Most food poisoning is caused by eating food that has been left to stand cooked or uncooked at temperatures that allow disease-causing bacteria to multiply.
These bacteria must usually be present in very high numbers to cause food poisoning. It is therefore essential to hold susceptible food at below 5°C or about 60°C to prevent the bacteria’s multiplication.
Food poisoning can generally be avoided by careful selection and handling. Food poisoning should be suspected when people eating the same food become ill and have the same or similar symptoms.
Botulism is the best known and most feared of food poisonings. It can develop after eating inadequately heat-treated canned or bottled low-acid foods. It is vital to boil food properly when home preserving.
Botulism is potentially fatal but cases are rare. Symptoms of botulism usually appear within between 12 and 36 hours and primarily relate to the nervous system, with visual difficulty, dry mouth and throat usually being the first symptoms. Vomiting and diarrhea may occur, followed by more severe symptoms, including paralysis, usually of the respiratory system.
Salmonella and Staphylococcus aureus
Bacteria of the salmonella group are quite common on raw meats and poultry contaminated by animal excreta at slaughter. They may also originate in human excreta and be transferred to food when personal hygiene is inadequate.
The most common source of Staphylococcus aureus is human. It is frequently present in nasal passages and on the skin. It is most likely to be a problem in cooked foods such as meat and poultry that are eaten cold and in prepared foods such as custards and creams, all of which are readily contaminated by hands. Growth of Staphylococcus aureus does not occur below about 10°C and although the organism is destroyed by cooking the toxin or poison it produces is quite heat-resistant.
How long does it take to get food poisoning?
Both bacteria can cause some form of gastroenteritis (abdominal pain, diarrhea and vomiting). There is an incubation period of 2 to 4 hours with Staphylococcus aureus and a 12 to 24 hour period with salmonella.
When shopping, we can make informed choices and avoid food that may have deteriorated in quality, or may be potentially dangerous.
- Cans which are swollen or badly dented, or have rust marks. Swollen cans indicate microbial or chemical activity and should be brought to the notice of the store manager.
- Swollen chilled food packages. This fault is not uncommon. Foods which can be affected include fruit juices, unprocessed cheeses, made-up pastry and yogurt.
- Dairy products and delicatessen items kept outside a refrigerated cabinet, they should be cold at the time of purchase.
- Frozen food packs containing ice crystals or packets with lumps of ice between them. Both conditions indicate refreezing and probable loss of quality. The ice present in the pack is water which has been withdrawn from the food and the result usually is an undesirable change in the flavor and texture of the food.
- Foods in torn packages or with imperfect seals: the food has probably deteriorated in quality.
To avoid bacterial food poisoning:
- Avoid unpasteurized milk and unchlorinated or inadequately treated drinking water.
- Check food and food containers for visible signs of deterioration and discard those that are suspect: “When in doubt, throw it out”.
- Avoid excessive handling of food be cause bacteria are always on our bodies. Although “fingers were made before forks”, suitable utensils should be used to serve food and everyone handling food should be very careful in their personal cleanliness.
- Thoroughly cook susceptible foods, particularly minced meat, sausages and poultry.
- Never handle cooked and uncooked meats at the same time. Do not cut them up with the same utensils or use the same boards without thoroughly washing the board and the utensils, and your hands.