Appendices
Appendix B
Food Poisoning Reference Tables
This appendix lists, by cause, the kinds of food poisoning that can happen in a sushi restaurant. The incubation period and the symptoms help you narrow down the cause when a guest calls to say they feel unwell. The last column on the right shows whether heating, freezing, or disinfection works against each cause. Some toxins are not destroyed by heat, and some bacteria and viruses are not killed by freezing. Use these tables to confirm this.
The figures are general values based on materials published by Japan's Ministry of Health, Labour and Welfare (MHLW) and other bodies. Incubation periods vary from source to source, so the tables give typical values.
The causes of food poisoning fall into four main groups: parasites, viruses, bacteria, and natural toxins and chemicals. Bacteria are further divided into two types. In the infection type, the bacteria multiply inside the body and cause illness. In the toxin type (intoxication), the bacteria make a toxin in the food, and people become ill by eating that toxin. With the toxin type, illness occurs if the toxin remains, even after the bacteria have been killed.
In a sushi restaurant, the three causes that need the most care are Anisakis, norovirus, and Vibrio parahaemolyticus (Chapter 3). Food poisoning from Vibrio parahaemolyticus has fallen sharply since a standard for seafood eaten raw was set in 2001. Even so, the other causes can also lead to serious harm once an outbreak happens.
B.1 Parasites and Viruses
The parasite listed is Anisakis. The viruses listed are norovirus and hepatitis A virus. Freezing kills parasites, but it does not kill viruses.
| Cause | Type | Main foods involved | Incubation period | Main symptoms | Main prevention in a sushi restaurant | Can heating, freezing, or disinfection destroy it? |
|---|---|---|---|---|---|---|
| Anisakis | Parasite (the larva of a nematode, or roundworm; it looks like a white thread 2–3 cm long) | Mackerel, horse mackerel, sardine, Pacific saury, skipjack tuna, salmon, squid, and others. After the fish dies, the larvae may move from the guts into the flesh | In the stomach: a few hours to a dozen or more hours after eating. In the intestine: a dozen or more hours to a few days | Severe pain in the pit of the stomach, nausea, and vomiting. In the intestine, pain in the lower abdomen and, rarely, peritonitis. Allergic symptoms such as hives may also occur | Choose fresh fish and remove the guts quickly. Check by eye and with a black light (a black light shows only the larvae within about 0.5 mm of the surface). If you serve the fish raw, freeze it at −20°C or below for at least 24 hours (count from when the center of the fish reaches −20°C). Vinegar, salt, wasabi, and soy sauce do not kill it | Heating: dies at 60°C for 1 minute, or at 70°C or higher. Freezing: dies at −20°C or below for at least 24 hours (in Japan, this is advice from the MHLW). Disinfectants: not relevant |
| Norovirus | Virus | Raw or undercooked bivalves (especially oysters). Any food contaminated by the hands of an infected person | 24–48 hours | Vomiting, diarrhea, abdominal pain, and a mild fever. It usually clears up in 1–2 days, but watch older people and young children for dehydration. It is said that 10–100 particles are enough to infect | Cook bivalves until the center reaches 85–90°C for at least 90 seconds. Serve raw only those labeled "for raw consumption." Manage staff health and run stool tests. Treat vomit with 1,000 ppm sodium hypochlorite. An infected person may shed the virus for 1 week to 1 month after symptoms end. So anyone who has been infected must not touch food directly until a stool test confirms the virus is gone | Heating: destroyed at 85–90°C for at least 90 seconds. Freezing: does not die. Disinfection: sodium hypochlorite works. Alcohol works poorly |
| Hepatitis A virus | Virus | Raw or undercooked bivalves, contaminated water, and food touched by an infected person | 2–7 weeks (about 4 weeks on average) | Fever, tiredness, loss of appetite, and jaundice (the skin and the whites of the eyes turn yellow). Because the incubation period is long, it is hard to find the food that caused it | Cook bivalves thoroughly and wash your hands. Outside Japan, be careful with water and ice. Vaccinating staff is effective | Heating: destroyed at 85°C or higher for at least 1 minute. Freezing: does not die. Disinfection: sodium hypochlorite works. Alcohol works poorly |
B.2 Bacteria
Eight bacteria are listed: Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella, Campylobacter, enterohemorrhagic E. coli, Listeria, Clostridium perfringens, and Bacillus cereus. The toxin of Staphylococcus aureus remains after heating. So do the spores (heat-resistant shells) of Clostridium perfringens and Bacillus cereus.
| Cause | Type | Main foods involved | Incubation period | Main symptoms | Main prevention in a sushi restaurant | Can heating, freezing, or disinfection destroy it? |
|---|---|---|---|---|---|---|
| Vibrio parahaemolyticus | Bacterium (infection type). Lives in seawater and likes salt | Sashimi and sushi made from seafood in summer. Foods that the bacteria have spread to from seafood | 8–24 hours (about 12 hours on average) | Severe abdominal pain, watery diarrhea, vomiting, and fever | Wash fish under running fresh water (the bacteria are weak against fresh water). The bacteria stop growing at 4°C or below, so store fish at 10°C or below, and if possible at 4°C or below. Under the best conditions for growth, the bacteria double in about 10 minutes, so do not leave fish at room temperature. Do not let the bacteria spread to other foods from tools and hands that have touched fish | Heating: dies at 75°C for at least 1 minute. Freezing: stops growing, but does not always die. Disinfection: weak against ordinary disinfectants |
| Staphylococcus aureus | Bacterium (toxin type). Found on human skin, in the nose, and in cuts on the hands. Can grow even at about 15% salt | Rice balls, sushi, boxed lunches, and other foods handled with bare hands | 1–6 hours (about 3 hours on average) | Severe nausea, vomiting, and abdominal pain. There is usually little fever | Wash your hands well. When you have a cut or an infected wound on your hand, do not touch raw foods. Do not leave prepared food at room temperature. Keep it at 10°C or below. Heat does not destroy the toxin. So the two pillars of protection are keeping bacteria off the food from your hands, and not letting any bacteria that do get on it grow | Heating: the bacteria die, but the toxin (enterotoxin) is not destroyed even by heating at 100°C for 30 minutes. Freezing: the toxin remains. Disinfection: works on the bacteria |
| Salmonella | Bacterium (infection type) | Chicken eggs and meat. It gets into the ingredients for tamagoyaki (Japanese omelet) through dirt on the eggshells | 6–72 hours (usually 12–48 hours) | Fever, abdominal pain, diarrhea, and vomiting. Young children and older people tend to become seriously ill | Refrigerate eggs and use fresh ones. Do not leave cracked eggs at room temperature. Cook tamagoyaki all the way to the center (a core temperature of 70°C for at least 1 minute; the general guide is 75°C for at least 1 minute). Wash your hands and any tools that have touched the shells | Heating: dies at 75°C for at least 1 minute. Freezing: does not die. Disinfection: works |
| Campylobacter | Bacterium (infection type). Prefers places with only a little oxygen | Chicken, untreated water, and unpasteurized milk. Foods it has spread to from chicken | 1–7 days (usually 2–5 days) | Diarrhea, abdominal pain, fever, and headache. Rarely, it causes Guillain-Barré syndrome (paralysis of the arms and legs) a few weeks later | In restaurants that handle chicken, keep the tools, hands, and work areas for fish served raw completely separate. Cook chicken at 75°C for at least 1 minute. Just a few hundred bacteria are enough to cause illness | Heating: dies at 75°C for at least 1 minute. Freezing: the numbers fall, but the bacteria do not die out. Disinfection: works. Weak against drying |
| Enterohemorrhagic E. coli (O157 and others) | Bacterium (infection type; makes Shiga toxin (verotoxin) inside the body) | Beef, raw vegetables, lightly pickled vegetables, and well water. Foods it has spread to from beef | 3–8 days (usually 3–5 days) | Severe abdominal pain, watery stools, and bloody stools. Young children and older people may develop hemolytic uremic syndrome (HUS), a disease in which the kidneys stop working, and there have been deaths | A few dozen to about 100 bacteria are enough to cause illness. Wash raw vegetables such as daikon sprouts, cucumber, and shiso (perilla) well. If needed, sanitize them with 200 ppm sodium hypochlorite. Keep them separate from tools used for meat. Cook at 75°C for at least 1 minute | Heating: dies at 75°C for at least 1 minute. Freezing: does not die. Disinfection: works |
| Listeria monocytogenes | Bacterium (infection type). Grows even at 4°C and tolerates salt | Ready-to-eat foods that have been refrigerated for a long time, such as smoked salmon, natural cheese, and uncooked cured ham | 1 day to several weeks (in long cases, about 70 days to 3 months) | Fever, muscle aches, and headache. In pregnant women, miscarriage or stillbirth. In babies, older people, and people with weak immune systems, meningitis or sepsis | Do not rely too much on refrigeration. Keep to the dates, and use up anything that has been refrigerated for a long time. Do not serve uncooked foods that have been refrigerated for a long time to pregnant women | Heating: dies at 75°C for at least 1 minute. Freezing: does not die. Disinfection: works |
| Clostridium perfringens | Bacterium (infection type; makes a toxin in the intestine). Dislikes oxygen and forms spores | Curry, simmered dishes, soups, and cooking liquids made in large pots. In a sushi restaurant, cooking liquids made ahead in large pots, such as the liquid for simmered anago (conger eel). (Once it is reduced into tsume (sweet reduced sauce) with a high sugar content, the bacteria grow less easily) | 6–18 hours (about 10 hours on average) | Diarrhea and abdominal pain. Most cases are mild and clear up in 1–2 days | Do not let cooked liquids cool at room temperature in the large pot. Divide them into small portions, cool them quickly, and refrigerate them. When reheating, stir well and bring the whole amount to a boil | Heating: the spores of the strains that cause food poisoning survive heating at 100°C for 1–6 hours. Freezing: the spores do not die. Disinfection: works poorly on spores |
| Bacillus cereus | Bacterium. There is an emetic (vomiting) type (toxin type) and a diarrheal type (infection type). Forms spores | Emetic type: rice, fried rice, and pasta. Diarrheal type: meat dishes and soups | Emetic type: 30 minutes to 6 hours. Diarrheal type: 8–16 hours | Emetic type: nausea and vomiting. Diarrheal type: diarrhea and abdominal pain | Do not leave cooked rice at room temperature for long. Set a time limit for keeping shari (sushi rice) warm, and throw it away once the limit has passed. Cool anything made ahead quickly and refrigerate it | Heating: the emetic toxin (cereulide) is not destroyed even by heating at 126°C for 90 minutes. The spores survive 100°C. Freezing: the spores do not die. Disinfection: works poorly on spores |
B.3 Natural Toxins and Chemicals
Five are listed: histamine, pufferfish toxin, shellfish toxins, ciguatera, and the tetramine in whelks (tsubugai). None of these five is destroyed by heating or by freezing.
| Cause | Type | Main foods involved | Incubation period | Main symptoms | Main prevention in a sushi restaurant | Can heating, freezing, or disinfection destroy it? |
|---|---|---|---|---|---|---|
| Histamine | Chemical (bacteria make it by breaking down a substance in fish flesh called histidine) | Red-fleshed fish such as tuna, skipjack tuna, mackerel, Japanese amberjack (buri), sardine, and Pacific saury, and products made from them | A few minutes to 1 hour (usually within 1 hour) | Flushed face, hives, headache, a pounding heart, and diarrhea. While eating, the lips and tongue may tingle | Buy fish that has been kept cold the whole time since it was caught. Remove the gills and guts quickly. Do not leave thawed fish at room temperature. Even in the refrigerator (around 4°C), histamine can build up if the fish is kept for a long time. It may be present even when there is no rotten smell. So do not use red-fleshed fish that has lost its freshness. Once histamine has formed, it cannot be removed | Heating: not destroyed. Freezing: stops new histamine from forming, but what has formed remains. After thawing, it forms easily again. Disinfection: not relevant |
| Pufferfish toxin (tetrodotoxin) | Natural toxin from an animal | The liver, ovaries, skin, and intestines of pufferfish (fugu). The strength of the toxin differs by species and by body part | 20 minutes to 3 hours | Numbness of the lips and tongue, vomiting, inability to move the body, and difficulty breathing. The death rate is high | Anyone without a license must not fillet, handle, or serve pufferfish. Serving pufferfish without the proper qualification is against the law | Heating: not destroyed. Freezing: not destroyed. Disinfection: not relevant |
| Shellfish toxins (paralytic and diarrhetic) | Natural toxin from an animal (bivalves build up toxins from poisonous plankton) | Bivalves such as scallops, Mediterranean mussels, Manila clams, and oysters. The toxins build up in the digestive gland (the shellfish's internal organs) | Paralytic: about 30 minutes. Diarrhetic: 30 minutes to 4 hours | Paralytic: numbness and paralysis. In severe cases, breathing becomes paralyzed and the person dies. Diarrhetic: diarrhea, vomiting, and abdominal pain (clears up within 3 days) | Do not use shellfish from sea areas or periods in which shipments have been stopped. Buy only from trusted suppliers, and do not use shellfish you have gathered yourself. Check information on the place of origin and the test results | Heating: not destroyed. Freezing: not destroyed. Disinfection: not relevant |
| Ciguatera (ciguatoxin) | Natural toxin from an animal (toxins from tiny algae build up in large fish as they pass along the food chain, from the eaten to the eater) | Large fish that live on coral reefs in tropical and subtropical seas, such as two-spot red snapper, yellow-edged lyretail, spotted knifejaw, and great barracuda | 1–8 hours (sometimes 2 days or more) | Diarrhea, vomiting, joint pain, a disorder of temperature sense in which cold things feel hot, a slow pulse, and low blood pressure. Symptoms may last for weeks to months | Take special care in tropical and subtropical regions outside Japan. Check the place of origin and the species, and avoid large individual fish. In Japan too, be careful with fish from the Nansei Islands and with fish that have moved north as the sea has warmed | Heating: not destroyed. Freezing: not destroyed. Disinfection: not relevant |
| Tetramine in whelks | Natural toxin from an animal | The salivary glands of whelks related to the ezobora (Neptunea) whelk, such as hime-ezobora and ezobora-modoki. They are milky-white to pale yellow lumps called "abura" (fat) | 30 minutes to 1 hour | Dizziness, headache, abnormal vision, unsteadiness like seasickness, and a feeling like being drunk. It usually clears up in a few hours | Always remove the salivary glands. Do not skip this, even for small whelks. Do not let anyone who does not know how to remove them prepare whelks | Heating: not destroyed (it dissolves in water, so it passes into the cooking liquid). Freezing: not destroyed. Disinfection: not relevant |
B.4 Three Principles from These Tables
The first principle is that heating does not solve everything. The toxin of Staphylococcus aureus, the emetic toxin of Bacillus cereus, histamine, pufferfish toxin, shellfish toxins, ciguatera, and tetramine are not destroyed by heat. The spores of Clostridium perfringens and Bacillus cereus survive even boiling. Against these, the only options are "do not let them form," "do not let them in," and "remove them."
The second principle is that you can safely assume that freezing kills only parasites. Bacteria and viruses only go to sleep when frozen. Once thawed, they start to multiply again.
The third principle is that alcohol does not work on some of them. For norovirus and hepatitis A virus, use sodium hypochlorite.
What works is different for each cause. Only a chef who knows this can choose the right prevention.