On Food And Cooking Part 20

Smelt Smelt

Herring Herring

Snapper

Sole: Dover Sole: Dover

Mackerel Mackerel

Tuna: bigeye, yellowfin, skipjack

Striped ba.s.s Striped ba.s.s

Pompano Pompano

Sturgeon

Sablefish Sablefish

Turbot

Swordfish Swordfish

Salmon: Atlantic, king, sockeye Salmon: Atlantic, king, sockeye

Tilapia

Escolar*

Trout Trout

Shad Shad

Orange roughy*

Tuna: bluefin, albacore Tuna: bluefin, albacore

Ruvettus/walu*

Whitefish Whitefish

*These fish contain oil-like wax esters (p. 187) that the human body can't digest; they therefore seem rich but are really low-fat fish. *These fish contain oil-like wax esters (p. 187) that the human body can't digest; they therefore seem rich but are really low-fat fish.

Infectious and Toxin-Producing Microbes Seafoods carry about the same risk of bacterial infections and poisonings as other meats (p. 125). The riskiest seafoods are raw or undercooked sh.e.l.lfish, particularly bivalves, which trap bacteria and viruses as they filter the water for food, and which we eat digestive tract and all, sometimes raw. As early as the 19th century, public health officials connected outbreaks of cholera and typhoid fever with sh.e.l.lfish from polluted waters. Government monitoring of water quality and regulation of sh.e.l.lfish harvest and sales have greatly reduced these problems in many countries. And scrupulous restaurant owners make sure to buy sh.e.l.lfish for the summer raw bar from monitored sources, or from less risky cold-water sources. But lovers of raw or lightly cooked seafood should be aware of the possibility of infection. Seafoods carry about the same risk of bacterial infections and poisonings as other meats (p. 125). The riskiest seafoods are raw or undercooked sh.e.l.lfish, particularly bivalves, which trap bacteria and viruses as they filter the water for food, and which we eat digestive tract and all, sometimes raw. As early as the 19th century, public health officials connected outbreaks of cholera and typhoid fever with sh.e.l.lfish from polluted waters. Government monitoring of water quality and regulation of sh.e.l.lfish harvest and sales have greatly reduced these problems in many countries. And scrupulous restaurant owners make sure to buy sh.e.l.lfish for the summer raw bar from monitored sources, or from less risky cold-water sources. But lovers of raw or lightly cooked seafood should be aware of the possibility of infection.

As a general rule, infections by bacteria and parasites can be prevented by cooking seafood to a minimum of 140F/60C. Temperatures above 185F/82C are required to eliminate some viruses. Some chemical toxins produced by microbes survive cooking, and can cause food poisoning even though the microbes themselves are destroyed.

Among the most important microbes in fish and sh.e.l.lfish are the following: Vibrio bacteria, natural inhabitants of estuary waters that thrive in warm summer months. One species causes cholera, another a milder diarrheal disease, and a third ( bacteria, natural inhabitants of estuary waters that thrive in warm summer months. One species causes cholera, another a milder diarrheal disease, and a third (V. vulnificus), usually contracted from raw oysters and the deadliest of the seafood-related diseases, causes high fever, a drop in blood pressure, and damage to skin and flesh, and kills more than half of its victims.

Botulism bacteria, which grow in the digestive system of unchilled fish and produce a deadly nerve toxin. Most cases of fish-borne botulism are caused by improperly cold-smoked, salt-cured, or fermented products.

Intestinal viruses, the "Norwalk" viruses, which attack the lining of the small intestine and cause vomiting and diarrhea.

Hepat.i.tis viruses A and E, which can cause long-lasting liver damage.

s...o...b..oid Poisoning s...o...b..oid poisoning is unusual in that it is caused by a number of otherwise harmless microbes when they grow on insufficiently chilled mackerels of the genus s...o...b..oid poisoning is unusual in that it is caused by a number of otherwise harmless microbes when they grow on insufficiently chilled mackerels of the genus s...o...b..r s...o...b..r and other similarly active swimmers, including tuna, mahimahi, bluefish, herring, sardine, and anchovy. Within half an hour of eating one of these contaminated fish, even fully cooked, the victim suffers from temporary headache, rash, itching, nausea, and diarrhea. The symptoms are apparently caused by a number of toxins including histamine, a substance that our cells use to signal each other in response to damage; antihistamine drugs give some relief. and other similarly active swimmers, including tuna, mahimahi, bluefish, herring, sardine, and anchovy. Within half an hour of eating one of these contaminated fish, even fully cooked, the victim suffers from temporary headache, rash, itching, nausea, and diarrhea. The symptoms are apparently caused by a number of toxins including histamine, a substance that our cells use to signal each other in response to damage; antihistamine drugs give some relief.

Sh.e.l.lfish and Ciguatera Poisonings Fish and sh.e.l.lfish share the waters with many thousands of animal and plant species, some of which engage in nasty chemical warfare with each other. At least 60 species of one-celled algae called dinoflagellates produce defensive toxins that also poison the human digestive and nervous systems. Several of these toxins can kill. Fish and sh.e.l.lfish share the waters with many thousands of animal and plant species, some of which engage in nasty chemical warfare with each other. At least 60 species of one-celled algae called dinoflagellates produce defensive toxins that also poison the human digestive and nervous systems. Several of these toxins can kill.

We don't consume dinoflagellates directly, but we do eat animals that eat them. Bivalve filter feeders - mussels, clams, scallops, oysters - concentrate algal toxins in their gills and/or digestive organs, and then transmit the poisons to other sh.e.l.lfish - usually crabs and whelks - or to humans. Accordingly, most dinoflagellate poisonings are called "sh.e.l.lfish poisonings." Many countries now routinely monitor waters for the algae and sh.e.l.lfish for the toxins, so the greatest risk is from sh.e.l.lfish gathered privately.

There are several distinct types of sh.e.l.lfish poisoning, each caused by a different toxin and each with somewhat different symptoms (see box below), though all but one are marked by tingling, numbness, and weakness within minutes to hours after eating. Dinoflagellate toxins are not destroyed by ordinary cooking, and some actually become more toxic when heated. Suspect sh.e.l.lfish should therefore be avoided altogether.

Finfish generally don't acc.u.mulate toxins from algae. The exceptions are a group of tropical reef fish - barracuda, groupers, jacks, king mackerel, mahimahi, mullets, porgies, snappers, wahoo - that prey on an algae-eating snail (cigua) and can cause ciguatera poisoning.

Parasites Parasites are not bacteria or viruses: they're animals, from single-celled protozoa to large worms, that take up residence in one or more animal "hosts" and use them for both shelter and nourishment during parts of their life cycle. There are more than 50 that can be transmitted to people who eat fish raw or undercooked, a handful of which are relatively common, and may require surgery to remove. Thanks to their more complex biological organization, parasites are sensitive to freezing (bacteria generally aren't). So there's a simple rule for eliminating parasites in fish and sh.e.l.lfish: either cook the food to a minimum of 140F/60C, or prefreeze it. The U.S. FDA recommends freezing at 31F/35C for 15 hours, or 10F/23C for seven days, treatments that are not feasible in home freezers, which seldom dip below 0F. Parasites are not bacteria or viruses: they're animals, from single-celled protozoa to large worms, that take up residence in one or more animal "hosts" and use them for both shelter and nourishment during parts of their life cycle. There are more than 50 that can be transmitted to people who eat fish raw or undercooked, a handful of which are relatively common, and may require surgery to remove. Thanks to their more complex biological organization, parasites are sensitive to freezing (bacteria generally aren't). So there's a simple rule for eliminating parasites in fish and sh.e.l.lfish: either cook the food to a minimum of 140F/60C, or prefreeze it. The U.S. FDA recommends freezing at 31F/35C for 15 hours, or 10F/23C for seven days, treatments that are not feasible in home freezers, which seldom dip below 0F.

Poisonings Caused by Toxic Algae

Type of Poisoning

Usual Regions Usual Regions

Diarrhetic sh.e.l.lfish poisoning

j.a.pan, Europe, Canada j.a.pan, Europe, Canada

Amnesic sh.e.l.lfish poisoning

U.S. Pacific coast, New England U.S. Pacific coast, New England

Neurotoxic sh.e.l.lfish poisoning

Gulf of Mexico, Florida Gulf of Mexico, Florida

Paralytic sh.e.l.lfish poisoning

U.S. Pacific coast, New England U.S. Pacific coast, New England

Ciguatera poisoning

Caribbean, Hawaii, South Pacific Caribbean, Hawaii, South Pacific

Type of Poisoning

Usual Sources Usual Sources

Diarrhetic sh.e.l.lfish poisoning

Mussels, scallops Mussels, scallops

Amnesic sh.e.l.lfish poisoning

Mussels, clams, Dungeness crab Mussels, clams, Dungeness crab