviar source.

In Europe, caviar is more narrowly defined by law as only the eggs of the Caspian Sea sturgeon. The most expensive, largest-grained caviar comes from the Beluga sturgeon. These fish can live for over 70 years and may grow to a length of 25 feet. Like chicken eggs, roe is very high in cholseterol – about 94 mg per tablespoon. It is also high in salt, but the best caviar is malassol, which in Russian means “little salt”. To protect the taste of caviar, it is served with a bone or shell spoon, because metal imparts an off-flavor. It is sometimes served on a neutral-tasting bread that has been toasted on one side, with the caviar being gently placed on the untoasted side.

Vertebrate Fish

Fish can be purchased fresh or frozen as whole, drawn, dressed, steaks, fillets, and sticks.

• Whole fish. The body is entirely intact.
• Drawn fish. Whole fish that have had their entrails (inner organs) removed.
• Dressed fish. The head, tail, fins, and scales have been removed in addition to the entrails.
• Steaks. Cut from dressed fish by slicing from the top fin to the bottom fin at a 90 degree angle at varying thicknesses. Steaks contain a portion of the backbone and other bones.
• Fillets. Made by slicing the fish lengthwise from front to back to avoid the bones.
• Fish sticks. Uniform portions cut from fillets or steaks. They can also be made from fish that has been minced, which is then shaped, breaded, and frozen.

Sniffing for aroma may be the safest, easiest method of determining whether or not fish is fresh, but other criteria can be applied in addition to the “sniff test”. When selecting whole fish, look for skin that is bright and shiny and eyes that bulge, are jet black, and have translucent corneas (the part surrounding the pupil). They should have a “fresh fish” aroma, tight scales, firm flesh, a stiff body, red gills, and a belly free of swelling or gas. The same criteria hold true for drawn fish with the exception of the potential gas-filled belly, which, of course, has been removed.

A stiff body is preferred when selecting a finfish because it is an indication that it is still in rigor mortis, which occurs after slaughter. Flesh that is allowed to go through rigor mortis (stiff to relaxed muscles) has a better texture and flavor. The water-holding capacity of the proteins is increased, which makes the flesh juicier than fish that have not undergone rigor mortis. For these reasons, it is better that handling, packing, processing, and freezing be avoided while fish are in the rigor state. it is also recommended that fish, prior to slaughter, not be subjected to excessive stress if possible, because the resulting stronger rigor mortis is detrimental to texture.

Rigor mortis in fish can last anywhere from several hours to days, depending on the species, temperature, and condition of the fish when caught. Stiffness is delayed if caught fish are immediately placed on ice and kept chilled. Freshness is extended under these conditions because bacterial spoilage does not occur until after rigor mortis has passed. Freezing fish immediately after capture, rather than chilling them on ice and allowing rigor mortis to proceed until the muscles relax again, results in a tough-textured flesh. Cooking fish prior to rigor mortis also results in tough texture.

The meat of the fish should not be slimy, but these can be tricky to judge, because any slime present may have been produced by the fish having been soaked in a special phosphate-containing solution to prevent moisture loss. This solution increases the pH of the tissue, which denatures the proteins and makes them more capable of binding water. Fishermen frequently treat fish with this solution to cut down on the water loss, which might endanger their weight-based profits. Without this solution, fish that is refrigerated may lose up to 80 percent of its water-binding capacity within five days after harvest. The phosphate-containing solution restores the binding capacity of the muscle proteins and prevents the flesh from becoming dry and stringy. Treatment with phosphates also partially inhibits the oxidation of the natural fats in fish, which can result in “fishy” smells when the phosphates bind with the metal ions that promote oxidation.

Other changes that occur in a fish after death is that the eyes flatten and become concave (although this may also be a result of the fish having been picked up by the eye sockets), the pupil turns gray or creamy brown, and the cornea becomes opaque and discolored. In addition, the bright red gills turn a paler brown and as a result are sometimes removed. When the gills turn brown and the eyes lose their bright look, the fish may be cut up as steaks, fillets, or fish sticks. Steaks and fillets should have a shiny, smooth surface that has no signs of curling at the edges. The pieces should be cut clean with no signs of blood, skin fragments, or loose bone, and they should be firm and free of gaping. Although gaping is a sign of aging, it may also be result of rough handling, processing before rigor mortis is complete, the fish having been caught after spawning, or even genetics. Certain fish, like blue fish, and hake, are known to gape more easily.

Part of selecting finfish is knowing how much to buy. A few general guidelines exist. About one-third pound of steaks, fillets, or sticks make an appropriate portion per person. Purchases of half pound for each person will be required when buying dressed fish, and three quarter pound per serving for whole or drawn fish.

Yes. What you put in your body can sometimes sap the strength of certain vitamins or undermine your body’s ability to process or manufacture them. Whenever this happens, you will probably need to consume more than the U.S. recommended daily allowance of vitamins (although these allowances are more than ample for most people).

Chain smokers, for instance, need extra vitamin C, and booze-hounds and sugar fiends require more of the B complex vitamins than their moderate companions. Additional B complex vitamins are also recommended for people using antibiotics for extended periods of time, and for women taking birth control pills (who also need extra vitamin C).

However, you need not offset a lack or loss of vitamins with supplementary vitamin pills. Increasing one’s intake of fruits and vegetables usually accomplishes the same mission more efficiently.

Unlike meat and poultry, the inspection of finfish is voluntary. Such inspection, when it occurs, is based on the wholesomeness of the fish and the sanitary conditions of the processing plant. The National Marine Fisheries Service of the U.S. Department of Commerce is responsible for fish inspections, which are paid for by the processor.

Only inspected finfish can be graded. Grading, too, is voluntary and paid for by the processor. Fish products are graded U.S. Grade A, U.S. Grade B, and substandard. Quality grades are based on appearance, texture, uniformity, good flavor, fresh odor, and an absence of defects. Breaded fish products are further evaluated in terms of their breading and bone-to-fish ratio. Labels should be read whenever possible to find out whether or not the fish product has been inspected and graded.

The Department of Commerce also oversees the publication of the Interstate Certified Shellfish Shippers List, which lists department-certified shippers of oysters, clams, mussels, and scallops. Only shellfish from these certified waters, which have been tested and found to be free of excessive levels of various microorganisms, can be sold for consumption.

Wholesale containers of shellfish must then be labeled to include the harvester’s name, address, and certification number, the date and location of harvest, and the type and quantity of shellfish. Shellfish that have been “shucked”, or removed from their shells, must also be tagged with a “sell by date” (under 64 fluid ounces) or “date shucked” (over 64 fluid ounces). These tags are required to be kept by food service operations for at least 90 days upon receipt. If shellfish are not properly tagged or if they are obtained from uncertified waters, the Department of Commerce may report the violation to the Food and Drug Administration, which is the regulatory agency with final jurisdiction over commerce in shellfish.

Regardless of their classification, fish are usually tender when they come to the table, and three structural factors contribute to this tenderness. When compared with meat or poultry, fish muscle has lower amounts of collagen. The bodies of land animals average 15 percent connective tissue by weight, while fish are only 3 percent collagen. Another reason fish is tender is that there is less of a certain amino acid (hydroxyproline) in the connective tissue, so when fish is cooked, the collagen breaks down more easily at a lower temperature and converts to gelatin. Also, unlike mammals and birds, whole muscles are arranged in very long bundles of fibers, the muscles of fish are shorter (less than an inch in length) and are arranged into myotomes, which are separated by myocommata. This combination of structure and chemistry contributes to the characteristic flaking of prepared fish as the heat softens the collagen in the myocommata.

Pigments in Fish

When fish flesh is exposed to air during preparation, it will vary in color as a result of the presence of white, pink, or red pigments. The color of a fish’s flesh depends on whether that fish relied predominantly on quick or slow movements to stay alive. “Red” or darker meat flesh, such as that seen in salmon, has a higher concentration of the “slow-twitch fibers” needed for long-distance swimming and endurance. “White” meat, like that of the sole, has more “fast-twitch fibers”, which are designed for quick bursts of speed of brief duration between long periods on “cruise control”, Some fish, such as tuna, are comprised of both fast-twitch and slow-twitch fibers, giving them dark, light, and white meat.

The concentration of myoglobin contributes to the overall color of fish flesh. The more oxygen required by the muscle, the more myoglobin proteins are necessary, because they carry the oxygen. Unfortunately a higher myoglobin concentration results in quicker rancidity because the iron in myoglobin accelerates the oxidation of fat found in the muscle. Sometimes a specific pigment adds a special hue. For example, a carotenoid pigment, astaxanthin, imparts a characteristic orange-pink color to certain salmon and trout that feed on insects and crustaceans containing this pigment. A higher fat content will also darken the color of the flesh, as seen in fatty fish like mackerel and tuna.

The majority of the fish eaten in the United States are taken from salty waters, but many also come from fresh-water lakes, ponds, and streams. Saltwater fish often have a more distinct flavor than freshwater fish. Sole, however, is a very mild-flavored saltwater fish, and is one of several exceptions to the taste generalization. Some saltwater fish other than sole are halibut, cod, flounder, haddock, mackerel, red snapper, salmon, shark, striped bass, swordfish, and tuna. Catfish, perch, pike, and trout are the most common freshwater varieties.

Lean or Fat

Fish are sometimes identified by their fat content, but in this case, “fat” is a relative term. Fish are not very fatty compared to most other meats. Fat content in a 3-ounce cooked portion is less than 2.5 grams in lean fish (less than 5 percent fat) which includes cod, pike, haddock, flounder, sole, whiting, red snapper, halibut, and bass. The same portion of fatty fish (more than 5 percent fat) yields 5 to 10+ grams of fat. Examples include salmon, mackerel, lake trout, tuna, butterfish, whitefish, and herring.

The vertebrate category includes sea mammals, all of which must get their oxygen from above the water’s surface, and finfish, which obtain their oxygen from the water itself through their gills. Sea mammals include dolphin, whale, and seal, which are consumed in some cultures. Finfish are found in the fresh water of rivers, lakes, and streams, and the salt water of oceans and seas. The most popular finfish in North America are tuna, cod, Alaska pollack, salmon, catfish and flounder/sole.

Shellfish, which is a commercial rather than a scientific classification, includes the invertebrate crustaceans and mollusks. Examples of crustaceans are shrimp, crab, lobster, and crayfish. Mollusks include bivalves, univalves, and cephalopods. Bivalve creatures, including clams, oysters, mussels, and scallops, are contained within two hard shells that are hinged together. The univalves, such as conch and abalone, have only a single hard shell. Cephalopods, which include octopus and squid, have an almost rubbery soft inner shell, which will be familiar to parakeet owners as a cuttlebone.

Humans were eating fish, shellfish, and sea mammals long before they started cultivating plants or domesticating animals for food. Excavations of Stone Age sites have uncovered fish nets, spears, and fishing hooks made from the upper beaks of birds. Seafood is now the only major food source that is still being hunted, most other sources being raised or grown. At present, there are over 20,000 known species of edible fish, shellfish, and sea mammals. Of these, approximately 250 species are harvested commercially in the United States, with millions of tons annually being served up for the consumption of humans and domesticated animals.

Classification of Fish and Shellfish

The staggering variety of creatures harvested from the water makes it difficult to classify them using only one set of criteria. As a result, several categories have arisen in order to distinguish them from each other: vertebrate or invertebrate, salt or fresh water, and lean or fat. Although these classifications are used to separate the identity of different fish, a vertebrate could be in salt or fresh water, and either lean or fat. The Food and Drug Administration has attempted to standardize fish nomenclature by publishing a “Guide to Acceptable Market Names for Food Fish Sold in Interstate Commerce”, and requiring that fish be named according to this publication.

Precautions should be taken in the handling of poultry, because of the possibility of their being contaminated with bacteria. Salmonella is one of the most common causes of foodborne illness. Some of its major sources include raw poultry, eggs, and stuffing. In 1993, the irradiation of poultry was approved for commercial use in the control of Salmonella following several studies that showed it reduces bacterial concentration. Irradiated poultry, however, is not sterile and should be handled using the same precautions used for non-irradiated raw poultry. In 1992, the use of trisodium phosphate (TSP), a colorless, odorless, flavorless chemical mixture, also received approval for use by the poultry industry on poultry carcasses to further aid in reducing Salmonella contamination.

Fresh, ready-to-cook poultry can be kept safely in the refrigerator at 40^oF (4^oC) or below for up to three days. It should be stored in the vapor-proof wrapping in which it is purchases, since repackaging increases the risk of bacterial contamination. It is best kept in the bottom portion of the refrigerator to prevent its drippings from contaminating other foods. Chickens labeled “fresh” should not have gone below 26^oF (-3^oC), the temperature at which chickens freeze. Frozen whole poultry can be stored from six to twelve months at 0^oF (-18^oC), while leftover cooked poultry can be frozen for up to four months. The meat will decline in moistness and eating quality if it is kept frozen beyond the recommended times.

Breaded or fried poultry should never be thawed and refrozen. Defrosting is recommended in the refrigerator, where it will take about a day to defrost an average chicken, and one day for each five pounds of turkey. Once defrosted, poultry or any other meat should not be refrozen unless it has been cooked. Stuffing should be refrigerated promptly and consumed within two or three days.