Almost all of us have experienced salmonella poisoning at one time or another. Soon after we begin to digest the contaminated food the symptoms begin: nausea, vomiting, diarrhea, stomach cramps and even fever.
Bacterial food poisoning
Food poisoning can occur in a number of ways: food might be contaminated with pesticides or might contain naturally occurring toxins (oxalic acid in rhubarb leaves, for instance), but the food poisoning most of us know and dread comes from bacteria, or from the toxins produced by the bacteria as they multiply in food.
Bacterial food poisoning is more common in summer, when food spoils more rapidly, and contaminated food can look and taste normal. Most bacteria are destroyed when food is heated, but the toxins the bacteria have produced might not be so easily disposed of.
The most common harmful bacteria causing food poisoning are Salmonella. Salmonella are present inside the human body in controlled numbers, as well as in the bodies of household pests, and they can be transmitted from one host to another through excreta, as well as by flies and cock roaches.
High standards of hygiene — always washing hands after using the toilet and before eating — are crucial to controlling the spread of salmonella. Cooking will destroy salmonella, as the bacteria cannot tolerate high temperatures, but if the cooked food comes into contact with raw food before it is consumed, or if a knife which has been used to prepare the raw meat is used to carve the cooked meat, the bacteria will multiply afresh.
The most common bacteria which produce toxins which can cause food poisoning are Staphylococcus. Staphylococcus bacteria, like salmonella, are present in large numbers in the environment. They secrete a toxic substance which affects food without causing any change in appearance or taste, and which cannot be destroyed by cooking. Common culprits in the spread of staph food poisoning include custards, cold meats, meat pies and cream cakes.
3. Clostridium perfringens
The Clostridium perfringens (formerly known as C. welchii, or Bacillus welchii) bacteria are the cause of much of the food poisoning spread within institutions, since they are commonly found in large cuts of meat which are not heated through thoroughly, or in food which is left standing at room temperature before being served.
Sources of food poisoning:
- Dirty hands used preparing food are a source of contamination. Even apparently clean hands, which have not been thoroughly washed, for example, after stroking the cat, replenishing the fire, visiting the toilet or wiping the baby’s nose are dangerous.
- Fingers with cuts, sores or burns uncovered or covered with slovenly bandages are breeding grounds for dangerous germs.
- Uncontrolled coughing or sneezing which can deposit on food hundred of germs, notably the staphylococci which are commonly found in the nose and throat even of healthy persons. These may multiply rapidly in foods producing poisonous toxins.
Obviously, personal hygiene is the first matter to attend to. Where possible, people with respiratory infections causing coughing or sneezing should avoid preparing food for others and any utensils used on raw foods should be washed thoroughly before they are allowed to come into contact with cooked foods.
- Foods which are to be served cold should be refrigerated straight after cooking (most modern fridges can cope well with the temporary overload caused by adding hot food) and food which is to be served hot should be served just that way.
- Keep pet food away from food intended for human consumption, and make sure you do not wash the dog’s bowl in the same soapy water as the baby’s bottle or the family cutlery.
- Speaking of baby’s bottles, they are a wonderful source of bacteria. The tiny holes in teats and the threads on the bottle tops trap traces of milk even after the most thorough washing, and sterilization procedures must be followed precisely to avoid contamination.
- Make sure you pay attention to the use-by dates on perishable foods, too. Salted butter will keep in the fridge for a maximum of about eight weeks. Eggs in the shell are best eaten within 3 to 6 weeks of laying, and even blocks of cheese won’t last beyond one or two months before they deteriorate.
- Sliced ham should be eaten within 3-5 days, fresh fish will not keep beyond about 3 days and most meat cuts must not be refrigerated for more than 3-5 days. Offal and minced meat should be eaten within a day or two, unless they are frozen straight after purchase.
- If you have leftover roast chicken, remove the stuffing and refrigerate it in a separate container, to reduce the risk of it contaminating the chicken meat.
- Cover all refrigerated foods tightly and if possible, reheat left overs thoroughly before serving. Leftover soups and gravies should be boiled for several minutes before re-serving.