Food poisoning occurs when people eat food that has been contaminated with harmful micro-organisms (bacteria and viruses) or with harmful substances (toxins deriving from micro-organisms, plants and fish, chemicals and metals). Many bacteria are dangerous for humans, such as those that cause food poisoning. However, there are forms of bacteria that are associated with good health and it is important to know that not all bacteria are harmful.
Because the bacteria enter the body via the digestive system, symptoms will generally be in this part of the body - nausea, vomiting, abdominal cramps and diarrhoea. The length of illness can vary from several hours to a week or more, but usually it lasts for one or two days. In some cases, food poisoning can cause very serious illness or even death.
Bacteria need food, warmth, moisture and time to grow. Bacteria reproduce by multiplication, so one bacterium becomes two and then two become four, and so on. In the right conditions one bacterium could become several million in eight hours and thousands of millions in 12 hours.
This means that if food is contaminated with a small number of bacteria, and you leave it out of the fridge overnight, it could be seriously contaminated by the next day. Then just one mouthful could make someone ill. If you put food in the fridge, it will slow down the multiplication of bacteria.
Since you can't see, taste or smell bacteria, the only way that you can be sure that food is safe is to follow good hygiene practices at all times.
Cross-contamination occurs when bacteria spread between food, surfaces or equipment. It's most likely to happen when raw food touches, or drips onto, any ready-to-eat foods, equipment or surfaces or when people touch raw food with their hands then touch ready-to-eat food.
So, if raw meat drips onto a cake in the fridge, bacteria will spread from the meat to the cake. The whole cake could be contaminated with harmful bacteria, so it would not suffice to cut off the piece of cake that can be seen to be contaminated: the whole cake would need to be thrown away.
If you cut raw meat on a chopping board, bacteria will spread from the raw meat to the board and knife. If you then use the same board and knife (without washing them thoroughly) to chop a cucumber, the bacteria will spread from the board and knife to the cucumber.
Hands can also spread bacteria. If you touch raw food and don't wash your hands thoroughly, you can spread bacteria to other things you touch.
Preparing and storing safely
Raw meat and poultry can contain harmful bacteria that spreads very easily to anything it touches, including other food, worktops, chopping boards and knives. Always keep raw meat and poultry separate from ready-to-eat foods such as salad, fruit, cooked meats and bread, as any bacteria that get onto the foods won't be killed by cooking.
To help stop bacteria from spreading, remember the following points:
• Don't let raw meat touch other foods.
• Never prepare ready-to-eat food using a chopping board or knife that you have used to prepare raw meat, unless they've been washed thoroughly first.
• Always wash your hands thoroughly after touching raw meat and before you touch anything else.
• Always cover raw meat and store it on the bottom shelf of the fridge where it can't touch or drip onto other foods.
• Clean surfaces and equipment thoroughly before you start to prepare food and after they've been used with raw food.
Cooking food safely
Thorough cooking is very important because it kills harmful bacteria in food. If bacteria do manage to survive in food because it hasn't been cooked properly, it could make you ill.
Only serve food that has been properly cooked (e.g. check that it's piping hot all the way through or that meat juices run clear) and either serve it immediately or keep it hot until serving. If you're cooking food in advance, cool and chill it quickly
Chilling food safely
Some foods need to be kept chilled to keep them safe, for example, perishable food with a 'Use-by' date, food that you've cooked and won't serve immediately, or other ready-to-eat food such as prepared salads. If these foods aren't properly chilled, bacteria can multiply and make people ill.
Put food that needs to be chilled in the fridge straight away and cool cooked food as quickly as possible, then put it in the fridge. Don't put hot food straight into the fridge, as doing so will raise the temperature in the fridge and put other food in the fridge at risk, and don't overload the fridge.
When you're preparing food, keep it out of the fridge for the shortest time possible. Generally, you shouldn't leave food out of the fridge for more than two hours. Cool leftovers as quickly as possible (ideally within one to two hours) and then store them in the fridge. Eat any leftovers within two days.
Your hands can easily spread bacteria around the kitchen and onto food. This is why it's important to always wash your hands thoroughly with soap and warm water at each of these times:
• Before starting to prepare any food.
• After touching raw meat, including poultry.
• After going to the toilet.
• After touching the waste bin.
• After touching pets.
Don't forget to dry your hands thoroughly, because if they're wet they'll spread bacteria more easily.
Often bacteria can collect in places that you might not expect them to. Anything that's touched by food or by people's hands could be covered in bacteria. Common bacteria hot-spots include: Fridge/freezer handles, tap handles, telephones and pens, work surfaces, chopping boards, bin lids and can openers.
Cloths used to clean dishes and surfaces, and tea towels, can also spread bacteria. Make sure you wash and dry them thoroughly and replace them regularly, particularly when they're worn or damaged.