Food poisoning
Practical Action
Snack foods
Dried
Fried
Fermented foods
Alcoholic drinks
Yoghurt
Cheese
Oils and fats
Fresh foods
Fruits
Vegetables
Meat and fish
Milk
Eggs
Root crops
Cereal grains
Prepared foods
Sausages, beef burgers, fish cakes
Desserts
Ice cream
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3
1
1
1
1
1
1,2
1,2
1,2
LOW
MEDIUM
LOW
LOW
MEDIUM
LOW
LOW
LOW
HIGH
MEDIUM
MEDIUM
LOW
LOW
HIGH
MEDIUM
HIGH
The foods which are most at risk of causing food poisoning are low acid, moist foods such as meat
(especially poultry), fish, sea-foods, vegetables, milk and eggs. This is especially so if the foods
are not heated to high temperatures. Such foods include those that have been frozen, dried,
chilled or fermented. Generally, the main risk comes from heated foods (those which have been
baked, fried, canned or roasted) and dried foods, after the food has been processed. Usually the
risk is associated with poor handling and storage procedures. The main exceptions to this are
herbs, spices and some types of nuts (especially groundnuts) where contamination of the raw
materials is a major problem. Any prepared food that contains these products as ingredients is a
potential source of food poisoning. In general, acid foods such as fruit products are not a source
of food poisoning.
Types of food poisoning
Staphylococcus aureus
This bacterium produces a poison in food which can withstand heating and is resistant to the
levels of salt (sodium chloride) which are commonly present in such foods as pickles. High levels
of salt can normally kill many other types of bacteria. Staphylococcus aureus can be carried by
workers and transmitted into processed food when they handle it.
The symptoms of poisoning are nausea, vomiting, diarrhoea and stomach cramps. They appear
within 1-4 hours of eating contaminated food and last for 10-12 hours. Poisoning is rarely fatal.
The main sources of poisoning are dairy products, especially cheese, processed meats and
pastries. The bacteria are carried by people, in the throat, and in infected cuts and other skin
disorders. People should not therefore handle food if they have coughs or skin complaints. This
type of poisoning is difficult to trace because the bacterium can produce the poison before the
food is processed. Heating can kill the bacterium but leave the poison in the food.
Salmonella
Salmonella is the most common cause of food poisoning in many countries and these bacteria
occur in foods that are not heated sufficiently or are contaminated after heating. The main
sources are poultry, eggs and egg products but dairy products are also a potential risk. Particular
care is needed to keep raw foods away from cooked foods, to carefully clean utensils and
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