Foodborne Intoxications ◾ 333
associated predominantly with fish while types A and B were associated with vegetables. The major
cause of outbreaks was improper home canning of the contaminated products. Between 1983 and
1987, out of 231 botulism outbreaks in the United States, 56 occurred at home. Between 1990
and 2000, there were 263 cases from 160 foodborne botulism events, of which 103 (39%) cases
and 58 events occurred in Alaska. Toxin type A caused 51% of all cases while Toxin E was involved
in 90% of Alaska cases. Home-canned vegetables were involved in 44% cases. 9 The occurrence of
botulism from meat, poultry, and dairy products is low. This is probably because they are mostly
heated and eaten quickly. Several outbreaks from unlikely foods (sautéed onions, baked potatoes,
home-canned bamboo shoots) have been recorded, but in many instances, the foods were subjected to temperature abuse (held for a long time at warm temperature). Some condiments, such
as chili peppers, relish, and sauce, have also been associated with outbreaks.
Growth of proteolytic strains in meats and low-acid, high-protein vegetables generally produce
obnoxious odors and gas. In low-protein vegetables, these characteristics may not be obvious. The
growth of nonproteolytic strains, even when growing in meat, fish, and other high-protein foods,
do not produce spoilage characteristics. As the toxins are heat labile, high uniform heating (90°C
for 15 minutes or boiling for five minutes) of a suspected food will destroy the toxins and make
the food theoretically safe. However, as only a small amount of toxin is enough to cause disease,
it is better to avoid a suspected food.
Prevention of Botulism 6
The single most important control method is to use proper temperature and time in home canning
of low-acid products. Commercial processors use the 13D concept (Chapter 33). Directions for
pressure canning of foods at home are available, and they should be strictly followed. Proper and
uniform cooking of some foods (e.g., fish) at high temperatures should be followed as outlined. 6
(1) Foods cooked at temperatures in which spores survive should be stored at low temperatures (at
3°C or below); (2) at refrigerated temperatures (4°C–5°C), storage should not be prolonged (the
10-day rule) unless some additional precautions are used, such as NO 2 , low pH, low A W , NaCl,
and others; (3) a heat treatment of 90°C for 10 minutes or equivalent lethality (e.g., 80°C for 129
minutes, 85°C for 36 minutes) combined with storage at chill temperatures (designed to give a 6D
process for nonproteolytic Clo. botulinum); (4) a pH ≤ 5.0 throughout the food, combined with
storage at chilled temperatures; (5) a NaCl concentration of ≥3.5% throughout the food, combined with storage at chilled temperatures; (6) an A W ≤ 0.97 throughout the food, combined with
storage at chilled temperatures; and (7) combinations of heat treatment and other preservative factors, which can be shown consistently to prevent growth and toxin production by Clo. botulinum,
combined with storage at chilled temperatures. Suspected foods should be properly heated prior
to consumption, but it is better not to eat them. Even tasting a small amount of a suspected food
without giving high and uniform heat treatment can be dangerous.
Identification Methods
In a suspected food, the presence of Clo. botulinum can be determined by enumeration techniques
using selective agar media and anaerobic incubation, followed by biochemical and toxicological
testing. The presence of toxins in the food is more often tested. This involves injection of a food
extract intraperitoneally to mice. Development of characteristic neurological symptoms, followed
by death in 92 hours suggests the presence of toxins. The people engaged in testing for the organism or the toxins need to immunize themselves prior to handling the materials.
associated predominantly with fish while types A and B were associated with vegetables. The major
cause of outbreaks was improper home canning of the contaminated products. Between 1983 and
1987, out of 231 botulism outbreaks in the United States, 56 occurred at home. Between 1990
and 2000, there were 263 cases from 160 foodborne botulism events, of which 103 (39%) cases
and 58 events occurred in Alaska. Toxin type A caused 51% of all cases while Toxin E was involved
in 90% of Alaska cases. Home-canned vegetables were involved in 44% cases. 9 The occurrence of
botulism from meat, poultry, and dairy products is low. This is probably because they are mostly
heated and eaten quickly. Several outbreaks from unlikely foods (sautéed onions, baked potatoes,
home-canned bamboo shoots) have been recorded, but in many instances, the foods were subjected to temperature abuse (held for a long time at warm temperature). Some condiments, such
as chili peppers, relish, and sauce, have also been associated with outbreaks.
Growth of proteolytic strains in meats and low-acid, high-protein vegetables generally produce
obnoxious odors and gas. In low-protein vegetables, these characteristics may not be obvious. The
growth of nonproteolytic strains, even when growing in meat, fish, and other high-protein foods,
do not produce spoilage characteristics. As the toxins are heat labile, high uniform heating (90°C
for 15 minutes or boiling for five minutes) of a suspected food will destroy the toxins and make
the food theoretically safe. However, as only a small amount of toxin is enough to cause disease,
it is better to avoid a suspected food.
Prevention of Botulism 6
The single most important control method is to use proper temperature and time in home canning
of low-acid products. Commercial processors use the 13D concept (Chapter 33). Directions for
pressure canning of foods at home are available, and they should be strictly followed. Proper and
uniform cooking of some foods (e.g., fish) at high temperatures should be followed as outlined. 6
(1) Foods cooked at temperatures in which spores survive should be stored at low temperatures (at
3°C or below); (2) at refrigerated temperatures (4°C–5°C), storage should not be prolonged (the
10-day rule) unless some additional precautions are used, such as NO 2 , low pH, low A W , NaCl,
and others; (3) a heat treatment of 90°C for 10 minutes or equivalent lethality (e.g., 80°C for 129
minutes, 85°C for 36 minutes) combined with storage at chill temperatures (designed to give a 6D
process for nonproteolytic Clo. botulinum); (4) a pH ≤ 5.0 throughout the food, combined with
storage at chilled temperatures; (5) a NaCl concentration of ≥3.5% throughout the food, combined with storage at chilled temperatures; (6) an A W ≤ 0.97 throughout the food, combined with
storage at chilled temperatures; and (7) combinations of heat treatment and other preservative factors, which can be shown consistently to prevent growth and toxin production by Clo. botulinum,
combined with storage at chilled temperatures. Suspected foods should be properly heated prior
to consumption, but it is better not to eat them. Even tasting a small amount of a suspected food
without giving high and uniform heat treatment can be dangerous.
Identification Methods
In a suspected food, the presence of Clo. botulinum can be determined by enumeration techniques
using selective agar media and anaerobic incubation, followed by biochemical and toxicological
testing. The presence of toxins in the food is more often tested. This involves injection of a food
extract intraperitoneally to mice. Development of characteristic neurological symptoms, followed
by death in 92 hours suggests the presence of toxins. The people engaged in testing for the organism or the toxins need to immunize themselves prior to handling the materials.